1 |»°^?Y^T^Tf^ 1 "f" Class XK If >( Book.__y_:zj^ Gop)iiglit}v'^ CQPXRIGHT DEPOSm Electrical Tables and Engineering Data A Book of Useful Tables and Practical Hints for Electricians, Foremen, Salesmen, Solici- tors, Estimators, Contractors, Archi- tects and Engineers By HENRY C HORSTMANN and VICTOR H. TOUSLEY Authors of *' Modern Wiring Diagrams," " Modern Electrical Con- struction," "Practical Armature and Magnet Wind- ing," "Electrician's Operating and Testing Manual," "Modern Illumination, Theory and Practice," "Alternating Cur- rent," "Motion Picture Oper- ation, Stage Electrics and Illusions." ILLUSTRATED CHICAGO FREDERICK J. DRAKE & CO. Publishers Copyright 1916 by Henry C. Horstmann and Victor H. Tousley t> ojw Tsl 1 7 05 oi ot OCO O OO 0} (M 1 1 1 1 CO 00 r< u , Cd 1-^ r^ QDQOX QO QDOO r-i r-i CDCD lOiO CO" . • . . , iHrH tn : • • ; ; '. '. '. 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Where moisture exists the con- ductors should be lead-covered under the armor. Ar- mored cable is not nail proof under all circumstances. TABLE I Outside Diameters of Armored Cables and Weight Per 100 Ft. Greenfield Flexible, Steel Armored Conductors Solid Stranded Dia. Wt. Dia. Wt. B&S in. lbs. ] B&S in. lbs. Single conductors, type D.J4 .378 20 10 .450 23 12 .384 21i 8 .469 28 10 .434 26 6 .631 54 8 .464 28 4 .717 63 6 .609 54 2 .783 71 1 .900 98 Twin conductors, BX 14 .630 45 8 .830 77} 12 .670 48 6 1.116 121 10 .720 54 4 1.203 143 Three conductors, BX3 14 .675 53 8 .890 93 12 .715 564 6 1.144 153 10 .785 6Q Single conductors, DL 10 .506 53 8 .564 72 Lead covered, and steel 6 .713 95 4 .780 110 armored 2 .825 125 1 .897 165 Twin conductors, BXL 14 .730 68 8 .978 136 Steel armored and lead 12 .758 78 6 L152 205 covered 10 .863 .782 110 78 8 1.056 Three conductors, BXL3...14 164 Lead covered and steel 12 .815 97 armored 10 .933 129 Steel armored, flexible 18 .414 20 cord, Type E 16 .447 22 14 .625 38 Steel armored, flexible re- 18 .530 25 inforced cord, Type EM. 16 .540 26 14 .652 48 12 ELECTRICAL TABLES AND DATA Armory.— Armories are often classed with thea- tres and assembly halls, and must be wired accord- ingly. The most important part of an armory is the drill hall. This requires an illumination equal to about two or two and one-half foot candles. This is best obtained by placing large units high up out of the range of vision. Artists. — Require an adjustable light and pendant drops are most serviceable. Art Gallery. — Art galleries are also often classed with assembly halls. In illuminating statuary, the aim must be to produce some shadow effect because of the uniformity of color. Lights should be hung high. For white statuary an illumination of two- foot candles will be sufficient; for bronze statuary about four times as much should be provided. Paint- ings are often illuminated by stnps and reflectors, and also by indirect lighting or Holophane globes. As many paintings must be viewed from a distance, a bright illumination of about five foot candles is recommended. Asbestos. — This becomes a conductor when wet, and must not be used in damp places. Asbestos le'ss than -J inch thick is not considered serviceable. As- bestos covered wires are much used for connecting arc lamps and rheostats where the wire is subject to much heat. Assembly Halls. — The National Electrical Code prescribes that if any part of a building is *^ regu- larly or frequently used for dramatic, operatic, moving picture, or other performances or shows, or has a stage used for such performances used with scenery or other stage appliances,'^ it must be classed as a theatre, and wired according to theatre rules. It is usual to specify that all wires must be in con- duit and that there must be a separate system of lighting, independent of the main system, for use of ELECTRICAL TABLES AND DATA 13 the audience in leaving the building in case of fire, or other emergency. Attachment Plugs. — Must be of approved type. They should be of the pull-out type, and the socket so placed that the plug can pull out in case strain is put upon it. Automatic Cut-outs are required to protect every device, or wire, which is connected to any power circuit, except alternators and constant current generators. For details see Cut-outs, Automobiles. — In wiring automobiles it is custom- ary to disregard all ordinary construction rules. Electric motors are connected without any fuse pro- tection. A fuse blowing on a heavy up-grade might cause disaster. Auto-Starters. — As a general rule, auto-starters are not used with motors smaller than 5 H.P. Auto- starters provided with overload release devices, and so arranged that the handle cannot be left in the starting position, are obtainable and should be used. Small auto-starters have usually three taps, and these are arranged to give about 50, 65 or 80 per cent of the line voltage. Larger starters usually have four taps arranged respectively for 40, 58, 70 and 80 per cent of the line voltage. Always make connections to the lowest voltage tap that will give the necessary starting torque. "Wherever possible, place starter in sight of motor. For motors smaller than 5 H.P., throw-over switches are often used. Bakeries. — In bakeries, hot places will be found in which rubber-covered wire is not suitable. Balanpe Sets. — Balance sets are made up of motor generators or transformers, and exist for the pur- pose of obtaining a neutral wire and low voltage for a small lighting load operated in connection with a higher voltage two-wire generator. They are also used where motors operate at two voltages. The 14 ELECTRICAL TABLES AND DATA capacity of a balancing set is usually only a small percentage of the total load. Balancing. — Three-wire systems are usually ar- ranged so that a minimum of current may pass through the neutral wire. A good balance cannot always be obtained, and in some cases considerable judgment is required to determine which is the best arrangement of apparatus. Three wires should be carried to every center supplying more than one circuit. Safety rules require the neutral wire to be of same size as the outside wire, but in large systems this wire will seldom be called upon to carry more than 10 per cent of the current used at any time. Ball Rooms. — Ball rooms are often classed with theatres. The illumination should be general, and lamps hung high. A general illumination of from two to four foot candles is recommended. Recep- tacles for musicians' use should be provided. Banana Cellars. — These places are always hot and moist and the vapors are very corrosive. Conduits corrode very fast, and especially the small screws in outlet boxes; brass screws are often used. Open wiring, if it can be protected, is preferable. 'Banks. — In that part of a bank occupied by the clerical force, a general illumination of from three to four foot candles is recommended. These lights are in use most of the time, and high efficiency lamps should be arranged for. In that portion used by the public the illumination is not so much used, and may be of a lower order. Numerous outlets for adding machines and fan motors should be provided. In ^some banks the private , depositors' rooms are fitted with two lights, one above and one below desks, and provided with three-way switches so that only one light can be used at a time ; this for con- venience of customers who may have dropped things on the floor. ELECTRICAL TABLES AND DATA 15 Barber Shops. — Good illumination of barber shops can be arranged for by placing clusters of fairly large candlepower close to the ceiling and a little to the rear of chairs. Placed in this manner, the light will not be forced directly into the line of vision of the customer, and yet give the desired illumination. The mirrors in front of chairs will reflect much of the light back to the chair. Often lights are placed along the mirrors, but this practice is not to be recommended. Outlets for cigar-lighters, curling-iron heaters, vibrators, etc., will be appre- ciated. Bams. — The use of brass shell sockets should be avoided in horse barns. Avoid placing lights in front of horses, and keep all lights well up above horses' heads. Use weatherproof construction in wash rooms. Place lights in all dark comers. Bases. — All electrical contacts must be mounted on non-combustible, non-absorbtive insulating material. Other materials than slate, marble, or porcelain are not favored much, and are allowed only when the first named are too brittle. Sub-bases are generally provided for all switches and other devices which would otherwise allow the wires to come against wood or plaster. Base Frames. — Base frames are required under all generators and motors, and where the voltage is not in excess of 550 volts it is customary to use insulated base frames. If the motor operates at a voltage in excess of 550, it is better to ground the frame thor- oughly. Where frames cannot be insulated they must be grounded. Basements. — Basements are often damp, and must then be wired in accordance with rules for such places. As ceilings are usually low, protection against mechanical injury is often necessary. 16 ELECTRICAL TABLES AND DATA Batteries, Primaiy. — Dry batteries are much used at the present time. They require no attention an when worn out are simply thrown away. The dr^ battery is at present made only for open circuit work. The wet battery used mostly for open circu* work consists of carbon and zinc elements immerse*, in a solution of sal-ammoniac. The carbon is the positive pole. This battery is charged by dissolving about four ounces of sal-ammoniac in sufficient water to fill the jar about three-fourths full. Never use more sal-ammoniac than will readily dissolve. It is preferable to make a saturated solution and, after filtering it through cloth, to add about 10 per cent of water. Keep jars in a cool place to prevent evapo- ration. Never allow water to freeze. Keep exposed parts covered with paraffine. Do not allow battery to be short circuited or run down. If this has oc- curred, it will often pick up if left on open circuit for a few hours. If the solution appears milky, more sal-ammoniac is required. Impure zincs which do not eat away evenly facilitate the formation of crystals which greatly increase the resistance. The best known of the closed circuit batteries is the gravity type. The elements in this cell are zinc and copper, immersed in a solution of sulphate of copper (blue vitriol). The copper element rests on the bot- tom of the jar, and the blue vitriol is placed around it and the jar filled with clean water. The cell must be short circuited for a few hours to start the action. The blue solution should rise to about midway be- tween the two elements. This cell must be kept in action or it will rapidly deteriorate. Connect all batteries so that the resistance of the battery is nearest equal to the resistance of the de- vices it is to operate. Series connection should be used when the external resistance is higher than the internal battery resistance. If the external resist- ELECTRICAL TABLES AND DATA 17 ance is lower than that of the battery, group cells bin multiple. When arranging small storage batteries rto be charged from lighting or power circuits, pro- ^ vide double throw switches to entirely disconnect ^fcattery from power circuit while it is on the bell i>circuit. Install all wiring subject to power voltage in accordance with rules for that voltage. Batteries, Secondary. — Small storage batteries may be carried about and used. The larger ones must remain stationary and are used as compensa- tors for feeder drop, equalizers on three-wire sys- tems, preventives against shut down and as a com- bination of all of these. Medium size storage batteries are also much used with automobiles. All storage batteries with exception of the Edison, use lead plates. The active material is sponge lead im- mersed in a weak solution of sulphuric acid. The positive plates when fully charged are of a chocolate color and the active material is quite solid. The negative plate is more of a slate color and softer. The unit of capacity is the ampere hour. A 60- ampere-hour battery, for instance, can deliver a cur- rent of three amperes for twenty hours, or seven and one-half amperes for eight hours. High voltages are obtained by connecting a number of cells in series. High amperage is obtained by connecting plates in parallel. The voltage is independent of the size of the cell, but the amperage capacity varies with the surface of the opposed plates. The effi- ciency is roughly about 75 per cent. The safe rate of charge and discharge varies from five to ten am- peres per square foot of positive plate surface, both sides of plate being measured. The voltage should never be allowed to fall below 1.8, and when fully charged is about 2.6. The condition of full charge is indicated by both the positive and negative plates gassing freely. 18 ELECTRICAL TABLES AND DATA Before manipulating or attempting to connect any storage battery, the instructions of the maker should be obtained. The following instructions form only a general guide : Keep electrolyte well above plates. See that the cells are kept clean and allow nothing that could short-circuit the plates to accumulate at the bottom. Keep whatever separators there may be in place. Allow no metal except lead in the battery room. Insulate cells from ground and from each other. See that battery is recharged as soon as pos- sible after being used. Do not overcharge. When the negative plates begin to give off gas, it is time to quit. Never allow the voltage to fall below 1.75 per cell. The temperature of the battery should not rise above 110 degrees. The capacity of battery needed is governed by number of units in the gen- erating plant. It is not likely that more than one unit will give out at a time. Bells. — Bell-ringing transformers are much used in connection with alternating current in place of bat- teries. To operate bells in series, jump circuit breaker on all but one. If bells are to be operated from lighting circuits, the wiring must be installed in accordance with rules for the voltage used, and the bell must be specially approved for that service. The chief hazard that exists \vith low voltage bell wires is the possibility of coming in contact with other wdres. If storage batteries of high amperage capacity are used, the wires should have fuse protection. Belting. — Figure 1 is an illustration of a service- able method of belt lacing. Thread lacing from left to right according to heavy lines, double up at ends and return to starting point; cross lacing on out- side of belt only, and keep laces on inside parallel with length of belt. ELECTRICAL TABLES AND DATA 19 Holes should be punched as nearly as possible according to the following table : TABLE II Width of Belt 2 to 6 to 12 to 18 to Distance from edge of belt — 6 in. 12 in. 18 in. 24 in. First row i § J 1 First row i f j 1 Second row | 1 IJ IjJ Second row 1 H 1^ 2 Distance apart of each row of holes 1 1^ IJ 2 Size of lace leather i% J f ^ If pulleys are of same size, or far apart if of different sizes, the length of belt can be quite approx- imately found by the following rule : Add diameters Figure 1. — Method of Belt Lacing. of pulleys and multiply by 1.57 ; to this add 2 times the center-to-center distance. The length of belting contained in a roll can be found by reference to Table III. Multiply number of layers in roll by number found where outside diameter of roll and diameter of hole in center cross. Example. — A roll of belting of 48 inches outside diameter has a hole in the center six inches in diam- 20 ELECTRICAL TABLES AND DATA eter, and there are 88 layers of belting. Where the line pertaining to 48 inches outside diameter crosses the line pertaining to 6-inch hole, we find the num- ber 7.04, which multiplied by 88 gives 619.52 feet of belting. The width of a single belt necessary to perform a certain amount of work can be found by the formula Ty = 1200xH.P. -fF, where W stands for width, H.P. for horsepower, and V for velocity of belt in feet per minute. This formula will give a belt of ample size, and a smaller one can be made to do the work by giving it greater tension. Table IV is calculated from the above formula and shows the capacity of belts of various widths and operating at various velocities. Belts should run horizontally and the pull should be on the under side. Tightener should be on slack side and close to main pulley. Belts running ver- tically must be kept very tight, especially if the lower pulley is small. The proportion between two pulleys close together should not be greater than 6 to 1. Double belting should not be used on pulleys less than 3 feet in diameter. Rubber belting is pref- erable in damp places. Thin belting is best for high speeds. Belts operating at high speeds should be cemented, not laced. Pulleys should be perfectly smooth. Billboards. — A very bright illumination of from ten to twenty foot candles is often used. Lights must be encased in reflectors so as not to be visible to the observer. Install wiring according to rules for outside work. Billiard Halls. — A general illumination of about one foot candle is recommended. Above each table there should be an illumination of four or five-foot candles. The light over the table should be uniform. At least two lamps should be provided for each table, and should be so encased that the lights are ELECTRICAL TABLES AND DATA 21 TABLE III Table for Calculating Length of Belting, Eope or Wire in Coils Outside r- — Diameter of Hol( 3 in Inches — ^ Diameter 2 3 4 5 6 7 8 9 10 11 12 6 in. . .1.05 1.17 1.30 1.44 7 in. . .1.17 1.31 1.44 1.57 1.70 8 in. . .1.31 1.44 1.57 1.70 1.83 1.96 9 in. . .1.44 1.57 1.70 1.83 1.96 2.09 2.23 10 in. . .1.57 1.70 1.83 1.96 2.09 2.23 2.46 2.49 11 In. . .1.70 1.83 1.96 2.09 2.23 2.36 2.49 2.62 2.75 12 in. . .1.83 1.96 2.09 2.23 2.36 2.49 2.62 2.75 2.g8 3.01 13 Ln. . .1.96 2.09 2.23 2.36 2.49 2.62 2.75 2.88 3.01 3.14 3.27 14 in. . .2.09 2.23 2.36 2.49 2.62 2.75 2.88 3.01 3.14 3.27 3.40 15 in. . .2.23 2.36 2.49 2.62 2.75 2.88 3.01 3.14 3.27 3.40 3.53 16 In. . .2.36 2.49 2.62 2.75 2.88 3.01 3.14 3.27 3.40 3.53 3.66 17 in. . .2.49 2.62 2.75 2.88 3.01 3.14 3.27 3.40 3.53 3.66 3.79 18 in. . .2.62 2.75 2.88 3.01 3.14 3.27 3.40 3.53 3.66 3.79 3.92 19 in. . .2.75 2.88 3.01 3.14 3.27 3.40 3.53 3.66 3.79 3.92 4.06 20 in. . .2.88 3.01 3.14 3.27 3.40 3.53 3.66 3.79 3.93 4.06 4.19 22 n. . .3.14 3.27 3.40 3.53 3.66 3.79 3.92 4.05 4.19 4.32 4.45 24 in. . .3.40 3.53 3.66 3.79 3.92 4.05 4.19 4.31 4.45 4.58 4.72 26 ] in. . .3.66 3.79 3.92 4.05 4.18 4.31 4.45 4.57 4.71 4.84 4.97 28 ^ in. . .3.92 4.05 4.18 4.31 4.44 4.57 4.71 4.83 4.98 5.11 5.24 30 ] m. . .4.18 4.31 4.44 4.57 4.70 4.83 4.98 5.09 5.23 5.36 5.50 32 ] n. . .4.44 4.57 4.70 4.83 4.96 5.09 5.24 5.35 5.49 5.62 5.75 34 ] m. . .4.70 4.83 4.96 5.09 5.22 5.35 5.50 5.62 5.75 5.88 6.01 36 ] m. . .4.96 5.09 5.22 5.35 5.48 5.67 5.76 5.88 6.02 6.15 6.28 38 ] in. . .5.22 5.35 5.48 5.61 5.74 5.88 6.02 6.14 6.28 6.41 6.54 40 ] n. . .5.48 5.61 5.74 5.87 6.00 6.14 6.28 6.41 6.57 ^.^% 6.82 42 i m. . .5.74 5.87 6.00 6.13 6.26 6.40 6.54 6.67 6.81 6.94 7.08 44 ] in. . .6.00 6.13 6.26 6.39 6.52 6.66 6.80 6.93 7.07 7.20 7.34 46 i m. . .6.26 6.39 6.52 6.65 6.78 6.92 7.06 7.19 7.33 7.46 7.60 48 i n. . .6.52 ^.^^ 6.78 6.91 7.04 7.18 7.32 7.45 7.56 7.72 7.86 This table may also be used to estimate length of rope or wires in coils if number of turns can be determined. 22 ELECTRICAL TABLES AND DATA TABLE IV The table below is calculated from the above formula and shows the number of H. P. belts will transmit Belt Speed in Ft Per Mi n. '~ Widtl I of Belt in Inche-s — 1 2 o 4 5 6 7 8 9 10 200 . .. .16 .33 .50 .66 .83 1.00 1.16 1.33 1.50 1.66 300 . .. .25 .50 .75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 400 . .. .33 .66 1.00 1.32 1.66 2.00 2.33 2.66 3.00 3.32 500 . .. .42 .84 1.25 1.67 2.10 2.50 2.95 3.34 3.75 4.20 600 . .. .50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 700 . .. .58 1.14 1.75 2.33 2.90 3.42 4.08 4.67 5.25 5.80 800 . .. .67 1.34 2.01 2.66 3.34 4.02 4.67 5.33 6.00 6.68 900 . .. .75 1.50 2.25 3.00 3.75 4.50 5.25 6.00 6.75 7.50 1000 . .. .83 1.66 2.49 3.33 4.15 4.98 5.83 6.66 7.50 8.30 1200 . ..1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.0 1400 . ..1.16 2.32 3.50 4.67 5.80 7.00 8.13 9.34 10.5 1L6 1600 . ..1.33 2.66 4.00 5.33 6.66 8.00 9.33 10.6 12.0 13.3 1800 . ..1.50 3.00 4.50 6.00 7.50 9.00 10.5 12.0 13.5 15.0 2000 . ..1.67 3.34 5.00 6.67 8.36 10.0 11.7 13.4 15.0 16.7 2200 . ..1.83 3.66 5.50 7.32 9.15 11.0 12.8 14.6 16.5 18.3 2400 . ..2.00 4.00 6.00 8.00 10.0 12.0 14.0 16.0 18.0 20.0 2600 . ..2.16 4.32 6.50 8.66 10.8 13.0 15.1 17.3 19.5 21.6 2800 . ..2.33 4.66 7.00 9.33 11.6 14.0 16.3 18.6 21.0 23.2 3000 . ..2.50 5.00 7.50 10.0 12.5 15.0 17.5 20.0 22.5 25.0 3200 . ..2.66 5.32 8.00 10.6 13.3 16.0 18.6 21.2 24.0 26.7 3400 . ..2.83 5.66 8.50 11.3 14.1 17.0 19.8 22.6 25.5 28.2 3600 . ..3.00 6.00 9.00 12.0 15.0 18.0 21.0 24.0 27.0 30.0 3800 . ..3.16 6.32 9.50 12.6 15.8 19.0 22.1 25.2 28.5 31.6 4000 . ..3.33 ^.m 10.0 13.3 16.6 20.0 23.3 26.6 30.0 33.2 4200 . ..3.50 7.00 10.5 14.0 17.5 21.0 24.5 28.0 31.5 35.0 4400 . ..3.67 7.34 11.0 14.6 18.3 22.0 25.6 29.2 33.0 36.6 4600 . ..3.83 7.66 11.5 15.3 19.1 23.0 26.8 30.6 34.5 38.2 4800 . ..4.00 8.00 12.0 16.0 20.0 24.0 28.0 32.0 36.0 40.0 5000 . ..4.17 8.34 12.5 16.7 20.9 25.0 29.2 33.4 37.5 41.8 ELECTRICAL TABLES AND DATA 23 TABLE V Table showing approximate lengths of material which must be cut out of belts to double the tension; sag on upper and lower sides assumed equal. Reducing sag by one-half ap- proximately doubles the tension. Distance Between Pulley Centers in Feet r Dimensions Below in 64th of an Inch ^ 4— Sag 31 46 62 77 92 108 123 138 154 Cutout 2 3 5 7 10 13 17 20 6— Sag 46 69 92 115 138 161 184 207 231 Cutout ... 1 3 5 7 11 15 19 25 30 8— Sag 62 92 123 154 185 216 246 277 308 Cutout ... 1 4 6 10 15 20 26 33 41 10— Sag 77 115 154 192 230 269 307 346 384 Cutout ... 1 4 8 12 18 25 32 41 50 12— Sag 92 138 184 230 276 322 368 415 462 Cutout ... 2 5 9 14 21 29 38 49 59 15— Sag ......115 173 231 288 345 402 459 518 577 Cutout ... 2 7 12 18 28 37 48 62 76 .18_Sag 138 207 277 346 415 485 554 623 693 Cutout ... 3 8 14 22 33 44 58 74 91 21— Sag 161 242 323 404 485 566 647 727 807 Cutout ... 3 9 16 26 39 51 70 87 106 25— Sag 192 288 384 480 576 672 768 864 960 Cutout ... 4 12 19 31 46 61 81 104 127 30— Sag 231 346 461 576 691 806 9211036 1151 Cutout ... 4 14 23 37 55 74 97 124 152 The above table is based upon the ratio of deflec- tion and elongation of wires in spans, and it is assumed that the additional strain produces no immediate elongation of the belt. 24 ELECTRICAL TABLES AND DATA not visible to the players. A switch for each table will be a convenience. Outlets for cigar-lighters and fan motors should be provided. Bonds. — Rail bonds should not be smaller than No. 000. The area of contact should be about eight times the cross section of the bond. In some in- stances the size of bond is determined by the size of supply w^ires, the total cross section of all bonds at any point being made equal to the cross section of the supply wires for that point. For a ratio of 1 : 12 the copper in circular mils necessary to equal the conductivity of steel rails can be found by multiply- ing the weight per yard of rail by 10,000. •Boosters. — Boosters may be in the form of trans- formers or motor generators, and are used to raise or lower voltage, also in some cases in return rail- w^ay circuits to lessen electrolysis. The installation of boosters is not profitable except on long lines when the cost of copper to prevent the drop is greater than the cost of boosters. Boosters may be compounded so that the regulation becomes auto- matic. Bowling Alleys. — The illumination should be ar- ranged so that no light is visible to the players. An illumination equal to one and one-half or two foot candles is advisable for the alley, and about double that much for the pins. Branch Blocks must always provide double pole fuse protection for each circuit. Branch Circuits. — The term, ''branch circuit," is here used to describe that part of the wiring between the last fuse and the lights, motors, heaters, or other translating devices. Branch circuits should be grouped as far as possible and arrang*ed so that the cut-out cabinet may be in a safe and convenient place. It is advisable to place the switches outside of cut-out cabinets. In the best arranged theatres ELECTRICAL TABLES AND DATA 25 all branch circuits, except those for emergency lights, are carried to stage switchboards. By run- ning mains as far as possible, and shortening the branch circuits, a much evener voltage at lamps will be secured than is possible from long branch cir- cuits. The drop in voltage should never be over 2 per cent. Most lamps are marked for three voltages, top, ipiddle, and bottom, and there is a difference of four volts between them. With a 4 per cent drop a 110-volt lamp will be at different times subject to all three voltages and the illumination will vary greatly. For best location of cut-outs, see table on calcu- lation of materials. The following table shows drop in voltage with different wires at different distances. A run of No. 14 wire 110 feet long feeding twelve lights evenly spaced ten feet apart will cause a drop of about one and one-quarter volts between first and last lamps. The table below shows the drop with wires from No. 14 to 6, carrying six amperes the dista,nces given at top of table. TxVBLE VI Distance in feet; one leg & s 20 40 60 80 100 120 140 160 180 200 14 .. ,63 1.3 1.9 2.5 3.2 3.8 4.4 5.0 5.7 6.3 12 .. .40 .80 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0 10 .. .25 .50 .75 1.0 1.3 1.5 1.8 2.0 2.3 2.5 8 .. .15 .30 .45 .60 .75 .90 1.1 1.2 1.4 1.5 6 .. .10 .20 .30 .40 .50 .60 .70 .80 .90 LO Burglar Alarm. — A good burglar alarm is one so wired that it is under constant test, so as to give immediate notice when any part of it is out of order. The closed circuit system complies with this require- ment. With open circuit systems it is best to pro- vide ** silent test" by which it can be tried out every night without causing an alarm. To guard against purposive incapacitating, some installations are 26 ELECTRICAL TABLES AND DATA mixed open and closed circuit system, so that it is impossible to know which wire to cut or short-circuit in order to prevent an alarm. In some systems ''balanced'' relays are used and the wires are inter- woven so that it is impossible to interfere with them in any way without giving an alarm. "Where either the simple open or closed, circuit system is used, the wires and batteries should be protected against inter- ference. Bus-Bars. — The term, ''bus-bar," refers, strictly speaking, only to those conductors on a switchboard which are connected directly to all of the machines. In common practice, however, it is understood that all of the current-carrying bars on a switchboard come under this classification. For high voltages it is usual to cover the bars with insulation, but for low voltages it is customary to leave them bare. The proper separation of bus-bars is 2| inches for volt- ages less than 300, and 4 inches for the higher, in- cluding 550 volts. Copper and aluminum are used. Systematize bus-bars by placing all positive poles at top or right-hand side of circuit. A current density of 1000 amperes per square inch is common practice for bus-bars, but is too high for the large ones. Table number VII shows the current-carrying capacity of bus-bars calculated on a basis of 1000 amperes per square inch cross section. For very small bars IJ times as much current may be allowed, while for the very large ones not more than half the current given in the table should be used. The carry- ing capacity of aluminum is given as 84 per cent of that of copper. Bushings. — In connection with very high voltages, specially constructed bushings must be used through walls. Ordinary bushings cause trouble. If possible the wires should be run in without touching any- thing. ELECTRICAL TABLES AND DATA 27 TABLE VII hick- ness Width Area ir Sq. in. ible of Bus I Lbs. Copper i-Bar Data Per Foot Aluminum Carrying Capacity 840 1000 Amperes Amp. Per Sq. In. Per Sq. In. Alumi- Copper num iV i .0313 .1205 .0361 32 27 iV i .0469 .1807 .0542 47 39 A 1 .0625 .2410 .0723 63 53 ^ H .0938 .3615 .1084 95 80 J i .0625 .2410 .0723 63 53 J f .0938 .3615 1084 95 80 i 1 .1250 .4820 .1446 125 105 i n .1875 .7230 .2169 188 158 i 2 .2500 .9640 .2892 250 210 i f .1875 .7230 .2169 188 158 i 1 .2500 .9640 .2892 250 210 i li .3125 1.205 .3615 315 265 i 1* .3750 1.446 .4338 375 315 i IJ .4375 1.687 .5061 435 365 i 2 .5000 1.928 .5784 500 420 i 2J .5625 2.169 .6507 565 475 i 2i .6250 2.410 .7230 625 530 i f .3750 1.446 .4338 375 310 i 1 .5000 1.928 .5784 500 420 i U .6250 2.410 .7230 625 525 i li .7500 2.892 .8676 750 630 i IJ .8750 3.374 1.1122 875 735 i 2 1.000 3.856 - 1.1568 1000 840 i 2J 1.125 4.338 L3014 1125 995 i 2i 1.250 4.820 1.4460 1250 1050 i 2f 1.375 5.304 1.5912 1375 1155 i 3 1.500 5.784 1.7352 1500 1260 i 3J 1.625 6.266 . 1.8798 1625 1365 i 3i 1.750 6.748 2.0244 1750 1470 i 3J 1.875 7.230 2.1690 1875 1575 i 4 2.000 7.712 2.3136 2000 1680 1 1 .750 2.892 ^ .8676 750 630 f li 1.125 4.338 1.3014 1125 945 1 2 1.500 5.784 1.7352 1500 1260 i 21 1.875 7.230 2.1690 1875 1575 1 3 2.250 8.676 2.6118 2250 1890 1 3i 2.625 10.122 3.0366 2625 2260 1 4 3.000 11.568 3.4704 3000 2520 28 ELECTRICAL TABLES AND DATA The Aluminum Company of America recommends 1200 amperes per square inch for the smaller bars and 500 for the largest. Cabinets. — Metal cabinets only are .used in con- nection with conduit systems. Cabinets are obtain- able in four thicknesses of steel, viz., 16, 14, 12, and 10 U. S. Standard gauge, equal to 1/16, 5/64, 7/64, and 9/64 inches respectively. The thin metal is used only for the smaller boxes, and the heavy for the large ones. The depth of cabinets is usually great enough to allow door to close with small switches in any position, and the large ones thrown way back. For necessary dimensions, see Cut-outs y Panel Boards, or Switches, Where conduits enter all from one end, a wiring gutter space equivalent to about I square inch for each circuit of number 14 twir conductor should be allowed. Cabinets should be provided to enclose all cut-outs. If practicable locate them so as to reduce likelihood of rubbisl being stored in them to a minimum. To locate switches outside of cut-out cabinets is good practice In ordering cabinets note the following points : Wooc or metal. Wall or flush mounting. With or withou^ lining. With or without wiring gutter. Thickness of steel desired. Over-all dimensions of cut-outs panel board, or switch. Inches of back wiring pocket. Inches of side wiring pocket. Spring hingei or not. Type of handle or lock. Side on whicl hinge must be. Finish and nature of door. Candle Power. — This term is rather loosely usee and has no very definite meaning, unless qualifiec by one of the following terms: Apparent candL power ; equivalent candle power ; mean lower hemi spherical candle power; mean horizontal candl power ; maximum candle power. The candle powe of no lamp is the same in all directions. ELECTRICAL TABLES AND DATA 29 Canopies. — The number of lamps to be used for :he illumination of outlines in canopies is usually governed by the design of the canopy. The best effect, where outline lighting is to be installed, is obtained from many small lamps of low intrinsic 3rilliancy. Keep lamps and sockets out of the v^eather. Fixture canopies must be insulated wher- ver an insulating joint is called for on fixture. Carbons. — For life of carbons with various types yf arc lamps, see Arc Lamps. The upper carbon is usually the positive, and for projecting arcs is larger than the lower. The positive carbon holds its heat longer than the negative. If carbons are too large, the arc will travel around them. With direct cur- rent, the upper or positive carbon is consumed twice as fast as the other. Flaming arc carbons contain special materials in the core, and the color of the arc is governed by this material. Car Houses. — A main switch is usually provided by which all wires in the car house can be cut off. Where a car house contains many sections it is better to provide a switch for each section. The illumina- tion of car houses is usually by series incandescent lighting. Carriage C%lls. — These are usually made up in the form of electric signs, and located above canopies of theatres and hotels. They consist of a large num- ber of monograms and require a large number of wires to be run to them. Outdoor wires should be run in water-tight conduit system. If armored cable is used outdoors it must be lead-covered insulation. Cathode. — The cathode is the negative pole. This term is used in connection with batteries and electro- lytic devices, mostly. Ceiling Fans. — These must never be fastened rigidly, but in such a manner as to allow them to find their own ''centers" when running. Not more 30 ELECTRICAL TABLES AND DATA than 660 watts may be connected to one circuit One fan to 400 or 500 square feet floor space is com- mon practice. Celluloid is highly inflammable, and must never be used exposed to heat or flame. "Where a trans- parent medium of a similar appearance is needed, gelatine is used. Cement when wet is a good conductor and may easily cause grounds. Centers of Distribution. — In most cases the loca- tion of centers is governed by other conditions than economy of copper, and is dictated by the desire of the user. Where, however, free choice of location is given, the following tabulation showing the rela- tive number of circular mils for each branch cir- cuit of 660 watts at 110 volts will be of use. The table shows that with small mains, and especially three-wire systems, the amount of copper in the mains may be much less than in the branch circuits, and that it will be more profitable to run mains into the area to be served. This advantage grows less with larger mains. Branch circuits require 8214 circular mils per circuit of 660 watts. The theoretical requirements per 660 watts for mains supplying centers is given belo^: TABLE VIII Mains B. & S. 2 Wire 3 Wire 14 3286 2460 12 3957 2968 10 5000 3752 8 5693 4270 6 6325 4744 5 7227 5426 4 7200 5397 3 7914 5934 Chandeliers. — No part of any chandelier should be less than six feet two inches above floor. The usual ELECTRICAL TABLES AND DATA 31 height ranges between this and seven feet. In thea- tres and similar places where chandeliers hang very high, arrangement should be made for either raising or lowering to admit of lamp renewals. For large chandeliers special permission to use 1320-watt* cir- cuits can usually be obtained. Chemical Works. — Before undertaking work in such places, investigate the nature of fumes, and chemicals used, with reference to effect upon copper and insulating materials, especially metal conduits, if considered. Choke Coils. — These are used mostly in connec- tion with lightning arresters. They must be as well insulated as the circuit wires to which they are connected. Churches. — Some of the large churches require a lighting equipment similar to that of theatres. In choir lofts and at altars, pockets for special lights are often required. Indirect lighting is very useful in churches, as the light should be kept out of the line of vision of the speaker as well as the audience. From two to three foot candles are necessary. Emer- gency lighting should also be provided. Circuit Breakers are much more sensitive than fuses. Many of them are so constructed as to allow a considerable overload for a short time, and the length of this time is adjustable. Circuit breakers should ordinarily not be set more than 30 per cent above the rated carrying capacity of the wire they are to protect. Coils. — The coils of a magnet must be connected so as to form a continuous spiral. Coloring Lamps. — Coloring and frosting of lamps reduces the light from 30 to 50 per cent. Amber coloring reduces the light about 20 per cent, while green and red take up from 50 to 90 per cent, according to the density and shade. Prepared color- 32 ELECTRICAL TABLES AND DATA ing materials can be had at all supply stores. A few amber-colored lamps are sometimes mixed in with white lights to give a warmer glow to the light. Color of Light Sources. — Moore tube (carbon dioxide gas) White Intensified arc White Magnetite arc White Open arc Nearly white Tungsten lamp Nearly white Tungsten lamp, gas-filled White Nernst lamp Nearly white Enclosed arc (short arc) Bluish white Tantalum lamp Pale yellowish white Gem lamp Pale yellowish white Carbon lamp Pale yellowish white Regenerative flame arc Yellow Flaming arc Variable with different carbons Mercury lamp (glass tube) Bluish green Enclosed arc (long arc) Bluish white to violet High sun White Low sun Orange red Skylight Bluish white Welsbach mantle -. Greenish white Common gas burner Pale orange yellow Kerosene lamp Pale orange yellow Candle Orange yellow TABLE IX Comparison of Fahrenheit and Centigrade Thermometers Fah. Cent. Fah. Cent. Fah. Cent. Fah. Cent. Fah. Cent. 212 100 165 73.8 118 47.7 71 21.6 24 4.4 211 99.4 164 73.3 117 47.2 70 21.1 23 — 5.0 210 98.8 163 72.7 116 46.6 69 20.5 22 — 5.5 209 98.3 162 72.2 115 46.1 68 20.0 21 — 6.1 208 97.7 161 71.6 114 45.5 67 19.4 20 6.6 207 97.2 160 71.1 113 45.0 66 18.8 19 — 7.2 ELECTRICAL TABLES AND DATA 33 Fah. Cent. Fah. Cent. Fall. Cent. Fah. . Cent. Fah. Cent. 206 96.6 . 159 70.5 112 44.4 ^^ 18.3 18 — 7.7 205 96.1 158 70.0 111 43.8 64 17.7 17 — 8.3 204 95.5 157 69.4 110 43.3 63 17.2 16 — 8.8 203 95.0 156 68.8 109 42.7 62 16.6 15 — 9.5 202 94.4 155 68.3 108 42.2 61 16.1 14 —10.0 201 93.8 154 67.7 107 41.6 60 15.5 13 —10.5 200 93.3 153 67.2 106 41.1 59 15,0 12 —11.1 199 92.7 152 m,^ 105 40.5 58 14.4 11 —11.6 198 92,2 151 66.1 104 40.0 57 13.8 10 —12.2 197 91.6 150 m.^ 103 39.4 m 13.3 9 —12.7 196 91.1 149 65.0 102 38.8 55 12.7 8 —13.3 195 90.5 148 64.4 101 38.3 54 12.2 7 —13.8 194 90.0 147 63.8 100 61.1 53 11.6 6 —14.4 193 89.4 146 63.3 99 37.2 52 11.1 5 —15.0 192 88.8 145 62.7 98 36.6 51 10.5 4 —15.5 191 88.3 144 62.2 97 36.1 50 10.0 3 —16.1 190 87.7 143 61.6 96 35.5 49 9.4 2 —16.6 189 87.2 142 61.1 95 35.0 48 8.8 1 —17.2 188 86.6 141 60.5 94 34.4 47 8.3 —17.7 187 86.1 140 60.0 93 33.8 46 7.7- - 1 —18.3 186 85.5 139 59.4 92 33.3 45 7.2- - 2 —18.8 185 85.0 138 58.8 91 32.7 44 ^.^- - 3 —19.4 184 84.4 1S7 58.3 90 32.2 43 6.1- - 4 —20.0 183 83.8 136 57.7 89 31.6 42 5.5- - 5 —20.5 182 83.3 135 57.2 88 31.1 41 5.0- - 6 —21.1 181 82.7 134 56.6 87 30.5 40 4.4- - 7 —21.6 180 82.2 133 56.1 86 30.0 39 3.8- - 8 — 22.2 179 81.6 132 55.5 85 29.4 38 3.3- - 9 —22.7 178 81,1 131 55.0 84 28.8 37 2.7- -10 —23.3 177 80.5 130 54.4 83 28.3 • 36 2.2- -11 —23.8 176 80.0 129 53.8 82 27.7 35 1.6- -12 —24.4 175 79.4 128 53.3 81 27.2 34 1.1- -13 —25.0 174 78.8 127 52.7 80 26.6 33 0.5- -14 —25.5 173 78.3 126 52.2 79 26.1 32 .0- -15 —26.1 172 77.7 125 51.6 78 25.5 31 - —0.5- -16 —26.6 171 77.2 124 5L1 77 25.0 30 - —1.1- -17 —27.2 170 76.6 123 50.5 76 24.4 29 - -1.6- -18 —27.7 169 76.1 122 50.0 75 23.8 28 - -2.2- -19 —28.3 168 75.5 121 49.4 74 23.3 27 - -2.7- -20 —28.8 167 75.0 120 48.8 73 22.7 26 - -3.3 166 ■ 74.4 119 48.3 72 22.2 25 - -3.8 To convert degrees Centigrade into Fahrenheit, if the temperature given is above zero, multiply by 1.8 34 ELECTRICAL TABLES AND DATA and add 32. If it is below zero multiply also by 1.8, but if this product is less than 32, subtract it from 32 ; if more, subtract 32 from it. To convert Fahren- heit into Centigrade, if the temperature given is above zero, subtract 32 and divide the remainder by 1.8 ; if below zero, add 32 and divide by 1.8. Concentric Wire. — Concentric wires are seldom used except in mines and similar places. Such a wire fully insulated would require more insulating material and be more bulky than the ordinary duplex wire. The concentric wire recently put upon the market has only one wire insulated. The other wire is a metal sheath which entirely surrounds the inner wire and its insulation. The sheath must always be thoroughly grounded. Condensers must be enclosed in noncombustible cases and installed with the same precautions as the wires of the system to which they attach. Con- densers are usually rated in microfarads, and a condenser of two or three microfarads is considered quite large. Conduits. — Conduit installations materially reduce the fire hazard, but to some extent increase the minor troubles. They produce many grounds and short circuits, but confine the trouble. Careful work- manship, especially at junction and outlet boxes, will reduce such troubles to a minimum. Install conduits so they will drain, and avoid their use in wet places unless lead-encased wires are used. Skilled conduit workers avoid the use of elbows' with small wires as much as possible. The following tables (X and XI) give the sizes of conduits recom- mended by the National Electrical Contractors' Association of the United States in connection with various sizes and numbers of wires. These recom- mendations are based on actual tests and can be relied upon. ELECTRICAL TABLES AND DATA 35 TABLE X Standard sizes of conduits for the installation of wires and cables as adopted and recommended by The National Elec- trical Contractors' Association of the United States and the N. E. Code. Conduit sizes are based on the use of not more than three 90° elbows in runs taking up to and including No. 10 wires; and two elbows for wires larger than No. 10. Wires No. 8, and larger, are stranded. One Wire Two Wires Three Wires Four Wires Appros :. in a Condui t ina< Conduit : in a Conduit ina( :::onduit B. &S. Diameter , — Diam.— -^ , — Diam. — ■> r — Diam. — > , — Diam.' — x Gauge of Wire Int Ext. Int. Ext . Int. Ext. Int. Ext. 14 1%4 Vi .84 y2 .84 1/2 .84 % 1.05 12 2%4 V2 .84 % 1.05 % 1.05 % 1.05 10 2%4 - Vi .84 % 1.05 % 1.05 1 1.31 8 2%4 Vi .84 1 1.31 1 1.31 1 1.31 6 S%4 V2 .84 1 1.31 1% 1.66 iy4 1.66 5 ^1/64 % 1.05 ly* 1.66 iy4 1.66 iy4 1.66 4 2%4 % 1.05 1% 1.66 11/4 1.66 iy2 1.90 3 3%4 % 1.05 ly* 1.66 1V4 1.66 iy2 1.90 2 2%4 % 1.05 ly* 1.66 1V2 1.90 iy2 1.90 1 4%4 % 1.05 iy2 1.90 iy2 1.90 2 2.37 4%4 1 1.31 iy2 1.90 2 2.37 2 2.37 00 4%4 1 1.31 2 2.37 2 2.37 2y2 2.87 000 5%4 1 1.31 2 2.37 2 2.37 2y2 2.87 0000 5%4 IVi 1.66 2 2.37 21/2 2.87 2y2 2.87 250,000 5%4 1% 1.66 2y2 2.87 2y2 2.87 3 3.50 300,000 6%4 1% 1.66 2y3 2.87 2y2 2.87 3 3.50 400,000 6y64 ly* 1.66 3 3.50 3 3.50 3y2 4.00 500,000 ^64 11/2 1.90 3 3.50 3 3.50 3y2 4.00 600,000 8%4 iy2 1.90 3 3.50 3y2 4.00 700,000 8%4 2 2.37 3y2 4.00 3y2 4.00 800,000 8%4 2 2.37 3y2 4.00 4 4.50 900,000 9%4 2 2.37 3y2 4.00 4 4.50 1,000,000 9%4 2 2.37 4 4.50 4 5.00 1,250,000 io%4 SVa 2.87 4y2 5.00 4y2 5.00 1,500,000 ll'/64 2y2 2.87 4y2 5.00 5 5.56 1,750,000 12%4 3 3.50 5 5.56 5 5.56 2,000,000 13%, 3 3.50 5 5.56 6 6.62 Duplex Wires 14 3%4 y2 .84 % 1.05 1 1.31 1 1.31 12 3%4 y2 .84 % 1.05 1 1.31 iy4 1.66 10 3%4 % 1.05 1 1.31 iy4 1.66 iy4 1.66 36 ELECTRICAL TABLES AND DATA TABLE XI Standard sizes of conduits for the installation of wires and cables. 3 Wire Convertible System 3 Wire Convertible System 2 Wires Size 2 Wires Size B. &S. 1 Wire Conduit B. & S. 1 Wire Conduit 14 10 % 00 350,000 21/2 12 8 '% 000 400,000 21/2 10 6 1 0000 550,000 3 8 4 1 250,000 600,000 3 6 2 1% 300,000 800,000 3 5 1 1% 400,000 1,000,000 31/2 4 11/2 500,000 125,000 4 3 00 11/2 600,000 1,500,000 4 2 000 11/2 700,000 1,750,000 4y2 1 0000 2 800,000 2,000,000 . 4% 250,000 2 Single Wire Combination. Number of single No. 14 wires in one conduit. Straight run; no elbows. Special permission is required. Conduit Size 3 No. 14 rubber covered double braid % 5 No. 14 rubber covered double braid % 10 No. 14 rubber covered double braid^ 1 18 No. 14 rubber covered double braid 1^/4 24 No. 14 rubber covered double braid 1% 40 No. 14 rubber covered double braid 2 74 No. 14 rubber covered double braid 2% 90 No. 14 rubber covered double braid 3 No. Wires B.&S 10 16 20 16 30 16 70 16 90 16 Signal Systems. Straight runs; no elbows. Conduit Sizes Lt. ins. fixture wire % Lt. ins. fixture wire % Lt. ins. fixture wire 1 Lt. ins. fixture wire 1^/4 Lt. ins. fixture wire 1% 150 16 18 18 30 18 40 18 100 18 130 18 200 18 ELECTRICAL TABLES AND DATA 37 No. Wires B.& S. Conduit Sizes Lt. ins. fixture wire 2 Lt. ins. fixture wire ^ Lt. ins. fixture wire % Lt. ins. fixture wire 1 Lt. ins. fixtrue wire l^/i Lt. ins. fixture wire 1^^ Lt. ins. fixture wire 2 Telephone Circuits. Not more than two 90° Elbows. No. 19 braided and twisted No. 20 braided and twisted pair switchboard or desk pair switchboard or desk instrument wires. instrument wires. No. Pairs Conduit N'o. Pairs. Conduit 3 1/2 5 % 6 % 10 % 10 1 15 1 16 1% 25 1^ 25 IVa 35 11/2 35 2 50 2 Conduits and Wires. — Two sides of the smallest rectangular enclosures that will contain a given B number of wires are : (P x a) + — and D x 6 x 86. D 2 being the diameter of the wire, a the number of wires in longest row, and 6 the number of rows. The nearer square this enclosure can be made* the greater the economy of material. The greatest number of wires that can be placed in a rectangular enclosure '"^{t -0''(^) is L being the length of the enclosure, H the height, and D the diameter of the wire. This formula is only approximate and in using it 7" JT all fractions obtained by -j: and t. — t^ must be i> i>x.86 dropped. 38 ELECTRICAL TABLES AND DATA Example. — Given an enclosure 6 inches long and 2 inches high, how many wires can it hold, the diam- eter of each wire being .7? 6 divided by .7 equals 8.6. Dropping the .6 and subtracting ^, we have 7.5 for the first factor. Next, .7 times .86 equals .602; 2 divided by this equals 3.3 ; dropping the .3, we now have to multiply the 7.5 by 3, which equals 22.5, or 22 wires. For circular enclosures no general formula can be given because the percentage of waste space varies greatly with different wires. The first chart may be used to determine the smallest conduit that will enclose a certain number of wires. This chart shows graphically how nearly different numbers of wires fill out circular spaces. To use this chart, multiply diameter of wire by the number given in connection with circle containing the requisite num- ber of wires. This will give the smallest diameter of tube or conduit that will receive these wires. How much larger the conduit to be used must be depends upon circumstances. The number and na- ture of bends, nature of insulation, flexibility of wire, as well as temperature and inspection require- ments, must be taken into consideration. The charts illustrate the relative spaces occupied by the different conduits, viz. : 3^^ 2i'^ 2^', 1^'^ li", V% etc., and the wires considered. The sizes of con- duits are marked in the various circles and each horizontal row pertains to one size of wire, with exception of the 4th and 5th in each row and a few at the top of one of the charts. The 4th shows a neutral wire of half the carrying capacity, and the 5th of double the carrying capacity of the outside wires. The different sizes of conduit given in each case will enable one to judge the most appropriate size to be used under different circumstances. The wires shown are all double braid stranded cables. ELECTRICAL TABLES AND DATA '69 40 ELECTRICAL TABLES AND DATA 1000000 CM. 1250000 CM. 1500000 CM. 800000 C M (D 900000 CM (D 600000 C ■■2Vy 700000 C .2yT 500000 CM 400000 CM 250000 CM. ELECTRICAL TABLES AND DATA 41 OGO B.&lS. 00B.<1S OB.d.S. 1 B.<&S. 2B.I&.S. ■^u f >>\ 3B. 42 ELECTRICAL TABLES AND DATA « In the preceding pages are given the conduit sizes recommended by the National Electrical Contractors' Association of the United States. These should be followed as far as they apply. Contacts. — The standard materials for mounting contacts are slate, marble, porcelain, and glass. Where these are liable to breakage, other materials are allowed, but they should always be submitted to inspection departments for approval. A surface contact of one square inch for each 75 amperes is good practice for knife-switches and similar devices. Controllers. — Methods of motor and light control are numerous. Lights are usually controlled by cutting resistance into the mains. A certain con- troller is suitable only for a certain number of lights requiring a certain amperage. The reduction of voltage is equal to the product of the amperes times the resistance, and the effect upon the lights is greater than indicated by the drop in voltage. The speed of motors may be altered by cutting resist- ance into the mains, altering the field connections, arranging taps of different voltages, and connecting armatures in multiple or series. Cooking. — Almost any kind of cooking can be accomplished electrically, but the expense is higher than with gas. It is best to be honest and advise customers correctly about these things than to cause disappointment. The advantages are con- venience and rapidity of results with many of the devices. Cooper-Hewitt Lamps (Mercury Vapor). — These lamps may be obtained for either alternating or direct-current use, and for 110 or 220 volts. The light given out is of a greenish hue, and gives a ghastly effect to faces and hands. Many persons object to working under it, while others seem to like it. The efficiency of the lamp compares favor- ELECTRICAL TABLES AND DATA 43 ably with others ; it is easy to operate, and the light is practically shadowless. With alternating currents the light flickers somewhat, and is said to give a deceptive appearance to some surfaces. Not more than one lamp should be installed on one circuit. Use double-pole switches and avoid plug cut-outs for 220 volts. Current sent through direct-current lamps in wrong direction will ruin tubes. Where inflam- mable gases exist, the sparking of some of the lamps is dangerous. The life of a tube is now claimed to be 5000 hours. The current ranges from 3.5 to 2.0 amperes for different types, and the efficiency is given as from 0.51 to 0.64 watts per mean lower hemispherical candle power. The light is mostly thrown downward. Copper weighs about 556 pounds per cubic foot; its specific gravity is about 8.9, and it melts at 1196 degrees Fahrenheit. The tensile strength of an- nealed copper may be taken as about 35,000 pounds per square inch, and that of hard drawn copper as about 55,000. Cross Currents pass between A.C. generators, and also between synchronous motors when they are operating in parallel and not perfectly in phase. These currents heat the wires and overload the machines unnecessarily. Cut-outs. — In connection with installations served by central stations, the type of cut-out and fuse preferred by that company should be installed. This will usually obtain free fuse renewals. The installa- tion of cartridge-type fuses is not advisable except in establishments where a competent electrician is always on duty. The dimensions of several types of cut-outs are given below. 44 ELECTRICAL TABLES AND DATA TABLE XII Paiste Panel Cut-Outs (See Figure 2). 125 Volt Sizes. Capacity of Switches 30 Amperes No. 4015 Figure 2. — Paiste Panel Cutouts. Cat. No. Main Branches Width (inches) Length (inches) 4012 4015 4026 4013 4103 2-Wire 2-Wire 3-Wire 3-Wire 3-Wire Single, 2-Wire Double, 2-Wire Single, 2-Wire Double, 2-Wire Single, 3-Wire 3y8 3 3% 3y8 5 5Vs lOVs loys 8% 250 Yolt Sizes Capacity of Switches 30 Amperes =4101 =4105 2-Wire 2-Wire Single, 2-Wire Double, 2-Wire 3% 3% 7' 11%' ELECTRICAL TABLES AND DATA 45 TABLE XIIT Dimensions for Plug Cut-Outs (See Figure 3) No. ^5 63 NO.8OZ0 No,l\6S No. 2365 JJ No.1935 No. 8042 Figure 3. — Plug Cutouts. No> 2.587 [o] ^ oy~gr No.xigq N0.XI3? it. No. Length Width Height (inches) (inches) (inches) 2569 2% 2 Ifi 2965 21/2 3tV 111 2165 2t% 4y2 HI 8020 3% 3% 11/2 1935 '341 3^ Hi 2587 5A 3 Hi 2150 478 3 IJi 2199 6^^ 211 Hi 8042 Hi 4M m 2135 eys 4i^^ isi 46 ELECTRICAL TABLES AND DATA EpL|j Lpcp A m ^ tfJ ni^ s r.gl SF.rtt Fi^T 9.PHL -'^^§'-^[:J PI ^^ I I . Pfe^ l i Figure 4.— D. <& W. Cutouts. ELECTRICAL TABLES AND DATA 47 TABLE XIV Dimensions of D. & W. 250 Volt Cut-Outs (See Figure 4). Amperes Fig. ABODE 0-30 1 H 1 lA 3i 14 0-30 2 3A 21 Ifs 3A U 0-30 3 3A 4 lA 3A U 0-30 4 4J 21 lA 4J 14 0-30 5 6 4 lA 6 li 0-30 10 7i 21 lA 71 H 0-30 6 8il 4^5 lA 8M n 0-30 11 SU 2J lA 8M H 0-30 12 3i 3f lA H H 31-60 1 45 ■ If lit 5A 2f 31-60 2 4i 3 A 11 5A lA 31-60 3 4i 5 11 5A lA 31-60 4 61 3A 1| 6ii lA 31-60 5 8 5 1| 8A lA 31-60 10 lOii 3| 2i llf Hi 31-60 6 12 5A 2i 121 iii 31-60 11 12 3iJ 2i 125 lU 61-100 7 6i 2i 2A 6f 45 61-100 8 8J 4A 2A 8J lit 61-100 9 8J 64 2A 8J lit 101-200 7 7i 21 3i 8i 51 201-400 7 9J 31 4A lOi 61 401-600 7 11 3i 4f 12f 81 Delta Connection. — This method of connection is used only with three-phase a. c. currents. If the connection of a generator is changed from ^^star'' to ^' delta/' its current will be increased 1.73 times 48 ELECTRICAL TABLES AND DATA for the same power delivery. If it is changed from ** delta'' to ''star/' its e.m.f. will be increased 1.73 times. A synonymous term for delta is "mesh." Demand Factor. — Before entering upon this sub- ject the reader should note that Inspection Depart- ments do not allow the installation of mains of a less capacity than would be required if all devices were to be in use at the same moment. The de- mand factor is the ratio of the maximum demand of any system, or any part of a system, to the total n J* B ^ r^ ^ !5 Qj f^ ^ "^ •> *v. V, -X*^ ■S.C? ^r^ <' -5^^ << c^l cn5|c>?|c^| Demand Factor Chart. connected power of that system, or that part of it under consideration. It must not be confused with the load factor, which is the ratio of the maximum load to the average load over a certain period of time. It is customary for Inspection Departments to demand wires of a carrying capacity equivalent to the current which would be needed if all devices connected were to be used at the same time. As long as most motors were used to drive shafting and ELECTRICAL TABLES AND DATA 49 were of comparatively large size, this seemed reason- able enough. Of late years, however, individual motor drive has replaced most of the large motors connected to line shafting. The average size of motors is smaller, their number is much larger, and their idle time individually is much greater. Under these circumstances it does not seem fair to demand mains figured on a basis assuming that all motors are to be running at the same time, when in actual prac- tice many of them are not used more than a few minutes per hour. The chance that all of the motors in a group of forty or fifty should happen to be operating at the same time is very small, and in many places the event would likely not happen once a year. With proper circuit breaker protection it would, furthermore, mean simply the opening of the circuit for a few minutes. Many tabulations of demand and load factors have been made, but they are all of too general a nature to be of any value except to those dealing with large central sta- tions. A simple method of determining the demand factor, and which can be applied with fairly accu- rate results to any installation, is described in the following: Take any piece of ordinary ruled office paper and designate as many spaces as there are hours of running time to be considered. Next draw a vertical line for each motor, the height of the line being made proportional to the length of time in hours the motor is supposed to be used per day. Draw all of these lines side by side as in chart above and mark on each line the H.P. of the motor it represents. If the motors are used indiscriminately at any time, the lines may all begin at the bottom, the main point being that they give a fairly correct record of the idle and running time of the motor during the time considered. If any of the motors are used 50 ELECTRICAL TABLES AND DATA only at certain hours, the lines pertaining to these motors may be plotted in the horizontal lines per- taining to the hours of the day, as, for instance, at A and B, Figure 5. These two motors never inter- fere with each other, but do occasionally come in at the same time with some of the other motors platted on the bottom lines. Considerable judgment is necessary in the use of the plan. We are not striving to gain absolutely correct results, but merely to form an opinion as to how many of the different motors may be quite often found running at the same time. It is certain that occasionally all of them will be running together for a short length of time, even though this might occur only once or twice in a year. Let us now consider an example. The length of the three lines plotted for the 25, 10, and 15 H. P. motors is greater than the length representing the whole day, so- that it seems certain that all of the motors will be running at the same time during some part of every day. We must therefore provide full wiring capacity for them. The length of the four 10-H. P. motor lines is also great enough to make it seem plausible that three of them will operate at the same time occasion- ally, although that time will probably be quite short. The rest of the motors operate only for such a short time that it seems correct to think they will require only their average current. We need, then, 50 H. P. capacity for the three motors platted at the left, 30 H. P. capacity for the four 10-H. P. motors, and about 20 per cent of the H. P. of the small motors listed at the right. The total is 82^ H. P. capacity for a connected load of 102^ H. P. This is about 80 per cent of the wire that would be required if all motors were assumed to run at the same time. The same lot of motors gives us a power consump- tion of only about 42 per cent of what would be ELECTRICAL TABLES AND DATA 51 used if all of the motors were running full time. Instead of plotting time by hours we may plot it by minutes or seconds. In elevator service, for instance, most of the runs cover only a very few seconds, while there may be a freight elevator mixed in with them which may run steadily for a minute. The question here to be solved is, how many pas- senger cars will be in use at the same time with this freight car. Express service also confuses the ques- tion somewhat. Owing to all of these varying con- ditions, no tabulation that has so far come to notice seems to possess any value that can be made use of in concrete cases. Their value is entirely for the central station man who supplies a large number of similar installations. Department Stores. — Such places usually require large quantities of power for illumination, electric signs, and motors. The demand factor for lighting is very close to 100 per cent. If economy is not too much insisted upon, a bountiful circuit capacity should be provided. This will allow brilliant illumi- nation wherever it is needed. As department stores contain nearly all of the goods handled in other stores, hints on illumination of special places should be looked up under the corresponding headings — dry goods stores, jewelry, etc. As there are usually large areas visible from any one place, good appear- ance demands some uniform arrangement of fixtures. If this does not provide sufficient light for certain goods in show cases, local illumination is provided in the cases. If branch circuit capacity for five watts per square foot is provided, it will enable very brilliant illumination of spots without over- loading circuits and not interfere with the frequent changes which are made. The capacity of general mains need not be greater than two watts per square foot on the most important flows. 52 ELECTRICAL TABLES AND DATA Depreciation. — Depreciation must be duly consid- ered in dealing with any form of apparatus. The depreciation is governed entirely by the useful life of the device, but this in turn is governed by the amount of wear and tear which cannot be repaired for from time to time; obsolescence, possibly in- adequacy after a time, or probable cessation of busi- ness. Depreciation should not be confused with maintenance, to which should be charged all mis- haps which do not permanently lessen the natural useful life of the apparatus. From 10 to 20 per cent is often charged to depreciation, but it is better to estimate it carefully in each case unless a parallel case is well understood. Desk Lighting. — The illumination of desks by indi- vidual lamps is never to be advised, except in the case of individuals with very poor eyesight or in locations where desks are far apart or used but a few hours per day. Where individual desk lighting is provided, the cost of energy may sometimes be lower, but the first cost of installation, and also maintenance, is always high. There is, further, al- ways a considerable fire hazard,, and all of these offset the saving in energy to a large extent. A general and fairly shadowless illumination also adds much to the efficiency of clerks. The following table shows the comparative cost of proper general illumination as compared with local for desks of various spacing. It is assumed that a general illumi- nation of 1^ watts per square foot is provided, and that at each desk a 25-watt lamp is also used, while the general illumination with which this desk light- ing is compared is obtained through the medium of the most efficient large wattage lamps at present on the market. One watt per square foot will give good general illumination, which will need to be helped out by local lighting only for persons with ELECTRICAL TABLES AND DATA 53 weak eyes. Where local desk lighting is resorted to the wattage requirements will be about as follows : Av. sq. ft. per desk 20 25 30 35 40 45 50 Total watts per sq. ft.. 1.5 1.25 1.08 0.96 0.87 0.80 0.75 It will be noted that where desks are close to- gether the general illumination is not only the easiest installed but also the cheapest to operate. If the desks are used only a small part of the time the local illumination will be the cheaper. Lamps used for desk lighting should either be frosted or encased in diffusing globes. Diamagnetic. — Zinc, antimony, bismuth, and cer- tain other metals are repelled when placed between the poles of strong magnets, and are said to be dia- magnetic. Metals which are attracted by magnetism are said to be paramagnetic. Dielectric. — Any substance which is an insulator and allows electrostatic induction to take place through its mass. Usually taken as synonymous with insulation. Dry Kilns. — Such places are too hot for rubber- covered wire. Use asbestos-covered. Place cut-outs and switches outside. Eddy Currents. — Useless currents which are pro- duced in the iron of pole pieces, etc., subject to motion in a magnetic field, or to the influence of coils in which a fluctuating current exists. They cause a waste of energy and heat the metal. Efficiency. — The efficiency of motors, transformers, and other similar translating devices is found by dividing the output by the input. In connection with sources of electric illumination the term efficiency has an entirely different meaning. The efficiency of such devices is spoken of as a certain it 64 ELECTRICAL TABLES AND DATA number of watts per candle power. In this case, the higher the efficiency, the more uneconomical is the lamp. See Motors and Illumination for practical applications. Egg" Candling.— One light must be provided for each workman, and it should be located about waist high. The wires should be run at this height so as to avoid use of long cords. The light is always made adjustable, and is encased in a small metallic hood with a small opening. Electric Braking. — This is also sometimes termed dynamic braking." If an electric motor is dis- connected from its source of supply, and its arma- ture circuit closed while the armature is still in motion, it will generate current and consume power, and may be brought to rest very quickly in this manner. Where the necessary provisions for this purpose are installed this method of braking is very successful. Electrolysis. — Nearly all electrolysis is due to the fact that piping and other metallic structures near a ground return system of electrical distribution afford a return circuit of such low resistance as compared to the return circuit provided, that a large part of the current returns over the piping. It is impossible to prevent electrolysis entirely ex- cept by insulating the return wires. The troubles may, however, be materially reduced. The current does damage only where it leaves the pipes or other structures which it has entered, and the damage is in proportion to the amperes carried. The methods used for lessening electrolysis are the following : 1. Protection of structures by concrete or other forms of insulation, or keeping them as far as pos- sible from ground return circuits. Insulation of piping is not advisable; it is likely to concentrate the trouble at spots where it is poor. ELECTRICAL TABLES AND DATA 55 2. Bonding pipes, etc., so as to prevent current which has once entered them from leaving, except at predetermined places, and then never to earth. 3. Negative boosters have been suggested, but have not been extensively tried. A negative booster is a low-voltage dynamo connected into the return circuit in such a manner as to draw current from the rails and earth and deliver it back to the sta- tion. 4. Reinforcing the rails, etc., by large conductors, thus increasing the conductivity of the return, and lowering the p. d. between the rails and the sta- tion. In most cities ordinances mention the difference in potential which may be allowed to exist between any two points on the return wires. In Chicago it is provided that all uninsulated electrical return circuits must be of such current-carrying capacity and so arranged that the difference of potential between any two points on the return circuit will not exceed the limit of twelve volts, and between any two points on the return 1000 feet apart within a one-mile radius of the City Hall will not exceed the maximum limit of 1 volt, and between any two points on the return 700 feet apart outside of this one-mile radius limit will not exceed the limit of 1 volt. In addition thereto, a proper return conductor system must be so installed and maintained as to protect all metallic work from electrolysis damage. The return current amperage on pipes and cable sheaths must not be greater than 0.5 amperes per pound-foot for caulked cast iron pipe, 8.0 amperes per pound-foot for screwed wrought iron pipe, and 16.0 amperes per pound-foot for standard lead or lead alloy sheaths of cables. All insulated return current systems must be equipped with insulated pilot wire circuits and volt- 56 ELECTRICAL TABLES AND DATA meters, so that accurate chart records will be obtain- able daily, showing the difference of potential be- tween the negative bus-bars in each station and at least four extreme limits on the return circuit in its corresponding feeding district. Also with recording ammeters, insulated cables, and automatic reverse load and overload circuit breakers which will record and limit the maximum amperes drained from all the metallic work (except the regular return feed- ers) to less than 10 per cent of the total output of the station. Figuring on the basis of the average resistance of cast iron, wrought iron, and lead, the above amperages will exist with the following differ- ence of potential per running foot, and will be inde- pendent of the thickness or size of pipe : Cast iron, 0.000711 volt per foot ; measurements must be taken on solid pipe and not across any joint. Wrought iron, 0.001568 volt per foot; measurement to be taken as above. Lead sheaths, 0.007497 volt per foot; as joints in lead sheaths are always soldered and wiped, no attention need be paid to them. The lower amperage for the iron piping is specified be- cause joints will usually be found of higher resist- ance than the piping, and at each joint current is likely to leave piping and enter it again just beyond. The proper treatment of electrolysis may require all four methods outlined above. The method most to be recommended in a general way is that of re- inforcing the return conductors sufficiently to limit the difference of potential as prescribed. The following table shows the size of copper con- ductors necessary with rails of various weights per yard to reduce electrolysis to -J, ^, and }, etc.; the ^ecific resistance of the rails being taken as 10 times that of copper, and the resistance of bonds as negligible. ELECTRICAL TABLES AND DATA TABLE XV 57 Showing c. m. of copper necessary to reduce p. d. of electrolysis to the fraction of its original value given. Walght of Circular Rails Pei Mils 1 -2 1-3 1-4 Yard Of Rail 40 4,950,000 495,000 990,000 1,485,000 45 5,600,000 560,000 1,120,000 1,680,000 50 6,230,000 623,000 1,246,000 1,869,000 60 7,500,000 750,000 1,500,000 2,250,000 70 8,770,000 877,000 1,754,000 2,631,000 80 9,900,000 990,000 1,980,000 2,970,000 90 11,200,000 1,120,000 2,240,000 3,360,000 100 12,500,000 1,250,000 2,500,000 3,750,000 Weight Circular of Rails Mils 1-5 1-6 1-7 1-8 Per Yard of Rail 40 4,950,000 1,980,000 2,475,000 2,970,000 3,465,000 45 5,600,000 2,240,000 2,800,000 3,360,000 3,920,000 50 6,230,000 2,492,000 3,115,000 3,738,000 4,361,000 60 7,500,000 3,000,000 3,750,000 4,500,000 5,250,000 70 8,770,000 3,508,000 4,385,000 5,262,000 6,039,000 80 9,900,000 3,960,000 4,950,000 5,940,000 6,930,000 90 11,200,000 4,480,000 5,600,000 6,720,000 7,840,000 100 12,500,000 5,000,000 6,250,000 7,500,000 8,750,000 For a comprehensive treatment of electrolysis a map of the return circuits and adjacent piping should be made. Tests determining p. d. and direction of cur- rent should be made, and results marked upon the map. In many cases currents will be found in oppo- site direction at the same point at different times. In estimating the current strength from p. d. noted between track and piping the distance of the latter from the track must be taken into consideration. If this is small a low p. d. may deliver considerable current. Often the trouble can be reduced suffi- ciently by running comparatively short lengths of heavy copper. In testing p. d.'s it is best to use a sensitive galvanometer. Such an instrument may be calibrated with reference to a milli-volt meter. 58 ELECTRICAL TABLES AND DATA TABLE XVI The table below shows the approximate amperage per milli-volt p. d. per foot which will be found in the various kinds and sizes of piping and sheaths given. Cast Iron, Averag'e Wrought Iron, Average Lead Sheaths. %" Inside wt., Am- Inside wt., Am- Outside Amperes Diam. Per Ft. peres Diam. Per Ft. peres Diam. Approx. 3 . 16 12 i .87 4i 1.26 5 4 22 15 i 1.15 5i 1.50 6 6 35 25 1 1.70 8 1.58 6 8 50 37 U 2.25 11 1.65 6.6 10 67 50 1^ 2.75 14 1.68 6.9 12 87 65 2 3.60 18 1.72 7.0 14 110 82 2i 5.80 30 1.78 7.1 16 135 102 3 7.65 40 1.84 7.2 18 165 123 3i 9.00 48 1.90 7.5 20 190 141 4 11.0 57 1.95 7.7 24 255 190 H 12.5 66 1.98 7.9 30 370 275 5 15.0 80 2.00 8.0 36 500 375 6 19.0 100 2.05 8.2 42 665 500 7 24.0 125 2.10 8.4 48 850 635 8 29.0 155 2.15 8.6 54 1,050 775 9 34.0 180 2.19 8.8 60 1,300 970 10 41.0 220 2.21 8.9 72 1,575 1,200 11 46.0 250 2.24 9.0 84 1,850 1,400 12 51.0 275 2.32 9.3 Electrolyte is the name given to the solution used in storage batteries and other batteries. Electromagnets. — The magnetic flux is equal to the magnetomotive force divided by the reluctance. The magnetomotive force is the product of current times number of turns of wire and is known as ampere turns. The reluctance of the iron of all well designed magnets is very low but that of the air gap is high, so that roughly speaking we can judge the total reluctance by the air gap. In any given case the magnetic flux is approximately proportional to the current strength up to a point at which the iron ELECTRICAL TABLES AND DATA 59 becomes nearly saturated. After this the increase is slow until the point of full saturation is reached and after this it is very slow. To increase the magnetization (e. m. f. being fixed) we must increase the size of wire ; winding more turns of the same wire upon a spool simply decreases the current required for a given magnetization but does not alter the magnetization itself. The self-induction and the sparking are proportional to the square of the number of turns of wire. The heating is pro- portional to the square of the current used. The heating of the coils sets the limit of the current which may be used. A radiating surface of from 1 to 3 square inches per watt consumed in the coil is usually provided. One watt per square inch will heat the coil very much if it is in use continuously. The possible traction of electromagnets is about 200 lbs. per square inch for good annealed wrought iron, and 75 for cast iron. This, however, varies widely vdth the quality of iron used. In laboratory experiments as high as 1,000 lbs. per square inch has been obtained. Single phase a-c. magnets do not give a constant pull but two and three phase magnets are very serviceable. The ** chattering ' ' of single phase magnets can be lessened by a ^^ shading coil." Lifting magnets are extensively used. They are built with the two poles concentric and the material to be lifted constitutes the armature. Per- manent magnets are used only in small sizes. USEFUL FORMULAS AND TABLES In the foUovring formulas it is assumed that the wires lie squarely over one another in the coil, each wire fully occupying a space equal to the square of its diameter. As in most coils some insulating me- dium is placed between the different layers, this is about the condition which exists in practice. 60 ELECTRICAL TABLES AND DATA The symbols used in the formulas are as follows: d= diameter of wire, in inches, over insulation. i= length of wire, on spool, in inches. nt = number of turns. r = resistance of one foot of wire. r5= radiating surface. B = diameter of core and insulation, in inches. D = diameter over outside of completed winding, in inches. L = length of winding space on spool, in inches. iV= depth of winding from core to outside, in inches. W = weight of wire. UyCfk- constants for use in the formula, given in the tables below. Each constant has a different value for each size and kind of wire used. Number of turns in a given spool (see Figure 5) : z D m Figure 5. LxN nt = m Diameter of wire to give a certain number of turns d [LxN ELECTRICAL TABLES AND DATA 61 Cross-section of winding space, or LxN, necessary to accommodate a certain number of turns of a given wire: LxN -d^xnt. Length of wire on a given spool : 1= (D^-B^) Lxk. See table below for value of k. Weight of wire on a given spool : W= (D^-B^) Lxc. See table below for value of c. Resistance of wire on a given spool : R= (D^-B^) Lxa. See table below for value of a. Radiating surface for a given spool : rs^Dxd.UxL. TABLE XVTI l^ CONSTANTS. Constant for Length Constant for Weight Constant for Resistance bo o fl o ti § fi •4^ o ■*-> o 4-> o o 4_> 4-> M o ^ 4-> o -t-i ^ O 3 s O 6 m O o O m «} 0) s CI 02O b£ c^iT" •i-i ^ /■ — V o ^ Americ WireG (B. & i Birmin WireG (Stubs Old En Wire G (Londc (Britis Standa WireG bfl O 23 2^6 25.8 25. 27.0 153. 24. 23 24 2ai 23.0 22. 25.0 151. 22. 24 25 17.9 20.4 20. 23.0 148. 20. 25 26 la.9 18.1 18. 20.5 146. 18. 26 27 14.2 17.3 16. 18.75 143. 16.4 27 28 12.6 16.2 14. 16.50 139. 14.8 28 29 11.3 15.0 13. 15.50 134. 13.6 29 30 10,0 14.0 12. 13.75 127. 12.4 30 31 8,9 13.2 10. 12.25 120. 11.6 31 32 8.0 12.8 9. 11.25 115. 10.8 32 33 7.1 11.8 8. 10.25 112. 10.0 33 34 6.3 10.4 7. 9.50 110. 9.2 34 35 ^.Q 9.5 5. 9.00 108. 8.4 35 36 5.0 9.0 4. 7.50 106. 7.6 36 37 4.5 8.5 6.50 103. 6.8 37 38 4.0 8.0 5.75 101. 6.0 38 39 3.5 7.5 5.00 99. 5.2 39 40 3.1 7.0 4.50 97. 4.8 40 41 6.6 95. 4.4 41 42 6.2 92. 4.0 42 43 6.0 88. 3.6 43 44 5.8 85. 3.2 44 45 5.5 81. 2.8 45 46 5.2 79. 2.4 46 47 5.0 77. 2.0 47 48 4.8 75. 1.6 48 49 4.6 72. 1.2 49 50 4.4 69. 1.0 50 The American Wire Gauge sizes have here been rounded off to about the usual limits of commercial accuracy. The Steel Wire Gauge is the same gauge which has been known by the various names: ^^ Washburn and Moen, ^^Roebling/^ <^ American Steel and Ware Co.^s.^' Its abbre- viation should be written ' ' Stl. W. G./^ to distinguish it from **S. W. G./' the usual abbreviation for the (British) btand- ard Wire Gauge. 84 ELECTRICAL TABLES AND DATA Generators. — Alternating Current generators may- be of the revolving field or revolving armature type. The revolving field type is easier to insulate and less troublesome to maintain, hence is most widely used. There is another, known as an indtoctor type, in which usually all electrical parts are stationery and an iron spider is caused to revolve, it being so arranged as alternately and regularly to alter the magnetic flux and thus cause induction of e.m. f. This type is not much used. The so-called hid-iiction generator is another type, and is similar to an induction motor; in fact, an induction motor, when driven above the speed of synchronism becomes an induction generator, and delivers current to the line. This type of generator cannot operate unless other alternators provide it with the necessary exciting current. The capacity in generators for field excitation must be nearly equal to one-third of the capacity of the induction gener- ators. This type of generator is well suited for fluc- tuating speeds such as are given by gas engines, but it can never constitute an entire plant. Alternating current generators are made to operate single-phase, two-phase and three-phase. The single-phase machine is not well suited for power work, and is more expen- sive per unit of output than polyphase machines. The two-phase generators are, as a rule, used only on old direct current installations which have been adapted to a.-c. operation. The three-phase system is the most economical and is almost universally used. It is well suited for either light or power transmission. Alternators may be built to be self -exciting, but this is not often done. Most of them require a direct current exciter. Efficiency, — Approximate efficiencies of generators of various sizes are given about as follows: 100 K.V.A., 91 per cent; 500, 94; 1,000, 95; 2,000, 96; ELECTRICAL TABLES AND DATA 85 3,000, 96 to 97 ; 5,000, 97 or better. These efficiencies vary of course with the power factor, load, voltage, etc. Frequency. — The common frequencies are 25 and 60 cycles per second, the lower being used for trans- mission to substations and for power alone. The higher frequency is used for mixed lighting and power, and also for lighting alone. In a single-phase machine the current and voltage per phase have but one meaning. The power is equal to IxE x-power factor, and the product of volts and amperes gives the volt-ampere rating of the machine. In a two- phase alternator each half supplies half of the cur- rent and power. The usual four transmission wires are sometimes combined into three wires, and in such a case the voltage between the two outside wires is 1.41 times the phase voltage, and the current in the middle wire is 1.41 times the current in the outside wires. The power in such a combination may be found in two ways. Measuring current in the middle wire and the voltage across both phases, the power is equal to /xJS'xpower factor. Measuring current in one of the outside wires, and using phase voltage, the power is equal to /xJ?x2xpower factor. Three- phase generators are always connected by means of 3 main wires, and sometimes a neutral, but may be either delta or star. If the delta connection is used, the phase voltage is the same as the voltage between any two wires, but the current in any phase is 1.73 times the current in. any one of the wires. If the star connection is used, the voltage between any two wires is 1.73 times the voltage of any phase winding, and the current to deliver the same power will be only 0.58 of the former current in the line wires. The power with either connection is equal to /x£'xl.73x power factor. Frequencies. — The common frequencies are 60 and 86 ELECTRICAL TABLES AND DATA 25 cycles. The higher frequency is used for light, and mixed light and power loads. The* lower is used for power alone and also for transmission lines to substations or converters. The frequency of any gen- erator depends upon the speed and number of poles and may be found by the formula: ,_ r. p.m. number of poles ^" 60 ^ 2 The table below shows the speeds at which gener- ators provided with a certain number of poles must operate to deliver current at the frequencies given. TABLE XXYII 60 Cycles. No. Poles 4 8 12 16 20 24 E. P. M 1,800 900 600 450 360 300 25 Cycles. No. Poles 4 8 12 16 20 24 R. P. M 750 375 250 1871/2 150 125 Operation of Alternators in Parallel, — In order that alternators may be operated in parallel they must be identical in four respects. The frequency must be the same. The voltage must be the same. The current and voltages must be in phase, i.e., their maxima and minima must occur at the same instant. The wave form of the machines should be as near as possible alike. The frequency is governed by the speed, and if it is not correct, the speed must be adjusted either by ELECTRICAL TABLES AND DATA 87 adjusting the engine, or diameters of pulleys. The voltage can be determined by a voltmeter test. Whether the machines are in or out of phase can be determined only by properly connected S3nachroniz- ing lamps, or synchronizing instruments. The synchronizing and keeping in step of alter- nators will be made easier by synchronizing the piston strokes of engines as far as possible if they are sepa- rately driven, or, if driven from a common shaft, by running one of the machines with a slack belt, which will allow it to fall in step more readily. Where synchroscopes are used the pointer will indicate which machine is running too fast or too slow : Where the synchronizing is done with lamps they may be con- nected so as to indicate synchronism either by dark- ness or light. If the machines are not in phase there will be alternations of darkness and light in the lamps which will alternate with great rapidity if the ma- chines are much out of synchronism, but will be at longer and longer intervals as they are brought more nearly into step. The proper time to close the switch is just a moment before the period of full darkness. If the machines are nearly in synchronism when thrown together, there will be cross current which will help to bring them together, but it is best to have them synchronized perfectly before connecting. The load cannot be divided among alternators by increasing the field excitation as with direct-current machines; it is necessary to give more steam to the engine of the light running generator. This tends to advance the generator and causes it to take more cur- rent. The power factor can be improved or altered by adjusting the field excitation. Adjust fields so that power factor of each machine is the same. Single Machine^ Operation of. — See that machine is entirely disconnected from the load. Inspect all bearings and see that they are well oiled and that oil 88 ELECTRICAL TABLES AND DATA rings work properly. Adjust field rheostat so that all resistence is in circuit and close exciter circuit. Start machine, bringing it gradually up to speed and cutting out resistance in field rheostat until generator voltage comes to its proper value. Next throw in switches, bringing load on gradually if possible, and adjust rheostat to maintain voltage properly. Test speed to see that it is at its proper value ; the speed is of greater importance with alternators than with direct current generators. Bating. — For full details as to rating, the reader is referred to the Standardization Rules of the A. I. E. E., w^hich are too lengthy to be given here. The maximum, or continuous, rating of an alter- nator is commonly taken as the load in kilowatts it can carry at 100 per cent power factor with a maxi- mum rise in temperature of any part of 50° C. (122° F.) above the surrounding air when that is 25° C. (77° F). Corrections for other surrounding temperatures to be made according to A. I. E. E. Standardization Rules. Another rating, used mostly in connection with street railway work, allows a tem- perature rise of 45° C. (113° F.) under the same conditions as above, and requires that 50 per cent more than the rated load used for two hours shall not cause a temperature rise of more than 55° C. (131° F.). Voltage. — A voltage in excess of 12,000 or 13,000 is rarely generated direct; higher line voltages are ob- tained mostly by step-up transformers. Direct Current Generators, Compound Machines. — This is a combination of shunt and series dynamo, and a distinct improvement over the shunt machine. The compound winding can be adjusted to regulate the voltage as desired. It requires the same instru- ments as the shunt, and in addition heavy equalizing ELECTRICAL TABLES AND DATA 89 wires run between each pair of machines. These should be carried to the board and the main switch should be triple pole. The machine may be connected either long shunt (shunt winding bridging compound fields as well as armature), or short shunt (shunt field bridging only armature) ; it is merely a ques- tion of convenience. All these machines may be bi-polar or multi-polar, direct or belt connected and provided with commutating or interpoles. Rating. — Machines are commonly rated on the basis of their continuous output in kilowatts with a maximum rise in temperature of 50"" C. (122° F.) above the surrounding air at 25° C. (77° F.). For full information see A. I. E. E. Standardization Rules. The common voltages are 110 volts for light- ing and small power (used mostly in isolated plants) ; 220 to 250 also for lighting and power, but used mostly in larger plants, and for short distance dis- tribution; 500 to 600 volts, used almost exclusively for street railway work ; 2,000 to 6,000, or more, used for series arc lighting by direct current. The Series Machine is used only for constant cur- rent work. It requires the following instruments and fittings : Short circuiting switch for fields. Ammeter, a switchboard equipped with plugs and jacks. A polarity indicator is often advisable. The Shunt Machine is used for all variable current work. Its voltage regulation is poor, and requires constant attention. It requires a field rheostat, fuses, main switch or circuit breaker, volt meter, ammeter, ground detector, switchboard and pilot lamps. The voltage of this machine is variable and automatically decreases with an increase in the devices it supplies. Greek Alphabet. — Greek letters have become the standard symbols for many quantities dealt with in 90 ELECTRICAL TABLES AND DATA electrical and mechanical calculations. The letters and their pronunciations are given below : A a — Alpha. I t — Iota. P p — Rho. B ^ Beta. K AC — Kappa. 2 o- — Sigma. r y — Gamma. A A — Lambda. T r Tau. A 8 — Delta. M /x — Mu. Y V — Upsilon E € — Epsilon. N 1/ — Nu. 4> — Phi. Z ^ — Zeta. S .^-Xi. X X — Chi. H 77 Eta. o- — Omicron. ^ i^ — Psi. © 6 Theta. n TT— Pi. w — Omega. Gram or Gramme. — The gramme is the mass of a cubic centimeter of water at the temperature of its greatest density. It is the unit of mass and is equal to 15.43235 grains; 7,000 grains equal 1 lb. av. Gravity Cell. — This is a cell in which copper and zinc immersed in a solution of blue vitriol are the active elements. It is used for continuous work and where small constant currents only are required. Ground Detectors. — It is customary to provide ground detectors on all switchboards from which entirely insulated circuits are run. Tests should be made quite frequently, so as to catch a ground as soon as it comes on. When grounds exist on both sides of a system, detectors are not reliable and the part to be tested must be disconnected from the board. Con- tinuously indicating detectors are preferable; static instruments are made which can be so used even on high voltage lines with perfect safety. Grounding. — Any connection of any paxt of a cur- rent carrying conductor, or live metal part of any device which has become connected to a foreign con- ducting medium so as to deliver current or potential to it, is spoken of as being grounded. Some devices and circuits are purposely grounded, the frame or the earth being relied upon as return conductors. ELECTRICAL TABLES AND DATA 91 The purposive grounding of wires used in connection with electrical work may be divided into two classes: The grounding of frames, conduits, etc., which are not supposed to become alive except through a break- down of the insulation, and the grounding of wires, or devices which usually do carry current. The life and fire hazard from electrical sources^ may be greatly reduced by improving the insulation, so that the chance of any person or material being affected by the current is small, or by arranging a bypath which shall carry the current safely away in case live parts of the conductors come in contact with it. To provide such a shunt is the object of all grounding. Wherever a ground connection is provided, it in- creases the liability of a breakdown in the insulation of the device, but at the same time reduces the possi- bility of serious damage from that source. Connect- ing the frame of any device to ground weakens the natural insulation of that device, but protects persons and property otherv/ise liable to injury to a consider- able extent. Good cause for the grounding of live parts of electrical circuits for the purpose of protec- tion exists only in cases where two or more voltages exist in such close proximity that there is liability of the higher voltage becoming impressed upon parts normally intended only for the lower voltage. And even under these conditions the N. E. C. authorizes the grounding only when, normally, no current is supposed to be flowing over the ground connections. The grounding of any part of a live circuit under the above conditions increases the chances of trouble but confines the trouble to that which may be possible with the lower voltage. If, for instance, the ground on the secondary of a transformer is in perfect con- dition, it will give positive assurance that the primary voltage cannot be impressed upon any part of the secondary system, but it will also give assurance that 92 ELECTRICAL Tx\BLES AND DATA any workman who may come in contact v/ith live parts on the ungrounded side, while making a ground himself, will receive the full benefit of the secondary voltage. In general, since the grounding takes av/ay the natural insulation, which is often relied upon to some extent but quite often does not exist at all, it will force upon manufacturers a higher standard of construction, and the net result will be increased safety in all respects except life. In order to keep the life hazard within bounds it is not customary to ground live wires operating with a potential above 250. As a general rule, all metallic structures or pipes not normally connected to electrical sources, but liable to be accidentally so connected, should be grounded. Connection to an extensive water pipe system makes the best possible ground. Steam and hot water piping is not so reliable even if connected to water pipe systems. The steel fram^es of buildings are useful only with supposedly small currents con- fined to the same building. Gas piping is likely to cause fires if contacts work loose, or if there is any electrolytic action. "Where the above means of making ground connections are not available the most eco- nomical connection is made with a galvanized iron pipe driven into the ground. The practice of one large company is to use a H-inch pipe 8 feet long, and drive its full length into the ground, burying the connection with it. Another company uses a -J- or |-inch pipe. The resistance of the ground itself is so much higher than that of the pipe that the con- ductivity of the larger pipe is not much better than that of the smaller, but it is more reliable for driving purposes. "Where the ground is of very great impor- tance, it is advisable to use several pipes. The pipe should enter the earth at least 6 feet, and it is prob- able that an additional foot or two will more than ELECTRICAL. TABLES AND DATA 93 double the usefulness in dry seasons. The resistance of the earth varies with its composition, its degree of moisture, and distance from piping, etc. Gravel and sand, because so easily drained, make very poor grounds, and rock cannot be used at all. Overhead cables and messenger wires are provided with about one ground per mile. Ground connections may be tested with an ammeter and a voltmeter. Connect one pole of current source to nearest hy- drant or other available piping and the other to the ground. The voltage divided by the current will equal the resistance of the ground, since the piping itself may be considered as comparatively without resistance. Hanger Boards are required for incandescent lamps indoors on series circuits, but are not neces- sary with arc lamps, although advisable. Heat Coils are usually installed in connection with signaling circuits. They are arranged to open the circuit when a large current flows through them for a short time or a small current for a longer time. Their office is to guard against sneak currents too small to blow fuses. Heating by Electricity. — The heating of buildings by electricity is not commercially practicable, except on a small scale, or under particularly favorable cir- sumstances. It is used on a large scale only in con- nection with street cars. In residences, offices, fac- tories, etc., it is used only for small spaces, or where a limited quantity of heat is required for a short time only. Since there is practically no heat wasted, no air vitiated, little space occupied, no dirt caused, the fire hazard greatly reduced and the heaters are easily portable, it compares under suitable conditions, very favorably with other means of heating. One watt hour will raise the temperature of 1 cubic foot of air about 200 degrees Fahrenheit. 94 ELECTRICAL TABLES AND DATA The heat represented by one B. T. U. is sufficient to raise the temperature of 1 lb. of water or 55 cubic feet of air 1 degree Fahrenheit. One watt equals 3.412 B. T. U.S. In order to heat a room properly we must first supply sufficient heat to raise the temperature the required amount; next, furnish a steady supply of heat to make up for the absorption of walls, floor and ceiling; third, heat the fresh air which must be ad- mitted for ventilating purposes. For a rough esti- mate it is customary to require from one to two watts per cu. ft. in room. The wattage necessary to raise the temperature of a room may, however, be more accurately found by the formula : Ty— X 200 m where W = watts C - cubic feet of air in room i = number of degrees F. that temperature must be raised m=the number of minutes in which this rise must take place. The above formula makes no allowance for radiation or ventilation. Under average conditions it may be assumed that every square foot of wall, ceiling, and floor space will absorb heat as given in Table XXX for various tem- peratures. If we multiply the surfaces by the num- bers given we shall obtain the rate at which watts must be supplied to maintain the temperature in a hermetically sealed room after the desired tempera- ture has been secured. Every human being should be provided with 3,000 cubic feet of fresh air per hour, although it is possible ELECTRICAL TABLES AND DATA 95 to do comfortably with 2,000 feet. If the allowance per hour, however, is as low as 1,000 feet, conditions will be decidedly injurious to health and also imme- diately uncomfortable. Since all rooms electrically heated are small, fresh air requirements demand that the air must be changed several times per hour. In order to facilitate the calculations three tables are provided. Table XXVIII shows the number of cubic feet of air contained in rooms of various dimensions likely to be warmed with electrical heat, the height of rooms being assumed as 9 feet. This table also shows the number of square feet of radiating surface, includ- ing ceiling and floor. There is further given, in connection with each size of room, the number of times the air should be changed per hour for each occupant to afford fair ventilation. The figures given are such as it is believed the occupants will naturally provide by opening windows or doors. In Table XXIX we have constants by which the cubic contents of rooms must be multiplied to find the number of watts necessary to raise the tempera- ture of rooms the number of degrees given at top, in the number of minutes given at the left. To find the watts necessary to provide for air changes per hour we must multiply the cubic contents by the constants given for 60 minutes and by the number of times per hour the air is to be changed. To find the watts lost in radiation we multiply the wall surface by the figures given in Table XXX. Example. — ^A bathroom 6 by 8 feet is to be heated 20 degrees F. above the temperature of the surround- ing rooms and the rise in temperature must be brought about in five minutes and then maintained for an hour afterward. What size of heater will be required ? There are 432 cu. ft. in such a room and by Table XXIX for 20 degrees and five minutes we find 1.20 and multiplying this by 432 we have 518 watts re- 96 ELECTRICAL TABLES AND DATA quired to heat the air without allowing for condnetion or ventilation. From Table XXVIII we also see that there are 348 feet of surface which, multiplied by 2.5, taken from Table XXX, for twenty degrees, give us 870 watts to make up for conduction through walls. Table XXVIII further shows that the air ought to be changed five times per hour; hence, tak- ing the constant 0.10 from Table XXIX for 60 min- utes and 20 degrees and multiplying this by 5, we have 0.50, and this, multiplied by the number of cu. ft., gives us 216 watts for air changes, and this, added to 870 watts for conduction, gives us a total of 1,088 watts to keep up the temperature of (our bathroom 20 degrees above that of the surrounding rooms. A 1,-500-watt heater would serve such a room very nicely. Every occupant of such a room will contribute about 125 waits of this. With all doors and windows closed the average house is supposed to allow a change of air at least once per hour. If a room is to be used only for a short time, a change of once per hour may thus be calculated upon. In laying out heating plants in residences where com- fort of the user is the main desideratum, it is advis- able to err on the side of plentiful capacity ; in com- mercial installations where the installation is more for the benefit of workmen it may be more judicious to err in the interest of a somev/hat small capacity. In small rooms a heater should always be placed as near as possible where the cold air enters, but in large rooms, if only a portion of the room is to be heated, it should be located out of the way of drafts. The coils should be divided into proportional sections equal to 1 and 2. This will enable l/3d, 2/3ds or the full capacity of the heater to be used as desired. Electric heating has one advantage over other forms, ELECTRICAL TABLES AND DATA 97 and this consists in its ability to give instantaneous results, and these are best attained with heaters of comparatively large capacity, so that there will be no temptation to keep up the temperature except when it is actually needed. TABLE XX^^II Showing number of cu. ft.; wall surfaces (includ- ing ceiling and floor) and necessary changes of air per occupant per hour in room of dimensions given ; height of ceiling 9 ft. Width Length in Feet. 5 6 7 8 9 10 11 12 rCu. feei: 225 270 315 360 405 450 495 540 5 J Wall surf ace.. 230 258 286 314 342 370 398 426 [Air changes.. 98 7 65544 rCu. feet 270 324 378 432 486 540 594 648 6 i Wall surf ace.. 258 288 318 348 378 408 438 468 [Air changes.. 86654443 rCii. feet 315 378 441 504 567 630 693 756 7 h^all surf ace.. 286 318 350 382 414 446 478 510 [Air changes.. 76544333 rCu. feet 360 432 504 576 648 720 792 864 8. ^Yv'all surf ace.. 314 348 382 416 450 484 518 552 [Air changes.. 65443333 rCu. feet 405 486 567 648 729 810 891 972 9 ^W^all surf ace.. 342 378 414 450 486 522 558 594 [Air changes.. 5 4 4 3 3 2.5 2.2 2 rCu. feet 450 540 630 720 810 900 9901,080 10 jWall surf ace.. 370 408 446 484 522 560 598 636 [Air changes.. 4.4 4 3.2 3 2^.0 2.3 2 2 rCu. feet 495 594 693 792 891 990 1,0891,188 11 h¥all surf ace.. 398 438 478 518 558 598 638 678 [Air changes.. 4 3.2 3 2.6 2.2 2.0 1.9 1.7 rCu. feet 540 648 756 864 972 1,080 1,188 1,296 12 ^ Wall surf ace.. 426 468 510 552 594 636 678 720 [Air changes.. 4 3 2.6 2.3 2 2 1.8 1.7 98 ELECTRICAL TABLES AND DATA TABLE XXJX To find watts required to heat air in room (no allowance for radiation or changes) multiply cubic feet of air by factor in table below. Minutes in which Bise in Temperature, F. rise is to take place 10 15 20 25 30 35 40 5 0.60 0.90 1.20 1.50 1.80 2.10 2.40 10 0.30 0.45 0.60 0.75 0.90 1.05 1.20 15 0.20 0.30 0.40 0.50 0.60 0.70 0.80 30 0.10 0.15 0.20 0.25 0.30 0.35 0.40 . 45 0.07 0.10 0.14 0.17 0.20 0.23 0.27 60 0.05 0.07 0.10 0.12 0.15 0.18 0.20 TABLE XXX To find watts needed to make up for conduction multiply wall surface by factors below. Temperature Eise 10 15 20 25 30 35 40 1.5 2.0 2.5 3.1 3.6 4.3 5.0 To find watts necessary for ventilation, multiply watts required to heat air in 60 minutes by number of changes of air required per hour, DOMESTIC HEATING DEVICES (V7estinghouse Electric & Mfg. Co.) Apparatus Watts Broilers, 3 ht 300 to 1,200 Chafing dishes, 3 ht 200 to 500 Cigar lighters 75 Coffee percolators 380 Coil heaters 110 to 440 Corn poppers 300 Curling irons 15 Curling iron heaters 60 ELECTRICAL TABLES AND DATA 99 Apparatus Watts Double boilers for 6 in. 3 lit. stove 100 to 440 Flat irons, 3 to 8 lbs., domestic sizes ; 250 to 635 Foot warmers 50 to 400 Frying kettle, 8 in 825 Frying pan 250 to 500 Griddle cake cookers, 9x12, 3 lit 330 to 880 Griddle cake cookers, 12x18, 3 ht 500 to 1,500 Grill 600 Heating pads 50 Instantaneous flow water heaters 2,000 Kitchenettes (complete), average 1,500 Nursery milk warmers 500 Ornamental stoves 250 to 500 Ovens 1,200 to 1,500 Plate warmers 300 Radiators 500 to 6,000 Eanges, three heats, 4 to 6 people 1,000 to 4,515 Ranges, three heats, 6 to 12 people 1,100 to 5,250 Ranges, three heats, 12 to 20 people 2,000 to 7,200 Samovar 500 Saute pans 165 to 660 Shaving mugs 150 Stoves (plain) 4 in 50 to 220 Stoves (plain) 6 in., 3 ht 125 to 500 Stoves (plain) 7 in., 3 ht 120 to 600 Stoves (plain) 8 in., 3 ht 165 to 825 Stoves (plain) 10 in., 3 ht 275 to 1,100 Stoves (plain) 12 in., 3 ht 325 to 1,300 Stoves, traveler 's 200 Toaster stoves, 5 in. by 9 in 500 Toasters, 9 in. by 12 in., 3 ht. 330 to 880 Toasters, 12 in. by 18 in., 3 ht 500 to 1,500 Urns, 1 gal., 3 ht 110 to 440 Urns, 3 gal., 3 ht 220 to 440 Urns, 3 gal., 3 ht 330 to 1,320 Urns, 5 gal., 3 ht 400 to 1,700 Waffle irons, two waffles 770 Waffle irons, three waffles 1,150 Water cup 500 Water heater, bayonet type 700 to 1,500 100 ELEQTRICAL TABLES AND DATA ELECTRIC HEATING DEVICES FOR INDUSTRIAL PURPOSES Apparatus Watts Annealing furnaces 200 Bar or barbers' urns, 1 to 5 gal., 3 ht 200 to 1,700 Bakers' ovens, 30 to 80 loaves 6,000 to 10,000 Branding tool 10 to 500 Button dye heater 100 Chocolate v^armers 55 to 250 Coffee urns, 1 to 20 gal 200 to 4,000 Corset irons 350 Dental furnaces 450 Embossing head 100 to 1,000 Glue pot, % pt. to 25 gal 150 to 5,000 Glue pots 110 to 880 Hat irons (small) 200 Hatters' iron, 9 to 15 pounds 450 Instrument sterilizers 350 to 500 Japanning oven 1,000 to 10,000 Laboratory apparatus flask heaters 500 Linotype pots ; 485 Machine irons, 2 to 18 lbs 770 Matrix dryer •. 28,000 Melting pot 13,000 to 30,000 Oil tempering bath 6,000 to 20,000 Pitch ke-ttles, 12 and 15 in. 3 ht 300 to 1,500 Polishing irons, 3.5 to 5.5 lbs 330 to 550 Radiators, various sizes 700 to 6,000 Sealing wax pots, .5 to 1.5 pt 175 to 300 Shoe irons 200 Soldering irons (various sizes) 100 to 450 Soldering pots, 4 to 15 lbs. capacity 200 to 440 Tailors' iron, 12 to 25 lbs 660 to 880 Vulcanizers for automobile tires 100 to 450 ELECTRICAL TABLES AND DATA 101 High Tension. — The N.E.C. classifies as ''high potentiaP' all voltages above 550 and below 3500, allowing a 10 per cent additional in the case of 550 volt motors. Voltages above 3500 are classed as ''extra high potential/' Special points to be noted with very high potentials are the Corona effect and the fact that ordinary bushings must not be used where wires enter buildings. It is best to enter wires through large open spaces. Horsepower. — 746 watts equal 1 horsepower, abbreviated H. P. One H. P. is sufficient to raise 33,000 lbs. 1 foot per minute or 1 lb. 33,000 feet per minute. Hospitals. — In the corridors, only an indifferent illumination of about 0.5 watts per square foot is needed. Good exit and emergency lighting is usually insisted upon and as most of the inmates are helpless every possible precaution against the fire hazard should be taken. Good ventilation is also essential. In the public wards inverted lighting or lights encased in strongly diffusing globes would give the best results. By no means should direct lighting from the ceiling be favored. A plentiful supply of outlets for heating pads, etc., will be found convenient. In the private wards the illumination should be by means of lights placed at the head of bed and never by ceiling lights. Each lamp should be controllable by pendant switch, so as to enable patient to operate it. Separate receptacle for heating pads and other devices should be provided. In the operating rooms a very bright shadowless illumination should be pro- vided, and this should be fitted with ample switching facilities so as to adjust it to the special needs of any operating physician. Arrange the operating lights so that no one fuse can put all of them out, or at least provide throw over switch to another set of fuses. Signaling circuits are usually also provided for all patients. 102 ELECTRICAL TABLES AND DATA Hotels. — Exit and emergency lights should be pro- vided in all large hotels. It is a good plan to arrange the lighting so that two circuits enter each room or apartment which contains more than one outlet. Where floors are alike this can sometimes be done by running branch circuits straight up and down, and locating all cut-outs in basement. Hall circuits should always be independent of room circuits, so as to reas- sure guests in case of a blowout of large fuse, or other accident which darkens a large part of the house. Door switches will be found useful for closets as well as for rooms. Vacuum cleaner circuits should be pro- vided in all halls, close enough together to avoid the use of very long cords. In the case of hotels planned for families, a large number of outlets with which to supply lights for illumination of pictures, lamps in cozy comers, etc., will be useful. If these are not pro- vided, the rooms will likely soon be found strung full of flexible cord, which mil introduce a considerable fire risk. Special systems of wiring enabling one to turn on lights in rooms even though they be switched off there, will be very serviceable in case of fire or panic, but will add considerable to the expense. In large hotels equipped with banquet halls, carriage calls are often provided. In such halls a special outlet for moving picture arc, or stereopticon should be provided. Hunting. — Whenever anything causes fluctuations in the speed of an alternator operating in parallel with others, it will either deliver current to the others or draw current from them. Under certain circumstances this condition may become fixed and the machines are then said to be hunting or phase swinging. This condition is liable to be most severe with machines having a large number of poles. To prevent hunting the prime mover should have a governor which is not too sensitive. The connections between the machines ELECTRICAL TABLES AND DATA 103 should not have too much resistance, and the ma- chines should be equipped with damping coils. To prevent excessive short circuits, reactances are some- times cut into the external circuit. To prevent over- heating, thermometers or pyrometers electrically con- nected are sometimes embedded in the hottest parts of machines and arranged to indicate temperatures at the outside. Hysterisis. — This is the term vrhich describes the lagging of the magnetism behind the magnetizing force. It causes heating of the iron and loss of energy, and is much greater with steel than with soft iron. Illumination. — Illuminating engineering is more an art than a science, and to master it properly re- quires considerable experience and knowledge of many factors which can only be hinted at in a work of this kind. By means of the hints given out and the tables following, anyone, however, should be able to design a pretty satisfactory installation where ordinary com- mercial effects are desired. "Where special effects in illumination of statuary, altars, etc., is desired, experi- ments with temporary lights should be made. The main requisite, where economy is not too much insisted upon, is plenty of capacity. It is never advisable to figure illumination for light colors, since colors are apt to be changed. If there is plenty of circuit ca- pacity, a wide choice as to candle power of lamps is possible and many experiments may be made until the most satisfactory effects are obtained. In addition to the matter contained in this chapter, practical hints on the illumination of special places are given in the alphabetical order of locations referred to, and it is advisable to consult these before deciding upon any work. The circuit capacity necessary to be installed to arrange for any degree of illumination can be deter- 104 ELECTRICAL TABLES AND DATA mined readily by reference to Table XXXI. Multiply the floor area to be illuminated by the number of watts per square foot recommended with the various illumi- nants and by the foot candles desired. The result will give the number of watts for which provision should be made. Except in special cases (see National Elec- trical Code Rules) one circuit at least should be pro- vided for each 660 watts. If large units are used, the first cost T\dll be less, but evenness of illumination will be sacrificed unless lamps can be hung high. The intensity of illumination obtainable from a given source varies with the height and distribution of lamps; condition, type and kind of reflectors or enclosing globes; nature and color of ceilings and walls; also with the voltage maintained, and is never quite the same at all parts of the working plane. The figures given below are intended as approxima- tions and for quick determination of the number of lamps required. The watts per square foot given in connection with the various illuminants are thought to be sufficient to provide an illumination of one foot candle ; for greater intensities they must be multiplied by the number of foot candles desired. Table XXXII is prepared to illustrate the difference in the quantity of wiring material required for illumi- nation brought about by the use of large and small units or clusters of lamps. The line ^^Wire used per sq. ft." refers only to the wire (one leg) used between lamps. The A\dre needed to feed the circuits must be separately calculated. In case of arc lamps, or large incandescent lamps using one per circuit, no wire between lamps will be used. No allowance is made for switches or drops to brackets and it is assumed that circuits are run according to N. E. C. rules, never more than 660 watts per circuit. The table is not quite accurate unless the space illuminated is of such size as to allow of the use of full circuits. ELECTRICAL TABLES AND DATA 105 o orq P CD CD Pj cq P CD >-• CD t-. CQ CD o p CO 05 CO CD "^ QfQ "• CD '"■^ CO H O rs CD Ob CD CD OfQ t-J v.. OQ H-< v.. O p OQ ^ o a- CD CD p o CO oo S* £ § O t-. 0 CD C^ hP^ en CO cji t3d !zj S. p P CD p P I— I h— I CD CD CD P CD CD o' o" S- I— I* h-i» <^ OD OD CD t=r tr, C-+-* c-t- CD O orcj tr P O •-< O o" CD o CD •-< CD ^ CD 21 a ~ rt- O •-< 05 Pj CD O CO CD pi O •& P c-t- CQ CD 106 ELECTRICAL TABLES AND DATA • rH o O X X X pq «4H O o go o ?:! q; .r-l 2 fl ^ f^ b '^ ^ 1^ c3 ^ > ^^ •- O ^ r— 1 O 1^ pq h:] lO 00 o o o ^ ^ o o a o O fl r- ^ P 'tH o o o o 1—4 "o o o o rH O TtH t^ O CO lO t^ o o o CO CO t^ i>. o CO O O O tH o o o o o o o 00 o CO CO as '5 ^ pq t^ ^ ^ ^ be o P^ 00 o o <1 iq o o o 00 o CO CO o o o o CO CO t^ b^ CO o o o d d oo CO PI CO O) CM u d d be : ^ ^ • ft E ^ - £ 0^ o -M rQ 7:! CO O H ft s CO ^ bJO .^ oQ "D CD S - bC c3 O ft 02 10 o d d Q © >-i ^ o ^^ 'bJD "Hid "^ cvj o d d ^ CO ..N CO o £ o a (D 5^ o cd ^ S o) ^ o QjCC PjOD P^Cfi Pjoq pJO} P-iGC PjGC Ojoq ^^^^^^^^ « . . ►Ti . « . « iT3ph::ipD'T:Jp3'TDp'T::Ja3'T3cD*^p'^p (i)ft)CD(rt)OQ(t>o fDoCDofDo^tJrs ^fD^(X)^S^CD ^S^S^fD^fD J-gl^^^^^ ^^^^^^^^ • Hi • Hi • tii • Hi • Hi • Hi • Hi • Hi r^5 i_^ I~t5 H^ ^^ H->i ^^ »-J HfS H^ ''^ h-' ''^ *-^ ^^ H— ' -' p p p 00 o o:> o en p en p hI^ h^ b b b *en J-^ b 'h-^ m t— ' CO 1— ' ^ CO h- 1 to en 00 CO O CO o^ 00 o en o f-* h- » p ^-l p p p p p -^i o en p en p ^^^ p oo H-* b b i-* ^ H-i CO h-i b I— iQOI— 'hf^tOOOtO^ '■o CO O M ^^ "<1 CO 1— » ^ en M I— k pt-*popQoo- o* (P p p h-. •^ 5 3 "" Q ^ £. ^'^2 O O ^ S ^ ^. 02 .^ H^ tS- ci o ^^ CQ C) , ►-i. «r»- •^ ty- . <^ a> d ^•^ 52 P ^ o ti H l-b r-t- >> ^ 3 o rt ^ H-b IH QO s! O ^ a P ixj t-t- «-•■ CO a P O w P S ct> OQ S d m 0) pi • ^.(g ft) •-J ti ^ r/i -. CD c p CD quir not ^ 3 S. o o o ft- to connect re than 660 108 ELECTRICAL TABLES AND DATA Average illumination, if made up of spots of very bright light alternating with low illumination, is no criterion of the value of illumination. The very bright spots only make the others appear less brilliant. The eye has great powers of adjustment and can^get along with low illumination if it is even, but with elderly persons it cannot rapidly and often change its adjust- ment without causing pain and injury. The quantity of illumination should be adjustable, for not all per- sons can be comfortable with the same intensity. The source of light should never be visible, especially if it is of high intrinsic brilliancy. The best light is one sufficiently diffused to cast but a slight shadow. In offices, however, where one source of light must serve many persons, an absolutely shadowless inverted light is desirable. It is good practice to space outlets so that the space between lamps is from one to two times the height of lamps above the working plane. This rule requires large units for high ceilings and small ones for low places. Special reflectors, however, have a certain ratio of spacing to height which should be obtained from the maker. Buildings containing many windows require more artificial light for night work than the ordinary building. The following tables are based on Holophane Intensive, or medium reflectors, and will give fair approximations of results to be expected from other reflectors. Holophane reflectors are of high efficiency and in some cases allowance must be made for this. Incandescent Lamps. — These lamps are operated mostly in multiple, and when so used never at a higher voltage than 250. On series circuits the voltage used runs into the thousands, but special lamps are re- quired. Most lamps are built marked with three voltages: top, middle, and bottom. The top voltage is preferably used; with this voltage the efficiency is the highest but the life shortened ; with botton voltage ELECTRICAL TABLES AND D^ Height of lamps in feet above plane to be illuminated. I-* 1 ^ 1 1 1 1 1 1 fo 1 c 1 cs 1 -1 1 o 1 c-T 1 >;^ 1 ITA 05 4^.65 ooo< 0001 Cirf^tO OOOt Orfi-tO 05rf>^tO 05rf^tO Cirf^tO OOOl OOOl OOOl oocn cobb hobibi Ol CO to p CO to coMo Mbco > bi*^bi coMO bbi'ca f-tobx 3.13 5.53 8.24 ^5 03 h- tOMC CCMM rf^MM rf^tOM or CO to O5C0tO OCC7TC0 Be- tween lamps OtOlCD tOCOtO Mtfi.Ol <1<100 COtOM 05CDOT tOOtO wt-*o tOM M COMM COtOM 4^tO^-i OlCOtO <{>{^tO P V CO 33 >-i H-CCOO 02 05O COCCtO OOtOrf^ rf^ Mboto COtOM rfs.tOM Igtoi^ i^Kf^b tOMM COMM tobto rf^tOM oi>;^to Un- der I'mps MOO bibb MMO bMb to M M to M ui 050IO ODOOM tOMM Be- tw'en I'mps |-' P P Mpp h-^hif^ CO bo or MMO t>- M^Ifi. ^99 05 CO 05 tOMp bM XCQiH drHoi l>Ol> diH r-l lOOO'tf ddiH qqoi o iH lOCDO ddiH CD 00 CO dd>-H l>Oiq diHrH diHi-i aqcQ05 drHiH t>;THOq CDOCD dr^rH 4*1 rHOiOO lOWOO r-ll>05 05 Tt*-^ XCQrH l>r-ll> 00510 OJOTiO r-lOlCO T-lrHO^ OrHC^ OriW OiHrH OOlH 00 OJOCO rH r-5ci W05O iHr^CO 05 05^ jHtHCO THoqq iHtHCO OCDCD r^tHOi 05tJXCO COW-* WOO rHOicO T-t05X T-irHOJ OCDCD r-itHN 00-^ CO dr-ioi CO 05 tHtHOQ r-5ojco TJJCOCD rHoiCO ooq^jH rHcicO tHXO t-irHCO qqq rHrHCQ p5S -^Jf-^Tf O5 001> CDTt^05 Tt^r-llO CO 05 CO 1-1X05 0510W Wt}X- OQCO'lO r-(C0lO wcoid 05OO T-5co*»d XXCD iHoi^* TjHOOOq THoico 0}05Tt< rHrHCO Ui en i>oqo 03C01O oicoio 05 05I> r-^* Oi '<^* CDlOrH OOrHq th'cqco CQqrH rHrHOd ® C5r-CD CDOX oirjJcD COCDO oicocD rHCOlO oiooo xi>o -"tCOX iHoico CO CD CO 00*0 00 lOXCO oJcocd WtHCD oiooid qc5C0 oicoid X CDl>lO tHOJtjJ "^OOX rHCicO •oft THO500 l>O5 00 coidoi ofidoo 05TtXCD rHCiT}5 ^ ft C00500 X05QO CO id 05 COtHCD co'idod 05l>t* 1>OQO wqoq woo id xxoo iHoi-'t CO A^ft 05OC0 XtHi-I to 05* id Xl>05 Td^CDTH CDXIO co»do5 XCD05 wo5cd Pi3 T}<(X)00 codcD fHtH looqcD idooTt* tH tH r^LOX Tj^CDO* qi>i> 00 id 05* oqioq OJCDrJ oicocD 1 lOOO lOOO OlTjiCO lOOO WrJiCD lOOO OjTtCD lOOO CQ-^CD »ooo OJTJ^CD iOOO 03t}^M OOOl 05rf^M OOOl 05rf».M OOOl 05tf».M o Ol ODOICO Qobio 4.0 6.6 11.1 5.2 8.3 14.0 5.8 9.3 15.6 6.6 10.6 17.7 7.6 12.3 20.3 8.6 14.3 22.4 ^d Bl ^1 CO CD at 00 4.0 6.5 10.9 4.9 7.9 12.9 5.5 8.8 14.6 6.2 9.8 16.3 7.1 11.0 18.0 8.1 12.6 20.8 Be- tween lamps coMb ODOtCO coioM CDOTi^ bcbb 4.1 6.5 10.7 4.5 7.0 11.7 5.0 7.8 12.5 5.4 8.8 13.4 HTd OD -J ^ ^ r Oico^^ ooboD pDCnCO Mrf>.bo - Ol .3 or COM bMco OlCOtD .M bihbi 05rfi.M bbo. ^^MM Mb>MM bbcD OlCOM COMM 05>t>.M boCOM - w r o Q w h^rc s^ C/2 O S3 o 2 > o O Ul 50 CO o O o o o W to Ol C/2 s ^ § O g H o a ffi^ o Ol o o 5 ^ a k! 112 ELECTRICAL TABLES AND DATA > X X X pq Table Showing Illumination in Foot Candles from 25, 40 and 60 Watt Mazda or Tung- sten Lamps Arranged in Four Rows at Heights and Distances Apart Each Way as Given in Table. Bowl Frosted Lamps Equipped with Holophane Intensive Clear High Efficiency Eeplectors Nos. 106,125, 106,130 and 106,150 Re- spectively. Distance Apart op Lamps. Be- tw'en I'mps odd ddd ddr-H ddr-; qqco d d rH* dr-HrH CD05Tt< ddr-I Un- der I'mps r-l05I> dec id rJHWOO OCDX rHr-HOJ qcoq oor^o d rH OJ d rH rH i>qq OrHrH COOlO ddr; O Be tw'en I'mps lOQOr^ OOtH drHrH drHTH 00WO5 drHrH OStJItH ' XOOrH OrHCi 1 dr^W XWO dr-5cQ Un- der I'mps ci T}5 id T-i oi T^ CQ05O r^T-HCO OL0l> rHrHCQ rHr-;CQ dr-HCi XCOtH drHCi 00 Be- tw'en I'mpe T-HrHCQ lOWCO iHCQCO r-^cicO Ti^rHlC OOrHW C5Q0O T-i-HCO Un- der I'mps TjJCOOO CiTind 05iHOO r-ic6T}5 T-HoiT^; T-HOJCO TjlO00 THoico 00I>CO I>!>C5 T} rHOicO Un- der I'mps 1>XC5 oirj^d WCOtJ< wcoid OOCD Oicorj^ oqi>iq oob;-^ r-5 Oi rj5 r-^ CQ '"t lOCDO rHOirP Tt^Tj^OO rHWcd CD .g^ lOXOO I>WlO. COQOr^ lO 00 -^ ^CDC2 (S S § ojcoio cQTi^cd cqoq6 wcocd oiwid THCOld r^Wld ®a WC005 XOCD I0l>0 ODCDO 00lOl> ocooo cS c6io{> d^^ oicocD oJcdid oicoid oicoio 05 05 00 TH0irj5 -J . O ^ CDCD05 CDCD05 "^OtJJ ^^S 0616 00 COlQQO COlOOO r-jqq 9®^ ^"^9 '^'^'^ oo-^t^ oo-^t^ oi"^i> CQcod ®ft OC-O 1>C01> tHCOiO c S rj^cdcj co'idod coidod Pi2 wqq rHoqq J^tOO'-J oqoqoo co'^x odr^i> oi'^t^ ciood ■ oft '-J^® C5CDtj; CD^IO '*CDOq iHiOCD CCI>W OQOC? £§g^S idaJCQ Ttit>ciH ^^<6 rj^cod coidoi od-^oo .^,2 tH r-l rH r-l tH ^ a ^CQ05 "^coth 05CDCD ioiHi> ior>o I>OI> c 9 idc35c6 idooco tjhj>cq Tjii>rH TtlcDiH oocooi p^ r-l tH tH rH tH TH05C0 co-^jHod CO Be- tween lamps 9.2 14.2 23.2 Tj^oqq qqq ^'^9 wqco oooJd i>THd codoo ddd r-lCQ iHrH rHrH r-l idoo-^ TticdrH 1=5 9.2 15.2 23.6 rjjcooq iqoqcD i>cdcd tjjooco a6oor-3 t>r-^d cDdt> ^di^ rHOi rHr-l rH r-l rH qoTij O'^j^os ""a^QOOO Tj^dd 1 IS iOOO WOO CQTfCD IOOO »ooo CQrtCD lMrM:0 woo IOOO IOOO CQt}^ mJOCT g 3 0505(0 ^bbi wbb »*^bb5 05btrf^ -o a, en "-J CiCCtO CD0105 05 Be tween lamps 05 COW ODt^W CDCTCO l_i05C0 i-i»3*^ |_iOC>f>- ^^^0\ 00 CD to O05 05 00 05 to Moob ^H^'o >^k><^ OC<105 M »^ O 1 g|w rf^WM ^f^-WM otooM ! 05coto t^to oo^-to •-'►<^ CD 00 05 CDrfi-CD Ot.bco bcorf^ rf^tOM CntOM OiCOM CTCO- ^(i>M;>>tOM CTtOM 05 CO to OD^f^tO m05C0 i^s-^ OOOICD rf^ODO rfi>rfi.rfi. MCD05 OOCTO OCTC5 MOCT r^? M 05 ! '-rel- WMO COMM COMM COMM COMM COMM tOMO 02 3 r >tOM CTtOM 05 CO to rfi'00 05c;tod 05CTC0 05CTCD CT'rf^-bo toco^ hhbi W-O WMO rf».WM ><^tOM 05 CO to - r w ^ w o C>2 iT| o L' > O !2: ^ W o w ^ Ml o fn !^ o Kj O W w a o w t^ > % ^ Ml c! o3 H r/^ !^ :^ O Xfl P o M< O 3 Ml 1— I 00 p Ml Q > o ^ h^ o 2 o > tr" ^ o 1 ^ ^ 00 or > O ♦^ r/2 > Q Ml 12J % t?j ^ O l-H > &3 o O .^ V* o 0^ > g > r^ > § c H w Ml < 1— 1 en < Kl Ml o O ♦51 H C/2 »— 1 1 r 114 Eh ELECTRICAL TABLES AND DATA ^^2 12; o >1 ITS !-i (MO w?= lo ^ ;:; D5 o o o fin Q Q o o o c/2 O Eh CA2 o I— I S ^ fa^Q 12; o I— I Eh CA2 o o W Oh O o a w Eh H O o o tH Q ^ o in di h3 Be- tween I'mps 0.30 0.50 0.84 0.35 0.62 1.04 0.39 0.70 1.20 0.43 0.82 1.40 0.52 0.90 1.56 0.60 1.06 1.84 0.74 1.14 1.96 Un- der I'mps 3.49 6.03 10.5 2.63 4.51 7.82 2.04 8.53 6.10 1.63 2.84 4.92 1.39 2.37 4.11 1.01 1.78 3.07 0.87 1.45 2.48 X tH Be- tw'en I'mps 0.34 0.68 1.15 0.43 0.77 1.40 0.47 0.94 1.66 0.55 1.06 1.87 0.64 1.19 2.09 0.76 1.33 2.36 0.82 1.43 2.47 Un- der I'mps 3.52 6.10 10.7 2.66 4.59 8.07 2.07 3.62 6.40 1.65 2.95 5.27 1.42 2.49 4.50 1.10 1.92 3.55 0.93 1.64 3.05 4i CD iH Be- tw'en I'mps 0.60 1.12 1.98 0.70 1.34 2.40 0.86 1.60 2.80 0.98 1.76 3.10 1.08 1.90 3.34 1.20 2.02 3.48 1.20 1.98 3.46 Un- der I'mps 3.59 6.20 10.9 2.72 4.73 8.30 2.16 3.77 6.68 1.77 3.13 5.59 1.52 2.71 4.87 1.20 2.19 4.01 1.11 1.90 3.51 tH Be- tw'en I'mps 0.76 1.56 2.80 0.90 1.88 3.32 1.10 2.16 3.84 1.26 2.36 4.12 1.40 2.48 4.36 1.36 2.56 4.44 1.32 2.48 4.32 Un- der I'mps 3.69 6.36 11.15 2.84 4.93 8.57 2.29 4.01 6.98 1.89 3.40 5.95 1.71 2.99 5.26 1.40 2.52 4.43 1.31 2.25 3.93 tH Be- tween lamps 1.34 2.54 4.56 1.66 2.98 5.24 1.86 3.24 5.64 1.94 3.34 5.80 1.96 3.36 5.80 1.82 3.22 5.52 1.68 2.96 5.14 a 0^ 3.95 6.74 11.6 3.10 5.36 9.28 2.55 4.52 7.80 2.17 3.98 6.85 2.04 3.62 6.21 1.82 318 5.39 1.65 2.92 4.85 tH Be- tween lamps 2.46 4.44 7.94 2.79 4.89 8.52 2.95 4.94 9.04 2.83 4.86 8.54 2.72 4.71 8.26 2.44 4.29 7.56 2.14 3.79 6.82 fc- CO '^ d fi a piS 4.19 7.33 12.9 3.45 6.09 10.6 3.00 5.34 9.4 2.72 4.85 8.47 2.62 4.49 7.88 2.25 4.00 6.98 2.11 3.61 6.30 X Be- tween lamps 4.66 8.18 14.0 4.04 8.06 13.7 4.32 7.72 13.3 4.06 7.22 12.5 3.82 6.76 11.7 3.26 5.84 10.2 2.92 5.12 8.8 II 5.01 8.81 15.4 4.45 7.72 13.7 4.14 7.03 12.4 3.77 6.49 11.5 3.52 6.05 9.63 8.16 5.30 9.35 2.83 4.67 8.35 CD Be- tween lamps 7.88 14.1 24.2 7.16 12.9 22.3 6.60 11.6 20.2 6.00 10.6 18.3 5.48 9.6 16.6 4.52 8.00 13.8 3.88 6.68 11.7 t- GO p^ 7.03 12.6 21.6 6.53 11.4 19.6 6.01 10.5 18.2 5.46 9.7 16.8 5.12 9.00 15.6 4.46 7.73 13.5 3.86 6.76 11.7 be 000 OlOlO THr-IOl 000 010 iO rHt-lO} 000 OlOiO ^tHW 000 OiOlO iHrHOi 000 000 000 2S§ •P' CD 1 t- =0 d 9Aoqt i " i (J99J in ! 2 edtuBi 1 2 JO !|q3i9 3 H ELECTRICAL TABLES AND DATA 115 the opposite will be the ease. See Table XXXIX for approximate effects. The efficiency of all lamps decreases with use. In- candescent lamps will not give good results with fre- quencies lower than 40 ; for outdoor illumination they have, however, been used with 25 cycles. The fluctua- tions are less noticeable with heavy filaments. Circuit Limitations, — Not more than 660 watts are generally allowed on circuits, but where small fixture wire and fiber lined sockets and flexible cords are not used there is no serious objection to 1320 watts per circuit, or 32 lights instead of the usual 16. Frosting. — Lamps are frosted to reduce the intrinsic brilliancy and through it become less harmful to the eye. Ordinary frosting reduces the c.p. from 5 to 10 per cent, but shortens the life from 25 to 50 per cent. Bowl frosting has no appreciable effect upon the life. The effect of coloring upon the life of the lamp is about the same as that of frosting. The effect upon the c. p. varies with the color and its density. Amber, opal and yellow absorb the least ; blue, green and pur- ple the most; blue and red are the most used colors. Not much illumination can be expected from colored lamps. In some cases lamps are merely bowl colored. The efficiency of incandescent lamps increases with the voltage, but the length of life decreases. To a certain extent, therefore, what is gained on the one haiid is lost on the other. Table XXXIX is prepared to facilitate the calcula- tions necessary to be made in order to determine the most economical voltage at which to operate lamps. In the column ^^K.W. wasted" we give the K. W. wasted by the use of the middle or bottom voltage during the length of life corresponding to top voltage, which is considered the standard. In the column headed *^ Saving in lamp renewals" we give the per- centage of lamp renewals avoided by the use of lamps 116 ELECTRICAL TABLES AND DATA at the lower voltages. In order to find the money vahie of the watts wasted by any lamp we must multiply the figure given in the table by the c. p. of the lamp and the rate per K. W. In order to find how mnch^the same combination will save us in lamp renewals we must multiply the cost of lamp by the figure in the column on ''Saving in lamp renewals." If our calcu- lation shows a net saving it will be more profitable to use the lower voltage, otherwise use the higher. Ex- ample: With energy at 5 cents per K. W. and 25 watt tungsten lamps costing 20 cents each, is it more economical to use the middle voltage than the top volt- age? A 25 watt lamp gives 20 c. p. and the K. W. wasted at middle voltage is 0.050; v/e have therefore 20x0.050x0.05, which equals 0.05, or 5 cents wasted during 1,000 hours. On the other hand, we save 0.23 X 0.20, which equals 0.046. The saving in cost of lamp renewals does not quite offset the loss by the lower voltage, hence the higher voltage is more economical. In many cases such a calculation has merely an academic value. As long as the parties using the light are satisfied with that obtainable from the use of the lower voltage there is no economy in using the higher. Smashing Point. — The useful life of a lamp is gen- erally considered to be over when its c. p. has dropped to 80 per cent of its original value. The following table is based on average values. The improvement in lamps is at times very rapid and in case great accuracy is required the manufacturers ' guaranteed data should be obtained and used instead of values here given. Inductance. — This is that property of an electric circuit which causes a current in it to create lines of force and thus produce a counter e. m. f . proportional to the rate of change of that current. ELECTRICAL TABLES AND DATA 117 TABLE XXXIX Comparative cost of illumination and lamp re- newals. Saving Name of Voltage Watts Hours of K.W. in Lamp Lamp Eating Per C.P. Life Wasted Eenewals Mazda or Top 1.22 1,000 Tungsten Middle 1.27 1,300 0.050 0.23 Bottom 1.33 1,700 0.110 0.41 Tungsten Top In large units tlie type ^'C" or Gas Filled Middle gas filled lamp is fully twice as Bottom efficient as the common tungsten lamp but in connection with small units there is no saving, but a whiter light is obtained. Top L84 800 Tantalum Middle 1.91 1,075 0.056 0.26 Bottom 2.00 1,350 0.128 0.41 Gem or Top 2.50 500 Graphitized Middle 2.65 700 0.075 0.28 Filament Bottom 2.83 1,000 0.165 0.50 Less Than 50 Watts Top 3.16 750 Carbon Middle 3.40 1,100 0.180 0.68 Bottom 3.61 1,600 0.337 0.47 50 Watts and Over. Top 2.97 650 Carbon Middle 3.18 925 0.136 0.30 Bottom 3.39 1,425 0.273 0.54 118 ' ELECTRICAL TABLES AND DATA ^ V.^ci O Tt^ O O ^ t>|cc-53 : 2; °^ ^ ^ § ^ o £ S .2 „'S'^« §000000 J. S m § ^ '^ <^ ^. ^. o^ a; cd CD Q^ ^ I8:^8UIBTQ i-lr-lrHrHC0 »OlOCOairt< COinOiiHOi OOOIO^OIO CQt^'^OCvl QOQOCOCOCO -^IO^OOt— I r^QOOOTt^QO C5 rt^QOOa?— lO OQOt^CilO t^lOOOOCO i— Ib-CvlCOOO Oi O^ ^ iO ZO t:^ CO OO Oi Oi OOi— IrHrH C^C\|-«O00T^ COrHOiCOCO (MOOrHOOCO COOCdJOO OG^rHt^Cq TtlLOO-'^CCl TtlCX>CC)l>'OiT— I COCvJCMtJHtH OOrHt^OSO OOIOO'^CO O^OTtHt^GO CDCOOSrtHGS COt^OCOl>» ai(MlOt-Ci OC\]tH»OCO t-OOOOGiGS OOt-HrHrH »-IC-t^O:)C-OiQO^ »OOtHQOC CiC.0(X> Ci'^rHO|>. 1— |(X)t^rt rHi— IO:iC0t^ 1— |lOQ0Lt)(M fOrtlCO'QCO i-HrHlOlOCvI O0^^*^C<] OOO^tOrttCM lOTt^OCOr:H COO^OO^jCvI |>-O^^CO rtii— IQOCOQO (MCOOCOCO OJC^J^tloai t^ oq TtH »o <:o t^ 00 00 OS o^ o o '-' ^h i-h r-i cm ca cq . rHt^OiCOCO COtj^Ot— lO O0<^t^^fO OCMlOOit^ rH0-C0t-0 Cit>"G5'^lO TtirHt^. 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CDCvlCOlOGi OOIOIOOCO Oq 1-lOiCqlOcO COCvlt^COCO OOOiCOOCM rnoiiooco ot^-^Ocq I— io>o,— i(:o o^tioocMu^ ooocoooo COOOOIOCO t-t^OOc^jOi OOOrHrH rH(MCaiT+^ cqcviOit^ir-i t^(^oait^(^o OCOcMCOt- lOCO'^'^O fOCOt^^MOq OiOOCiCOO rH O'— ICMtHCCJ t^LO'— IQOO) '^lOOqt^Oi QOCD(Ml>-rH O^C.0OOiCi OOOrHiH rHCvl(M(MCQ b-lOOOiTf OOiOOr^CO OiCQlOt^lO OtH'— lOCvl OCO'HairH Or- iTfiC^Jb- OOQO^COCvl OrHCiCOCO CO^OLOQO C5l>-^0>0 OTtlt^rHT^ t^OCOlOr>» coi>.oog:»o^ ooOr-Hi-i rHoacgoqcq lOCOt^QOGi Oi— (G^CO-^ lOCDt^OOCi o CO oq CO O O rH o o O rH t- Oa O o t^ O O CO Tt^ CO i O rH Oq CO Tfl ELECTRICAL TABLES AND DATA 127 cococococo cococococo tototN^roro tsorototorsD i^ CncriOicnOi cr«C;iOTrf^4^ ^;».^;i.^;i.^^CO coCoCaPcoCO Oioooo^-i ooh-'aiaito ooiO^arfi* t— »oototoco OiCriCriaiCn OlCiai^^rfi. l4x^fx^^^^CO cooowcoco COQOOiC^^^ cot— '0'X)-tN0CX> COOOtOOiCO tOCOl4^rf^CO I-* I— 'ococ^co -^iQocn^ioi Qo- ooicoroi— » OiCnCTIOiOl OiCJlOlwfi^hf^ ^4x^;».^^^^^;:». COCOCOCOCO CDoo^oih;^ cotoo^co Oicncoi— ic:> oooh^too COtOOQOOi i4i.h-i^4xO CriOi4^QOI-* cocno^iOjcn ^^ iNOOOi^ai oi— »Qoi— 'O cotoo^co^;^ ooh^^cococo COOirf^l— '►f»« tOCOCnOlO OOrf^OiOO I— 'OOCJICOOl o O^OiCnOiCJT O^C7IO^^P^^^ ^;x^tu.^^l^^^ COCOCOCOCO t3 h> cooo-Qo-^ P rj cncoooi-io ci-^cncoQo coco^oioo coi>oiNOrf*'ai 2. n oco*.^^ OJOiQoCOOt ^^ 3 a g 01 en CR cji en 01 ci 01 rfi. ►^ hii. h^. rfi. ^fx rf:w cococococo ^ S CD00- "X) 00 01 -^J CO I— ' 00 t3 CD Oi O QO Kfi^ CO I— I O Ol 05 oiCfCnOioi cncnoicnrf^ ►^^li^rf^Kfu.h^ cococococo COQO^OiOl h^lNDI-*OQO ^Olrf^tOO CO^OlCOI-i oo-^COf4^C»l— » >f^ Oi "^l CC CO OO QOQOh^OOQO CnCDOOHf^Ol tOCOOl— »Oi rf^CHCOtf^O C»COCOOlQO -|ik cococococo OOO^OiCn >^COI— kOGO "^OiKf^lNOt— » C0-<10lHP>.tv3 OCOQO"-OqT:HT^lC^l OOr-iCOCOtH b-i-HrtllOLQ Ttl1-^CDrHTl^ Ci »— lO;iCvICvl(M 1-HrHOOiOO CDIOCOt— (Gi t-lOOCIOt^ r-{ O-l CO ^ iO COt^OOQOGi 0»— iCvJCOCO rtllOOt^b- CO CO O CO CO «X? CO CO CO CO t^ t^ t^ t>- t- t^ t^ t^ l>- t^ COQOrfit^OO t-lCCOOdCO COCOCOOOOO COIOCOQOO. CO»— I'^TtlCM OOCClT^Tt^C^ OOCOCOt^b- <:OCCG5COt>- OO Oi— IrHrHrH OOOiOOt^ >OTt^C-t>-O0C:( Oi— ICviCOCO rtnLOCOCOt-- ^OCOCO^ ^COCOCOCO l>>t>.t^t>-t>- t>.t>-l>-l>-t^ Oi tH CO OO tH C^ (M , CiOOOO C5C:OOt^CO lOCOrHO:)l>- lOCOrHQOlO OCqcOTH'O lOCOt^OOOi OrH- CDCOCOCOCO COCOCOCOCO t^t^t^t>.l>- t^t^-t^t-t- COOii— iCiCO COCirH-^QO lOLOCTiCOOi t^CMCvJOlQ tOO^TtiCO OiCOCOCOTt^ I— ICOGirHT— I OOOrtHCiCQ CO OOOiCiOiOi Q000l>.CO»O rHCvlOCit^ lOCQOt^iO CDi— lOJCO'* »OCOl^QOOi Oi— iCvIcacO TH'OCOCOb- COCOCOCOCO COCOCOCOCO t^t^t^t>.|>. t^t^t^t^t* CO lO Oi Oi CO 1-1 IC Ci "* T-H O^ rH CO lO O Ci lO b- CO CQ "•^OCOTtlCO OTt^COt-CO (MOOtHcOtH dOCOrHio JO t^OOQOQOQO OOb-COlO-^ COrHOcOCO ThiC-Tt< OrHOdCO^ LOCOt-.00Oi Oi-HCvlC\lCO Tt^^lOCOl>. COCOCOCOCO ;ococococo" t^i>.t>-r>-r>- t>.t^t>.t^i>. OOOt^OiOO COCvlQOlOCO COCOCOtHO rHQOrHrHCi COOCOrtiCO OlOt^OOt- '^'^tiCOlOCO OCvlOi'^l>- -H COt^t^t^t^ t^COlO^CO CvlOCil>.lO CO'— loococo Oi— IC\IfO^ lOCOr^OOO OrHrHCQCO rht^lOCOt>- COCOCOCOCO C0CO9OCOC0 l>-l>.t^l>.t>- t^t^t^t— t^ 1-HLOrHOiO OOOCOICIO t^dOCOO COrHlOt^lO COOiCO^Th 1— ILO00C500 LQi— (lOt-OO t^LOT— ICOO CO lOLOCOCOCO CO'O^COCM i-HOOOCOTf* (MOQOLOCO OrHCMCOTt* lOCOt^GOCi Ot-Hi— l(MCO TJ^i-OlOCOt^ COCOCOCOCO COCOCOCOCO t-«t>.t-t:^t^ t^t^t^I>.t^ COOi— lOOCvl -^TtlTHLOt^ Ot^b-1-n'O THTtlOdCM CMGiCOrt^'^ rHi-HOiOC:i t-OJCOOiO C^it^TftOiCO Ca "^'^IQIO^ lO'^COCOrH OOit^lO^ rHOt^rtlOQ Ot— ICvlCOrtH lOCOt^OOO OOrHCMCO rtHTt^lOCOt— COCOCOCOCO COCOCOCOCO t-t^t^b-t^ t^t^t^t^t^ '^ ^ oo ao ^ coocMiooo Tt-t^t>.t>- t't^t^t^t^ COOOlOb-lO T-HCOOTtHO t^t^OOOCi COOib-COlo OL^CvlTfTti (Mt-i— IC^JCM Gi>OOC\lCO COi— IQCTfoO CO CMCvlCOCOCO COCMCvJi— lO QOt^COrHCvl OOO^COo OrHCMCO'^ lOCOI>-00ai CiOi— l-t>. t-t^t— t-l> k5 Or-HCMCOrtH lOCOt— OOGi OrHCMCOrjn »OCOt-Q0Ci ^ "Tii ^ ^ -^ T^ Tti'^TtiTjlT^ IQIOLOIOIO lOlO^U^lO 'C CO O) rC a • rH J3 C3 12; o 1 O hi CO s -4-3 M ^ be o i-:i H ►^ o pq s < s o o ELECTRICAL TABLES AND DxiTA 129 ^"l^l^^l^l ^q— l^l^l^ Oi Oi Oi Oi Oi Oi Oi Oi Oi Oi ^ o OOOO^OiCH tfi.C0D0h-»O COOO^O^Ol rfi^COtOl— 'O QOQOOOOOOO OOOOQOOOQO OOOOQO'OOOO OO^l-^l^l^ COCDOOOO^ CiCriOlOlHPi. CoCOtOk-ii— ' 0<^<^QO^ ciOrf^ooo tococotoo oocnocn*© mcocoooi— » COaiciii4^ cocolodoi— » oococx)^ »— 'CiOCOOi OOCOCDQO-<1 rf^i— '^^DOOl QOOOOQO •^OlCnOOHP^ I— »l— 'OO^ai— » OOCnbOOOO OiCOCOtf^^ OOOOOOOOOO OOOOOOOOOO OOQOOOOOOO CX^OO^!^--! COCOOOOO-q ^CSOiC^lh^ ^^COtOtOI— I OOCDOO^l QOCO^H- lOi O^^^Q0t005 oco--iorf^ ^qocooiO to ^ItOOiCDtO ^^C^C^rfi^OO »-*^COQOCO CJI^l^l^qOS r.0O(-»0^t-* Ot-'COQOCO t-»00^OiCJl rf^tOCOO^O OOOOOOOOOO OOOOOOOOOO OOOOOOOOOO 0000- QOOCOCOCTI COtOtOI— iH- ^ h-^O^OtitO OOOOOOOOOO OOOOOOOOOO OOOOOOOOOO oooo-ocnooh-' h^ ooco^oco cnoi^OiOi coooit-'Oi ooOMt-io tOl— ihl^CO^ ^COCO^ OiOiOi^QO cocooo^^^ COOOOOOOOO OOOOOOOOOO OOOOOOOOOO 0000«OI— ' OOCOQOOO OhJ^COW^ tOCiOrf^QO I— lOlCOtOCi COtOCJiOOl— ' CJl COOOCOCiCO h-»tOCOCO|-i COOiCOOOtO CJT^OOOO^ Oi ^ O C5 rf^ C;i 00 CO O 00 00 CD O to Hfi. Oi ^ 00 00 Oi ^OOOOOOOO OOOOOOOOOO OOOOOOOOOO 0OO0-:i^'o <:ji "^lOococoQo oicoCDhF^co tOf^cncnrf^ ^ t-*tOC5tOtO CO-ICOI— 'O (— 'tOOl^O COOi^CX-^l OOOOOOOOOO OOOOOOOOOO OOOOOOOOOO oooo-^j-^i^ OCOCOOO-<1 ^OiCiOlrf^ rfi.COCOtO)— I I— iO^«000 ^-»C^O^^i>'CO CO^qi— iCnCO COOiOrf^'-l orf^--joco -^l rfxco4i^- B td o tr^ ^ W t-^ o ^ >< 3 M OQ 1 O Ms 1 o o 1^ c-t- 5* cr CD . CO rH rH CO CO lo CO o CO oq rH oq 00 as CO 00 CO t- rH iO 05 t^ CO 00 CO 00 O ^ tH (M - as OS OS o^ OS rH CO O lO OS OO OO OS OS OS OS OS OS OS OS ^ lo CO th oi rt^ t^ O Cvl CO oo (M as ^ t- Tji lo Ttt Tt^ oq 00 rt^ T^ O O O 00 lO (M QO CO t- CO bO CO CO 00 CO t- rH 00 t^ oq 00 CO 00 O I— 1 rH C0 CO CO t- t- OS OS OS OS O) rH VO O Th OS 00 00 OS OS OS OS OS OS OS OS t^ CQ O CQ 00 OO C<1 lO t- 00 OO oq Ooq a> OS o o as t^ O CO 00 tH »0 CO CO O t- CO rH oq as rH 0> OS ^ OO CO CO l>- CO cq t^ cvi t- Oi 535 05 05 C5 oq 00 CO t- oq CO CO TtH ^ lO OS as OS as as t^Cq b- rH CO iO CO CO t- t- OS OS as OS OS O ^ OS TtH 00 OO 00 00 OS OS OS OS OS OS OS OT CO Oi 00 rH t>. CO o OS oq CO t- rH O CO O Tt^ u:) lO Tf CO oq as rH t- OS iH 00 CO oq 00 »o t^ lO t- lO Th OS Th 00 oq CO CO -— 1 CO c^ »• O i—i '^ Cvl <^ Ci Oi Ci as 05 oi t- oq t^ cq CO CO rh rt- o OS OS as OS as t>- rH CO rH lO LO CO CO t- t^ cs OS OS OS as O ^ OS CO 00 OO 00 OO OS OS OS OS as OS OS .2 PI o ;3 Oi ^ ^ 00 ^ t>. T— 1 Ttl O QO CO i-t O TjH oq OS O O OS 00 ^ oq Tj^ rH 00 CO TjH rH 00 Tt^ o oq o CO oq O ^ O Th 00 o s o o lO rH CO rH CO O '— 1 rH oq CVI 05 Oi Ci as ^ tH t- oq CO rH CO CO Tf Tt^ »0 OS OS OS OS as CO rH O O LO LO CO CO t- t- cjs OS OS as OS o ;5J OS CO t- 00 00 00 OS OS OS OS 05 OS OS lo cq eg CO ^ Oq CO ai rH CO CO tH r-l LO CO -^ iO O Tt^ CO CO r^ t^r^ t- rH OS CO CO as Th t^ lo a: 00 iO O lo OS CO S TtH >0 O lO rH CO o »— 1 '-H oq c^ 05 as OS as <^ ,-H CO 1-H ?0 rH CO CO T^ rh LO OS cs OS OS as CO o LO O rH o (:o CO t>- 1- OS as OS as as OS ;^ OO oq t- tr- 00 OO OS OS OS OS OS OS OS PQ 1-1 as o T^ oq t- O Th CO 00 LO) rH rH CO to OS O O OS 00 00 t^ O 00 rH CO ^ oq 00 ^ OS oq rH lO "^ O CO rH IQ OS o S s Q CO rtH O lO O UO o 1— 1 rH oq oq OS OS OS as a5 O CO rH LO O CO CO T:t^ tH LO OS OS as OS as ITD O LO OS -^ lO CO CO CO Ir- as OS OS OS OS OS CO 00 oq CO t- OO OO OS OS OS OS OS OS OS u t- lO t^ Oq rH rH lO 00 rH CO TjH O rH CO CO^ Ttl ^ LO Tf CO O OS CO rH lO oq OS t- TtH o CO Ir- CO r-l rH CO rH <:0 M lO OQ ^ as T^ o ic o o rH oq oq as as as as as O lO O LO O CO CO tH -* LO OS OS OS OS OS >o OS Th as TtH iO LO CO CO t- OS OS OS as as 00 CO t- oq CO t- OO OO OS OS OS OS OS OS OS CO oq Tt^ o as CO O CO CO t- CO O 1-H t^ t^ OS O O OS 00 oq rH CO lO OS t- lO oq OS lO 00 oq r-^ CD b- rH t- oq CO O r-» CO as TJ^ as Tt< o o th rH oq OS as as as OS OS Lo o T^ as oq CO T:t^ Tt^ rt^ OS OS as OS as Ttl OS Tt^ 00 CO lo ^ CO CO Ir- as OS OS OS OS 00 oq t- rH CO t- 00 OO as OS OS OS OS OS OS as 00 rH t>. t^ o T^ 00 o oq rH OS rH 00 OS T:tH TJH O rt^ CO Tt" -^ OO 00 oq oq O t- Ttl rH oq t- t- oq CO tr- oq t- oq CO O d CO 00 CO as TtH o o th ^ oq as OS as as as OS Tfi OS Tf OS oq CO CO tH T*^ OS OS OS OS OS TfH OS CO 00 CO lo uo CO CO Ir- as OS OS OS OS ir- oq CO rH lO tr- 00 00 a; OS OS OS OS OS OS o T-H oq CO* Tt- 00 00 00 00 00 lo CO t- 00 as* 00 00 00 00 00 O rH oq CO -^ OS as OS as OS lO CO t-* OO OS OS OS OS o> a> ELECTRICAL TABLES AND DATA 131 sideration, and b the difference between the two man- tissae; next add this number to the lower number. Example : Our mantissa is 2.851 60, and looking into our table, we find that it is not tabulated. The next lower is .851 26, which corresponds to the number 700 ; the next higher is 2.851 87, which corresponds to 710. Now, .851 60- .851 26 leaves us 34, and the difference between 851 26 and 851 87 is 61. We have now 34 — X 10, which equals 5.57, and this added to 700 gives us the approximate value of the number correspond- ing to the mantissa of 2.851 60, viz., 705.57. Magnetic Blowout. — A strong magnetic field repels an arc and is often used to break it. It is made use of in lightning arresters, and at other places where the arc is troublesome. TABLE XXXXIY Melting Points of Various Substances in Degrees Centigrade and Fahrenheit Aluminum 659 1218 Antimony 630 1166 Bismuth 271 520 Brass 900 1652 Bronze 900 1652 Carbon 3600 6512 Chronium 510 950 Cobalt 1490 3714 Oerman Silver. aiOO 2012 Glass 1300 2372 Gold 1063 1945 Gutta Percha... 100 212 Iridium 2300 4140 Iron 1520 2768 Lead 327 620 Manganese 1225 2237 Marble 2500 4532 C. F. Mercury — 38.7 —-37.7 Nickel 1452 2645 Paraffin 52 126 Photo emulsion. . 32 90 Platinum 1755 3191 Eubber 100 212 Silenium 218 424 Silicon 1420 2588 Silver -960 1760 Steel, Av.. 1400 2552 Sulphur 110 230 Tantalum 2850 5162 Tin 232 449 Tungsten 3000 5432 Vanadium 1730 3146 Wax, Bees 62 143 Zinc 419 787 Bureau of Standards as authority for the majority. 132 ELECTRICAL TABLES AND DATA Mains. — This term properly used applies only to the last set of wires feeding the final distribution point. Primary mains are those which feed the individual transformers. The wires leading from transformers are usually spoken of as secondary mains, although '/9, ?.\ Figure 8. — Measurement of Heights and Distances. there may be conditions in which they would be sec- ondary feeders. Measurement of Heights and Distances. The measurement of heights and distances requires first of all the use of right angles. Where no instruments or squares are available, a right angle can be laid out as in 0, Figure 8, setting stakes or stretching lines so ELECTRICAL TABLES AND DATA 133 that the dimensions given, or multiples of them, obtain on the three sides. A square or rectangle can be proved by stretching diagonals from the corners. When both diagonals are the same length we have a perfect rectangle. See if, Figure 8. The height of a pole or other object can be found by the method shown in 7, Figure 8. Set up two stakes, A and B, a known distance apart and of a height so that their tops form a straight line with top of pole. When this is done the length of pole C above DistoE as D is to F, hence C -—pT- If the total length of Z) + F is made equal to 27| feet and F = 2| feet, then (7 = 10x£'. Add distance below line D to this to ob- tain total height of pole. The distance between two points, one of which is accessible, can be found by means of the construction shown in J, Figure 8. Similarly to the foregoing, if B is made 10 times C, then A will be made 10 times D. The distance between two inaccessible points may be measured by the methods shown in K, Figure 8. If two stakes, C and D, be set up with reference to A and B, so as to be at right angles to each other and with diagonals pointing to A and B, also forming the same angles, the distance between C and D will be equal to that between A and B. Another method consists in setting up two stakes, E and F, and parallel to them drawing a line or lay- ing a tape line upon the ground and setting up stakes as indicated at S, Measure distances between the various stakes and draw a plan of them to any con- venient scale as indicated. Measure the distance be- tween A and B on this plan. This method does not require that E and F be parallel or centered with reference to A and B. 134 ELECTRICAL TABLES AND DATA Mensuration. — Area of a triangle = base x ^ altitude. Area of a parallelogram = base x altitude. Area of a trapezoid = altitude x ^ the sum of parallel sides. Area of trapezium: divide into two triangles and ' find area of the triangles and add together. Area of circle = diameter^ x 0.7854 = radius^ x 3.1416. •Area of sector of circle = length of arcx-^ the radius. Area of segment of circle = area of sector of equal radius -area of triangle, when the segment is less, and + area of triangle when the segment is greater than the semi-circle. Area of circular ring = diameters of the two circles x difference of diameters x 0.7854. Area of an ellipse = product of the two diameters x 0.7854. Area of a parabola = base x § altitude. Area of regular polygon = sum of its sides x perpen- dicular from its center to one of its sides -> 2. REGULAR POLYGONS Length Radius of Length of side when Area of circum- radius when side Perpen- scribed of dia. of Area when dicular circle circum- No . Inscribed when perpen- when when scribed of circle side dicular side side circle Side iS —1 =1 =1 =1 =1 =1 8 Triangle ..1.299 0.433 3.464 0.289 0.577 1.732 4 Square .. ..1.000 1.000 2.000 0.500 0.707 1.414 5 Pentag. . , . . 0.908 1.720 1.453 0.688 0.851 1.176 6 Hexag. . . ...0.866 2.598 1.155 0.866 1.000 1.000 7 Heptag. ...0.843 3.634 0.963 1.039 1.152 0.868 8 Octag. . , ...0.828 4.828 0.828 1.207 1.307 0.765 9 Nonag. . . ...0.819 6.182 0.728 1.374 1.462 0.684 10 Decag. . ...0.812 7.694 0.650 1.539 1.618 0.618 11 Undecag. ..0.807 9.366 0.587 1.703 1.775 0.563 12 Dodecag. ..0.804 11.192 0.536 1.866 1.932 0.518 ELECTRICAL TABLES AND DATA 135 Surface of cylinder or prism = area of both ends-f length X circumference. Surface of sphere = diameter x circumference. Convex surface of segment of sphere = height of seg- ment x circumference of the sphere of which it is a part. Surface of pyramid or cone = circumference of basex -| of the slant heights area of the base. Surface of frustrum of cone or pyramid = sum of cir- cumference at both ends x | of slant height + area of both ends. Contents of sphere = cube of diameter x 0.5236. Contents of cylinder or prism = area of end x length. Contents of segment of sphere = (height + three times the square of radius of base) x (height x 0.5236). Contents of f mstrum of cone or pyramid : Multiply areas of two ends together and extract square root. Add to this root the two areas x^ altitude. Contents of a wedge = area of base x | altitude. Circumference of circles diameter x 3.1416. Circumference of circle = radius x 6.2832. Circumference of circle = 3.5446 x square root of area of circle. Circumference of circle x 0.159155 = radius. Circumference of circle x 0.31831 = diameter. Circumference of circle x 0.225 = side of inscribed square. Circumference of circle x 0.282 = side of an equal square. Half the circumference of circle x half its diameter = its area. Square of circumference of circle x 0.7958 = area. Diameter of circle x 0.86 = side of inscribed equilateral triangle. Diameter of circle x 0.7071 = side of an inscribed square. Diameter of circle x 0.8862 = side of an equal square. 136 ELECTRICAL TABLES AND DATA Diameter = 1.1283 Vsquare root of area of circle. Length of arc = number of degrees x 0.017453. Degrees in arc whose length equals radius, 57.2958'^. Length of arc of 1° = radius x 0.017453. Meter Capacity. — It is a general rule to install meters of about one-half the capacity of the connected load in residences ; three-fourths this capacity in small stores, offices, etc., and full capacity for elevator motor service and similar installations where exces- sive starting currents are the rule. For more exact determinations, see Demand Factors. The d. c. meter is essentially a shunt motor, and its direction of rotation is independent of the polarity, but if fed from the wrong side, it will run backwards. On a. c. circuits wattmeter readings will not check with volt and ammeter reading; the latter must be multiplied by the power factor. Current transform- ers are used in connection with large capacity a. c. meters. Meter Location. — Meters must always be accessi- ble, never in places that are locked or where meter readers would cause annoyance to occupants. The location selected must be free from moisture and v^ibration. Meters should not be placed on curb walls of streets on which cars operate nor on thin partitions. If meters are placed in cabinets, these should be fire- proofed and no magnetic material should be brought close to the meter. Meters must be set level and level- ing can be accomplished by placing a small weight upon disk, and shifting meter until disk remains at rest in any position. In order that meters may be properly set, meter boards must be provided. The necessary dimensions of such boards vary with the service to be rendered and are given on Figures 9 and 10. These are the requirements in force in the City of Chicago. ELECTRICAL TABLES AND DATA 137 im lef ALTERNATiNG CURRENT WRIGHT DCMANO INDICATOR 22 WATT HOUi|, METER METER OUTLET il^ riTTINO ^ \er x, ♦ — O L-J 34 ^ le- Figure 9. — Meter Fittings and Meter Boards. Figure 9. — Showing Proper Location of Meter Fittings and Size of Meter Boards Eequired for Different Installations. A. C. Residence or Apartment Lighting. 30 sockets or 1500 watts, or under, sketch A. 31 to 48 sockets or 1501 to 2640 watts, sketch B or D. Above 48 sockets or 2640 watts, sketch C or E, 138 ELECTRICAL TABLES AND DATA A. C. Business Lighting. 24 sockets or 1320 watts, or under, sketch A. Above 24 sockets or 1320 watts, sketch C or E. A. C. Power. 5 H. P., and under, single-phase, sketch A. Above 5 H. P., and all three-phase, sketch C, I F >v A ( ^ le ( : i 1 I I :. > f m I— ,^-— J DIRECT CURREKt Figure 10. — Meter Fittings and Meter Boards. ELECTRICAL TABLES AND DATA 139 Figure 10. — Showing Proper Location of Meter Fittings and Size of Meter Boards Required for Different Installations. D. C. Residence or Apartment Lighting. 30 sockets or 1500 watts, or under, sketch F. 31 to 48 sockets or 1501-2640 watts, sketch G or I. Above 48 sockets or 2640 watts, sketch H or J, D. C. Business Lighting. 24 sockets or 1320 watts, or under, sketch F, Above 24 sockets or 1320 watts, sketch E or J. D. C. Power. 1500 watts, or under, sketch F, Above 1500 watts: 2-wire, sketch G or I. 3-wire, sketch H or J, If the meter is located at service entrance, the meas nred energy will exceed the delivered energy by the percentage of loss occurring in the feed wires. If it is located at some distance from this point the service company will stand part or all of this loss. The per cent loss per 100 feet ran with different voltages, wires assumed to be loaded to full capacity, is given in Table XXXXV. TABLE XXXXV B.& S. Amperes 110 V. 220 V. 440 v. 550 V. 1000^ 14 15 4.80 2.40 1.20 0.96 0.53 12 20 5.80 2.90 1.45 1.16 0.64 10 25 4.50 2.25 1.13 0.90 0.50 8 35 4.00 2.00 1.00 0.80 0.44 6 50 3.60 1.80 0.90 0.72 0.40 5 55 3.10 1.55 0.77 0.62 0.34 4 70 3.10 1.55 0.77 0.62 0.34 3 80 2.90 1.45 0.73 0.58 0.32 2 90 2.60 1.30 0.65 0.52 0.29 1 100 2.20 1.10 0.55 0.44 0.24 125 2.20 1.10 0.55 0.44 0.24 00 150 2.10 1.05 0.53 0.42 0.23 000 175 1.90 0.95 0.47 0.38 0.21 0000 225 1.90 0.95 0.47 0.38 0.21 300 000 275 1.90 0.95 0.47 0.38 0.21 140 ELECTRICAL TABLES AND DATA Reactances are not taken into consideration. Meters, Maximum Demand. — The cost of supply- ing electrical energy is properly divided into two parts: One of these consists in charges to be made for meter reading, bookkeeping, and investment of capital ; the other in the cost of energy consumed by the customer. The capital investment depends largely upon the maximum demand of the customer and also upon the time at which this demand occurs. A given trans- former, for instance, will serve perhaps twice as many families in which the ironing is done during the day, as it will where an iron is used at the same time with the lights. In order to obtain compensation for un- necessarily high demands for short times, maximum meters are installed, or a certain fixed charge per month is made against every customer whether cur- rent is used or not. The maximum demand meter may be any arrange- ment which will indicate the highest amperage, or rate of power consumption, during any month or other convenient term. The method of computing bills where these meters are installed is somewhat con- fusing to one who does not make a business of it, and to show the influence of max. meters the following table is presented : This table shows the average rate per K. W. hour brought about by different maximum demands and total K.W. consumption per month. TABLE XXXXVI :. Amp. Total K.W. Hours 25 50 75 100 125 150 200 300 25 11. 11. 11. 10.1 9.3 8.7 7.7 6.4 20 11. 11. 10.4 9.3 8.6 8.0 7.0 6.0 15 11. 11. 9.3 8.4 7.9 6.9 6.2 5.5 10 11. 9.3 8. 7. 6.4 6. 5.5 5. 5 9.3 7. 6. 5.5 5.2 5. 4.7 4.4 ELECTRICAL TABLES AND DATA 141 This table is based on a charge of 11 cents per K. W. hour for the first thirty hours of the maximum used ; 6 cents per K. W. hour for the next thirty hours of the maximum, and 4 cents per hour for the balance. The maximum load is found by multiplying the high- est amperage during the month by the volts. If we have a maximum of 10 amperes our first charge will be 10 X 110x30x0.11 = $3.63; the next will be 10 x 110x30x0.06 = $1.98, and for the remaining K.W. hours we charge 4 cents, which equals $1.60, giving us /r )0.000 100,000. 10,000 jo.ooo.ooo; 1.000 N^ JJ Figure 11. — Meter Dials. a total of $7.21 for the 100 K. W. hours used, or ap- proximately 7 cents per K. W. In the table the change in rates per K. W. is shown as affected by the propor- tion between the maximum demand and the total consumption. Meter Reading. — This is a very simple matter when one has become accustomed to it, but is very confusing to those who have not had it to do. Most meters have five dials arranged somewhat on the order shown in Figure 11. These dials are all connected by gearing and serve merely as counters. The one at the right is driven by the meter mechanism proper, and through it the others are driven in turn. In the 142 ELECTRICAL TABLES AND DATA whole train each one revolves in a direction opposite to that of the one driving it, as indicated by arrows and also by the numbers used. The proportion of the gearing is such that while the pointer on the driving dial makes one complete revolution, the one on the next dial to the left makes only one-tenth of one revolution. From this it follows that any pointer, except the one at the extreme right, can be fully on any number only at the same time that the pointer to the right of it is on 0. This is the principal point to bear in mind in meter reading. In Figure 11 a com- plete revolution of any pointer indicates the use of the number of watt hours found at the top of that dial. Meter reading is best begun by noting the read- ing of the dials from right to left, although persons who have become accustomed to it find no trouble in reading from left to right. Let us begin reading our meter from right to left and note this rule : Put down the indication of the right-hand dial, and unless its pointer is fully on, or has just passed, 0, choose the lowest of the two numbers between which the pointer may be on the next dial, and continue in this manner, putting down each number to the left of the last. Following out this rule we have first 900, next 8, then another 8, after that 1, and for the fifth dial another 1, giving us a total of 1 188 900 watt hours. Striking out 3 figures at the right reduces this to K. W. hours. It must be borne in mind that some meters are arranged to read directly in K.W. hours and some require the use of multipliers to determine the actual watts registered. Meter Testing. — In large cities meter fittings are usually provided for the connection of meters and the best of these are arranged to allow of easy con- nection for meter without interfering with the opera- tion of meters. On all meters the disk is arranged to make a certain number of revolutions per K. W. and ELECTRICAL TABLES AND DATA 143 if this is known the load on the meter at any moment can be determined. The relation between the num- ber of revolutions of the disk and the corresponding dial reading may be expressed by a multiplier which is known as the ^^ constant" of the meter and is usually marked upon the disk or somewhere near it. The value of this constant in any particular instrument depends entirely upon the gearing between the disk and dial. Meter constants may be expressed in the following ways (1) number of watt hours indicated by one revolution of the disk; (2) the number of watt seconds indicated by one revolution of the disk; (3) the speed in R. P. M. at full load or rated load. If K stands for the constant of the meter in either of the meanings given above and R for the number of revolutions made in S seconds, the load passing through the meter during any interval of time will be found by the following formulae : ^ ™ ^^ KB X 3600 1. Watts=- 2. Watts = 8 KR 8 3. Watts = ^ 8 The testing of meters is best done by connecting a standard meter in series with it, and comparing the readings. The test meter may be connected so as to measure the operating current in addition to the load of the one under test. In this case the meter under test will be found ^^slow" if it is arranged to measure that current; if the test meter is connected to avoid this current the other will be found ^'fast." Before making any test the meters should be allowed to be in circuit for about 15 minutes. A stop watch must be used if accurate results are required. On important 144 ELECTRICAL TABLES AND DATA installations it is advisable to test meters at least twice per year. In some cases two meters are installed in parallel; such meters are a constant check upon one another. Motion Pictures. — Photography. — Cooper Hewitt lamps are used almost exclusively for this purpose, and about 50,000 c. p. are required to do good work. Lamps must be arranged adjustable to suit whim of producer. Exhibition, — The exhibition of motion pictures may be carried on with one arc lamp, but it should have an adjustable rheostat or compensator. Many films are very dark, and require extra strong lighting. Good exhibitions require at least two machines and a corresponding number of arc lamps, one to be ready when the other runs out. Stereopticon lamps and spot lights must also often be provided for. It is customary to require at least a No. 6 wire for each motion picture arc, as they often draw as high as 50 amperes. There is conisiderable fire and life hazard connected with the exhibition of motion pictures, and each municipality usually has some rules governing the handling of films and apparatus, which should be consulted. Motors. — Alternating Current. — There are four general types of alternating current motors ; viz., in- duction, series, repulsion and synchronous motors. Induction Motors. — The stationary part of this motor is termed the ^^stator," the moving part the *' rotor.'' That part of the winding which receives current from the supply line is known as the ^^ pri- mary," the other as the ^ ^ secondary. ' ' From a me- chanical point of view this is the simplest and best of all motors, and it is also .the most used type. Poly- phase induction motors are self-starting, but single- phase motors require some special starting device. These motors are essentially constant speed motors, ELECTRICAL TABLES AND DATA 145 but their operation depends upon the ^^slip," which requires a slight reduction of speed with increasing load. This motor has a poor starting torque and often requires four or five times the running current to Btart it. The rotor of the common induction motor is not provided with any winding, but for special purposes, such as printing presses, cranes, etc., wound rotors are often used. Resistances can be used with such motors and the speed also thus controlled. The speed will, however, be variable with the load and the motor will require watching. With a wound armature the torque is the same for all speeds. Auto-starters, or compensators, are used to start the larger motors, but the smaller ones may be connected directly to the circuit. A throw over switch fused on one side only, and so connected that the starting current need not pass through the fuses, is generally used for medium size motors, up to 5 H. P. The synchronous speed of an induction motor can be found by the formula: jj p j^ 60 X frequency number of pairs of poles Below is a tabulation of all possible speeds of syn- chronism of 60 and 25 cycle motors with the numbers of poles given : Number Poles 60 Cycles 25 Cycles 2 .- 3600 1500 4 1800 750 6 1200 . 500 8 900 375 12 600 250 16 . 450 1871/2 24 300 125 Actual speeds, on account of *^slip," are from 3 to 10 per cent lower. 146 ELECTRICAL TABLES AND DATA Repulsion Motor. — The field winding of this motor is similar to that of a single-phase induction motor. There is no connection whatever between it and the armature, and the latter is always wound and pro- vided with a commutator and short-circuiting brushes. The currents induced in the armature always tend to oppose those in the field, hence the name, repulsion motor. The speed of this motor is variable with the load and may be above synchronism, but the operation at this speed is not satisfactory. In some types the direction of rotation, speed, regulation, and stopping and starting may all be accomplished by simply shift- ing the brushes. Some single-phase motors are ar- ranged to start as induction repulsion motors. When the motor is up to speed, the brushes are automatically thrown off, and the motor continues to run as a sim- ple induction motor. The starting current of this type of motor is from two to three times the full load current and the starting torque is good. Reversing Direction of Rotation, — The synchronous motor is not self-starting, and will run in whichever direction it is started. It is usually started by a small induction motor, and to reverse its direction of rota- tion the connections of the latter must be changed. Polyphase synchronous motors may be started by turn- ing on the a. c. current while the d. c. fields are open. In such a case the direction of rotation can be changed by reversing two-phase wires in the same manner that induction motors are reversed. To reverse the direc- tion of rotation of a two-phase motor, the two wires of one phase must be changed. If there are only three wires the connections must be changed so that the relative direction of current through one of the phases is reversed. Three-phase induction motors are reversed by changing the connections of any two-phase wires. The direction of rotation of a single-phase induction ELECTRICAL TABLES AND DATA 147 motor is indeterminate unless it is provided with some special starting apparatus. Some may be started by hand and will run in whichever direction they are started; others require that the connections of the starting coils (not starting box) be reversed. The alternating current series motor may be reversed in the same manner as d. c. motors. The repulsion motor may be reversed by either shifting the brushes or re- versing the field connections. Series Motor. — This type of alternating current motor has about the same general characteristic as the direct current series motor. Except in small sizes it cannot be used without constant attendance. The field magnets are always laminated and the fields must be obtained with as few turns of winding as possible, as the self-induction increases as the square of the num- ber of turns of wire. Series motors may be had for use either on alternating or direct current circuits. The armature is relatively more powerful than the fields, and the field distortion is therefore greater than in direct current series motors. To regulate this, many of the motors are provided with extra coils, some of which are in series with the fields and arma- tures, and others arranged to receive current only by induction. Synchronous Motors. — These motors may be either single of polyphase. They must run at an absolutely constant speed governed by that of the generator. This speed may be found by the formula R P M = 60 X frequency number of pairs of poles All synchronous motors require direct current for field excitation. They are not self -starting in the true sense of the word, and must be brought up to nearly the proper speed before current is finally turned on. 148 J3LECTRICAL TABLES AND DATA Synchronous motors are not much used, but where they are used they may be made to exert a beneficial effect upon the power factor of the line. They cannot be made to start under load, and if overloaded will come to a stop. ''Hunting'' or ''phase swinging" is one of the chief troubles encountered with synchronous motors. The two chief objections to synchronous mo- tors are : they require direct current for field excita- tion, and skilled attendance for starting. Starting of a, c. Motors. — Most synchronous motors are started by small induction motors and gradually brought up to the speed of synchronism. A synchro- scope is usually provided to determine when the proper moment to throw in switch has arrived. Polyphase synchronous motors may be made self- starting by opening the field circuit and allowing the line currents to pass through the armature. The arma- ture then creates its own fields, and begins to revolve on the principle of an induction motor. The speed gradually increases, and when it reaches about that of synchronism, the d. c. field circuit is closed. Where motors are started in this way, an ammeter should be in the circuit and the current observed. If the current grows less after the field circuit is closed, the motor is working properly; if otherwise, the switch must be opened again, and a new trial made. This method of starting should not be used unless it is known that the motor is arranged for it. Very high potentials may be induced and break down the insulation. The starting current of induction motors thrown directly onto the line is from three to ten times the normal running current, and to keep it from becom- ing excessive, compensators or auto-transformers are usually inserted in the line wires. This provides low voltage for starting. There are usually either three or four taps in the connections of an auto-transformer. When only three are provided it is customary to ELECTRICAL TABLES AND DATA 149 arrange them to give 50, 65, and 80 per cent of the line voltage. Four taps are used only with the largest motors and in such a case the taps are ar- ranged for about 40, 58, 70, and 80 per cent of the line voltage. Always make the connection for the lowest voltage at which the motor can be started. Modern starters are equipped with no-voltage and overload releases. Three phase motors may be connected either in star or delta. If the latter is the permanent connec- tion the switching arrangement may be such as to put the motor in star for starting, the switch being thrown over when the motor has attained some speed. In cases where the three transformers are near the motor the transformer connections may be switched in the same way, using the star connection to start the motor and throwing over to delta when it has gained some in speed. Medium sized motors are often connected direct to the line without any means of reducing the voltage. In such cases a throw-over switch unfused on one side, but properly fused on the other, is provided. The switch is closed on the unfused side until the motor has attained its speed and is then thrown over to bring it under the protection of the fuses. With this arrangement the fuses at motor may be provided to fit the running current while those at the beginning of supply line must be large enough to stand the starting current which is often very excessive. Speed Control. — The speed of a synchronous motor is unchangeable and governed entirely by the fre- quency and number of poles. The speed of an induc- tion motor varies directly as the frequency, and if we have means of changing this, we may obtain any speed desired. The same formula for speed which shows the above, also shows that the speed can be varied by varying the 150 ELECTRICAL TABLES AND DATA number of poles. This is sometimes accomplished by switching devices which combine poles so as to reduce their number by one-half. This method is not much used. The speed can also be altered by changing the volt- age applied to the motor. A fourth method of speed control consists in providing a wound armature in place of the ordinary squirrel cage armature and placing resistances in the armature windings. Some- times these resistances are located inside of the arma- ture spider, at other times the leads are brought out, and the resistances mounted outside of the machine. The loss in speed of an induction motor with increas- ing load is proportional to the resistance in the rotor circuit, and if carried too far will cause the motor to stop. A reduction in speed of from 15 to 20 per cent will cause the ordinary squirrel cage motor to stop, but with a wound rotor the variation may be much greater. The speed control of a.c. motors is never very satisfactory, but where it must be, the wound rotor method is the most practical. Variable Speed Arrangements of Motors, — A well known method of obtaining various speeds is that known as the ^^ tandem," ^^ cascade" or concatenation method of coupling two motors together to obtain variable speed. The first motor is fed direct from the line through suitable starters and the currents in the second motor are produced in the wound rotor of the first. The rotor of the second motor is also wound and equipped with controlling resistances. Four speeds are obtainable. First, the natural speed of motor 1 running alone ; second, that of motor 2 run- ning alone; third, the speed of the two motors com- bined when both tend to revolve in the same direction, and fourth, the speed of the two motors combined when one tends to run in the opposite direction. Connected in direct concatenation (both motors ELECTRICAL TABLES AND DATA 151 tending to run in the same direction) the speed can be found by the formula jj p j^ ^ 60 X frequency number of pairs of poles on both machines When one of the rotors is connected to oppose the other the speed is 60 X frequency R.P.M.= difference in number of poles in the two machines If the number of poles on the two machines is the same, they will run at half speed when connected in direct concatenation. This method of control is not of much use with fre- quencies above 25 cycles on account of a low power factor. With this method a wound rotor is also always employed. Motor Testing. — Motors may be tested to determine their capacity in H. P. or K. W. ; their insulation resistance; their heating; speed regulation, and efficiency. The H. P. capacity of a motor, other things being equal, depends entirely upon the current which the armature will stand, and this, assuming proper me- chanical construction, depends entirely upon the heat- ing. The heat generated is proportional to the square of the current, but the temperature of the wire is influenced considerably by the ventilation. The tem- perature also depends upon the length of time the current is used, and therefore the actual H. P. which any motor may develop depends very much upon whether it is to be used continuously or intermittently. Every motor thus has two ratings. The continuous rating of a motor is at present usually taken as the output in H. P., or K. W. which it can deliver continuously, with a maximum rise in 152 ELECTRICAL TABLES AND DATA temperature above the surrounding air at 25° C. (77° F.) of not more than 40° C. (104° F.) on field and armature, and not more than 55? C. (131° F.) on commutator. The intermittent rating differs from this in that it allows a temperature rise of 65° C. on field and armature and 90° on the eonmiutator to be attained in an hour's run. Motors designed to fulfill these requirements can be given a still higher over- load rating to be used in connection with apparatus which is in operation for only a few minutes at a time. The test for heating is made by a thermometer placed upon the parts and covered with waste to shut out the cooling influence of the air. The places of highest temperature should be selected. The H. P. output qf a motor may be found by the well-known prony brake test. To make the test, adjust the screws until the motor speed is reduced sufficiently to allow the desired current through the armature. The H. P. of the motor can then be found by the formula : sxlxp H.P. 33,000 where 5 = speed of pulley; ? = length of lever from center of pulley to scale attachment, and p = the pull on scales in pounds. The H. P. delivered to the motor is equal to the product of volts and amperes, and dividing the H. P. developed by the motor by that delivered to it, will give us the efficiency. The prony brake test cannot well be continued long enough to test heating of motor, and some other form of load must be placed upon it. The speed regulation of a motor may be found by operating the motor at various loads from zero to maximum, and noting the changes in speed. In testing alternating current motors we must mul- tiply the product of volts and amperes by the power ELECTRICAL TABLES AND DATA 153 factor, or use a wattmeter instead of volt and am- meters. The starting torque of a motor can be found in the same way as we found the H. P., but we must adjust the screws until the armature comes to a standstill. Motor Troubles. — // the fuses How at starting, contacts may be loose or dirty, or the fuses are of insufficient capacity. The motor may be overloaded or out of order in some way. The brushes may not be properly set. The rheostat may be manipulated too fast. It is usual to allow about 30 seconds to pass during the starting of the ordinary motor. The sup- ply voltage may be higher than the motor is intended for, or the rheostat may be too large, and not intro- duce sufficient resistance. The motor may be im- properly connected. The field circuit may be open. This would prevent the armature from generating the necessary counter e. m. f . There may be a short cir- cuit in the armature, or in the fields. If a short cir- cuit cuts out part of the field, it will indicate itself by undue heating and prevent the armature from pick- ing up. If the frequency is too low, there will be an excessive current; if it is too high, there will be insufficient current. If motor fails to start and the fuses do not blow, there may be a dead line ; test for current. In the case of a series motor there may be an open circuit in either armature or fields ; this can be in the armature only if a shunt motor. Insufficient tension or poor contacts of brushes also often prevent the motor from starting. In an alternating current motor the frequency may be too high. One or more phases may be open. Fields Ennning Hot. — The voltage at which ma- chine operates may be higher than that for which it was intended. Fields may be in parallel where they were meant to be in series. A part of the field may 154 ELECTRICAL TABLES AND DATA be short circuited, or cut out by grounding. In such a case one of the fields will be cool while the other runs abnormally hot. Heating of Armature. — This may be caused by an overload; the heating increases as the square of the current used. There may be a short-circuited arma- ture coil ; if so, it will speedily show itself by burning out. A strong odor of heated shellac will probably be the first indication. Poor ventilation is often the cause ; many motors are meant to operate either open or enclosed, and the enclosed capacity is always much less than the open. Shaft of Bearings Running Hot. — This may result from improper oiling, boxes too tight, shaft bent, belts too tight, rough bearings, or the armature may not be properly centered, and thus press too hard on one of the end collars. Shocks Obtained from Machine. — These may be due to static electricity or to grounding of some live part of the motor or the frame. The troubles from static electricity can be overcome by grounding the frame or fitting the belting with arresters. Sparking of Brushes. — This may be due to wrong position of the brushes. With increasing load, the brushes of motors must be shifted against the direc- tion of rotation, and, vice versa, with generators the opposite rule holds. The best motors, however, re- quire very little shifting of brushes. Rough commu- tator, ragged brushes, or dirty condition of either commutator or brushes are frequent cause of spark- ing. Insufficient tension is also a frequent cause of sparking. If the brush is too narrow it will leave one segment before making the proper connection with the next; if too wide, it will short circuit too many and thus cause sparking. Incorrect spacing of brushes will cause sparking. Compound wound motors, or those operating with light field, are subject to much ELECTRICAL TABLES AND DATA 155 sparking. To prevent this, inter-poles are often pro- vided. Test direction of current in series winding by starting motor with shunt field open. An open circuit in an armature coil will cause severe sparking, which will occur only at a certain place on commutator. Motors. — Direct Current, — There are three types 9f d. c. motors; viz., series, shunt, and compound. Tha Series Motor. — Small series motors, such as fan motors, can be made to work successfully under any conditions. Large series motors with a variable load require constant attendance. Lightening the load will allow the motor to speed up inordinately and be- come dangerous. Such motors are very useful where heavy loads are to be started, as the torque is the- oretically proportional to the square of the current as long as the fields are at a low point of saturation. And in all cases when the fields are not fuUv satu- rated, the torque increases faster than the current. The maximum torque exists at low speed and is inde- pendent of the voltage, depending entirely upon the current. Shimt Motors. — The shunt motor is the most used of all direct current motors, and if properly constructed operates at a fairly uniform speed for all loads within its capacity. Once started it requires no attention. It is suitable for all classes of work, except such as street car service where the current is often suddenly interrupted and as suddenly thrown on again by accidents to the trolley. Its starting torque is not as good as that of the series motor, but it is fair. The field strength varies with the voltage, but as long as this is maintained it is independent of the voltage at armature terminals. The Compound Motor. — This is a combination of shunt and series motor and has both windings. If the current in the compound winding is in the same direction as that in the shunt, the increased current 156 ELECTRICAL TABLES AND DATA strength necessary to handle a heavy load will strengthen the fields and slow the motor down. Such a motor is known as ^ * cumulative * ^ and has a very- good starting torque. If the compound winding is in the opposite direction, an increased current will lighten the fields and cause the motor to speed up, but will give it a poor starting torque. The compound winding may be so adjusted that the motor will run at a very even speed for all loads within its capacity. A motor so connected is known as ^ ' differential. " Owing to the fact that part of the field magnetization is destroyed by the series winding, the efficiency is somewhat low. Commutating or inter-poles are often inserted in d. c. motors. Such poles are provided to overcome the armature reaction and produce sparkless commutation. Motors so equipped can carry greater overloads. They are very useful where a good start- ing torque is required. Motors are further divided into open and enclosed types. The capacity of a totally enclosed motor is only about 60 per cent of that of the open motor. The capacity in H. P. depends upon whether the motor is to be used continuously or intermittently, and is governed by the heating limita- tion, the heat generated being proportional to P. The current required by any motor can be found by the formula ^ , H. P. delivered X 746 Current = ^ . v- emciency x voltage The efficiency of a motor can be found by dividing the input by the output. All motors are delivering their maximum power when the speed is such that the counter e. m. f . of the motor is one-half of that deliv- ered at the terminals. Reversing Direction of Rotation. — All d. c. motors may be reversed by changing the connections of either field or armature so that current passes through one ELECTRICAL TABLES AND DATA 157 of them in the opposite direction. If the current in both is reversed the direction of rotation will remain as before. Most multi-polar motors may be reversed by shifting the brushes sufficiently ; this is equivalent to reversing armature leads. Speed Control. — All d. c. motors tend to run at a speed which enables the armature to generate a counter e. m. f . equal to that of the supply. The speed can be varied by strengthening the field, which re- duces it, or weakening the field to increase it. The commonest method of accomplishing speed control is by means of resistance cut into the armature circuit. This method, however, causes a speed variable with the load, the fall in pressure at the motor terminals being equal to IE, Adjusting the field strength to regulate the speed causes much sparking at the brushes. This can be obviated to a large extent by the use of commutating or inter-poles. The armature current passes around these and tends to keep the neutral point at a certain place, thus preventing sparking. Speed control is further effected by switch- ing arrangements which enable one to connect several motors either in series or parallel; the parallel con- nection giving the higher speed and the series the lower. Such systems are used mostly in connection with d. c. street railway service. Starting of d.c. Motors, — All d. c. motors, except the small ones which are wound with a high resistance in armature circuit, require some extra resistance to keep the current down until the armature has attained sufficient speed to generate the counter e. m. f . which finally limits the current. This resistance must never be in the field circuit of a shunt motor, but always in the armature circuit. In the differential motor, the series winding should be cut out of circuit until the motor is started, otherwise the excessive starting cur- rent will weaken the field too much. In the cumu- 158 ELECTRICAL TABLES AND DATA lative type of motor, the series field adds to the start- ing torque. A motor may be tested as to whether it is cumulative or differential by starting it with the shunt field open. If cumulative it will run in the same direction as with the shunt field closed. The starting resistances of shunt motors are usually wound with fine wire which will overheat and burn out if left in circuit too long. Not more than thirty seconds should be consumed in manipulating the handle. In some cases, however, special apparatus is provided which can carry the current indefinitely. If motor does not start at once, open switch and look for the cause of trouble. Power Required to Operate Machinery. — When the H. P. needed to operate a given machine is not known it may in some cases be calculjated from the formula : _r Px27rxrxn xi. x^. = 12x33,000x6 where P =pull in pounds which must be applied at periphery of pulley to move it ; r = radius of pulley in inches ; n = number of revolution^ per minute ; e = the efficiency of a direct current motor or the product of efficiency and power factor in an alternating current motor or circuit. If the machinery to be started is equipped with heavy flywheels, or possesses considerable inertia of any kind, the size of the motor needed is governed by the starting requirements which depend largely upon the rate of acceleration demanded. In connection with other machinery, such as ventilating fans for instance, the power required increases faster than the speed and can be measured only when the device is operating at full speed. For such motors the above formula cannot be used and it is necessary to obtain data from manufacturers or other users. ELECTRICAL TABLES AND DATA 159 oooooooooo oooooooooo oooooooooo rfi^tSOQOOltOO^C/lba OOOOOOOOOO OiCJtOlrf^C^C^tOI— 'I— kO OiWO^tOOOOTO^CO oooooooooo 00-<105 0lOTh^WI}OI— kO 00i4^O05OrfikOrfi'OCri MOOOOOOOOO OOQO^OiCn^^C/ODOl— k OiOlrf^rf^OOCOtOh-AI— kO Orf^Q0l^00iO>^f!^CX)I^^05 MMI-iOOOOOOO t^Ol-^ooo^aiC^co^D^-^ -<|rfxMQOGiCOOOOC;ibO ^-i I-a M O O O O O O ►;i^cok-iooo--toh-k OMtOCOrfi'Ciai-vlQO^ l__i|— i|_i|_i|_ioOOOO GiUlCOl— lOGOOiOlCOl— ' COt005^b04i^CX50rfi^--'OOi^;^tOOOOCil4^DO tOOOQO^Oi^4^COtOl— k OQoai^^^^oQooirfs-^^ ^^t^0l-^^-lMI-^OOOO OaO^OiCOI-iOCirfi'tO OOOO^OOCOOsCOOOiCO t0O05l-A«©0lWC0^C0 bStOtOMh-iMMOOO aitoo-«qa?iNOo^(L^to 4^QO00^atO-qi— 'Oil— 'C7» oail^^Qo^ii>'OCi^^oo4^ ^^ CO Oi QO o ^^ o c a p-H^ o o w et- . tr (D h^ OS -« p :^. »-< M ^ ^i^ ft> as c w p ri' P3 e h::* Oj P-i h^ M* ^ H •-1 > o P3 ^ W H^s &. c ^ ^ B ^ o n ^ 3'^ d :3 • . 3 W M :ii <1 3 a 0) m ^* 3- O 3^ a' 3 3 3 •-< 160 ELECTRICAL TABLES AND DATA In the table below the values of — ; — .^J^,^^ — 12 X o3,000 X e {e being assumed as of about .75) are given wherever the horizontal line pertaining to speed crosses with a vertical line pertaining to radius of pulley. Care must be exercised in determining P; it must not be more than just enough to cause motion, and at best can be only an approximation. P may be deter- mined by a spring balance, or by a weight and lever. If the latter is used and attached to rim of pulley, multiply weight by distance from center of pulley and divide by radius of pulley. Group vs. Individual Drive. — The total H. P. ca- pacity of motors for individual drive must be equal to the H. P. demands of all the machinery. The H. P. capacity for group drive may be con- siderably less, because not all of the driven machinery is used at the same time. How much of saving there is in any given case depends upon circumstances. Very often the shafting necessary with group drtve requires as much additional H. P. capacity as is saved by the other consideration above. The total H. P. required for group drive can be found by the formula: where h. p. is the horsepower demanded by the total machinery if run all at the same time; / is the load factor; s the H. P. required to drive shafting, and e the efficiency of the motor. The large motors used for group drive are more efficient at full load than the smaller ones, but a group drive motor is seldom run at full load. If it is properly chosen it will be over- loaded part of the time and inevitably be running with no other load than the shafting part of the time. ELECTRICAL TABLES AND DATA 161 The nearer it can be kept running with full load the more efficient it will be. The total H. P. required for individual drive is equal to the sum of the H. P. of all the machines divided by the efficiency. The full load efficiency of the small motors is lower, but there is never any idle machinery or shafting to be moved, and if properly selected the motors may operate at full load efficiency most of the time. In most cases individual drive is the most economical where a per- manent installation is considered, but the cost of installation is generally somewhat higher. In addi- tion to the above advantages, which can be figured out in dollars and cents, the following considerations should be of interest and duly noted: With indi- vidual drive the fire and life hazard are somewhat increased, but the shafting and belting accidents are greatly decreased. In connection with low voltage (110 or 220) the life hazard is small, and the advan- tage is on the side of the individual drive. With high voltage group drive is probably safer. With individual drive the facilities for speed regulation are better and motor troubles cannot throw a whole shop out of order. There is no shafting to cause dirt and noise and interfere with illumination, and there is less vibration in the workroom. Individual drive, however, requires somewhat more care and atten- tion. Where we have the choice of motors of different efficiencies we can afford to expend for the motor of the better efficiency a sum of money upon which the annual interest charge mil be equal to the saving in the cost of energy effected by the better motor. We must, how^ever, select the rate of interest so as to cover all depreciation, and if we assume that the motor will be a dead loss at the end of the time it is to be used, we shall obtain the following rates of interest, using a 6 per cent basis: 162 ELECTRICAL. TABLES AND DATA . Motor to be used 1 year only, 106 per cent 2 years, 56 3 years, 40 4 years, 32 5 years, 27 6 years, 24 7 years, 2U 8 years, 20*^ 9 years, 18^ For longer periods of time the interest rate decreases slowly and the above will cover all ordinary cases. According to the above principles we can determine the amount of money we may economically invest in order to substitute a motor of higher efficiency for another with lower efficiency by the formula, per cent interest where C = capital to be invested; K. W. = the number of watts used; r = the rate per K. W. hour; h = the number of hours K. W. is used per day; d = the num- ber of days per year; 6 = the difference in efficiency of the two motors; per cent interest = the rate of interest governed by the number of years motor is to remain in use as given above. In the following table it is assumed that the motor will be used 300 days per year, and on this basis the numbers given represent the capital which could prof- itably be invested with K. W., r^ and h equal to unity, and e and the rate of interest as given in the table. To use the table for determining how much can prof- itably be invested to substitute a more efficient motor in place of a poorer one, it is but necessary to find the product of K.W. xrx/i^ and with this multiply the number found w^here the horizontal line pertaining to the difference in efficiency in favor of the better motor ELECTRICAL TABLES AND DATA 163 to M »-» i-i t-k i-» hri ^ i ! * . ..... o i M i i ; i : i i MM;' COCOtOCTiCD CO^^C75oo I— 'COt4i>'CiQOa; Orf^CX)b005 O^^^t-iQo OJ bO ^ Gi OO ^' to o o 00 -q 05 or tf^ hp^ CO CO to to h-l 1— I o OX^ ^ ^ 05 OI o\ f^ CO 00 to -q to Oi 1— I Oi h- » OI B CD o Hi b3 ►^ ^ o CO Oi to 00 OI 1— I 00 ^pi^ o • 03 bo 1-^ 1—1 CO 1— » CO bo *-o CD ^ b\ CO h-l CO bo ^ bi Oi rf^ CO to 1— ' p^- < ^^ CO -^ o\ CO h— I CO 00 ^ Oi ox hP^ CO to f—k to^ o t9 00 Oi ^^ to H-i CO 00 *q Oi ox ^^ CO to 1— I ^ :5 t— 1 CO 00 ^ Oi ox rfi^ CO to 1— t CO (D 3 M bo to to M M l-i M 1— k p Oi M* Ul to o ^ ax to 1— I o 00 ^ Oi en CO to h- 1 B o Ol o ZJl o Ol to o ^ on to o •^1 ox to to^ o o o o o o Ol o OI o ox o ox o ox ^^ ^ M« o o o o o o o CQ 3 CD to to to 1— I ^-t 1— I h- i 1— I - 4^ to h-* CO bo bi t4^ CO h- 1 o 00 OJ to t\0 o ^4^ oo to Oi o rf^ 00 LO Oi o o o o o o o o o o o o o o o o o o o o o 104 ELECTRICAL TABLES AND DATA fcH oo O O O O O >^ri CM Tt^ CD 00 O r^'^ lo oq T-H Tt^ oo CO CO '«^* TjH T^* o o o o o CM rJH CD QO O t-H Tin l^^ O TjH id id id CD* CD o o o o o CM TtH CD GO O l>. O CO CD O CD t-' t-' t-* OO* ;>,CM 00 ooooo ooooo ooooo ocDooo ooooo ooooo CO CD O CM lO 00 i-H TJH t>. O CO CD Oi CM IQ CO* CO* CO ^* '^* rjH* id id id CD* cd cd* cd t^ t^ fH ,—1 1-H o Ci OO OO >>CM t- lO cq o OO o CO CD Oi r-\ t^ CO* CO* CO* CO* ^ CO ^ Ttl o o o o O ;>iCM lO o L-O o lO CD t- o CM lO t- rt CM CO* CO* CO* CO* • l-H -M " fl O M o ?H t^ ^ ^ OO OO CO 1 ;>.CM rt^ CD OO o CO 1 lO rH o OO rH CO M CM* CM* cq* CO* CO* M ^ X ;_, CQ 1— 1 OO CD tH 1—1 rN P-.f'' CD TtH CO CM tH ^vy| O CM '^ CD OO tJH x CM CM* CM* CM* (M* w pq S*o O O o O O CO »o o LO o lO ; O CO iq rjH th id id id ooooo O >0 O) LO o O CM lO t>. O T^* t:1H* ^* TjH* id cq '^ CD CM rH lO t^ C5 CM r^H lO l>; Ci C] T^^ CO* CO CO rt^ -rJS* 00 00 CM O 00 Oi OO t^ CD TfH Oi r-\^ CO iq t>- CM* CO* CO* CO* CO* OOOOO O LO O lO O tH iq t>; 00 O CM* CM* CM* CM* CO lO CM as CD TtH tH Cq CM CO rtl b^ oq C5 O rH tH rH* rA CM CM* CD CM lO CM 00 ''^ CM O ; O^ id CD CD* CD CD OOOOO lO O lO O LO CM iq b-; O CM id >d id cJ CD CM 00 iH 00 LO CD OO tH CM lO CD oq r-\^ CO iq rfH* TjH id id LO CD CM O CD lO CO CM Cq Ci OO Ci r-\^ CO rtH CD CO "^ ^ T^l tJH OOOOO L^) O >0 O lO tH CO rfH CD l>; CO CO* CO CO CO* tH OO CD CM O LO LO CD t- GO CM CO Tt^ iq CO CM* CM* CM* CM* CM* OO LO Cq 00 LO OO rtH O lO rH T— I CM CO CO Tt< ^ CM tH CD OO O K-l CM CM CM CM CO <© O «3 03 .2 S3 M S CO .^ (T) ^ fl ^ n O o C fe| CO fl (D C -4-S CO 'rH cn ^ O O ^ O) "^ O) CH n; '^ — M O r- •^ oqEh O _. O) Jh ?^^ «^ ^ Sfi O) DQ CM ^ CD OO O CO CO CO CO TfH CM Ttl CD OO O Tf rJH rfl Tfl IQ s s5 .S c M* ^ O >, J. £ ^ S 03 fH • O 03 ^ ^ O Qj cd ^ Ph X? ;-. "^ 02 3 .pH 03 rj ELECTRICAL TABLES AND DATA 165 crosses with the rate of interest applicable to the problem. The result will be the sum in dollars and cents which can with profit be expended to procure the better motor. Rule of Table. — Find the difference in efficiency between the motors considered and the number of years the motor is to be used. Select the number found in the longitudinal line where the correspond- ing efficiency (given in vertical column at the left) crosses with the proper rate of interest (given at top) ; multiply this number by the K. W. hours per day, and by the rate per K. W. The result will give the amount of money which may be invested to procure the motor of higher efficiency. If this sum will make up the difference in cost, the better motor should be provided. Nails. — Use cut nails for driving into brickwork. TABLE XXXXIX Dimensions of Nails Common Nails Finishing Nails Diam. Approx. Diam. Approx. Nearest in number Nearest in number Size Length B. &S. inches per lb. B. &S. inches per lb. • 2d 1 13 %28 876 14 %28 1351 3d 1% 12 %4 568 13 %28 807 4d iy2 10 %4 316 13 %28 584 5d 1% 10 764 271 13 %28 500 6d 2 9 %4 181 11 %2 309 7d 2% 9 %4 161 11 %2 238 8d 2V2 8 1%28 106 10 %^ 189 9d 2% 8 1%28 96 10 %4 172 lOd 3 7 1%28 69 9 %4 121 12d 3% 6 1%28 63 9 %4 113 16d 3y2 6 . %2 49 8 1%28 90 20d 4 4 25/128 31 8 1%28 62 30d 4y2 4 2%28 24 40d 5 3 2%28 18 50d 5y2 2 ^l/i28 14 60d 6 2 33/ 2o 11 166 ELECTRICAL TABLES AND DATA National Electrical Code {Abbreviated N,E,'C.), — The N. E. C. contains the recommendations of the National Fire Protection Association in reference to electrical installations. It is revised every two years, and its recommendations are generally accepted as standard throughout the United States. Most mu- nicipalities pattern their regulations after this code, but introduce a few variations which local conditions seem to warrant. The National Board of Fire Under- writers issue ' ' The List of Electrical Fittings. ' ' This contains a list of appliances which have been tested and are considered safe. Those engaged in electrical construction work are advised to keep in touch with the N. E. C, the List of Electrical Fittings, and local requirements. Nernst Lamp. — This lamp is not as much, used as formerly. It has a high intrinsic brilliancy ; requires no reflectors; should be hung high. It requires con- siderable attention to keep in repair and cannot be used in theatres or similar places where quick changes are neceSsar^T-. Neutral Wire. — This term describes one of the three wires used in connection with the three-wire system. Normally this wire carries no current and is, therefore, often smaller than either of the outside » wires. In case an outside fuse blow^s, it may, however, be called upon to carry the full load current. It is always fused higher than the outside wires, and often is not fused at all. Blowing of the neutral fuse may do much damage. Ordinarily this wire is also grounded. In a star connected polyphase system, the point at which all of the wires connect is also spoken of as neutral. The fourth Avire in a three-phase system may also be so termed. Non-inductive Load. — A non-inductive load is dis- tinguished from an iiaductive load by the fact that ELECTKICAL TABLES AND DATA 167 the current is in phase with the voltage. Circuits supplying only incandescent lamps are very nearly non-inductive; arc lamps and motors make up a strongly inductive load. Office Lighting". — Desk lights are very common, but they are also a nuisance. They cause constant annoyance, and increase the fire hazard. Inverted lighting is very favorably received in many offices and deserves extended trials. The newer high efficiency lamps have done much to make it econom- ical. Where all employes are constantly at their desks there can be no difference of opinion regarding the superiority of a good general illumination in every respect. Local illumination can appear advisable only in such places where most of the desks are occupied for a short time per day only. Avoid large spreading chandeliers carrying many lamps. These often cause a multiplicity of shadows. If clusters are used, lamps should be close together. Do not run wires in any but the main walls or parti- tions; use three-fourths inch conduit so as to have plenty of capacity for changes which are always tak- ing place. Arrange lighting to harmonize with win- dows, so that furniture placed correctly for daylight will also fit the artificial illumination. Ohm. — The international ohm has been legalized in this country and is defined as the resistance which a column of mercury of a uniform cross section, at the temperature of melting ice, and 106.3 centimeters in length, and of a mass of 14.4521 grams, offers to an unvarying electric current. Ohms Law.— 7=^; IxR = E; R=-r Ohmic Loss or Drop. — The loss in e. m. f . or drop in p. d. caused by the resistance aa distiilguished from that caused by reactance. 168 ELECTRICAL TABLES AND DATA Overhead Construction. — The timbers most in use for poles are : Michigan cedar, Western cedar, chest- nut, pine and cypress. Of these the cedars and chestnut are the most used. The cedars are easier to climb and the taper is greater so that the tops of cedar poles are smaller in proportion to the butts than chestnut poles. On account of the variable nature of the wood and the fact that they soon begin to rot at the ground line, which is the point of greatest strain, the strength of poles must be calculated with a large factor of safety. In the tables following the breaking strain of the wood has been taken as 7,000 pounds per square inch and a factor of safety of 10 has been used. Poles are usually designated by their length in feet and diameter at top in inches; thus a pole 40 feet long and 8 inches in diameter at top is spoken of as a 40-8 pole. The standard or most used pole is 35 feet long and has a 7-inch top. In swampy places poles are often set in concrete. Poles should be set with the sweep in the line so that the wires may be straight. Use no iron poles where lines must be worked on while alive. Set pole steps 32 inches apart and stagger them. In cities place poles on lot lines. Avoid placing poles near lamp posts, hydrants or catch basins. Give comer poles a slight rake outward. Use the heaviest poles for transformers. Special attention should be given to tamping at bottom and top of holes, and the earth should be piled up a little around pole to keep water from running in. Keep one side of pole free for climbing. Double arm all poles subject to unusual strains. The lowest cross arm should be at least 18 feet above ground and 22 feet above railway tracks. Allow at least 2 feet between cross arms ; more if pos- sible. Insulate guy wires. Make cross arms of uni- form length. ELECTRICAL TABLES AND DATA 169 Standard cross arms are rounded on top ; 3^ inches wide by 4:^ inches high ; allow 24 inches between pole pins, and at least 12 inches between other pins ; this distance varies with number of pins, length of span and voltage. Junction arms usually have a wider spacing between inside pins. The high tension wires should be carried on the top arms; secondary wires are usually run below them, and the lowest arms are left for signal wires if any are to be run on same line. There should be a space of about five feet between the signal and the lighting and power wires. The lowest voltage wires are usually run next to poles; circuit wires should be kept together, and neutral of three- wire system should be run in center. The fourth wire of a three-phase system is also carried next to pole. Pole Line Calculations. — The first step in laying out a pole line must be to decide upon height of poles and maximum span lengths. The next step will be to calculate the strains to which poles may be sub- ject. The main body of a pole line is subject only to wind pressure, and this can be determined by use of Table LII. End poles are subject to half of this wind pressure and strain from the wires as well. Poles from which taps are taken have the full wind pressure and strain of wires leading off. Comer poles must be considered as subject to 1.41 times the strain on end poles. The wire strains upon poles can be found by the use of Table LI. The strains upon poles having been determined, the proper diameter at ground line can be determined by Table LIII. When the strains on a pole are found to be greater than a pole of desirable diameter can well bear, it must be reinforced by guying or bracing. The proper diameter of guy cables can be found from Tables LV to LVII. If the pole is light compared to the strain put upon it, it will be best to provide a guy cable to take care of the total strains. 170 ELECTRICAL TABLES AND DATA TABLE L It is common practice to string electric power wires in accordance with the following tabulation, which gives the sag in inches : Length of Temperature in Fahrenheit span 20° 30° 40° 50° 60° 70° 80° 90° 50... 8 8 9 9 10 11 11 12 60... 9 10 11 11 12 13 14 14 70... 10 11 12 13 14 15 16 17 80... 12 13 14 15 16 17 18 19 90... 14 14 16 17 18 19 20 21 100... 16 16 17 19 20 21 23 24 110... 18 18 19 21 22 24 25 26 120... 18 19 21 23 24 26 27 28 130... 20 22 24 26 28 30 32 33 140... 22 23 26 28 30 32 34 35 160... 24 26 28 30 32 34 36 38 With wires strung according to the above tabula- tion each wire at the lowest temperature given will cause a strain on poles as given below. To find total strain on pole multiply proper number in table below by number of wires. By allowing a greater sag the strain will be proportionately reduced. Length of Span 14 12 TABLE LI Bare Copper B. & S. Gauge 10 8 6 5 4 3 2 1 00 000 0000 80 10 16 26 47 63 80 101 127 160 202 255 321 405 512 100 13 22 34 62 85 107 135 171 215 272 343 432 545 688 120 15 24 39 70 95 120 151 190 240 303 382 481 607 (68 140 18 29 47 85 116 147 182 230 294 371 470 592 740 942 160 19 32 52 94 126 160 202 254 320 404 510 642 810 1024 Breaking Strains B. & S. Gauge Hard Drawn — 14 12 10 8 6 5 4 3 2 1 00 000 0000 219 343 546 843 1300 1580 1900 2380 2970 3680 4530 5440 6530 8260 110 174 277 441 700 884 1050 1323 1670 2100 2650 3310 4270 5320 Insulation and sleet may easily treble the strains. ELECTRICAL TABLES AND DATA 171 The Maximum wind pressure upon the pole alone will range from 125 to 250 lbs., according to length and diameter of pole. The side strain on a straight pole line (125 ft. span) can be found by use of the table below. Multi- ply number of wires on pole by number found under size of wire and in proper horizontal line. TABLE LII Wind Pressure B. & S. 14 12 10 8 6 5 4 3 2 1 00 000 0000 Bare wire.. 8 11 13 19 22 2(5 29 32 36 40 45 50 55 60 Insulated ..35 38 41 46 50 53 56 60 65 70 80 90 100 110 Sleet may easily treble these strains, but sleet seldom exists in stormy weather. TABLE LIII Table showing maximum strains (applied at top) to which poles of various heights above ground, and of various diameters at ground line, should be subject. Height of Poles Above Ground in Feet Dla ( groui in in( 20 25 30 35 40 45 50 55 60 65 70 8.. 147 118 98 84 74 66 58 53 49 46 42 9.. 209 168 138 120 105 93 83 76 70 65 60 10.. 286 228 191 164 143 127 115 104 95 88 81 11.. 381 304 254 218 191 169 152 138 127 117 109 12.. 495 396 330 284 247 220 198 180 165 121 141 13.. 624 500 416 356 312 278 250 226 208 192 178 14.. 786 628 524 450 393 350 314 287 262 242 224 15.. 960 768 640 548 480 427 384 349 320 296 274 16.. 1176 940 784 672 588 524 470 428 392 362 336 17.. 1407 1124 938 804 704 625 563 572 469 433 402 18.. 1658 1328 1106 948 828 756 664 604 553 510 474 19.. 1964 1572 1310 1120 982 872 786 716 655 604 562 20.. 2288 1831 1526 1284 1144 916 915 832 763 704 652 21.. 2665 2132 1764 1524 1333 1144 1066 968 885 820 762 22.. 3048 2440 2032 1740 1524 1356 1209 1108 1016 938 870 172 ELECTRICAL TABLES AND DATA Depth of Setting Earth 5 5} 6 6 6i 6J 7 7^ 8 8i 9 Kock 4- 4i 5 5 5i 5i 6 61 7 7 9J When erected along a curved line it is best to set somewhat deeper. TABLE LIV The following table probably shows the average of poles used for general telegraph and telephone purposes : Butt Top Wt. Butt Top Wt. Length Dia. Dia. App. Length Dia. Dia. App. 25... 9 to 10 6 to 8 350 50... 9 to 15 6 to 8 1350 30... 9 to 11 6 to 8 450 55... 16 to 17 6 to 8 1700 35... 9 to 12 6 to 8 600 60... 16 to 18 6 to 8 2200 40... 9 to 13 6 to 8 850 65... 16 to 19 6 to 8 2500 45... 9 to 14 6 to 8 1100 70... 16 to 20 6 to 8 3000 Guys. — Guys should be fastened to pole at point of strain and when so fastened the strain upon the guy can be found by the formula D where D = horizontal distance at ground of guy from pole; H- the height of guy, and P = the pull upon the pole. TABLE LV Table for Calculating Strength of Guys, — To find the proper size of wire or wire rope for guying, mul- tiply total strain upon pole by number found at point where line pertaining to height of guy fastening on pole crosses with line pertaining to horizontal dis- tance of guy at ground from pole. The product will equal the breaking strain of the proper cable or wire to be used. The table is calculated for a safety factor of 5. ELECTRICAL TABLES AND DATA 173 Height Horizontal distance in feet of guy guy or its support on pole 5 10 15 20 10 11 7.0 6.2 5.5 15 16 9.0 7.0 6.2 20 21 11 8.3 7.0 30 31 16 11 9.0 40 40 21 15 11 50 50 26 18 14 60 60 31 21 16 70 70 36 24 18 from pole to where leaves ground 40 30 '5.3 5.6 6.0 7.0 8.3 9.5 11 13 5.2 5.3 5.6 6.3 7.0 8.0 9.0 10 the 50 5.1 5.2 5.5 5.8 6.5 7.0 7.6 8.5 TABLE LVI Table Showing Breaking Strain of Cables and 'Wi7^es, — Standard Steel Strand. American Steel and Wire Company. Seven steel galvanized wires twisted into a single strand. Galvanized or extra galvanized. Approx. Weight Approx. r uaivanizea. oteei wire > Dia. per Strength Break- in 1000 in A. S. & ing Nearest inches feet pounds W. G. Dia. Strain B. & S. Dia. t 800 14000 12 .106 510 10 .102 A 650 11000 10 .135 774 8 .128 i 510 8500 9 .148 942 7 .144 t\ 415 6500 8 .162 1170 6 .162 f 295 5000 6 .192 1770 5 .182 A 210 3800 5 .207 2079 4 .204 i 125 2300 4 .222 2433 3 .229 5^ 95 1800 The American Steel and Wire A 75 1400 gauge is commonly used for ^^ 55 900 iron wire. TABLE LVII When a pole or mast is held in place by several guys equally spaced the figures obtained by the above calculation may be divided by the following guy fac- tors taken from publication of the American Steel and "Wire Company: 174 ELECTRICAL TABLES AND DATA Corresponding line of action of force Max. value of guy factor ^ Min. 3 value ^ of guy ^ factor 3 0.866 30° from 1 guy 1.000 4 1.000 Opposite 1 guy 1.414 5 1.538 18° from 1 guy 1.618 6 1.732 30° from 1 guy 2.000 Corresponding line of action of force Opposite 1 guy or half way between two Half way between 2 guys Opposite 1 guy or half way between two Opposite 1 guy Telephone Wires. — The tables below give the prac- tice of the A. T. & T. Co. No. 12 hard drawn copper wires are strung according to the following table : TABLE Lvin Temp. in Degrees Length of Span in Feet F. 75 100 115 130 Sag in 150 Inches 175 200 250 300 — 30 1 2 34 34 44 6 8 14 22 - 10 n 24 3 4 5 7 9 16 254 + 10 14 3 34 44 6 8 104 184 294 + 30 2 34 4 54 7 94 12 21 33 + 60 2i 44 ^ 7 % 12 16 264 424 + 80 3 54 7 84 114 15 19 31 49 + 100 44 7 9 11 14 18 224 36 55 The same sag is also allowed for iron wire. Messenger Cables. — The standard messenger strands used are the following: Size of Cable Strength ISTo. 22 Gauge No. 19 Gauge of Strand 100 pair or smaller 50 pair or smaller 6000 lbs. 100 to 200 pair 55 to 100 pair 10000 lbs. Larger than 200 pair Larger than 100 pair 16000 lbs. ELECTRICAL TABLES AND DATA 175 The above strands are about equivalent to -^-^, j% and f inch diameters of good quality steel and used for spans not exceeding 200 feet. The sag allowed is the following : Span in feet Sag in inches for heavy cables Sag when n 50 pair wire in inches ot more than No. 22 gauge will be used 80 16 10 90 20 12 100 .22 16 110 26 18 120 30 20 130 34 22 140 40 26 150 44 30 175 62 42 200 82 58 Panel Boards. — The panel board is a small switch- board, but circuits supplying more than 660 watts are seldom fed through it. Those described in the following figures and tables are designed for 660-watt branch circuits. Main bars have a capacity of 6 amperes per branch circuit at 110 volts, but only 3 amperes if designed for 220 volts. The figures in the tables are those furnished by the Cuthbert Electric Mfg. Co. "Wherever the depth of cabinet required is the same for all numbers of circuits, it has been given in the fourth column from the left. In other cases the special designations at each height will serve as a guide. Where no special mark is placed and no depth given, the required depth is 3^ inches. When ordering boxes, see points to be noted under Cabinets, 176 ELECTRICAL TABLES AND DATA " 1 [J a ill f" Type A- Type 'A-y c -" 1 3 ^0 Type 'A-2' Type 'A-a' Type *A-4' i i i n Type 'a-6' Type ♦B-l' Type ♦B-2' Figure 12. — Types of Panel Boards. C'^ ^n c:^ =.^::3 n:^ =-^:ni zz^ =.;.r2 c:: d^::3 cl: sp:3 ? i Type 'O-y m^ 3] SS ^1 ^ b^ :3iS: ^ E^ ^^ ^ ^^ 3^^ ^ ^3^ 3^- = zm. i i i Tvoe 'B.4' i ! 21§: ^ ^ ^ Type 'B-e' i i i Type »C-r Type '€-2' Type 'CO' Type •C.4' Figure 13. — Types of Panel Boards. ELECTRICAL TABLES AND DATA 177 :® = JKS^ ^£^ b §.m^ xmit ±m ^^i i.Es2 X?S^l S35S } 1 B g Type 'C^' Type C.6 = i i i i 1 T>pe 'D-r i 1 Type' D-2' i g s ^ Type»D-3' Type 'D-A' 'Type*D«5' Type 'D-©* Figure 14. — Types of Panel Boards. 3 Type •£ Type -E-r .^--o— — <-v^— 1 i i 1 Type 'E-a' Type* E-4' ^ „ .^...I ■F^ ^s5 ^^ ^ ^£ ^m ^ ^' ^5 ^^ .r g ^fe ■E ~ ^^ s^ ^ := iQTgp 3 ^yi^t* """ 1 Type'E.5' Type ♦£-©' Type 'F-I' Type 'f -2' Figure 15. — Types of Panel Boards. — TT-I § ! 1 ,^,_Q^_W%--« 1 Si r^^_ .w^ 1 1 i i Type*F.3' Type ^.4' Type ♦F^' Type 'f.6' Figure 16. — Types of Panel Boards. 178 ELECTRICAL TABLES AND DATA ^ ++++<<]<^^COtOT:^lOTJ^CO „o + ++4- .OiOQOT— iCOTt* COIOCOt— IC^JQOOiTjHooCvICOQO Pe^^ -Mi-H(MCOOqcoOOCOCqTtOilOOi^H■<^ iJo Po'vlTHC^COCMCO^MCOCqcOCOCOCO'^ OaCOOqcOCv|CO(MCOCOCOCOrJ< *-• '^ CO Jh Q h£ .^ ++++ + + So TH(MOqcgCvl(MCOC\ICOCOCOOlCO COOa5i-Ht-C0»Ot^tO00 ^'^T— li— ItHi— IrHi— It— li—ir-l,— InHr-t rHi—lT-lrHi— It— It— IrHrHr-HrHrH ZirZ PhH^;:^s^^ ^ ^ r^ >^ t-^ T-i^ h^ tH^ rH^ rH^ •SS ^COCOCOCO ^tO^lO-^LQT^lO lO IQ So ^ fl PL, CDO "^OOOlO^OOOCJOaOoCvICM rtHOC000TtOoiCO lOOtOOOOLOOtOOtOO «— • CM iO Cvj lO Cv] lO Cq lO C<] lO C0 cq lO CM lO Cvl lO C<] lO oi to Cvl »o O Or-ICf4^cotso(-'t-kh-k -<^OlaiOltf^^^orf^to^^Ol-*o^ ^ ++++ ■ o I— kCDOtOOOOi-^IQoaiHf^OlOi l-*^Ol— 'OOOl^^lOOitOOlCO^^ S^ + + + + + g.o- oitNOOooitocoi— 'I— lO-^icoQo oiococotO'^-^^D © oj + +++ + + ++ ^H.g /-s O Hi ooi^icoc:>ocococo- +++> S"o uxooi— 'tooco^Ci- +++> g Q +++> +++[> + g^^ 01 tfi^ 01 OJ 01 h^ ^^ >4x h^ CO h^ CO CJl ^^ 01 ^ Ol CO rf^ s^^ ^^ CO rf:^ CO IN3 CD© cn^i— 'Oh-aco- +++> + 3 01 01 S^ Pi CJl h4^ O! >^ ^|x t4^ ^fi^ rf^ CJl 4^ Ol ^f^ 01 CO C71 1^ ^^ "^ ^^ ^ to ^ CDO*^-^0100^00CJ1I-' o^^oi-^oiOoto'^'^(^*^to ^- +++> +++> + s Oi "^ ^ S ^ ^ ^ ^ ^ ^^ ^^ ^f^ Oi 4^ 01 hP^ 01 hP^ 01 ^^ 01 CO 4^ CO to ^ CO CO QO O^ COCOrf^tOCOCOOOh^^ COOiOO':OcDt0^4i^OlCOOiQ0^^4^ ^T +++!> +++> + !! ooooco^coto^oi^ot-k^ QoocotNocot^^-q-L> + + + + ++ p ^qoiai<^aiCJiCicnoii^C7ic;i ^^cn'^cncii^CiCnCiHf^oiv^to toi— 'Cito^oih- 'Qoi— icooii— ' to^^a5^4:i.^^i_lO^— 'I— ^oitooo ^50i^ai-hf^tOCJlCOOOCJlO l>t>l>[> l>[>+4-++++ 3 CD CfQ o o H» •u |> ts Cu CO 180 ELECTRICAL TABLES AND DATA CO o 3 fcJO O "* 1-H (M C\J T— I CO ^ CC> lO L- (T) OO rH t^ Oi CX) OO C\l lO LO ^ CO lO CO t- Tt^ CO CO lO oq Tt< lo Tti CO »o Tfi Tt^ O CO Oi oi C\I Tti O "^ O iO CM rH CO O Thl t^ CQ ^ TfH tH lO '"^ ^ Ph s " O 00 CCl t- O LO j3 a; Cq OO -^ CO o ^ fl <^ •5 ^ PI . OO TfH Ci CO »o o rH CO 00 CO "^ ''^ CO O to O rH (X> rH CO CO CO TtH CO Mi^-.g 'rt^ t- 1-1 t^ CO CO a^.gg3 1-H cq CO oq CO CO BLE anel Elect olts er of Oq '* t^ T}H ^ O T-l --H rH b- l>- 1-i c\i cq CQ oq oq fy, OO O^ t^ oq iH '^ T-i rH iH C\J C>q CO lO CO i-O CO lO o cq CO »o CO Oi cq CO lO Tt< 00 CO rtl CO QO CO CO CO tH O CO CO co cq cq oq rH Oi cq iH 00 CO CO '^ Tin t^ CO t- ^ QO - <]0 O O^ TJH '^ TJ^ "^3^ 00 1— I t^ lO CO -^ CO ^ T-l TtH 00 CO CO lO 00 1— I »o LO CO iO Lo t- oq lO O lO oq '^ Oi LO lO ^ t^ O CO tH O Tt^ lO t^ CO "^ ^ '^ '^ t^ CO rH CO CO CO ^ O ^ O t- CO CO CO CO t- O t^ CO oq CO oa CO o o t^ TjH rJH CO CO t^ CO CO CO CO CO CO O CO CO CO '^ CO Tt^ C5 oq cq oq cq rH CO 1— I LO oq oq oq oq 00 oi r>. o T— I th T-H oq o o t^ CO CO oq t- CO tH oq G\i oq tH 1— I Oi oq oq rH rH CO O Tt< CO t^ CO t^ CO «>• t- oq CO rH oq CO CO CO CO t>- 00 a: CO 00 QO ^ lO CO 'O ^ <]+++ rH o rH t- lO <+ + + ^ lO Tt^ tH 00 ^ rt^ '^ ^ ^ CO Oi t^-'O o CO CO CO 00 "^ ++++ oq lO ■rH CO rH CO CO CO CO CO 00 rH O oq 00 oq CO CO CO oq ++++ oq Lo CO to oq oq oq 03 oq OQ ^ CQ UO CO TtH t- CO ^ ^ rH rH rH tH rH 00 CO o: oi o 05 oq rH rH rH oq oq rH oq lO <1 CO P5 LOlO-'^COOOt^COQOOqOi— lOi ++++ ++++ rHOqrHCOCOrtlCOIOtOL-^lOOO rHrHrH OlCOTflCOTH^'^t^lO ^ . .a fH tH^ H^ tH^ H^ r-^ ^ Ttl Ttl ^ '^ -rtH "^ CM tH TtH CO oq Vr ^~^ ^-^ ^-^ ^~^ "^"^ -M LO O ID O Ift) •— ; oi )o oq »o oi . ® ^ oq rH Oa rH T^ ^ Tf '^ Ttl CO CM Tt< T^H CO O »0 O 'O O 1(0 O lO oq LO CM »Q CM iQ CM «— I CM '—t CM rH CM ^^ ^^ "^ ^^ ^^ ^t* ^t^ ^^ CM0QTHTt^CMOq'rt^Tt^oqOqTHri^ iooioo^oiooiooou:) CM >0 CM lO CM iO CM >0 CM »0 LO oq rHCMrHCMrHCMi— ICMrHCMCMrH + P^rH CM CO TtH iH) CO W H pq rH CM 00 TtH lO Ph pl< Ph Ph Ph CD ELECTRICAL TABLES AND DATA 181 Plans. — Except in the case of large office build- ings, hotels, street lighting, and other large under- takings, detailed plans cannot show much more than location of outlets and most of the information is gathered from specifications. In large installations it is customary to designate sizes of conduit as well as the wires. In making the installation according to such plans the work is often subdivided, separate plans being given to different workmen or groups of workmen. If each group is allowed to finish its par- ticular installation a very reliable check on the labor performed by each man or group is obtained. Small plans are usually drawn to a scale of | inch per foot ; for large plans the scale is often ^ inch, or even less. Details are drawn to a larger scale and sometimes even full size. Power. — This term expresses merely the rate of doing work. In order to obtain the quantity, it must be multiplied by time. Power is measured in watts and is usually expressed in watt hours, kilowatt hours, or horsepower hours, but any other length of time may be chosen. Preservation of Wood. — This is effected by impreg- nating the timber with some sort of poison which destroys the fungi and deprives them of food. Creo- sote is the most used, and there are various patented substances of a similar nature. The more thoroughly dried the timber is at time of application, the more it will absorb. Ordinarily the preservative is applied with a brush, but it is also applied under pressure, the whole pole or tie being submerged in a tank full of the impregnating material, to which pressure can be applied. Printing. — Printing presses are usually equipped with reversible and variable speed motors. For the larger sizes several motors are used. All of these are preferably fitted with remote control switches which 182 ELECTRICAL TABLES AND DATA enable the operator to govern the press from various points on and about it. Time is a very important consideration about large presses and the very best illumination should be supplied. On many presses from 10 to 20 lights are permanently installed so as to be ready at a moment's notice and obviate the neces- sity of using portable lamps. Such lights also assist in watching the mechanism while at work. Flexible conduit is serviceable, but it should be lead covered to guard against machine oil, which dissolves rubber. Composing Rooms. — A good general illumination is advisable in composing rooms, but there must be local illumination with it in certain places. In some com- posing rooms the work is of such a nature that it is advisable to fit each stand with a foot or arm switch by which a compositor can turn the light on or off without using his hands. Pumping. — One cubic foot of water weighs ap- proximately 62.5 pounds and contains about 7.5 gal- lons. One gallon weighs 8.33 pounds and contains 231 cubic inches. If the head of a column of water is expressed in feet and the pressure at the foot of the column in pounds per square inch, then Head - 2.31 x pressure Pressure = head 4^ 2.31, which equals 0.434 x head, and this is independent of size of column. The H. P. required to deliver a certain quantity of water to a certain height is directly proportional to the product of the two if the so-called ^'friction head'' is added to the actual height of lift. The friction head for various sizes of pipe and rate of flow through them is given in Table LXII. This friction head varies with the square of the velocity of the liquid, with the distance it flows, and with the conditions affecting its freedom of movement. Elbows, bends, burs, etc., increase it. The enormous losses in pres- ELECTRICAL TABLES AND DATA 18;^ sure which take place when a small pipe is used for the delivery of a large amount of water can be seen from the table. The efficiency of centrifugal pumps is sometimes as low as 35 per cent, and that of rotary and plunger pumps ranges from 60 to 80. Table LXII shows the resultant net efficiency of motors and pumps of Various efficiencies working together. From Table LXII we can take the number of cubic feet, pounds and gallons which one hofsepower will lift to a height of one foot, the machinery having a net efficiency as given. Rule for Determining Horsepower Needed, — Add to the actual head in feet the friction head as found in Table LXII and multiply this by the number of cu. ft., lbs. or gals., as the case may be. Next divide this sum by the number found in same table under the efficiency of the combination to be used: combined motor and pump efficiency. Table showing number of cu. ft., lbs., or gals, which can be raised 1 foot per minute by 1 H. P. at effi- ciencies given. TABLE LXII Combined Motor and Pump Efficiency. 64 60 oQ 52 48 46 43 40 Cu.Ft. 338 316 296 275 253 243 227 211 Lbs.. 21,120 19,800 18,480 17,160 15,840 15,180 14,190 13,200 Gals.. 2,535 2,370 2,220 2,062 1,897 1,822 1,702 1,582 Combined Motor and Pump Efficiency. 38 36 34 32 30 28 26 24 Cu.Ft. 200 190 180 169 Lbs.. 12,500 11,880 11,220 10,560 Gals. 1,500 1,425 1,350 1,267 158 148 137 127 9,900 9,240 8,580 7,920 1,185 1,110 1,027 952 184 ELECTRICAL TABLES AND DATA TABLE LXII— Continued Friction head per hundred feet of pipe of inside diameters given. Condensed from Westinghouse Electric & Mfg. Co. table. Inside Diameters of Pipes. Cu.F t. Lbs. Gals. %" 1" 11/4" IV2'' 2" 2y2" 3" 0.6 37 5 7.59 1.93 0.71 0.27 1.1 75 10 29.9 10.26 2.41 1.08 1.6 112 15 66.01 16.05 5.47 2.23 2.4 150 20 115.92 28.29 9.36 3.81 3.0 187 25 43.70 14.72 5.02 1.18 3.4 225 30 63.25 21.04 8.62 2.09 4.2 263 35 85.10 28.52 11.61 2.76 4.8 300 40 110.40 37.03 14.99 3.68 1.19 5.2 338 45 46.46 18.74 4.60 1.49 6.0 375 50 57.27 23.00 5.61 1.86 0.80 9.0 ' 562 75 129.09 51.52 12.23 4.14 1.70 12.0 750 100 89.70 21.75 7.36 3.01 15.0 937 125 34.27 11.24 4.57 18.0 1,125 150 48.76 16.10 6.55 21.0 1,312 175 64.63 21.75 8.85 24.0 1,500 200 86.25 28.68 11.54 30.0 1,875 250 45.21 17.84 36.0 2,250 300 64.53 25.76 42.0 2,625 350 34.96 48.0 3,000 400 44.85 60.0 3,375 450 57.50 75.0 3,750 500 70.84 ELECTRICAL TABLES AND DATA 185 Table for determining com- Theoretical and practical bined efficiency of pump and suction limit, motor. TABLE LXII— Continued Motor Altitud'e Theoretical Practical Efficiency Pump Efficiency Sea level 33.95 25 75 65 50 45 40 35 1,320 ft. above 32.38 24 70 52 46 35 32 28 24 2,640 ft. above 30.79 23 75 56 48 38 34 30 26 3,960 ft. above 29.24 21 80 60 52 40 36 32 28 5,280 ft. above 27.76 20 85 64 56 43 38 34 30 10,560 ft. above 22.82 17 Reactive Coils. — This term describes coils intro- duced into a circuit to produce a certain reactance. They are also known as reactors. They are used to limit short-circuiting currents. Reactors are usually designed for a high temperature rise, and should be treated as sources of heat. When used in connection with lightning arresters they are often spoken of as *' choke coils." Rectifiers. — The mercury-arc rectifier is the one most used for arc lamp operation and is very common in motion picture theaters. Other types are the elec- trolytic and rotary. The mercury-arc type is also much used for storage battery work in connection with automobile charging. It is usually fed through autotransformers, but sometimes through constant current transformers, and then delivers a constant current. Most rectifiers are operated on single-phase circuits, but they can be arranged for two-phase and three-phase circuits and operate more advantageously. They may also be operated in parallel. Rectifiers de- signed for 40 to 50 amperes usually have glass tubes, but if larger capacities are required, the tubes are metallic. The power factor is ordinarily about 0.90. The drop in voltage is always about the same, hence 186 ELECTRICAL TABLES AND DATA the lower the voltage the lower the efficiency. The average efficiency is about 75 or 80 per cent. If the vacuum is good, shaking the tube will cause a metallic sound ; if tube is dirty on inside, the vacuum is usually poor. Reciprocals of Numbers. — The reciprocal of any number is equal to 1 divided by that number. The reciprocal gives by multiplication what the number would give by division, and vice versa. The prin- ciple involved is made use of in many formulae and is much used to facilitate calculations. The recipro- cals have been given only for whole numbers and up to the number 100. The reciprocal of any number larger or smaller may, however, easily be found by adding a decimal point to the reciprocal for each num- ber added to its integer or subtracting one for each integer taken from the whole number. The larger the number, the more decimal places the reciprocal will contain. The smaller the number, the greater will be its reciprocal. Thus the reciprocal of 7.3 0.13698 73 0.013698 730 0.0013698 7300 0.00013698 0.73 1.3698 0.073 13.698 • 0.0073 136.98 To find the reciprocal of a number trace along until this number is found. Thus the reciprocal of 21.7 is 0.04608. To find the number pertaining to any reciprocal find the reciprocal and take the number. Thus the whole number of which 0.2710 is the reciprocal is 36.9. ELECTRICAL TABLES AND DATA 187 . . . !^ . 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The following table gives approxi- mately the percentage of light reflected by various materials : TABLE LXIY Per Cent Light Eeflected Well polished silver 92 Silvered mirror 70 to 90 Highly polished brass 70 to 85 Mirror backed with amalgam 70 Well polished copper 60 to 70 Well polished steel 60 Burnished copper 40 to 50 Chrome yellow paper 60 Orange paper 50 Yellow paper or painted wall 40 Pink paper 35 Blue wall paper 25 Emerald green paper 18 Dark brown paper 13 Vermilion paper 12 Bluish green paper 12 Cobalt blue paper 12 Deep chocolate colored paper 4 Black cloth 1.2 Black velvet 0.4 Refrigeration. — Refrigeration by machinery is much more reliable, effective and cleanly than that produced by the use of ice. Electric power compares favorably with steam power in large installations, but more especially so in the smaller plants. Its main advantages are : lower first cost, less space required ; less attendance and operation ; can be made automatic. For direct current, compound-wound motors are pref- erable, and where variable speed is desired, the speed control should be by means of field regulation. For alternating current, the squirrel cage type of arma- 192 ELECTRICAL TABLES AND DATA mre may be used, but if speed control is desired, a wound armature should be provided. The latter is much preferable for automatic control. The horse- power required for refrigeration can be determined by means of the curves in Figure 17, due to Westing- house Electric & Mfg. Co. The upper curve is for compressors of 50 H.P. and smaller; the lower curve Figure 17. for larger machines. For example: a 30-ton com- pressor requires a 52 H.P. motor; a 300-ton com- pressor requires a 470 H.P. motor. When the ice- making capacity of compressor is given, the motor H.P. required w^ill in general be about double the figure given in the curve. Refrigerators. — All refrigerators are at times very damp. As long as they are kept cold, ice forms, and as soon as they are empty the ice melts and all parts become wet. No very bright illumination is required, and in many of them workmen are required to get ELECTRICAL TABLES AND DATA 193 along with lanterns. Weatherproof construction is preferable to conduit in all places except where heavy coatings of ice form on the wires. This frost is scraped off from time to time, and open ^vires are likely to be torn loose. Porcelain sockets break easily and should not be used. Circuits should not enter or leave too close to entrances; the meeting of the cold and warm air at such places cause the deposit of much moisture. Lamps are usually placed only in runways, and in large refrigerators the circuits are apt to be long. In some of the large refrigerators watchmen are regu- larly making rounds ; in such places three-way switches at doors are useful. Keep cut-outs and switches out- side of damp rooms and avoid the use of the common fiber-lined brass shell socket. Residence Wiring. — As a general rule a total wattage capacity of about ^ watt per sq. ft. should be provided for the whole building, including cellar and attic. If these latter are not to be illuminated, 1 watt per sq. ft. will be ample for the balance of house. The best place for service switch and meters is in the basement. Select a location easily accessible to meter readers. If not too much economy is neces- sary, let two circuits enter each room that contains more than one outlet. Place all switches at doors where room is most likely to be entered, and if there are two entrances two-way switches will be a great convenience. In some elaborate residences circuits are sometimes so arranged that lights in all rooms may be thrown on by a master switch, even if turned off in rooms. This is useful as burglar protection and also in case of fires. A measure of protection against intruders can be obtained by placing lights above doors so that an intruder must show himself in the light before he can enter a room. The bright light will prevent him from seeing what is inside the door. 194 ELECTRICAL TABLES AND DATA Attics. — No part of residence requires light more than the attic. The use of matches is exceedingly dangerous in such places. Run wires where they will not be molested. Bath7'oom, — A center light in a bathroom is an abomination. Place a light at each side of shaving mirror if practicable, but locate them so that person in tub cannot reach socket. An outlet for heater will be a great convenience. If possible place or shade lamps so they will not cast shadows of persons on window. Place a switch at door. If expense is no object, inverted lighting will be very useful. Basement. — The wiring of the basement depends upon the use to which it may be put. Two or three- way switches, one at each entrance, will be very con- venient. Plenty of light will be an inducement for servants to keep basement cleaner than the average. Provisions should be made for motors to operate ice cream freezers, washing machines, mangels, or vacuum cleanioig motors. It is much preferable to place the motor for this purpose in the basement rather than to bother with portable machines. Fan motor outlets will assist in drying clothes. If part of basement is used as laundry and likely to be damp, use weather- proof construction and avoid placing sockets where one standing on wet floor will be likely to touch them. Provide outlet for flatiron. Bedrooms. — A center fixture should never be in- stalled in a bedroom unless it is intended also as a sort of living room. Lights should be arranged to suit the various positions in which a bed can advantage- ously be placed, and so that one can use the light for reading in bed or make easy connections for heating pads. Special outlets along baseboard for flatiron heaters, sewing machine motors, etc., will be found very useful. One light on each side of dresser mirror is a great convenience. Avoid placing lights so that ELECTRICAL TABLES AND DATA 195 they will cast shadows of occupants on windows. For protection against burglars, a switch by which lights in other rooms may be turned on is very effectual. See ^^ Modern Wiring Diagrams and Descriptions'' for circuits. Such a switch might be placed in each bedroom. Inverted lighting is very useful if only one light can be installed and if ceilings are light enough. Cellars. — A cellar is usually damp, and weather- proof construction should be used. Keep switch out- side at door. Closets. — The use of matches in closets is very dan- gerous and willbe entirely eliminated by good illum- ination. Place a light at ceiling and control by switch if closet is small. In large closets a pendant light may be advisable, but there is usually too much chance of clothing coming in contact with it and the cord. Dining Rooms. — Beam lighting is used to some ex- tent in dining rooms. Special illumination of buffet and china closet is also often practiced. Small lamps are used for the latter and should be located to show off cut glass, etc., to the best advantage. It is well to study the effect of such lights carefully before finally locating them. To show off silverware, fine table linen, etc., to the best advantage it is advisable to concentrate a strong light upon the table and leave balance of room somewhat dark. Side outlets for fan motors, and floor sockets for chafing dishes, are very useful. The low hanging fixtures often seen in dining rooms should not be recommended. They will soon become obnoxious. Halls. — Halls ordinarily require only a perfunc- tory illumination unless a showy appearance is de- sired. These lights are often combined with stair lights and fitted with two or three-way switches. Place switch for hall light close to the door. Ice Boxes or Chambers. — A light placed opposite door will be very useful. 196 ELECTRICAL TABLES AND DATA Kitchen, — If kitchen walls are of light color, a cen- ter light will give good illumination. With dark col- ored walls a light should be placed over sink and near range, but a little to one side, so as to avoid the cook- ing fumes as much as possible. A small motor to drive steam out will be of great use. Ozonators to destroy odors will also be much appreciated. As ironing is often done in the kitchen, an outlet for irons should always be provided. If electric cooking is indulged in this must be provided for. Laundry, — There should be a light directly over wash tubs and another arranged to be directly over ironing board. If clothes are dried in laundry a fan or ventilating motor will be of great service. Pro- visions should be made for washing machine motors, mangels and flatiron. Locate sockets so persons will not be likely to touch them while standing on wet floor. • Lavatory, — One light controlled by door-switch is. very useful here. Library, — Inverted lighting of sufficient c.p. to allow the reading of titles of books in cases is the best means of illumination here. In addition to this there should be outlets for reading lamps and brackets con- veniently located on walls to give a brighter light for those that need it. A direct light with strong reflector under inverted light is useful for reading purposes. Nursery, — The lighting of the nursery should be ample, but precautions should be taken to guard against the possibility of outlets being short circuited by children. Avoid placing sockets within easy reach. Electric toys should be confined to battery current, or a low- voltage transformer, to which children have no access, might be used. The lighting voltage is too dangerous for them. Control all lights by switches and keep them high. ELECTRICAL TABLES AND DATA 197 Pantry. — Provide bright illumination to show up dust and dirt and induce cleanliness. Parlor, — The illumination of the parlor is usually effected by means of quite elaborate chandeliers. Out- lets for piano and reading lamps should be provided. The center light does not illuminate pictures very v^ell, and for this reason inverted lighting is often useful. Really good pictures, however, deserve spe- cial illumination. Porch. — A light should be arranged close to main entrance and so located as to reveal features of per- sons applying for admission without making the party inside of house visible. The light should be controlled by a switch inside and should be out of reach from the outside. If porch is to be enclosed, other outlets for lamps or fan motors will be useful, but they should be arranged at ceiling so as to avoid moisture. Use no fiber lined sockets outside. Resuscitation from Electric Shock. — Rules recom- mended by commission on resuscitation from electric shock, representing The American Medical Associa- tion, The National Electric Light Association, The American Institute of Electrical Engineers. Issued and copyrighted by National Electric Light Associa- tion. Reprinted by permission. Follow these instructions even if victim appears dead. I. Immediately Break the Circuit, — With a single quick motion, free the victim from the current. Use any dry non-conductor (clothing, rope, board) to move either the victim or the wire. Beware of using metal or any moist material. While freeing the vic- tim from the live conductor have every effort also made to shut off the current quickly. II. Instantly Attend to the Victim* s Breathing. — (1) As soon as the victim is clear of the conductor, rapidly feel with your finger, in his mouth and throat 198 ELECTRICAL TABLES AND DATA and remove any foreign body (tobacco, false teeth, etc.). Then begin artificial respiration at once. Do not stop to loosen the victim's clothing now; every moment of delay is serious. Proceed as follows : a. Lay the subject on his belly, with arms extended as straightforward as possible and with face to one side, so that nose and mouth are free for breathing. Figure 18. Inspiration — Pressure Off. See Figure 18. Let an assistant draw forward the subject's tongue. b. Kneel straddling the subject's thighs and facing his head; rest the palms of your hands on the loins (on the muscles of the small of the back), with fingers spread over the lowest ribs, as in Figure 18. c. With arms held straight, swing forw^ard slowly so that the weight of your body is gradually, but 7iot violently, brought to bear upon the subject. See Fig- ure 19. This act should take from two to three seconds. Immediately swing backward so as to remove the ELECTRICAL TABLES AND DATA 199 pressure, thus returning to the position shown in Figure 18. d. Repeat deliberately twelve to fifteen times a min- ute the swinging forward and back — a complete res- piration in four or five seconds. e. As soon as this artificial respiration has been started, and while it is being continued, an assistant Figure 19. Expiration — Pressure On. should loosen any tight clothing about the subject's neck, chest or waist. (2) Continue the artificial respiration (if neces- sary, at least an hour), without interriiption, until natural breathing is restored, or until a physician arrives. If natural breathing stops after being re- stored, use artificial respiration again. (3) Do not give any liquid by month until the sub- ject is fully conscious. (4) Give the subject fresh air, but keep him warm. ///. Send for Nearest Doctor as Soon as Accident Is Discovered, 200 ELECTRICAL TABLES AND DATA Ropes. — TABLE LXV Standard Iron Hoisting Rope, 6 Strands — 19 Wires to the Strand — 1 Hemp Rope. American Steel & Wire Co. ■2 2 S a S.2 (D CO 0.2 Approximate Weight Per Ft. in Pounds Approximate Strength in Tons of 2,000 Lbs. bo .9 o o Diameter of Drum or Sheave Advised in Feet 2i 81 11.95 111.0 ■ 22.2 17 2h 7J 9.85 92.0 18.4 15 2J 7J 8.00 72.0 14.4 14 2 6J 6.30 55.0 11.0 12 u . 5i 5.55 50.0 10.0 12 u 51 4.85 44.0 8.8 11 IS 5 4.15 38.0 7.6 10 li 4i 3.55 33.0 Q.Q 9 It 4i 3.00 28.0 0.6 8.5 li 4 2.45 22.8 4.56 7.5 IJ 3J 2.00 18.6 3.72 7.0 1 3 1.58 14.5 . 2.90 6.0 i 21 1.20 11.8 2.36 5.5 f 2i 0.89 8.5 . 1.70 4.5 f 2 0.62 6.0 1.20 4.0 ■fo If 0.50 4.7 0.94 3.5 •i li 0.39 3.9 0.78 3.0 fs u 0.30 2.9 0.58 2.75 1 li 0.22 2.4 0.48 2.25 A 1 0.15 1.0 0.30 2.00 J J 0.10 1.1 0.22 1.50 For better grades of rope smaller sheaves are advised. ELECTRICAL TABLES AND DATA 201 Manila Eope. o o o o d a 0) • (U 9 ^ ^ S 03 {:ijo 4^ 0) en s rr3 O C3 ;3 II s C3 • pH CIT' -»-» O Q • rH • iH rr* -*^ O (D P 3 002 ^Ph ft O PQQ Pnfli i li 2,000 0.09 11 4J 13,500 0.65 f 2 3,250 0.14 li 4i 15,000 0.77 f 2i 4,000 0.20 If 4J 18,200 0.90 i 2i 6,000 0.27 If 5i 21,700 1.05 1 3 7,000 0.35 2 6 25,000 1.40 14 3f 9,300 0.45 2i 6i 32,000 1.75 li 3i 10,000 0.55 2i 7i 40,000 2.15 Splicing of Manila Rope. — The successive opera- tions for making a common or English splice in a If -inch 4-strand rope is as follows: 1. Tie a piece of twine, 9 and 10, A, Figure 20, around the rope to be spliced, about six feet from each end. Then unlay the strands of each end back to the twine. 2. Put the ropes together and twist each corre- sponding pair of strands loosely, to keep them from being tangled, as shown at A. 3. The twine 10 is now cut, and the strand 8 unlaid and strand 7 carefully laid in its place for a distance of four and a half feet from the junction. 4. The strand 6 is next unlaid about one and a half feet and strand 5 laid in its place. 5. The ends of the cores are now cut off so they just meet. 6. Unlay strand 1 four and a half feet, laying strand 2 in its place. 7. Unlay strand 3 one and a half feet, laying in strand 4. 202 ELECTRICAL TABLES AND DATA 8. Cut all the strands off to a length of about twenty inches, for convenience in manipulation. The rope now assumes the form shown in B, with the meeting point of the strands three feet apart. Each pair of strands is now successively subjected to the following operations: Figure 20. — Method of Splicing Ropes. 9. From the point of meeting of the strands 8 and 7 unlay each one three turns; split both the strand 8 and the strand 7 in halves, as far back as they are now unlaid, and the end of each half strand *' whipped" with a small piece of twine. 10. The half of the strand 7 is now laid in three turns, and the half of 8 also laid in three turns. The half strands now meet and are tied in a simple ELECTRICAL TABLES AND DATA 203 knot 11, C, making the rope at this point its original size. 11. The rope is now opened with a marlinspike, and the half strand of 7 worked around the half Figure 21. — Methods of Tieing Knots. strand of 8 by passing the end of the half strand through the rope, as shown, drawn taut, and again worked around this half strand until it reaches the half strand 13 that was not laid in. This half strand 13 is now split, and the half strand 7 drawn through the opening thus made, and then tucked under the two adjacent strands, as shown in Z>. 204 ELECTRICAL TABLES AND DATA 12. The other half of the strand 8 is now wound around the other half strand 7 in the same way. After each pair of strands has been treated in this manner, the ends are cut off at 12, leaving them about four inches long. After a few days' wear they will draw into the body of the rope or wear off, so that the locality of the splice can scarcely be detected. Figure 21 shows specimens of knots frequently used. A, Bowline; B, Stevedore knot; C, Reef knot; D, Weavers knot; E, Boat knot; F, Half hitch; G, Timber hitch; H, Clove hitch ; I, Timber and half hitch ; J, Blackwall hitch ; K^ Common noose; L, Fishermen ^s bend; M, Common knot; N, Turks head. Saloons. — In small saloons not much illumination is required. Where there is. any pretense of impor- tance, however, there is always some back-bar lighting, and this may often furnish the whole illumination. Special outlets for cash registers and hot water heat- ers should be provided. Nearly every saloon sooner or later provides a beer pump. In pretentious saloons a very elaborate illumination is often striven for. In case wine rooms, or other private places fitted with glass partitions, are to be illuminated the lights should be so placed that they will not cast shadows of occu- pants on glass. Schools. — In large cities schools are often classed as assembly halls and special rules for wiring are made. There should be emergency lighting. A stere- opticon outlet is a common requirement. Screws, — ^Formulae for wood screws. iV = number; D = diameter. D=(iV^x 0.01325) +0.056 P- 0.056 N = 0.01325 ELECTRICAL TABLES AND DATA 205 TABLE LXVI Dimensions of Iron Screws (Approximate). Trade Diameter Nearest Greatest ] dumber in Fractions B. & S. Gauge Obtains %28 15 '% 1 • %28 14 % 2 %4 12 % 3 %2 11 11/2 4 V^ SJ IV2 5 %2 8 21/2 6 1^128 7 3 7 1%28 7 3 8 %2 6 4 9 11/64 5 4 10 1%4 5 4 11 ^%4 4 4 12 2%28 4 6 13 2%28 3 6 14 1%4 3 6 15 % 2 6 16 1%4 2 6 17 %2 1 6 18 1%4 1 6 Service Entrance. — The service wires should be protected by fuses as close as possible to where they enter the building. There should be a service switch, and it and the fuses should be accessible. Shelving. — To illuminate shelving properly is a troublesome matter. Portable lamps are essential, but these introduce an appreciable fire hazard. It is best to suspend lamps from ceiling by reinforced cord, and fit each lamp with a substantial guard. It is usually necessary to have good light close to the floor, but this can be had by keeping lamps about 6| feet above floor. If shelves are deep and contain dark- 206 ELECTRICAL TABLES AND DATA colored materials carrying indistinct numbers, attach- ments to these cords will often be necessary. Where lights are not constantly in use, three-way ceiling switches will be very useful and economical. Provide each group of lamps commonly used together with its own switch. Show Windows. — In the best form of show-window lighting the lamps are always entirely hidden. Very brilliant effects are often striven for and the gas- filled mazda lamp is in great favor. Where there is bright illumination on the street in front, even greater illumination is required within. The object is, not only to make things visible, but to attract attention, and for this purpose the very brightest and whitest light is necessary. Most show windows are lighted from the top by reflectors, but in some cases an illum- ination from the bottom up must also be provided. In some cases the object is to show the lights and call attention to the fact that they are there. For this purpose small lamps. Well frosted, are preferable. If they are too bright they will blind people to the ob- jects in window. In some cases 32 c.p. lamps have been thickly studded over the whole ceiling of window. Time switches are much used for show-window light- ing and enable one to keep his windows illuminated for advertising purposes after the store is closed. Fan motor outlets are very useful for winter to keep window^s clear of frost. Place no wires near glass w^here water is liable to run down. Signs, Electric. — Signs should be wired with the two sides independent so as to enable flasher to be used. Small lamps of low intrinsic brilliancy are preferable. Letters should be glossy white and kept clean. The follo^\dng table gives dimensions and numbers of sockets of stock letters made by the Fed- eral Electric Co. of Chicago, which may serve as a general guide to present practice. ELECTRICAL TABLES AND DATA TABLE LXVII 207 10 Inch Letters 14 Inch Letters 16 Inch Letters 4 Lamp High 16 Inch Letters 5 Lamp High 24 Inch Letters m cc en CO CD Xi 4S 5 "? 5 ^ Si o •S J4 3 M 'O J4 2 M 5 C/3 ^ 8 S 8 '$ 8 5 C/3 5 A 8 10 8 12V2 8 1514 10 151/2 11 21 B 10 10 10 12/2 11 151/2 13 151/2 13 21 C 7 10 7 12H 7 151/3 8 151/2 8 21 D 8 10 8 121/2 9 151/2 11 151/2 11 21 E 9 10 9 121/2 9 151/2 10 151/2 13 21 r 7 10 7 12H 7 151/2 8 151/2 10 21 G 8 10 8 121/i 8 151/2 9 151/2 11 21 H 9 10 9 121/2 9 151/2 11 151/2 12 21 I 4 51/2 4 6 4 8 5 8 5 9 J 6 10 6 121/2 6 151/i 7 351/2 7 21 K 8 10 8 121/2 9 151/2 11 151/2 11 21 L 6 10 6 121/2 6 151/2 7 151/2 8 21 M 13 121/2 13 151/2 13 191/2 15 191/2 17 25 N 10 10 10 151/2 10 151/2 13 151/2 13 21 8 10 8 151/2 9 151/2 10 151/2 10 21 P 8 10 8 151/2 8 151/2 10 151/2 10 21 Q 9 10 10 151/2 9 151/2 10 151/2 11 21 R 10 10 10 151/2 10 151/2 12 151/2 12 21 s 8 10 8 151/2 8 151/2 10 151/2 10 21 T 6 10 6 151/2 6 151/2 7 151/2 8 21 u 8 10 8 151/2 9 151/2 10 151/2 10 21 V 7 10 7 151/2 7 151/2 9 151/2 9 21 w 12 12H 12 151/2 13 191/2 15 191/2 15 25 X 8 10 8 151/2 9 151/2 9 151/2 9 21 Y 6 10 6 151/2 6 151/2 7 151/2 8 21 Z 8 10 8 151/2 8 151/2 9 151/2 11 21 & 8 10 8 151/2 9 151/2 9 151/2 10 21 1 4 10 4 151/2 4 151/2 5 21 2 9 10 8 151/2 8 151/2 11 21 3 9 10 7 151/2 7 151/2 9 21 4 7 10 7 151/2 7 151/2 11 21 5 10 10 10 151/2 10 151/2 12 21 6 9 10 8 151/2 9 151/2 11 21 7 6 10 6 151/2 6 151/2 8 21 8 11 10 11 151/2 8 151/2 10 21 9 9 10 8 151/2 9 151/2 11 21 $ 8 10 8 151/2 151/2 8 151/2 151/2 8 21 The supporting cable is usually attached to the electric sign somewhat back of its outer end, and it may be assumed that the cable carries about 60 per cent of the weight of sign. V7ith this assumption and 208 ELECTRICAL TABLES AND DATA using a safety factor of 5, the strength of the cables necessary to support it can be found by the formula i. H where W = weight of sign; // = height of attachment to wall above sign, and D^the distance from attach- ment on sign to a point vertically under sign support. Table LXVIII is calculated according to this for- mula (omitting W), and to find the proper cable to support a given sign it is but necessary to multiply number found at intersection of line pertaining to height of support and that pertaining to distance of sign attachment from wall, by the weight of sign. The result will give the breaking strain of the neces- sary cable. T ABL ,E LXVIII Distance from Wall to Attachment on Sign in Feet Supports for Height of Weight Cable Fast of Si :cning gn. Above Sign in Feet 3 4 5 6 8 10 12 14 16 18 20 4 5 4 4 3.6 3.4 3.2 3.0 3 3 3 3 5 6 5 4.2 3.7 3.5 3.3 3.2 3 3 3 3 6 7 5.4 5.0 4.2 3.8 3.5 3.4 3.2 3 3 3 7 8 6.0 5.1 4.7 4.0 3.7 3.5 3.4 3.3 3 3 8 8.6 6.8 5.7 5.0 4.2 4.0 3.6 3.5 3.4 3.3 3 10 10.5 8.1 6.9 6.0 5.0 4.4 3.9 3.8 3.6 3.4 3.3 12 ]2.4 9.4 7.8 6.7 5.4 4.6 4.3 4.0 3.7 3.5 3.4 14 14.6 11.1 9.0 7.8 6.0 5.2 4.8 4.1 4.0 3.9 3.7 SIDE GUYS FOR SIGNS The wind pressure on the ordinary sign must be calculated on the basis of 20 lbs. per square foot and requires much better supports to mthstand it than are necessary to support the weight of sign, although they are never so provided. ELECTRICAL TABLES AND DATA 209 The table below has been calculated according to the same general formula as the one above. To find the proper size of cable for side guys, multiply the num- ber of square feet in sign by number found where lines pertaining to the two fastenings of side guys cross. TABLE LXIX Distance of Attachment on Distance of Guy Attachment on Wall from Sign from Wall Sign in Feet, ' 3 4 5 6 7 8 10 12 14 16 2 17 17 16 15 15 14 14 14 14 14 3 21 18 18 17 16 15 14 14 14 14 4 24 20 18 17 16 16 15 15 14 14 5 27 22 20 19 18 17 16 16 15 14 6 31 25 22 20 19 18 17 16 15 15 7 34 28 24 22 20 19 18 17 16 15 8 38 32 27 24 21 19 18 17 17 16 9 44 35 29 26 22 21 19 18 18 17 10 48 38 32 28 24 23 20 19 18 17 12 57 45 37 33 27 25 22 21 19 18 For signs hung at comers the distance of guy attachment on wall must be taken as the point at right angles to sign where the guy would strike wall if it were at right angles to sign. TABLE LXX Table showing approximate strength in pounds of Standard Steel Strand — American Steel & Wire Co. Diameter Approximate Diameter Approximate in Inches Strength in Inches Strength i 8,500 lbs. 3\ 1,800 lbs. A 6,500 lbs. 1% 1,400 lbs. 8 5,000 lbs. A 900 lbs. A 3,800 lbs. i 500 lbs. i 2,300 lbs. i2 400 lbs. 210 ELECTRICAL TABLES AND DATA Cable Supports for Signs Over Streets, — Signs of this kind are usually supported from steel cables swung across street, or other open place, from the tops of buildings or suitable poles. The table below gives the stresses caused by various loads per foot evenly dis- tributed, and also for loads suspended from center. The arrangement of sign is usually such that neither case exactly applies, so that an approximate mean of the two must be taken. The calculations are for a 100-foot span and a sag of 4 feet. - TABLE LXXI Diam- stress eter TVt. Approxi- Caused by- of per imate Cable Distr ibuted Load Load in i Center Cable Foot Strength Alone Pou] nds Stress Pounds Stress 15 4.85 84,000 1,500 50 17,140 2,500 15,625 1* 3.55 60,000 1,109 30 10,484 1,500 9,375 H 2.45 46,000 766 20 7,015 1,000 6,250 1 1.58 28,000 493 15 5,181 750 4,687 1 1.20 22,200 375 12 4,125 600 3,750 t 0.89 15,600 278 9 3,090 500 3,125 The above figures represent the maximum loads which should be suspended by such cables unless a greater sag is allowed, and do not take wind pressure into consideration. See ^'Side Guys." The above figures are based on the following for- mulae used by American Steel and Wire Co. : ^i~~qT' gi^iiig stress for evenly distributed load, and Wl So^-rr- for stress due to load in center. S = stress on cable W - weight per foot of cable and load if evenly dis- tributed, or load in center Z = length of span cZ=sag in feet. ELECTRICAL TABLES AND DATA 211 To find total stress those due to cable and load must be added. Slide Rule. — ^I^'igure 22 is an illustration of the ordinary slide rule. The numbers on the top, or A, scale, may be read naturally as 1, 2, 3, 4, etc., ending with the last figure 1 at the right, which would then be called 100, or these values may be considered in- creased or decreased to any extent by adding or prefixing the necessary number of ciphers. Thus if the 2 is called 20 or 200 the 3 would be called 30 or 300, etc. The same also holds true of the upper half of the slide, or B scale. The divisions between the main figures are of various dimensions, but serve only Figure 22. — The Slide Rule. to designate fractional values of the figures. The principle of operation can easiest be made clear by examples. Multiplication, — Set the 1 on upper half of slide under one of the factors on scale A, Find the other factor on the slide and directly above it you have the product. Multiply 4 by 2. Setting the slide as directed we find 8. This same setting might be used to multiply 40 by 20, or 4000 by 2 or 200. We have but to note as we go along by how much we increased the value of either of the factors, and add the cor- responding number of ciphers. Different settings could also be used for the same problem. Consid- erable practice is necessary before one can become really proficient in these calculations. Division. — In division the above process is reversed. Place the divisor on the slide under the dividend on 212 ELECTRICAL TABLES AND DATA scale A and the 1 on slide will be directly below the quotient. Miiltiplication and Division Combined. — -o 1 7x3x4 Example: — -^ Set 1 on slide under 7, note product above 3 ; next set 1 on slide under this product and note product above 4. Now move slide back until 6 is under last product and find answer above 1. Proportion, — By setting any number on B against any convenient number on A it can be seen that all other coinciding numbers are in the same proportion to each other. Hence any problem in direct propor- tion can be solved by simply setting the first term on B against the second on A; this being done, we shall find the last term directly above the third on B, Example: If 7 bushels of wheat cost $13.00, how much will 23 bushels cost? Answer, $42.71. In direct proportion all factors are either increasing or decreasing. If they are mixed it is termed Inverse Proportion. In order to solve a problem in inverse proportion we invert the slide, but continue to read A and B together. Example: If 9 men can do a piece of w'ork in 17 days, how many days will 13 men require? Inverting the slide and setting the 9 on the left under 17 and bringing the runner over the 13 at the right at about the center of the scale, we find 11.8 as the answer. Squaring Numbers and Extracting Square Roots. — When the slide is set even on all sides, the numbers in the scales A and B are the squares of those in C and 2). Hence also those in the last named scales are the square roots of the upper. They must, how- ever, be taken with the proper number of ciphers. The square of 2, for instance, is 4, that of 20 is 400 ELECTRICAL TABLES AND DATA 213 and that of 200 equals 40,000. In extracting square roots, if the number of digits is odd, 4, 400, etc., the root will be found directly under the number on left hand side of scale. If the number of digits is even, it will be found on right hand side, viz., square root of 40 equals 6.41. Extracting Ciibe Root, — Set the runner on the number, the root of which is to be found, and shift the slide until the same number found under this num- ber is also found under the index of the slide on the lower part D. According to location of runner either the right or left hand index must be used. Practice raising number to the third power; reversing this process will show method of extracting roots. Sockets. — Nearly all lamps used in this country are fitted with the well-known Edison base. A few old installations equipped With the T. H. base still remain, but are usually equipped with adjusters to permit the use of Edison base lamps. The standard sockets as recognized by the N. E.G. are given below : Classification. — Sockets to be classed according to diameters of lamp bases, as Candelabra, Medium and Mogul. Base to be known respectively as ^ inch, 1 inch and 1^ inch nominal sizes, with ratings as specified in the following table : > Eatings n Key * Keyless Max. Max. Amp. Amp. at any at any Nominal Volt- Volt- Class Diam. Watts Volts age Watts Volts age Candelabra i in. 75 125 f 75 125 1 Medium 1 ^^ 250 250 2i 660 250 6 (a)660 250 6 660 600 Mogul IJin. 1,500 250 (b) 1,500 600 214 ELECTRICAL TABLES AND DATA (a) This rating may be given only to sockets having a switch mechanism which produces both a quick ^^make'' and a quick ^^ break'' action. (b) Ratings to be assigned later, pending further discus- sion with manufacturers. Miniature sockets and receptacles having screw shells smaller than the candelabra size may be used for decorative lighting systems, Christmas tree light- ing outfits, and similar purposes. Double-ended Sockets. — Each lamp holder to be rated as specified above, the device being marked with a single marking applying to each end. In addition to these there is the Edi-Swan base, which is f inch diameter, and has bayonet-type con- nections and is sometimes used on automobiles and other places where there is muish jarring. The Edison miniature base is § inch in diameter and is used only for low voltages. Some very small lamps are made without bases, the wires connecting direct to lamp terminals. The mogul socket is used for series in- candescent lighting and often fitted with automatic cut-out. It is also used for gas-filled lamps of 300 watts or over. Fiber lined or brass shell sockets should not be used in damp places, or where corrosive vapors exist. Key sockets should also be avoided in damp places, or where inflammable gases may exist. Sparking Distances. — Very high-test voltages are often measured by their sparking distance. The fol- lomng table gives the sparking distances between sharp points corresponding to different alternating current voltages, when the ratio between maximum and mean effective voltages is equal to 1.41, or the square root of two. The values given were derived from a long series of careful and accurate tests. ELECTRICAL TABLES AND DATA 215 TABLE LXXII (Copyright, 1906, by Standard Underground Cable Co.) Spark Spark Spark Volts Distance Volts — Distance — Volts — Distance — A. orB. A. B. A. B. 1,000 0.028 18,000 0.945 0.945 35,000 1.840 1.895 2,000 0.098 19,000 0.995 0.995 36,000 1.900 1.958 3,000 0.159 20,000 1.042 1.042 37,000 1.945 2.020 4,000 0.216 21,000 1.092 1.097 38,000 2.012 2.085 5,000 0.270 22,000 1.143 1.150 39,000 2.062 2.153 6,000 0.324 23,000 1.195 1.206 40,000 2.127 2.220 7,000 0.378 24,000 1.247 1.260 41,000 2.190 2.290 8,000 0.432 25,000 1.300 1.314 42,000 2.247 2.360 9,000 0.487 26,000 1.353 1.373 43,000 2.308 2.434 10,000 0.540 27,000 1.405 1.427 44,000 2.370 2.506 11,000 0.595 28,000 1.460 1.485 45,000 2.432 2.580 12,000 0.644 29,000 1.512 1.540 46,000 2.495 2.660 13,000 0.695 30,000 1.566 1.600 47,000 2.560 14,000 0,746 31,000 1.620 1.655 48,000 2.625 15,000 0.797 32,000 1.675 1.712 49,000 2.692 16,000 0.845 33,000 1.728 1.772 50,000 2.760 17,000 0.897 34,000 1.785 1.833 SPARKING DISTANCES IN INCHES. Column A gives spark distances with 10 inch con- cave metal shields, the plane of whose edges was 1 inch back of the needle points. Column B gives the spark distances without shields. Sharp needles are essential for uniform spark dis- tances, as points measuring from 0.001 inch to 0.002 inch gave in many instances spark distances that were from 20 to 45 per cent greater than those ob- tained with sharp points. See also table of A. I. E. E. in Standardization Recommendations. Specific Gravity (Solids). — The specific gravity of a substance is defined as the ratio of the weight of that substance to the weight of an equal volume of water or air. Water is used as the standard of liquids and solids. Air at the temperature 0°, C. (32° F.) and 766 mm. mercury pressure for gases. By multiplying the specific gravity of any substance by the weight 216 ELECTRICAL TABLES AND DATA of an equal volume of water we find the weight of that volume of the material. The weight of a cubic foot of water is approximately 62.5 lbs. The weight of a gallon is approximately 8.33 lbs. To find the specific gravity of a body heavier than water approx- imately by experiment, weigh it in air and then weigh it in pure water. Divide the weight in air by the loss of weight (buoyancy) in water and the quotient will give the specific gravity. If the body is lighter than water load it down with a substance heavy enough to sink it. Then weigh the two submerged together. Also weigh both separately in air and the heavy body in water. Subtract the buoyancy of the heavy body from the buoyancy of the two bodies to- gether. The remainder will be the buoyancy of the lighter body by which its weight in air is to be divided as before. Specifications. — In many cases preliminary specifi- cations, setting forth what the purchaser desires, are made out. Unless these are quite broad many dealers or manufacturers may not be able to comply with them and for this reason often submit specifications of their own, and thus the final specifications which form the basis of contracts must be somewhat modi- fied. In general, specifications may be divided into two parts: one part which deals with machinery and materials, and another which deals with the installa- tion work and results to be obtained. If certain materials are specified, and at the same time require- ments as to certain results are made, there is always a chance for disputes as to who is responsible in case the installation does not fulfill requirements. Unless the work is to be carried on under the supervision of a consulting engineer, it is best to give the contractor free choice of materials and hold him entirely re- sponsible for the final result. ELECTRICAL TABLES AND DATA 217 All specifications should be based upon the stand- ards of the engineering societies governing the par- ticular kind of work. The A. I. E.E. have standard- ization rules which govern everything electrical, but these do not largely concern themselves with safety rules. In this regard the National Electrical Code should be adopted as the standard and all material and workmanship should be specified to conform wdth its requirements. This is a reliable guide in every respect except that of economy and efficiency and suitability of systems, etc. It deals only with safety and reliability. It is best always to have some sort of a plan show- ing location of cut-out centers, switches, lights and motors, or any other parts about which there may afterwards be disputes. If there are no plans the location of cut-outs and other conspicuous elements should be mentioned in the specifications. They should also mention how much conduit, open or mold- ing work is to be used. Every item mentioned should form a clause and these should be numbered for reference. Where accurate calculations are to be made, all circuits and runs of w^ire should be measured and the specifications thoroughly read and considered. The estimator should take plenty of time to understand every phase of his job. As a reminder of the many items so easily overlooked, he should have prepared an estimate sheet on the order of that following which is furnished by courtesy of the National Electrical Contractors' Association. Large apartments, hotels, etc., usually have many floors and rooms which are exact duplicates, and very careful measurements of one floor or room will answer for the whole building or that part of it which is typical. Table LXXIII shows approximate quantities of material used for rough wiring in average flats. 218 ELECTRICAL TABLES AND DATA p t^ 5r ►^ CO S05 a* 00 p ,E OP p (D OQ 3. El 03 fD CO O fD O • o =• p « P c p p CO » O n ►— • 2 » P i PC a. c All Center Lights. Switches, Moulding All Brackets. No Switches. Conduit if 1 IF ill t ^r; f 5 CfQ TO 3 • * .- • ' •- 1.0- G- 9 p ? El TO ? cn $. en. c_ TABLE SHOWING APPROXIMATE QUANTITY OP ROUGH MATERIAL PER OUTLET IN AVERAGE FLATS. ^^t tots 4^ >(■ = g: ^^^ : j Ft. Single Wire. 11 . M ^ M : : ^ Ft. Twin Wire. tsSOO •*- : *^ '^\ : tcoo ksH Ft. Loom. •^ No. Lock Nuts AND Bushings. >— ' • • • »— » No. Couplings, D Extra. | «»-<»♦-«♦-'• •Haf- »H*- •♦-•I*-**-. Lb. Nails. k*'- **-'• k:f -'• Oz. Brads. ; ; [ i ; i i ] ] Rolls Tape, Each Kind. il ELECTRICAL TABLES AND DATA 219 National Electrical Contractors' Association Universal Estimate Sheet. Bid Goes to Address No. Lights Architect or Engineer No* cTrcSuf : : : : : [Address Arch, or Engr No*. Base Plug's. *.*.'. Name of Job or Building Estimate No. .. No. Telephones... .Location of Job of Building.. S^^et No No. Motors ^ ,, mil TVT H. P. Motors See Mr Telephone No.... Date 19.. No. Fixtures. Bid Must Be In by M. . K. W. Generator. . o 1 Switchboard Salesman , job No Material Estimated by Labor Estimated by Priced by Approved by Conduit, Rigid Conduit Elbows Conduit Bushings Conduit Straps Conduit Hangers Lock Nuts Conduit Flexible Conduit Fittings Conduit, Non-Metallic Ceiling Boxes Br&cket Boxes Switch Boxes Floor Boxes Box Covers Fixture Hangers Cutout Cabinets Panelboards Metering Panels Meter Loops Cutout Boxes Asbestos Cut Out Blocks Fuse Plugs Enclosed Fuses Flush Switches D. P. Flush Switches 3 Way Flush Switch 4 Way Flush Switch Snap Switches! D. P. Snap Switches 3 Way Snap Switch 4 Way Snap Switch Knife Switches Door Switches Pendant Switches Rubber Covered Wire Lead Covered Wire Fixture Wire Special Wire Lamp Cord Reinforced Cord Packing House Cord Show Window Cord Molding Wood Molding Metal Molding Fitting Fixtures Clusters Key Sockets Keyless Sockets Wall Sockets Rosettes Socket Bushings Cord Adjusters Shades Shadeholders Adapters Attachment Plugs Lamps, Incandescent Lamp Guards Arc Lamp Cleats Knobs Tubes Screws Nails Toggle Bolts Annunciators Annunciator Wire Annunciator Cable Elevator Cable Bells Buzzers Push Buttons Silk Cord Door Openers Burglar Alarm Batteries Bell Ringers Telephones Telephone Cable Speaking Tube Whistles Letter Boxes Tape Solder Compound Acid Oil Car Fare Cartage Bond Drafting Inspection Incidentals Bid Sent to Following: Total Material Labor Overhead Expenses Profit Bid Per cent Per cent 220 ELECTRICAL TABLES AND DATA Figures 23, 24 and 25 will assist in illustrating the most economical manner of running wires for branch circuits. In Figure 23 the heavy black lines denote the mains, and at their terminals the cut-outs are located. It is never economical to push mains any farther than is necessary to enable one branch circuit to reach the far end of the space to be covered. In the arrangement shown in Figure 23 the greatest possible economy would be effected if a cut-out were ' Figure 23. — Comparison of Materials, provided for each cir(3uit, but for various reasons this is not advisable. The next best arrangement is to provide a number of cut-out centers as shown in the figure, locating each cut-out in the center of the group it is to supply. In case a given number of lights are to be fed with wires running at right angles, the most economical arrangement can be found by running a straight line through the space covered at such point as to leave an equal number of lights on each side of it, as in Figure 24. If the lights are to be fed by diagonal runs, the shortest runs can be quickly found by bearing in ELECTRICAL TABLES AND DATA 221 mind that from the cut-out center, or from any outlet, this point in connection with any two other outlets forms a triangle and it is merely necessary to avoid using the longest side of this triangle. The position X3r Q X3t- B- Q & ^ ^ Figure 24. Figure 25. of lamps shown in Figures 24 and 25 is identical, but Figure 25 requires about 10 per cent less material than Figure 24, The relative economy of running mains or branch circuits can be determined by Table LXXIV, which gives the equivalent in mains of vari^ ous sizes and branch circuits of 660 watt capacity. 222 ELECTRICAL TABLES AND DATA TABLE LXXIV Showing Mains and Their Equivalent in No. 14 Branch Circuits. 2 Wire Mains Branches 2 ft. No. 14= 4 ft. No. 14 2 ft. No. 12= 6 ft. No. 14 2 ft. No. 10= 8 ft. No. 14 2 ft. No. 8=10 ft. No. 14 2 ft. No. 6=16 ft. No. 14 2 ft. No. 5=18 ft. No. 14 2 ft. No. 4=22 ft. No. 14 2 ft. No.. 3=26 ft. No. 14 2 ft. No. 2=30 ft. No. 14 2 ft. No. 1=32 ft. No. 14 2 ft. No. 0=40 ft. No. 14 2 ft. No. 00=50 ft. No. 14 2 ft. No. 000=58 ft. No. 14 2 ft. No. 0000=74 ft. No. 14 3 Wire Mains Branches 3 ft. No. 14= 10 ft. No. 14 3 ft. No. 12= 12 ft. No. 14 3 ft. No. 10= 16 ft. No. 14 3 ft. No. 8= 22 ft. No. 14 3 ft. No. 6= 32 ft. No. 14 3 ft. No. 5= 36 ft. No. 14 3 ft. No. 4= 44 ft. No. 14 3 ft. No. 3= 52 ft. No. 14 3 ft. No. 2= 60 ft. No. 14 3 ft. No. 1= 64 ft. No. 14 3 ft. No. 0= 80 ft. No. 14 3 ft. No. 00=100ft. No. 14 3 ft. No. 000=116 ft. No. 14 3 ft. No. 0000=148 ft. No. 14 Street Lighting. — In villages and suburbs, the street lighting is often of a perfunctory nature. It consists often merely of an incandescent or arc lamp placed at each street intersection. Such lights should be over center of streets. In parks, the object of the illumination must be not merely the road or path, but fields and lagoons as well. At band-stands and sim- ilar places, arc lamps are preferable, but where the lights must be brought down under trees they are not very serviceable. Along curved driveways place lights on the outer curve; this will enable drivers to see farther, but will require more material. In business streets a very brilliant illumination is often desired. Tungsten lamps, installed on posts, ELECTRICAL TABLES AND DATA 223 are the most common illuminants at present where a permanent installation is contemplated. For tem- porary effects festoons are much used. The systems upon which such lights are operated will usually be governed by that which is already in use. The fol- lowing points should be noted in connection with street lighting: Large units are most economical in first cost, but waste much of their light outside of the street. At street intersections this waste is not so great. Large units should always be hung high. A bright illumination, except on business streets, is not necessary, but the light should be white. For series incandescent lighting special lamps are always used. The thicker the filament the less will the flickering effect of low frequencies affect them. For overhead work wires smaller than No. 6 are seldom used. No incandescent lamp should ever be used outside without a reflector to prevent light being wasted on the upper air. Time switches are often serviceable on street lighting. Those who undertake to install a system of street lighting should prepare themselves for an unlimited amount of annoyance from residents who imagine their trees will be ruined or who quarrel about the location of poles and lamps. Switches. — The standard height of switches in offices and residences is 4 ft. 6 in. above finished floor. If switches of the push button type are used the white button should be uppermost. Switches should con- tain sufficient metal to prevent a temperature rise of over 28° C. (50° F.). There should be a contact surface of about 1 sq. in. for every 75 amperes. To obtain this contact surface large capacity switches are made up of a number of blades in parallel. This arrangement also allows better radiation. The fol- lowing table shows the capacity of single blades of dimensions given, the clip being assumed as of some width. 224 ELECTRICAL TABLES AND DATA TABLE LXXV Width, in... J I 1 f J I 1 li li If IJ 1| Amperes ....8 15 30 58 85 115 150 180 215 280 330 395 These widths will not determine capacity of switch unless the temperature rise is within the limits. Below are given the dimensions and spacings of knife switches as required by the N. E. C. Over all dimen- sions of standard knife switches as made by the George Cutter Company are given on pages 226 and 230. Spacings a7id Dimensions. — Spacings and dimen- sions must be at least as great as those given in the following tables: TABLE LXXYI Not over 125 volts d. c. and a. c. For switchboards and panel boards: Minimum separation of nearest metal Width and Thickness parts of Minimum Clips opposite break Blades and Hinges polarity distance 30 amp . . .ixg^ in. 4x6% in. 1 in. 1 in. 60 amp liin. 1 in. TABLE LXXYII Not over 125 volts d. c. and a. c. For individual switches: Inch Inch Inch Inch 30 amp ixe\ Jx^^^ IJ 1 60 & 100 amp 1^ IJ 200 amp 2i 2 400 & 600 amp 2i 2i 800 & 1000 amp 3 2i A 300-ampere switch with the spacings of the 200-ampere switch above may be used on switchboards. ELECTRICAL TABLES AND DATA 225 TABLE LXXVIII 250 volts only d. c. and a. c. For all switches : Inch Inch Inch Inch 30 amp ix^\ ixe\ If 1^ TABLE LXXIX Not over 250 volts d. c. nor over 500 volts a. c. For all switches : Inch Inch Inch Inch 30 • amp fxj fx^V 2J 2 60 & 100 amp 2J 2 200 amp 2^ 2i 400 & 600 amp 2f 2i 800 & 1000 amp 3 2i A 300-ampere switch with the spacings of the 200- ampere switch above may be used on switchboards. Cut-out terminals on switches for over 250 volts must be designed and spaced for 600-volt fuses. TABLE LXXX Not over 600 volts d. c. and a. c. For all switches: Inch Inch Inch Inch 30 amp fxj fxJ^ 4 3i 60 amp 4 Si 100 amp 4i 4 Auxiliary contacts of either a readily renewable or a quick-break type or the equivalent are recom- mended for d. c. switches, designed for over 250 volts, and must be provided on d. c. switches designed for use in breaking currents greater than 100 amperes at a voltage of over 250. For 3-wire direct current and 3-wire single phase systems the separation and break distances for plain 3-pole knife switches must not be less than those required in the above table for switches designed for the voltage between neutral and outside wires. 226 ELECTRICAL TABLES AND DATA Hj d S> H^ -W< JN »JN W d O fcj 5 M O-M m < r^ laloo »o|ao «H« H» 'HN» HP, ffsH« OQ O p4 O •M • pH ^ 02 QQ fl M o H bO OS l-H n1 ^ eg fM cc O) ;h p - J3 4i h bo h- 1 Ph M 0^ P^ QQ M w a H • iH H oT tD d O CQ pj 05)30 >^» H* «lao "h Hoo "m Hao Hoo lolao t-loo r-iH< Hfrj Hc^ »H« Hhlt y^ rf* oiao eohi< C3H< H^ eshit Hn r ■) w}» H-H eolaj rHjoi eoloo H'-t ^ rH rH eg CO Tf* Tt^ CO CO t- M ,U K* O J rHle^ r^loO r^M< f-^hf r+* H^ rH|(N 0-<;rJHlOlOCOCOI>.t^OOOOOO 05 , o 1-tpi l-|^^^ eoHt CO CO CO Tt( lO lO CD (MCgcOCOCOTjHrtHlOLOCO JJj-.'O «N* r-ilso rH|Tj* t-i|Tj< i-i|c^ ,H|c^ esN* r^Cg(^^COCOrtlrt^L':)iOCOt>. f^N ihH4 nN< Hh* hH» hH» «I« i-i|oo t-GOOiCgcOrtllOCOt-OO 00 o ^^ (;C"t^ r-ir-iT— Ir-ir-ir-ir-ir- 1 . .O^ lOOt^OOCgcOCMCOrtHlO |o^ ^ ^ ^ ^ ^ ^ ^ ^ c^ P.& ooooooooooo dfiCOCOOOOOOOOOO U^ •»— 1— iCvlCOrtlCOOOOlOO *S * T—l 1— I eg ELECTRICAL TABLES AND DATA 227 00 t3^ CO O <^ O Oi« ^ ^ m 3 0) CD ^ H.^ O c: QQ ^ P= 2 CD O o <1 o p c-t- CD o' o Hi oooooooooo^cogp ooooooooooo -cP 08 K.^ OOlCd K^,H. OelM O > ^ <^ O Ci o «o (XH a|i" tM--9 ot)|Hk ooiis oc,i» to (_i o o oo oo o en rf=^ ^^^^ QdM ociax oc,-i iHw M,, tHHl l-i^ 0E|-» (W" OS!- * Oto >h^ l_a |_a i—k 1— k ^q Ol f+^ h-* • CO -^I h^ CO V. 6 :. or C. ^ OC,. . C^^ «« M.^ to 1— I I— I f-i H-l _ 00 V. D.C. r A.C O OO ^ h4^ • h-i O Oi Oi H. , W^"^ • 00|3X QD|W h-i- ^^ a-.;-' O K3 O 00 GO Oi • C7I >^ to t-* 50 V. D.C. r A.C. if^ca Hm W^ "W^ • ^03 M-l OtiM UiM (WW h-i I-' 1-^ to •—' 1— ' ^ * OO Oi rf^ rf^ 600 V. D.C. or A.C. .HM gu, (W^ W« • rf.qH' oeH <«"< ►^1-' OO CO CO to • l-i 1-^ 5^ (XiOT W-o • OdOT OBH lW« oolot to 1— i 1— I l-A ^ ^ 250" D.C or A. to "^ O Ci • to O Oi Ol H-;r-i If-I-^ <»|C0 . OOi-^ («C0 l-l-' p- <: C^ Q,iO Ot to to to M 1-A 1— ' .!>§ d to L-O CO • OT to CO • 9> H a o to a CO 0) u ELECTRICAL TABLES AND DATA 229 ->|--l 230 ELECTRICAL TABLES AND DATA H« y-^ r^ nH" t-|30 nbo 1-^ Hao €•** fj ^V" r-ijao kH" "-H M H» r-H n|oo Hoo Hoo r-H ^TH(MC^leOTt^iOlOlOCO;DCOOOOO w >< ^ w H H H p o • iH >^ H o o Q-^ C3 ^ 'Hoo Moo "Hoo '"'H' '-'(t^ '■^H' wH* wH* 'H|^ ■ Ji 1 1- _to »cto .to iftto Q H thIx Kl-f "-H M ^|» ihH eoloo HoO Hoo i-ff pq CO S o iH O o I »-<|c^ Hoo i^N* '^M H^ H"^ Hm H^ ecW eoH* r^jr^ r-|(N echjt CO CO CO TfH lO O CD t*to '-'l CqCOCOCOTtHTjHlOJOCOt^t-OO ecH< iHleo '-'W '-'W '-•ic^ Hn eoHt H^ H^ thh* e^ «W rH(MC\lCOCOTti'«^lOlOCDl:-t^OO iH|Tj( etHt t-W i-i|co t-loo Hf^ csloo H^ t-|oo H» l>.Q005Qt>.t>- ecto r-iH »-i(?< t~!oO »olaO i-i|ao --^H H^ H'-< "■ M CDODC^i— ICOrHUTJ^CDCDCDCiCi wto to «to ^to i-to r-to H«» H«o O wto iftS c.^^ w^ ""'^ «K e^^ t-'^ t-"^ riH i-i|(N Hoo Hrtl r-(|g0 >-l i'^ M r-,^ H ^^ "^M '^M Tt^O^>•OiO^H(^J(^^cOTt^Tt^l:^l^- ftft o o o o o o oJCCOCOOOOO ^^ •»— th c^^ CO ^ o o o o o o o o o o O b-^ o o o r-l rH (M CO "^ ELECTRICAL TABLES AND DATA 231 CO «rh CO o 2. o P CO § 3 " ^ <^ >-' * »b.O OOOatOOOCif^^^COtOt— « ^HlTca OOOOOOOOOOOOiCO 5-0 OOOOOOOOOOOOOtJ- to to ,fi|C9 K:ji-i iHh> «*-" oeH rf-(&9 (z^CT K:jH» oc|« «*» <«i8 *4-' •W-' w - cd , oiH cA-t. f5 ^ U K-j-^ rrj-^ Jii_, iKL. "I O *. I 00 00 ^ 3 -^^OiOiOiClC^^;^COcoto>•ghH^^• *-|M MiM *^C9 oqM OcfiT «(CT iHm cctca • o- O I— k|— '^•0?000«000--:i^OlCriHf^ uo.O| l_» 1-1 ^-i (_i t> MtO^ rfxcODOO* oocicotoro-c^l -q C5 oi CO > y^ "^ p\o^ O 00 Oi Oi a»- . *^i9 «(CT M„ icif or Y^ > p CD CD CD M« o p CO O Ha CD CD ^^ O 00 00 OCtM *4M to t)g1 ' o p.-< to •I-' 1— ' 00 OH ho p" p^ CO CO (WW OH CO to • Mm • I— i 1— ' I—' rf^jM 2 to l-i O 00 1— 1 to OCJM CO *4M 4^ P? to to CO h-» to o a- t— » 1— » 1— ' CO • p^ to to to LO to o • 1— « CO CO P^- o o 5* CD ►^OJCOtOtOtOh-»l— ' K*-" !<*-• iHl-* Mr-* it^-' iHM ►-*-• rf4is oclen »*- 232 ELECTRICAL TABLES AND DATA Switchboards. — The best material for mounting switches and bus-bars is marble. Slate may be used, but metal veins may cause trouble. A liberal allow- ance of space should be allowed back of board, and its panels should be kept well above the floor. Where more than one machine is connected it is customary to operate them in parallel on d. c. For dimensions of bus-bars, switches and fuses, see those headings. It is customary to provide the following instruments, etc., for good switchboards: One main three pole switch for each generator, where there are several operated in parallel. One ammeter for each gen- erator, or an ammeter arranged for connection to each machine. A voltmeter which may be connected to any machine, and also be used as a ground detector. One field rheostat for each machine. Sufficient pilot lights to illuminate board properly. In some cases also a wattmeter measuring the total current. Alternating current boards are also often equipped for parallel running, but not always. In some cases the board is divided and fitted with throw over switches so that either generator may supply every- thing connected, or only a part of it, as desired. The following equipment is commonly used : Main switch for each generator. Synchronizing lamps, or synchroscope. Frequency indicator. Power factor indicator. Voltmeter to be used as with d. c. machines. An ammeter for each phase, and also for each gen- erator. Exciter equipment. Wattmeters. To these must of course be added the necessary fuses and switches. The N. E. C, however, does not require fuses on a. c. generator or their exciters. If prac- ticable, light and power circuits should be kept separate. Symbols. — The following are the symbols recom- mended by the American Institute of Electrical Engineers. ELECTRICAL TABLES AND DATA 233 The following notation is recommended : Name of quantity Symbol Unit Voltage, e.m.f., potential difference. ... E, e, volt Current I, i, ampere Kesistance R, r, ohm Reactance X, x, ohm Impedance Z, z, ohm Admittance Y, y, mho Conductance . . .;4'ri; ; G, g, mho Susceptance ^,..»vv>. ; B, b, mho Power ^IJ, , .r . . . , P? P> watt Capacity . ,^1, ,. ^ ;",.,....... ^\ c, farad Inductance :^;. ........... L, henry Magnetic flifer. ." : . : ; . . : <|> maxwell Magnetic density. . . .'I. B gauss Magnetic forc'el .".'..'. *.X ,'^ .■..'........ ..H gilbert per cm. Length "; ;;. . *. . : . . : .^r .'.•: ; :\ L, 1, cm. or inch Mass i.-. . . . : ..-. .'. . . .-. . . .; M, m, gm. or lb. Time V.-s v v. ^ « » w . , 1 1 -:\ *w .-. . T, t, second or hour Em, Im and Bm should be used for maximum cyclic? values, e, i and p for instantaneous values, E and / for r. m. s. values, and P for the average value or effective power. These distinctions are not necessary in dealing with continuous current circuits. Vector quantities are preferably represented by bold face capitals. Testing. — It^:is assumed that the reader of this work is familiar with the general principles employed in testing, and therefore no attempt will be made to explain methods of using the various instruments. The list given in the following pages is intended as a reminder of the various instruments available for different purposes. Those about to undertake testing work with which they are not entirely familiar are advised to consult this list, and select those instru- ments needed. --Consult Standardization Rules of A. I. E.E. and N. E.G. and make tests in conformity with their standards. 234 ELECTRICAL TABLES AND DATA STANDARD SYMBOLS FOR WIRING PLANS As adopted and recommended by the Nattoaal Electrical CoNTRACTOHa Association of the United States. Ceiling Outlet; electric only. Numeral in center indicate! number of standard 16 c. p. incandescent lamps. 4 CJeiling Outlet; combination. 4-2 indicates 4-16 c. p. btand- ^ ard incandescent lamps and 2 gas burners. Bracket Outlet; electric only. Numeral in center indicates number of standard 16 c. p. incandescent lamps. 4 Bracket Outlet; combination. 4-2 indicates 4-16 c. p. stand* ^ ard incandescent lamps and 2 gas burners. Wall or Baseboard Receptacle Outlet. Numeral in center indicates number of standard 16 c. p. incandescent lamps. Floor Outlet. ^ Numeral in center indicates number of stand- ard 16 c. p. incandescent lamps. 6 Outlet for Outdoor Standard or Pedestal; electric only. Numeral indicates number of stand. 16 c. p. incan. lamps. S Outlet for Outdoor Standard or Pedestal; combination. #• 6-6 indicates 6-16 c. p. stand, incan. lamps; 6 gas burners. yj Drop Cord Outlet. dQ^ One Light Outlet, for lamp receptacle. Arc Lamp Outlet, m 9 Special Outlet, for lighting; heating and power current, as described in specifications. ^^(^^)^^Cei\ine Fan Outlet. C I S. p. Switch Outlet. Q 2 D. p. Switch Outlet. Q 3 3-Way Switch Outlet. Q 4 4-Way Switch Outlet. Show as many symbols as there are switches. Or in case of a very large group of switches, indicate number of switches by a Roman numeral, thus: SI XII; meaning 12 single pole switches. Describe type of switch in specifi- cations, that is. Flush or surface push button or snap. Copyright 1906 by the National Electrical Contractors' Association of too United States. Published by permission. ELECTRICAL TABLES AND DATA 235 STANDARD SYMBOLS FOR WIRING PLANS As adopted and recommended by the National Electrical Contbactobb Association of the United States. ^^ Automatic Door Switch Outlet. 5 ^ Electrolier Switch Outlet. 1^ Meter Outlet. [Distribution Panel, [junction or Pull Box. 6^ Motor Outlet; numeral in center indicates horse power. [Motor Control Outlet. 'Transformer. •■iii^i""""* •■■■■■■■» Main or feeder run concealed under floor, •■™iiiii"i"i"iiiiiiiM""""""» Main or feeder run concealed under floor above, •*• "» "i" "i" ■» ■■• Main or feeder run exposed. * — Branch circuit run concealed under floor, *■ ' ' ■ Branch circuit run concealed under floor above, '— — *— — — *-• Branch circuit run exposed. •^ —♦-——. — -.♦ — • Pole line. # Riser. Suggestions in Connection with Standard Symbols for Wiring Plans. Indicate on plan, or describe in specifications, the height of all outlets located on side walls. It is important that ample space be allowed for the installation of mains, feeders, branches and distribution panels. It is desirable that a key to the symbols used accompany all plans. If mains, feeders, branches and distribution panels are shown on the plans, it is desirable that they be designated by letters or numbers. 236 ELECTRICAL TABLES AND DATA STANDARD SYMBOLS FOR WIRING PLANS As adopted and recommended by the National Electrical. Contbactoss Association of the United States. ^ Telephone Outlet; private service. ^ Telephone Outlet; public service. Q BeU Outlet rV Buzzer Outlet. j ♦ 1 2' Push Button Outlet; numeral indicates number of pxishes. tm- ^bS Annunciator; numeral indicates number ot points. tmi ^ Speaking Tube. ^'^'^/C) Watchman Clock Outlet. Watchman Station Outlet. \J^ Master Time Clock Outlet, ■ | n Secondary Time Clock Outlet I I I Door Opener. jVj Special Outlet; for signal systems, as described in specifications 1 1 I 1 1 |Battery Outlet. ( Circuit for clock, telephone, bell or other service, ) run undc* floor, concealed. Eand of service wanted ascertained by symbol to which line connects. Circuit for clock, telephone, bell or other service, run under floor above concealed. Kind of service wanted ascertained by sjonbol to { which line connects. NOTE — If other than standard 16 c. p. incandescent lamps are desired, specifications should describe capacity of lamp to be used. ELECTRICAL TABLES AND DATA 237 TABLE LXXXIII Terminals. — George Cutter Co. Square Type, Cast. (See Figure 28.) O h-A-1 ]i m. u o r^-i « iO, o i-_j m }a=:^ ,-, £CK^^ Figure 28. — Terminals. Amps. 30 50 75 100 150 175 2oa 250 300 350 400 500 600 700 800 1000 Wire Size 8 5 3 1 00 000 0000 300000 350000 400000 500000 750000 1000000 1250000 1500000 2000000 Standard Dimensions, Inches A B C D E F G i li 11 If 2 2J 2i 2i J I A f J t 6 ■ A J il I if i 1 IS XG 1 1 li IJ li li If 2 2 1% i i A 3 i f ii 11 16 II 11 1 liV li I/b ij 2 2i A A 1 a's IS IJ A i^ li J4 i^ If A Ji IJ i Ji If il Ji If ih Ji 2 i Ji 2i A Ji 2f 11 Ji 2f lA JJ 3 lA il 3J lA il 3i li Ji 31 If §i 238 ELECTRICAL TABLES AND DATA Eound Type, Cast. Amps. Wire Size 30 8 50 5 75 3 100 1 150 00 175 000 200 0000 250 300000 300 350000 350 400000 400 500000 500 750000 600 1000000 700 1250000 800 1500000 1000 2000000 30 8 50 5 100 1 150 00 200 0000 300 350000 400. 500000 600 1000000 25- 50 6 75-100 3 150 200 000 300 300000 A B C D E F G A 9 IG i A i A A ii f 1*5 5 11 s'^a A a 1 A i li S-a & i-h 1 3^ i i§ Ji #2 lA 1 i t H A Ji lA li i ii li i Ji li U i 11 11 Jl Jl lA n A ii li ii ii U i§ A 1 2 f ii If u A 1* 2i il ii If 11 A li 21 il ii 2i Hi i If 3 lA ii 2| 2i f 11 3f lA ii 21 2i f li 3i lA ii 21 2i i 2 3i 11 ii 2i 21 5 2^- 4 If ii Eight Angle Type, Cast. i f i A A A A f 1 i 1 f ^\ A i§ f A' i 1 ii A 1 i A f li A ii u 1 1 il If i§ ii li li 1 1 li f ii li li f li If ii ii 2 If A If 2 lA ii Wrought Type. -^ A & A i A A i A i i li i i il ii i i li 1 ii lA i i i If i § li li i f 2 S ii ELECTRICAL TABLES AND DATA 239 Ammeter. — In choosing an ammeter one must con- sider whether it is for a. c, d. c. milli-amperes, full current, or shunt. Special instruments are made for each of these conditions; they are also made record- ing. Band Tester, — This is an instrument made espe- cially for testing the conductivity of rail bonds and rails. Cahle Testing Set. — Usually an instrument capable of locating faults in cables without cutting into the cable. Capacity Testing Sets. — A portable insulating and capacity testing set is made by the Leeds and North- rup Co. Other cable testing sets can also be used for this purpose. Current Transformers. — These instruments are used with a. c. circuits where large currents are to be measured ; also with wattmeters. Dynamometer. — This is a special form of galva- nometer which may be used for very accurate measure- ments of either voltage, current or watts. It can also be used for testing capacity and inductance and other tests for which volt or ammeters may be used. It is used mostly for a. c. work. Electrolytic Conductivity Apparatus. — The inter- nal resistance of batteries can be measured by means of the Wheatstone Bridge, but slight errors are pos- sible. To avoid these errors special apparatus has been constructed. Electrometer. — This is an instrument the operation of which is based on electric charges; used in lab- oratories for measuring difference of potentials. Frequency Meter. — Such instruments are used to determine the frequency of a. c. circuits. They may also be used as speed indicators. 240 ELECTRICAL TABLES AND DATA Fault Finder, — This is a name given to certain special forms of testing instruments containing a bat- tery and resistances and arranged to facilitate testing. Galvanometer, — The galvanometer is a very deli- cate testing instrument and exists in a variety of forms. It is more delicate than the telephone re- ceiver for d. c, and where there is much noise, but for fluctuating currents the latter is more serviceable. Ganges, — ^Wire gauges are used for measuring the diameters of wires, sheet metal, etc. See description under this heading. Ground Detectors. — Voltmeters and lamps are used for this purpose, as well as special electrostatic in- struments. Hydrometer. — This instrument is frequently re- quired in testing battery solutions. Illuminometer, — lUuminometers are of various kinds. Some of them are very simple and somewhat crude ; others are good photometers, a little more sim- ple and portable than the latter ; usually calibrated in foot candles. Induction Standards, — Self and mutual induction standards are used in connection with the Wheatstone Bridge for comparing inductances. Iron Loss Watt and Voltmeters, — This is a special instrument made by the Westinghouse Co. for meas- uring the iron losses in transformers. Keys, — For high potential or precision work spe- cially constructed keys or switches are employed. Lamp and Scale. — For reflecting galvanometers a special lamp and scale are often required. Megger. — This is a trade name for a special testing set gotten out for general purposes. Meter Testing Sets. — These are special plugs and connections to facilitate the testing of wattmeters. ELECTRICAL TABLES AND DATA 241 Micrometer, — This instrument answers the same purpose as the wire gauge, but is much more accurate and can be used for very accurate measurements. Multipliers, — These are resistances intended to be placed in series with voltmeters and which enable the voltmeters to be used for the measurement of higher voltages. Ohm-meters. — This is a simplified form of "Wheat- stone Bridge and is used for the same purposes; measuring resistances, detecting faults, etc. Oscillograph, — This is an instrument used for re- cording accurately the variation in the wave form of an alternating current or e. m. f . Permeability Meter, — The permeability meter is used for testing samples of iron as to their magnetic reluctance, or permeability. Phase Rotation Indicator. — This is an instrument used in determining direction of rotating field, or in connecting motors, etc. Photometer, — This device is used to measure inten- sity or degrees of illumination. Some photometers are cumbersome laboratory instruments; others are portable. Polarity Indicator, — This is*an instrument used to determine the polarity of electric currents ; also made to determine the polarity of magnets. Potential Transformer, — This is a piece of ap- paratus used mostly for reducing the voltage by a fixed ratio so as to bring it within the range of in- struments. Power Factor Meter, — This piece of apparatus indi- cates the phase relation between the current and e. m. f . of the circuit, or generator, to which it is connected. Pyrometer. — The pyrometer is used for measuring heat. Some pyrometers depend upon electrical prin- 242 ELECTRICAL TABLES AND DATA ciples for their action. They are sometimes used to determine the temperature of field coils. Resistances. — Separately mounted resistances are sometimes used in connection with the Wheatstone Bridge and other instruments to enlarge their scope. Rotating Standard. — This is a wattmeter in which a pointer moves rapidly, its movement being in pro- portion to the power consumed in the circuit at the time. It is especially designed to facilitate compari- son of meters with it. Sechometer. — This is an instrument used to measure coefficients of self-induction. Shunts. — These are used in connection with am- meters and so chosen that only a predetermined por- tion of the total current shall pass through the meter. Slide Wire Bridge. — This is a modification of the Wheatstone Bridge. Standardizing Set, — This is usually an arrange- ment of instruments of high grade which may be used to calibrate or standardize other instruments. Synchroscope. — This device indicates the phase dif- ference between two currents or e. m. f.'s to which it is connected. Tachometer. — This is a speed indicator, usually ar- ranged to be held against end of shaft. When fitted also with a stop watch, it is known as a tachoscope. Telefault. — This is a special type of testing instru- ment manufactured by Matthews & Bro., which en- ables certain tests to be made without cutting into the wires; can also be used for locating underground pipes. Telephone Receiver. — The receiver is very sensitive to fluctuations in current strength and is much used for testing. With d. c. it gives only one click when current is switched on or off. Where there is much noise it is somewhat handicapped. ELECTRICAL TABLES AND DATA 243 Thermometers, — These are used in testing ma- chinery and wires. Specially constructed instru- ments are mostly used. Voltameter. — An instrument measuring current strength by the amount of electrolyte decomposed. Volt-ammeter, — An instrument capable of measur- ing both current and voltage. Voltyneters, — They are used for measuring p. d. Not all are suitable for a. c. and d. c. ; some are elec- trostatic, some read in milli-volts and are recording. Wattmeters. — These are used for measuring power. Not all of them are suitable for d. c. and a. c. Wheatstone Bridge, — This is the best known of all electrical testing instruments. With it more tests can be made than w^ith any other device. It is, how- ever, cumbersome and more difficult to handle than many of the other instruments. Thawing Water Pipes. — Special stepdown trans- formers are generally used for a. c. and must have at least 200 amperes capacity for the smaller pipes and should have much more for larger ones. Storage batteries have also been used. Theatres. — A full treatise on this subject is given in ^^ Motion Picture Operation, Stage Electrics and Illusions. ' ' Arc Pockets, — These should be wired with no smaller than No. 6 ; switched at the board, and open at the bottom to prevent accumulation of dirt. Large theatres can well use pocket capacity for twenty arc lamps. The pockets should be arranged off stage, as close to the scenery as practicable. Each pocket usually contains four circuits. Auditorium, — Some auditoriums are thickly stud- ded with lamps, the purpose being to produce dec- orative effects. In such cases frosted lamps are advisable. The actual illumination may be brought 244 ELECTRICAL TABLES AND DATA about by arc lamps, or large chandeliers. Unless dec- orative effects are striven for, one 50-watt lamp will furnish enough illumination for twenty seats. From two to ten fan motors should be provided for, accord- ing to size of theatre. It is impossible to arrange a system of direct lighting in connection with which some of the lights will not be in the range of vision of part of the audience at least. If the expense is not prohibitive cove, or indirect lighting, would be very serviceable. Cove lighting is very useful to show off decorations about proscenium arch. Balcony. — In the balcony or gallery, provision for several arc lamps should be made. These should also be controllable from the main board. The ceilings in balconies are usually low,- and lights must be kept well back to avoid range of vision of spectators. Use inverted lighting or small e.p. lamps kept well up at ceiling. Provide for fan motors. Blinding Lights, — This is a row of lights sometimes placed about proscenium arch, the purpose being to blind the audience for a few moments to permit a quick change of scenery. Lamps of high intrinsic brilliancy should be used. If decorations are of a light color, or emergency lights must be kept burning, the plan is not very successful. Never frost lamps used for this purpose. Borders, — From one to six borders, according to size and pretensions of house, are installed. Feed borders to center. Leave cables long enough so bor- ders may be lowered to within five feet of stage floor. Use slow-burning wire and arrange for color circuits. Borders should be suspended by wire rope and in- sulated. Lamps are placed from six to twelve inch centers. The proportion of white and colored lamps is: two white, one red and one blue. Some borders are provided with a special circuit providing just light enough for rehearsals. ELECTRICAL TABLES AND DATA 245 Bridges. — This is a name given to small galleries usually located at each side of proscenium and open- ing on stage side. Arc lamps are often operated from these bridges and arc pockets should be pro- vided. This is also a good place from which to con- nect stage chandeliers. Bunch Lights. — These lights are mostly fed out of stage pockets. The bunch circuits should be switched at the board, and some of them at least should be grouped with color circuits. Plugs used for incan- descent circuits on stage should not be interchange- able with arc lamp plugs. Canopies. — Most theatres are equipped with cano- pies in front of house. These are often studded with lights. Arrange for low-wattage lamps and have them frosted. Arrange lamps to be out of weather. Sometimes provision is made for lamps in glass signs ; 1320 watts will be allowed per circuit with these lights if they are properly wired for. Chandeliers. — Large chandeliers are often used in theatres. These should be hung so they may either be raised or lowered for renewal of lamps. Curtain. — In large cities all theatres are fitted with heavy asbestos and steel curtains. These usually re- quire motors to operate them. In some cities hy- draulic operation is required. In some cases the drop curtain is also operated by motor. Damper. — All good theatres are provided with stage dampers which can be instantly opened in case of a fire on the stage. It is customary to hold the damper closed by an electromagnet, and to place a switch on each side of stage, said switch when opened releasing the magnet and allowing the damper to open. Dressing Rooms. — Arrange dressing room illumina- tion without cords if possible. Provide circuit for flatiron. Cover each lamp with a strong locked 246 ELECTRICAL TABLES AND DATA guard. Arrange lights so that each side of face is illuminated by at least one lamp. Door switches are useful in dressing rooms. Emergency Lighting. — Every theatre should have an emergency lighting system capable of furnishing sufficient light for the audience to leave the house in case the main system fails. The emergency system should be entirely independent of the other lighting and in no way connected with it. It is customary to provide capacity for about one 25-watt lamp for each 400 square feet of auditorium space. To this emer- gency system may also be connected a sufficient num- ber of exit lights to indicate doors and fire escapes. Allow no key sockets, fan motors, or other devices on emergency lighting circuits. Fire Alarm, — Provisions for fire alarm should be made. It is customary to connect the stage with the box office through a signal circuit that can be used for various purposes. Fire Pump, — This is provided to insure good pres- sure in case of fire. It must be wired for in the most substantial and reliable manner. Fly Floor. — This is that part of the gallery above stage, from w^hich stage hands operate the curtains. A few lights only are needed, but they should be located convenient for men lounging between acts. Footlights. — These form the most important and effective part of the permanently located stage lights. They must be very carefully located so as to illumi- nate the lower part of stage without obstructing the view of the audience. Lights are generally studded as thickly as possible, and about half of them arranged for white and the other half divided into two colors. Galleries. — On these pockets for arc lamps, etc., are usually provided. Grid. — This is the name given to that part of the rigging loft to which sheaves, etc., operating curtains ELECTRIC AL TABLES AND DATA 247 and drops, are attached. Provide one light for each 400 square feet. Lobby. — The lobby is usually very brilliantly illumi- nated, but the lights must be controlled by switches so that most of them may be turned out when the audi- ence is inside. Provide side outlets for picture illu- mination, etc. ; also for portable signs. Orchestra Lights. — The largest theatres have about 100 outlets for orchestra lights. Less than twenty should not be considered in any first-class house. Place fuses on switchboard and arrange control so that one of the musicians can control lights in dark scenes. Program Board. — This is an arrangement of lights by which the next number on the program can be given the audience. A special outlet at each side of stage should be provided for it. Run large conduit, as many wires must be accommodated. Proscenium Side Lights. — These lights are arranged at each side of proscenium opening on stage side. Sometimes they are wired for three colors. Retiring Rooms. — These are usually wired in imita- tion of homes, cozy comer effects, table lamps, etc. Illuminate pictures on walls. Stage Switchboard. — The stage switchboard is usually located on right hand side of stage, facing the audience, and it is preferable to elevate it above stage level. The wiring of a good board should be divided into four parts, each independent of the others. All of the house lights should be controlled by one main switch; the footlights and all of the upper part of stage lighting by another, and the stage pockets by a third. In addition to this there should be a division to which lights that remain in use all of the time are connected. The stage lighting is again divided into three color groups, the Avhite 248 ELECTRICAL TABLES AND DATA lights being equal numerically to all of the colored lights. A list of the circuits which should be independent of all others and make up group four is given in the following : Dusting circuit. Fan motor circuit. Ventilating motor circuit. Curtain motor. Orchestra lights. Dressing room circuits. Program lights. Electric signs Fly floor lights. Eigging loft lights. Pilot lights. Fig. 29 shows a well-laid-out switchboard. All of the lights in the auditorium are controlled by switches shown in the upper right hand corner^ and all of these are under control of the main switch. House lights are usually operated as a unit. The stage pockets are controlled by the bank of switches shown at F. Lights burning off of stage pockets are generally controlled by special operators or by actors, so that switches need not be so very convenient to switchboard operator. He must, how- ever, have them under his control. In the arrange- ment shown in Figure 29 the white lights predom- inate in the ratio of two to one, and are laid out in two groups, A and B. Both groups are controlled by the switch C. The switches A and B do not control the lights at all if the smaller throw-over switches at the right are thrown downward. A diagram of these switches is given in Figure 30, where the switches B and C are indicated. The object of the switches A and B is to help in quickly increasing or decreasing the illumination on the stage. If in the beginning of a certain scene, for instance, only a small quantity of light is wanted, the low illumination may be obtained by throwing the proper switches dowli ; the additional ELECTRICAL TABLES AND DATA 249 illumination which will be wanted a few minutes later may be prepared for by setting the other switches needed to the upward position and at the proper r IE3 C3 S3 ^ C3 ^ (S3 (E3 (^ riii»i cwg wy t csB r^ r»~ rfjttfcftjjM itpnlmrara ^i\ CO' IQ J]] D u IQ jhjm m QD 111 111 IP Q| SJ m :]tirflrtrtitt::itt f-^ 01 IB OD n 8D B IB ^^ m iSI Ql SiSl s elflfctrtiiifi 1^ MMSMftifflftMftft Figure 29. — Stage Switchboard. moment closing switch B, In the same way, by a reversal of the process, the illumination may be instantly reduced. This feature is very valuable in many stage settings. To throw off all of the white 250 ELECTRICAL TABLES AND DATA lights the switch C must be opened. The switches D and E are main switches controlling the colored lamps. All lamps of one color should be connected to one or the other of these switches. From these three groups of switches circuits extend into all borders, proscenium side lights and footlights, BO that the color scheme may be carried out in any or all of them. The handles of all switches in the same row should be of the same height. Switches should be extra heavy. Dimmer handles should be located directly above switches controlling them. Figure 30. The fuses or switches controlling lights not usually manipulated by switchboard operator are generally worked into the vacant spaces between the groups mentioned above. All branch circuits are preferably located behind the board. This wall allow of trouble being instantly rectified. '■ Transformers. — The transformer capacity which must be provided ranges from .20 to .80 percent of the connected load. The full load efficiency of transformers varies from about 0.95 to 0.985. The smaller transformers are ELECTRICAL TABLES AND DATA 251 less efficient than the larger, cost more per K. W., and give poorer regulation. Their installation is, however, much more economical in regard to wire. Transformers are properly rated in kilo-volt-am- peres (K.V.A.). They cannot accurately be rated in K. W. (although this term is often used), because the wattage depends upon the power factor, which is governed mainly by the load and line to which the transformer is connected. The efficiency of a trans- former can be found by dividing the output by the input. The polarity is generally such that the current is entering the primary side at the same time it is leav- ing the secondary side corresponding to it. Oil cooled transformers are the most reliable, but should not be used where overflowing oil could do harm. The principal losses are the core or iron losses and the copper losses. The iron losses are the most impor- tant in transformers which are idle but connected the greater part of the time. Iron losses are continu- ous while the transformer is connected, whether it is delivering power or not. The copper losses take place only at time current is being used. The drop in voltage caused by them is proportional to the cur- rent, while the power loss is proportional to the square of the current. The iron losses are not of much importance at time of full load, but at this time the copper losses are the most disturbing. The core losses can be ascertained by measuring the current delivered to the primary side while the sec- ondaries are open and noting the percentage of this to the full load current. The copper loss can be found by applying voltage enough to the primary wires to cause the full load current to flow in the secondary, which must be short- circuited. This power must be measured by a watt meter and the percentage to the total power noted. 252 ELECTRICAL TABLES AND DATA Test all transformers for insulation before con- necting. All transformers should have their secondaries grounded, preferably at some neutral point. Shells of transformers should also be grounded. Tables for Determining the Most Economical Num- ber and Location of Transformers. — In a territory which has but few customers, and these somewhat scattered, each transformer constitutes a system by itself and is not connected to any other transformer. As the number of customers increases it becomes nec- essary either to extend the lines from one transformer or provide additional transformers and transfer part of the load to them. If the number of customers keeps on increasing, the mains from the various transformers soon meet, and may then be connected together, although, if transformers are far apart, there is no great advantage in this. Under these circumstances we have a number of transformers feeding a common line extending along a street. Finally, if the custom- ers still increase, or the load becomes greater, lines must be run on cross streets and these are connected to the others and we have a network of wires. In all three stages of the evolution of a secondary system of distribution, the determination of the most econom- ical arrangement of conductors and transformers is an important one. To keep the cost of wiring down to a minimum we must install a large number of small transformers. Small transformers are, however, more expensive in proportion to their capacity than large ones ; and full load, as well as all-day efficiency, is also much lower. The most economical arrangement from the point of view of first cost of installment is that with which the investment for wires plus the investment for transformers is a minimum. There are three differ- ent conditions under w^hich it may be necessary to ELECTRICAL TABLES AND DATA 253 determine the most advantageous location of trans- formers: The first is that where a secondary system exists at the terminus of a primary extension. Since the secondary wires usually carry about ten times as much current as the primary, it is generally econom- ical to extend the primary line to the center of the secondary system. If, for instance, the secondary system consists of a straight run, by doing this we may use a wire with four times the impedance that would be required if the transformer were at one end, or with a given wire, we may distribute four times the current for the same drop in voltage. These observations also hold good in case a number of transformers are to feed a continuous main. If we double the number of transformers, we quadruple the capacity of our wires or divide the drop by 4, provided, of course, they are evenly spaced through- out. When the secondary system finally reaches the net- work stage and, if we assume wires leading out from each transformer in four directions with an equal load in each, we should be able to do with wire of sixteen times the impedance of the first-considered case. There, is however, no great advantage in using such small wires, and at this stage large transformers are indicated. The whole network of wires is also interconnected so that current from any one trans- former tends to distribute toward any part in which an area of low potential develops. In order to facilitate calculations concerning sec- ondary lines the following tables have been prepared. By their use, if we assume even distribution of cur- rent, and even distance between distributing points, the drop at any part can be easily determined. In the lower table, LXXXVI, we have given the impedances for one ampere of 100 feet of line at 60 cycles and of various sizes of wire and at various separations. In '254 ELECTRICAL TABLES AND DATA the upper table, LXXXIV, are given multipliers with which to multiply these impedances. It is assumed that the secondary line extends over a certain number of poles, and that at each of these poles a certain num- ber of amperes are taken off. In order to use this table we select the horizontal line pertaining to the number of poles covered by the line, and in it select the num- ber found where the vertical line pertaining to the pole at which we wish to determine the drop, crosses it. Multiplying this number by the current assumed to be taken off at each pole and by the impedance of the wire, we obtain the drop in voltage at this pole. Example : We have a line extending over six poles (100 feet apart) and wish to find the drop at the third pole. We find the number 15 where the two lines cross ; our wire is No. 1 and the separation 36 inches, while the current at each pole is 5 amperes; we have then for our drop 15x0.036x5= 2.7 volts. In case we wish to determine the smallest wire that can be used under similar circumstances or conditions, we use the formula IK in which Z is the impedance of the wire to be used, V the volts to be lost, / the current and K a number selected from the table as explained above. Values of -r^ have been calculated for all of the figures given in Table LXXXIV, and in order to find the smallest wire to deliver any amperage considered over any number of poles given, and at the desired loss, it is but necessary to follow the horizontal line pertaining to the proper constant K until it crosses ELECTRICAL TABLES AND DATA 255 the vertical line pertaining to the amperes to be trans- mitted, and at this place we find the impedance of the wire, which will give us the drop of 2.7 volts. By referring the impedance to the table of impedances we can then select the proper size of wire. These tables enable us to make trial calculations very rap- idly, and we can thus easily determine the most economical arrangement of conductors and trans- formers. Example : Suppose we have twelve poles spaced 100 feet apart, and at each pole 5 amperes are to be used, while the drop must nowhere be greater than 2.2 volts. Is it cheaper to feed this line with one large transformer or with two small ones? Placing the large transformer at about the center, we have six poles on one side and five on the other. In table LXXXIV for the sixth pole we find the constant 21, and in table LXXXV, where the line pertaining to this constant crosses with that pertaining to 5 amperes, we find the impedance 0.021. Looking up table LXXXVI for a corresponding impedance under 12- inch separation, we find 0.022 as the nearest, and that a 0000 wire is needed to come that near to our purpose. On the other side of the transformer we have only five poles, and the constant for this is 15, which in the same way we find requires an impedance of 0.029 or a No. wire. Making the calculations for two trans- formers, and for a continuous main, we may use the constant for the third pole, which is 6. Looking this up as before, we find an impedance of 0.07, which indicates a No. 5 wire continuous main for us. In order to find which is the cheapest we must now bal- ance 1,100 feet of No. 5 wire and two 30-ampere transformers against 600 feet of 0000 wire plus 500 feet of No. 0, plus one 60-ampere transformer. Tables for calculating the most economical arrange- ment of transformers and conductors. 256 ELECTRICAL TABLES AND DAT TABLE LXXXIV Number of poles covered by line 1 2 3 4 5 6 Transformer pole not counted. 1st Pole 2nd 3rd 4th 5th 3 5 7 9 11 6 9 12 15 10 14 18 6th 15 20 21 TABLE LXXXV Showing Values of j^ Con- stants Amper es K 1 2 3 4 5 6 7 8 9 10 12 15 1 2.20 : 1.10 .733 .550 .440 ,367 .314 .275 .244 .220 .183 .147 2 1.10 .550 .366 .275 .220 .183 .157 .138 .122 .110 .091 .073 3 .733 .366 .244 .183 .147 .122 ;104 .092 .081 .073 .061 .049 4 .550 .275 .183 .137 .110 .092 .078 .069 .061 .055 .046 .037 5 .440 .220 .146 .110 .088 .073 .063 .055 .049 .044 .037 .029 6 .366 .183 .122 .092 .073 .061 .052 .046 .041 .037 .030 .024 7 .314 .157 .105 .079 .063 .052 .045 .039 .035 .031 .026 .021 9 .244 .122 .081 .061 .049 .041 .035 .031 .027 .024 .020 .016 11 .200 .100 .067 .050 .040 .033 .029 .025 .022 .020 .017 .013 12 .183 .092 .061 .046 .037 .031 .026 .023 .020 .018 .015 .012 14 .157 .078 .052 .039 .032 .026 .022 .020 .018 .016 .013 .010 15 .147 .074 .049 .037 .029 .024 .021 .018 .016 .015 .012 .010 18 .123 .061 .041 .031 .025 .021 .018 .016 .014 .012 .010 .009 20 .110 .055 .037 .028 .022 .017 .016 .014 .012 .011 .009 .007 21 .105 .052 .035 .027 .021 .017 .015 .013 .012 .010 .009 .007 TABLE LXXXVI . . Showing Impedance Per Eun of 100 Feet; 60 Cycles. Separation in Inches. Separation in Inches. B. & S; 8 6 5 4 3 2 12 24 36 B. &S. i 12 24 36 .126 .127 .128 .128 .128 1 .081 .082 .083 .083 .084 .066 .068 .069 .070 .071 00 .051 .054 .055 .056 .057 000 .041 .044 .046 .047 .048 0000 .032 .038 .040 .041 .026 .031 .033 .035 .036 .021 .027 .029 .031 .033 .017 .023 .026 .028 .030 .014 .021 .024 .026 .028 .011 .019 .022 ,025 .027 ELECTRICAL TABLES AND DATA 257 An inspection of table LXXXVII will show that large transformers have a much higher all-day effi- ciency than small ones; for instance, by placing one 4-K. W. transformer in place of four of 1 K.W. 's, we raise the efficiency (assuming the full load to be used three hours per day) from .84 to .91. In addition to this we also gain some in capacity, for the greater the number of customers connected to a transformer the greater will be the diversity factor. If we have a large number of small residences connected to one transformer, we need provide only about one-fourth the capacity of the connected load, whereas if we have one transformer for each customer we should be called upon for nearly the whole connected capacity. This gain in capacity comes in to such a marked extent only as long as we are dealing with trans- formers which are about fully loaded by one cus- tomer. As soon as the number of customers on any transformer reaches about twenty, they can be served w^ith a transformer capacity which a larger number will not materially improve. A transformer capacity of one-fourth of the connected load will be sufficient for residence or flat lighting, but for stores, churches, and theatres a special study should be made as to w^hat the maximum load of each is, and whether they are likelv to occur at the same time. *' The use of larger transformers effects a saving in cost of transformers and in operating expenses, but entails a greater outlay for conductors, and to find which is the more economical we must balance the increased cost against the saving, and the most eco- nomical arrangement will be that in connection with which the value of the energy lost equals the interest on the investment of capital that must be made to save it. This must be found by trial calculations, and the various tables given will facilitate the calculations. It \\411, however, seldom be necessary to make such 258 ELECTRICAL TABLES AND DATA calculations, for in the first place the regulation of incandescent lamps limits us to a drop of about 2 volts, which alone requires the use of comparatively large wires; in the second place very low efficiency comes in only where the transformers are idle a large part of the time. This condition, even with low efficiency, causes only a nominal loss of power. TABLE LXXXYII Tal)le Showing All Day Efficiency of Various Commercial Sizes of Transformers Used for Various Hours Per Day. K.W. Equivalent Full Load Hours Per Day. 2 3 6 9 12 18 24 1 .66 .78 .84 .89 .92 .93 .94 .96 li .70 .81 .86 .90 .93 .94 .96 .96 2 .72 .84 .88 .93 .94 .95 .96 .96 3 .77 .86 .90 .94^ .95 .96 .96 .97 4 .79 .87 .91 .94 .95 .96 .96 .97 5 .81 .88 .92 .95 .95 .96 .96 .97 n .82 .90 .92 .95 .96 .97 .97 .97 10 .83 .90 .93 .96 .96 .97 .97 .97 15 .85 .91 .93 .96 .97 .97 .97 .98 20 .86 .91 .94 .96 .97 .97 .97 .98 25 .87 .92 .94 .96 .97 .97 .97 .98 30 .87 .93 .95 .96 ,97 .97 .97 .98 40 .88 .93 .95 .96 .97 .97 .97 .98 50 .89 .94 .96 .97 .98 .98 .98 .98 Trolley Lines. — Trolley wires range in size from to 0000 ; No. is seldom used and 00 and 0000 are the most used. Standard voltages d-c. are 600 and 1,200 ; a-c, 3,300, 6,600, and 11,000. A trolley system usually consists of feeders, trolley, and track return. The track return is often reinforced with negative feeders, and negative boosters are also used. (See also Electrolysis,) The height of trolleys ranges from about 15 to 22 feet above the street; 22 feet is about the minimum allowed above tracks. ELECTRICAL TABLES AND DATA 259 Trolley sections range from a few hundred yards to several miles in length; heavy traffic zones are usually fitted with short sections. Poles range from 30 to 40 feet in length, and wooden poles usually have 7-inch tops. The rake of poles varies from 4 to 12 inches, according to nature of soil. There are various ways of trolley wire connections. The trolley may be run alone ; it may be reinforced by feeders, trolley and feeders being in parallel, or Figure 31. — Train Sheet. it may be cut in sections, each section being fed by its own feeder. Alternating current systems do not usually have any secondary feeders. The drop allowed in d-c. systems ranges from 10 to 25 per cent ; for a-c. systems it is 5 to 10 per cent. The current used at any point can be approximately determined by use of the "train sheet'' illustrated in Figure 31. The height of the figure represents the length of the road or of any part of it to be considered. The width of it may represent the length of time during which the load is to be determined. For each car, or train, entering a section of trolley, draw a line beginning with the time the car enters 260 ELECTRICAL TABLES AND DATA the section at the bottom and to meet the time point at the top at which it leaves that section. Draw lines beginning at the top of the figure in the same manner for all cars moving in the opposite direction. These lines will then cross, and to find the load on this section at any desired time, it is only necessary to draw an ordinate such as 1 at that point and count the number of car lines this crosses. This will give the number of cars fed over this section of trolley at that time, and the maximum current used can be easily determined. TABLE LXXXIX Table Sh owing '. Drop in Voltage Per 100 Given. Amp eres for Distance Feet Miles B.&S. 1,000 : 2,000 3,000 4,000 1 2 3 4 5 11.9 23.8 35.7 47.6 62.8 : L25.6 188.4 251 314 00 9.44 18.9 28.3 37.8 49:8 99.6 149. 199 249 000 7.48 15.0 22.4 29.9 39.5 79.0 118. 158 198 0000 5.94 11.9 17.8 23.8 31.4 62.8 71.4 126 157 CM. D . C. Only. 500000 2.513 5.0 7.5 10.5 13.26 26.5 39.8 53.0 66.3 1000000 1.256 2.51 3.7 5.0 6.63 13.3 19.9 26.6 33.2 2000000 0.628 1.26 1.88 2.51 3.31 6.6 10.0 13.2 16.6 3000000 0.419 0.84 1.26 1.67 2.21 4.4 6.6 8.8 11.0 4000000 0.315 0.63 0.95 1.26 1.65 3.3 5.0 6.6 8.3 5000000 0.251 0.50 0.75 1.00 1.33 2.65 4.0 5.3 6.6 TABLE LXXXX Table Showing P.D. on Eeturn for Distances Above 1. Wt. of Rails. Per Yard. 2 Rails Used. 40 1.23 2.46 3.69 4.92 6.5 13.0 19.5 26.0 32.5 45 1.09 2.18 3.27 4.36 5.8 11.6 17.4 23.2 29.0 50 0.98 1.96 2.94 3.92 5.2 10.4 15.6 20.8 26.0 60 0.81 1.62 2.43 3.24 4.3 8.6 12.9 17.2 21.5 70 0.70 1.40 2.10 2.80 3.7 7.4 11.1 14.8 18.5 80 0.61 1.22 1.83 2.44 3.2 6.4 9.6 12.8 16.0 90 0.55 1.10 1.65 2.20 2.9 5.8 8.7 11.6 14.5 100 0.49 0.98 1.47 1.96 2.6 5.2 7.8 10.4 13.0 110 0.45 0.90 1.35 1.80 2.4 4.8 7.2 9.6 12.0 ELECTRICAL TABLES AND DATA 261 The copper loss calculations are based on resistivity of hard drawn copper at 65° C 149° F. Rails are supposed to be standard and of specific resistance of 10 times that of copper. The losses in return circuit will be less than indicated because part of current returns through piping and earth. The combined drop in conductors and rails in parallel is 1 equal to ^+ "71" + 752 ^^®^® ^> ^^f ^^f ^^^-y represent the drop in the different conductors. The impedance of the rails at 25 cycles is said to be from 6 to 7 times as high as the ohmic resistance. Impedance of trolley=1.5 times ohmic resistance. Tables LXXXIX and LXXXX have been especially prepared to facilitate calculations concerning drop in trolley circuits. Every trolley circuit consists of three elements: trolley proper, its feeders and the track return, and in order to effect distribution econom- ically, it is necessary to consider all of these sepa- rately. The upper part of table LXXXIX gives the drop in voltage caused by the trolley proper, and the lower part that caused by feeders, either overhead to rein- force trolley or underground to help out track rails, and table LXXXX the drop caused by the iron rails. The calculations have not been carried out for a-c. be- cause the circuits used for this method of transmission differ materially from d-c. systems. In a-c. systems the ground return may be considered as made up of a number of comparatively short sections, the current returning not to the central station but to its trans- former. This is also true of the trolley. With energy distributed at 25 cycles, the drop caused by the rails will be about 6.5 times as great as for d-c. and that in the trolley about 1.5 times. The drop caused by 262 ELECTRICAL TABLES AND DATA trolley and feeders, when they are in parallel, is equal to the reciprocal of the sum of the reciprocals of their lines. This is also the case with track rails and their reinforcement. As far as these are used in series the various losses must be added. The use of the tables can perhaps be best made clear by an example. Example : The train sheet shows that 1,200 am- peres will be required on a certain section of trolley one mile long and fed in the center by a feeder two miles long. The loss at' far end of trolley must not exceed 15 per cent of the voltage, which is 600. The rails weigh 100 lbs. per yard, and the difference in potential between any two points must not exceed 5 volts. What size of feeder and reinforcement of track rails will be necessary? Table LXXXIX shows that a 0000 trolley wire will cause a drop of 31.4 volts in one mile per 100 amperes. Our trolley is fed in the center and must be con- sidered one-half mile long; each half carries half of the current, viz., 600 amperes; therefore, the drop caused by a 0000 trolley will be six times the drop in half a mile, or, according to our table, 94.2 volts. This alone is more than 15 per cent of our. voltage, 600, hence we must divide our trolley into shorter sections. Making two sections out of the same length, or feeding it in two places, will give us a loss equal to 300 amperes for one-fourth mile, or just one- fourth of what we had before, viz., 23.6 volts lost in trolley. We have next to deal with the size of feeder, and are allowed a loss of slightly over 60 volts in it. The loss in feeders two miles long is given in table LXXXX, and we may use any feeder the loss of which, multiplied by 12, does not exceed 67 volts. ELECTRICAL TABLES AND DATA 263 12 times 6.6 equals 79.2, and is the loss caused by a 2,000,000-cm. cable. This we must not use, but the next larger one will give us a loss of only 52.8, and this, added to the trolley loss, makes a total of 76.4 volts. If it is desired to lose the full 90 volts a smaller trolley wire may now be considered. The loss in one mile of 100-lb. track is 2.6 volts per 100 amperes, which makes 31.2 for 1200; a 5,000,000-cm. cable causes a drop of twelve times 1.33, or 15.96 volts. The drop caused by both in parallel will be the reciprocal of the sum of the reciprocals. By the table of reciprocals we find the reciprocal of 31.2 is, roughly, 0.032051, and that of 15.96 is 0.062500. Adding these, we have 0.094, ap- proximately. The number corresponding to this from the same table is 10.6, which is more than two times too high. Let us now consider the use of two 5,000,- 000 cables. The drop in the cables will be just half of what it was before, or about 8. The reciprocal of 8 is 0.01250; this added to 0.032 gives us 0.157, and the number corresponding to it is about 6.4. This is still above what we require, but it must be borne in mind that not all of the current returns over the rails and negative feeders, hence, this will give us about the righ{ p.d. The loss in trolley lines, track, and feeders can be lessened very much by increasing the number of substations from which they are fed, and the most economical arrangement can be determined by the same calculations laid out for locating trans- formers. Underground Construction. — Underground con- ductors are usually lead encased and as the lead is not very strong it is best to run the conductors in some form of conduit which protects them and facilitates removal in case of trouble. These conduits usually consist of some kind of clay, concrete or fiber, and their heat conductivity is generally not as good as 264 ELECTRICAL TABLES AND DATA that of moist earth. Conduits arranged as shown in Figure 32 carry away more heat than those shown at Figure 33, but if there are many^of them they also require more trench area. All conduits should be arranged to drain, and at suitable intervals should be provided with splicing chambers. If space between them is to be filled with concrete they must be anchored to prevent floating. Figure 32. Figure 33. Underground Ducts. The following tables and information is taken from Handbook No. 17 of the Standard Underground Cable Co. (Copyright by Standard Underground Cable Co., 1906). Recommended Current Carrying Capacities for Cahles, and Waits Lost per Foot^ for each of four equally loaded single conductor paper insulated lead covered cables, installed in adjacent ducts in the usual type of conduit system where the initial tem- perature does not exceed 70° F. (21.1° C), the maximum safe temperature for continuous operation being taken as 150° F. (65.5° C). ELECTKICAL TABLES AND DATA 265 TABLE T.XXXXT size B.&S. Safe Cur- rent in Amp. Watts Lost Per Ft. at 150" F, Size B. &S. or . C. M. Safe Cur- rent in Amp. Watts Lost Per Ft. at 150° F. Size Circular Mils. Safe Cur- rent in Amp. Watts Lost Per Ft. at 150° F. 14 18 0.97 2 125 2.77 900000 650 5.71 13 21 1.03 7 146 3.00 1000000 695 5.86 12 24 1.09 168 3.23 1100000 740 6.01 11 29 1.15 00 195 3.46 1200000 780 6.13 10 33 1.25 000 225 3.69 1300000 820 6.25 9 38 1.39 0000 260 3.92 1400000 857 6.37 8 45 1.53 300000 323 4.22 1500000 895 6.49 7 53 1.67 400000 390 4.61 1600000 933 6.61 6 64 1.85 500000 450 4.91 1700000 970 6.73 5 76 2.08 600000 505 5.16 1800000 1010 6.85 4 91 2.31 700000 558 5.36 1900000 1045 6.97 3 108 2.54 800000 607 5,56 2000000 1085 7.09 Assuming that unity (1.00) represents the carrying capacity of single-conductor cables, the capacity of multi-conductor cables would be given by the fol- lowing : 2 Cond., flat or round form, 0.87 ; concentric form, 0.79. 3 Cond., triplex form, 0.75; concentric form, 0.60. The following experiment on duplex concentric cable of 525,000 cm. indicates clearly the danger in subjecting this type of cable to heavy overloads of even short duration. The cable was first heated up by a current of 440 amperes for five hours. An over- load of 50 per cent was then applied, the results in degrees Fahrenheit above the surrounding air being as follows : Time from start min. 15 min. 30 min. 45 min. 60 min. 90 min. Inner condr... 70° 84° 98° 111° 123° 142° Outer condr... 55° 65° 76° 85° 94° 108° Lead cover... 31° 35° 40° 45° 49° 57° 266 ELECTRICAL TABLES AND DATA As it is the final temperature reached which really affects the carrying capacity, the initial temperature of surrounding media must be taken into account. If, for instance, the conduit system parallels steam or hot water mains, the temperature of 150 F., which we have assumed in the table to be the maximum for safe continuous work on cables, will be reached with lower values of current than would otherwise be the case; and as 70 is the actual temperature we have assumed to exist in the surrounding medium prior to loading the cables, any increase over 70 must be compensated for by reducing the current. For rough calculations it will be safe to use the following multipliers to reduce the current carrying capacity given in table LXXXXI to the proper value for the corresponding initial temperatures. Initial temp. F. 70° 80° 90° 100° 110° 120° 130° 140° 150° Multipliers ...1.00 0.93 0.86 0.78 0.70 0.60 0.48 0.34 0.00 When a number of loaded cables are operating in close proximity to one another, the heat from one radiates, or is carried by conduction, to each of the others, and all are raised in temperature beyond what would have resulted had only a single cable been in operation. And if the cables occupy adjacent ducts in a conduit system of approximately square cross- section laid in the usual way, the centrally located cable or the one just above the center in large installa- tions (A in Figure 32) will reach the highest tem- perature. This is equivalent to saying that its cur- rent carrying capacity is reduced and while this re- duction does not amount to more than 12 per cent (as compared with the cable most favorably located, 2), Figure 32) in the duct arrangement given it may easily assume much greater proportions where a large number of cables are massed together. ELECTRICAL TABLES AND DATA 267 Assuming that not more than twelve cables, ar- ranged as shown in Figure 32, can be used, the aver- age carrying capacity may be taken as the criterion for proper size of conductor, and for cables of a given type and size the carrying capacities of all cables, even though placed in adjacent ducts, will be represented by the following figures, taking unity as the average carrying capacity of four cables. (See Table LXXXXI.) Number of cables 2 4 6 8 10 12 Multiplier 1.16 1.00 0.88 0.79 0.71 0.63 Recommended Power Carrying Capacity in Kilo- watts of Delivered Energy, — The tables below are based on the carrying capacities of cables as given in Table LXXXXI. A power factor of unity was used in the calculations and hence the values found in the lower table are correct for direct current. For alter- nating current the kilowatts given must be multiplied by the power factor of the delivered load. Units. — Synopsis of units and symbols in general use. Defining Equation Unit Name Sym- bol Direct Current Alternating Current ^ Electromotive force Volt Current Ampere E, e I, i IR E-f-R IZ E--Z Resistance Power Ohm Watt R, r P E-M EI V Z2 _ X2 E I X p. f . Impedance Ohm Z, z V R2 4- X2 Eeactance Inductance Capacity Quantity Ohm Henry Farad Coulomb X, X L, 1 C, c Q, q $-^1 Q-^E I X time V Z2 — R2 Q^E I X time Admittance Mho Y, y I — Z = V G2 + B2 Conductance Mho G, g I4-R R--Z2=: VY2 — B Susceptance Mho B, b X — Z2 = V Y2 — Q2 268 ELECTRICAL TABLES AND DATA TABLE LXXXXn Size in J. 11 It ;c v^uiiv> lUVy VKJL y illl cc- J- llOrOC yjfXKfLKDO B. &S. Volts. ] LlOO 2200 3300 4000 6000 11000 : L3200 22000 Kilo-Watts . 6 92 183 275 333 , 549 915 1098 1831 5 109 217 326 395 552 1087 1304 2174 4 130 260 390 473 781 1301 1562 2603 3 154 309 463 562 927 1544 1854 3089 2 179 358 536 650 1073 1788 2145 3575 1 209 418 626 759 1253 2088 2506 4176 240 481 721 874 1442 2402 2884 4805 00 279 558 836 1014 1674 2788 3347 5577 000 322 644 965 1172 1931 3217 3862 6435 0000 372 744 1115 1352 2231 3717 4462 7435 250000 413 827 1240 1503 2480 4132 4960 8264 Single Conductor < Cables, A. C. or D. C. Volts. 125 250 500 1100 2200 3300 6600 11000 Kilo-Watts . 6 8.0 16.0 32 70 141 211 422 704 5 9.5 19.0 38 84 167 251 502 836 4 11.4 22.8 45 100 200 300 601 1001 3 13.5 27.0 54 119 238 356 713 1188 2 15.6 31.2 62 138 275 413 825 1375 1 18.3 36.5 73 161 321 482 964 1608 21.0 42.0 84 185 370 554 1109 1848 00 24.4 48.8 97 215 429 644 1287 2145 000 28.1 56.3 113 248 495 743 1485 2475 0000 32.5 65.0 130 286 572 858 1716 2860 300000 40.4 80.8 162 355 711 1066 2132 3553 400000 48.8 97.5 195 429 858 1287 2574 4290 500000 56.3 112.5 225 495 990 1485 2970 4950 600000 63.1 126.3 253 556 1111 1667 3333 5555 700000 69.8 139.5 279 614 1228 1841 3683 6138 800000 75.9 151.8 304 668 1335 2003 4006 6677 900000 81.3 162.5 325 715 1430 2145 4290 7150 1000000 86.9 173.8 348 764 1529 2294 4587 7645 1100000 92.5 185.0 370 814 1628 2442 4884 8140 1200000 97.5 195.0 390 858 1716 2574 5148 8580 1400000 107.1 214.3 429 943 1885 2828 5656 9427 1500000 111.9 223.8 448 985 1969 2954 5907 9845 1600000 116.6 233.3 467 1026 2053 3079 6158 10263 1700000 121.3 242.5 485 1067 2134 3201 6402 10670 1800000 126.3 252.5 505 1111 2222 3333 6666 11110 2000000 135.6 271.3 543 1194 2387 3581 7161 11935 ELECTRICAL TABLES AND DATA 269 Ventilation. — Ventilation for the purpose of pro- viding a certain quantity of fresh air to occupants of rooms or shops requires the apparatus to be in use continuously while the rooms are occupied, regardless of temperature. Where it is provided mainly to carry off surplus heat, it is used only in warm weather. The capacity in such cases must be sufficient to take care of the hottest weather. The quantity of air moved by any fan varie? directly as the speed, but the power required to run the fan varies as the cube of the speed. The net result is that the cost of moving different volumes of air by any given fan varies about as the square of the speed at which the fan must operate to move it. This is the theoretical relation, but this is somewhat dis- turbed by the difference in efficiency of large and small motors operating at various speeds. Owing to the above facts it is often a difficult task to decide whether it is more profitable to install a small, cheap fan and run it at a high rate of speed, or to provide a more expensive one and operate it at a lower cost per unit of air moved. Which is the more profitable in the long run depends upon the number of hours per year the fan is to be used at its various speeds. In any case the most economical ventilator will be the one in connection with which the cost of energy saved per year will equal the interest charge upon the in- vestment of capital necessary to provide it in place of the cheapest fan which can do the work. The follow- ing tables are taken from publications of the American Blower Co. and give all the necessary data for com- parison of various fans. In order to find the most economical fan select the smallest fan capable of mov- ing the requisite amount of air and note the K. W. necessary to run it (divide H. P. given by 1.3). Next select some larger fan and note the K. W. necessary to move the same volume of air with this fan and sub- 270 ELECTRICAL TABLES AND DATA tract it from the first. The next step is to find the value of the annual saving, by multiplying the number of hours per year this power is used by the rate per K. W. Having found this, if we divide it by the rate of interest applicable, we shall obtain the sum of money which we can afford to spend to substitute this fan in place of the smallest one we were consid- ering. The rate of interest by which we must divide is determined by the number of years the installation is to remain in use and is as follows: One year, 1.06 per cent ; 2 years, .57 ; 3 years, .40 ; 4 years, .32 ; 5 years, .27 ; 6 years, .24 ; 7 years, .21^ ; 8 years, .20; and 9 years, .18f. We have now the following formula by which we can determine the amount of capital which can with profit be invested in a larger fan : ^ _ K. W. - k. IV. xhxr 7o where C = capital to be invested ; K. W. - k. w. - the saving in energy per hour, and h and r = the number of hours per year and rate per K. W. hour of energy. In case the fan is used intermittently at various speeds the calculations should be made accordingly, since the power required at high speeds is much greater than at low speeds. The capacity of a fan used only to provide a sufficient quantity of fresh air is best determined by allowing from 30 to 50 cubic feet of air per minute for each adult, and from 20 to 35 for each child. In special places such as hos- pitals this quantity is often doubled. The maximum quantities given will secure ample ventilation for all ordinary persons. In public places such as toilet rooms, waiting rooms, etc., it is customary to require from three to six changes of air per hour. ELECTRICAL TABLES AND DATA 271 TABLE LXXXXIII '^Ventura'' Disc Ventilating Fans. General Capacity Table. — ximerican Blower Co. Capacities, Speeds and Horse Powers with Unobstructed Inlet and Discharge. No. of Velocity of Air in Feet per Minute. Fan 600 900 1200 1500 1800 2100 Cu. Ft. Per Min.. 950 1420 1895 2370 28-10 3320 3 Pres. Ins. W. G.. .0225 .055 .09 .1406 .2025 .2755 R. P. M 625 980 1255 1565 1880 2190 H. P 0097 .036 .079 .153 .265 .42 C. F. M 1620 2430 3240 4050 4860 5670 4 Pres. ins 0225 .055 .09 .1406 .2025 .2755 Pv. P. M 470 735 945 1175 1410 1645 H. P 0168 .062 .13 .262 .455 .72 C. F. M 2500 3750 5000 6250 7500 8750 5 Press. Ins 0225 .055 .09 .1406 .2025 .2755 E. P. M 375 585 755 938 1125 1310 H. P 026 .095 .207 .405 .701 1.10 C. F. M 3560 5350 7125 8900 10700 12500 6 Press. Ins 0225 .055 .09 .1406 .2025 .2755 R. P. M 315 492 632 786 945 1100 H. P 037 .136 .295 .575 1.00 1.59 C. F. M 4800 7200 9600 12000 14400 16800 7 Press. Ins 0225 .055 .09 .1406 .2025 .2755 R. P. M 268 419 537 669 803 936 H. P 05 .182 .398 .776 1.345 2.13 C. F. M 6250 9375 12500 15600 18750 21850 8 Press. Ins 0225 .055 .09 .1406 .2025 .2755 R. P. M 234 366 470 584 702 817 H. P 065 .237 .516 1.01 1.75 2.77 C. F. M 7875 11800 15700 19650 23600 27500 9 Press. Ins 0225 .055 .09 .1406 .2025 .2755 R. P. M 209 326 419 521 626 730 H. P 082 .30 .65 1.27 2.20 3.48 272 ELECTRICAL TABLES AND DATA TABLE LXXXXIV Capacities, Speeds and Horse Powers with Kesistance of Average Piping System. No. of Fan Velocity of Air in Feet per Minute. 600 900 1200 1500 1800 2100 Cu. Ft. Per Min.. 950 1420 1895 2370 2840 3320 8 Press. Ins. W. G.. .06 .15 .24 .37 .53 .73 R. P. M 716 1075 1435 1790 2150 2510 H. P 022 .085 .18 .34 .59 .93 C. F. M 1620 2430 3240 4050 4860 5670 4 Press. Ins 06 .15 .24 .37 .53 .78 R. P. M 540 808 1075 1345 1615 1885 H. P 037 .14 .30 .58 1.00 1.59 C. F. M 2500 3750 5000 6250 7500 8750 5 Press. Ins 06 .15 .24 .37 .53 .73 R. P. M 430 644 860 1075 1288 1500 H. P 057 .21 .46 .90 1.54 2.45 C. F. M 3560 5350 7125 8900 10700 12500 6 Press. Ins 06 .15 .24 .37 .53 .73 R. P. M 361 540 720 900 1080 1260 H. P 082 .30 .65 1.27 2.20 3.50 C. F. M 4800 7200 9600 12000 14400 16800 7 Press. Ins 06 .15 .24 .37 .53 .73 R. P. M 307 460 614 767 920 1075 H. P 11 .40 .88 1.71 2.96 4.69 C. F. M 6250 9375 12500 15600 18750 21850 8 Press. Ins 06 .15 .24 .37 .53 .73 R. P. M 268 402 535 670 803 940 H. P 143 .53 1.14 2.23 3.85 6.10 C. F. M 7875 11800 15700 19650 23600 27500 9 Press. Ins 06 .15 .24 .37 .53 .73 R. P. M 239 358 477 597 716 835 II. P 18 .67 1.43 2.80 4.84 7.68 Pressures noted are static pressures. ELECTRICAL TABLES AND DATA 273 Where it is desired to reduce temperature or remove steam, etc., we must proceed to find the necessary capacity in another way. If we remove all of the heated air in a room and replace it with air from the outside in the same length of time required to heat it, we shall reduce the temperature by one-half the dif- ference between that of the air in the room and the air brought in. From this fact we can deduce the fol- lowing method for determining the amount of air which must be taken out of a room in order to lower its temperature by any desired amount. Before the room has attained its full temperature place one or more thermometers at representative locations and note the temperature rise for any convenient length of time, but be sure that you are observing the maximum or general temperature rise which is to be ventilated for. By providing ventilator capacity to exhaust all of the air in the room one or more times in the same length of time in which the rise took place we shall reduce it according to the following tabulation which shows the number of degrees F. which the room tem- perature will be above the outside temperature with the number of changes taking place as given at the left in column 0. The column is correct only when the room is so tightly closed that there is no natural ventilation. Under the other columns, headed by 1, 2, 3, 4, and 5, are given the number of times the air must be changed to limit the temperature rise in room to the increases above the outside air as given in right hand section of table. Thus, if the increase in temperature allowed over the outside air is 30 degrees and the air is naturally changing three times w^e must change it twelve times to limit the rise to 5 degrees. 274 ELECTRICAL TABLES AND DATA TABLE LXXXXV Number of natural changes of air assumed. 5 4 3 2 1 10 8 6 4 2 15 12 9 6 3 20 16 12 8 4 25 20 15 10 5 4 Increase in deorrees F. above outside air. 5 10 15 20 25 30 35 40 2J 5 7i 10 12i 15 17i 20 n 2J 3| 5 6J 7i 81 10 f IS 2i 3J 4i 5 5f n n 31 4| 5 Ride, — Determine difference in temperature be- tween outer and inner air which is to be ventilated for, and trace down column headed by this temperature until the allowable temperature of inner over outer air is reached. Next estimate number of natural changes taking place during the time of previous test and in section of table at left headed by this number trace down to same horizontal line in which the per- missible temperature was found. At this point the necessary number of changes in air will be found. These changes must take place in the same length of time in which the temperature rise took place. If there is a temperature rise accompanied by nat- ural ventilation the reductions in temperature given in Table LXXXXV, column 0, can be obtained only by doubling the number of changes taking place dur- ing the time that the rise in temperature was going on. Suppose, for instance, that a certain temperature rise takes place in an hour while during the same time the air is naturally changing ten times. The starting of the ventilator, if of sufficient capacity, immediately ELECTRICAL TABLES AND DATA 275 ends all natural ventilation because every former out- let for air now becomes an inlet and all air passes through the fan. The number of changes which were naturally taking place now count for nothing and to reduce the temperature by one-half we must provide ten more changes per hour, i.e., change the air by means of the fan twenty times to obtain the effect of one change as given in column 0. Thus to find the number of changes necessary to obtain the effects given in the table in column we must use the formula c=(ax&)+a, where c = the number of changes that must be made ; a = the number of natural changes tak- ing place, and b = the figure in column which corre- sponds to the desired rise above the outside air at the difference in temperature. Example. — The increase in temperature in a certain room is 10 degrees above that of the outside air and is to be limited to 2^ degrees; the dimensions of the room are 100 x 20 x 12, while the natural change of air is assumed to be about three times per hour. What must be the capacity of the ventilating fan ? Tracing down in Table LXXXXV under 10 degrees to where 2^ is found, and then in the horizontal line to the left, to column pertaining to three changes of air per hour, we find the number 9, which signifies that we must have capacity to change the air nine times per hour, and since the room contains 24,000 cubic feet we must select a fan which can move 3,600 cubic feet per minute. Practical Ei7its.-—FlsiQe ventilators at end of room opposite to where most of the air enters or so that all disagreeable air is nearest to the fan. Protect fan against wind blowing into it. Avoid noise by selecting large fans to operate at low speeds. Air in motion does not feel as warm as stationary air. It is best to provide a separate fan for kitchen ranges, etc., and attach it directly to hoods placed over such apparatus. 276 ELECTRICAL TABLES AND DATA In wide or square rooms provide several ventilators so as to secure a more uniform movement of air over the whole space. If fan capacity is small compared to size of room and cooling is the only consideration it is best to blow air into the room. An exhaust fan which does not change the air oftener than it is naturally changing has little effect. Even in well constructed places the air is supposed to change itself once per hour at least. Voltage Regulation. — In a network of wiring the regulation is always fairly good because a heavy de- mand at any point immediately causes current from all sides to rush in. The drop at feeder ends can be easily compensated for if they are all of the same length. If they are not of the same length they should be divided into groups of the same length and each group separately regulated. For d. c. work individual feeder regulators waste too much energy to be con- sidered except with very short lines. In long lines a booster is often installed. To deter- mine whether it is profitable to install a booster we must compare its cost and the losses due to its opera- tion, with the cost of increasing the size of conductors proportionately and the losses incident to the im- proved lines. Obviously this depends upon the length of the line, and the drop which may be allowed. De- termine investment for booster, interest and deprecia- tion and cost of operation and losses. This amount can be saved by the installation of proper feeders, and if we can obtain the larger feeders by an invest- ment of capital upon which the above sum will be the proper interest it will not be profitable to install the booster. For a. c. work individual feeder regulators are much used, and as they waste comparatively little energy, they may be used in each feeder and all feeders con- nected to a common line. Such regulators may be ELECTRICAL TABLES AND DATA 277 arranged either to boost or choke. For low tension work, either a. c. or d. c., pressure wires are often run from the end of feeder back to switchboard to indicate the pressure at feeder end. The same object is also attainable by line drop compensators, or if the size and length of line be known the drop at the far end or any other point may be calculated from the number of amperes. The following table (LXXXXVI) is provided to assist in making the necessary calculations for the set- ting of a. c. line drop compensators, and also to deter- mine the drop in voltage occurring at any part of the line so that the voltage at the station may be raised correspondingly. To find the drop in voltage we may use the formula IZxd; in which / is the current in amperes; Z the impedance as given in the table for various sizes of wire and separation, and d the number of 1,000 feet of line. For line compensators it is necessary to find the percentage of the reactive, and ohmic drop. The same formula may be used substituting X or R for Z and dividing the result by the transmission voltage. This will give the percentage according to which the two sections of the compensator must be set. See detail instructions sent out with com^|pensators. The values of Z, R and X are for 1,000 feet of wire. A single phase installation can be served by a single compen- sator, but then the drop will be double that given, or for 2,000 feet instead of 1,000 feet of wire. The same may be said of a two phase installation which is served by two compensators, but in two phase three wire, or in three phase systems, a compensator must be in- stalled in each wire, and a four wire three phase sys- tem requires four, so that in connection with these systems the value given in the table need not be doubled. 278 ELECTRICAL TABLES AND DATA TABLE LXXXXVI Table Showing Resistance, Reactance and Impedance of 1,000 JPeet of Wire of Sizes Given and at Various Separations, Separation of Wires in Inches. 12 24 3G 48 60 72 B. &S. R XZXZ XZXZ XZXZ 8 .G27 .126 .640 .142 .640 .151 .640 .157 .640 .163 .640 .167 .640 6 .397 .120 .415 .136 .415 .145 .420 .152 .420 .157 .420 .161 .420 5 .314 .118 .345 .134 .350 .143 .355 .150 .357 .155 .360 .159 .362 4 .250 .115 .275 .131 .280 .140 .285 .147 .290 .152 .292 .156 .294 3 .198 .112 .230 .128 .235 .137 .240 .144 .245 .150 .248 .153 .251 2 .157 .110 .190 .126 .200 .135 .205 .141 .212 .147 .215 .151 .217 1 .126 .107 .165 .123 .175 .132 .180 .139 .187 .144 .191 .148 .194 .100 .104 .145 .120 .155 .129 .165 .136 .169 .141 .173 .145 .176 00 .079 .102 .130 .118 .140 .127 .150 .133 .156 .139 .159 .143 .162 000 ,063 .099 .120 .115 .130 .124 .140 .131^.145 .136 .149 .140 .153 0000 .050 .096 .110 .112 .125 .122 .135 ,128 .138 .133 .140 .137 .146 Weights of Materials in Pounds (Approximate). — Aluminum, cu. ft., 167 ; cu. in., 0.095. For wires, see tables. Antimony, cu. ft., 418; cu. in., 0.242, Asphaltum, cu. ft, 84 ; gal., 11.2, Bismuth, cu. ft., 612; cu. in., 0.354. Brass, cu. ft, 522 ; cu. in., 0.302. Brick, cu. ft., 119 ; per thousand, 4500. Bronze, cu. ft, 537; cu. in., 0.311. Cement, loose, cu. ft., 88 ; bu., 95. Charcoal, cu. ft., 25 ; bu., 27. Coal, anthracite, piled loose, cu. ft., 52 ; bu., 56. *^ bituminous, piled loose, cu. ft., 50; bu., 54. Coke, piled loose, cu. ft., 27 ; bu., 29. ELECTRICAL TABLlfcS AND DATA 279 Concrete, eu. ft., 150; cu. yd., 4050. Copper, cu. ft., 555; cu. in., 0.321. For wires, see tables. Cork, cu. ft., 15.6. Crushed Stone, cu. yd., 2700. Earth, cu. ft, 109; cu. yd., 2943. Glass, cu. ft., 165. Gold, cu. ft, 1225 ; cu. in., 0.709. Gravel, cu. ft., 119 ; cu. yd., 3213. Ice, cu. ft, 56; cu. yd., 1512. Iridium, cu. ft., 1400; cu. in., 0.81. Iron, cu. ft., 490; cu. in., 0.225. For wires, see tables. Lead, cu. ft, 709; cu. in,, 0.41. Limestone, cu. ft., 165; cu. yd., loose, 2700. Loam, cu. ft, 78; cu. yd., 2106. Mercury, cu. ft, 850; cu. in., 0.492. Nickel, cu. ft, 540; cu. in., 0.312. Oils, olive, gal., 7.6. cottonseed, gal., 8.0. linseed, gal., 7.8. turpentine, gal., 7.2, lard, gal., 7.9. n '* whale, gal., 7.8. '* gasoline, gal., 5.7. petroleum, gal., 7.3. mineral lubricating, gal., 7.8. Paper, cu. ft., 56. Paraffine, cu. ft., 56; gal., 7.41. Pitch, cu. ft., 67; gal., 8.9. 280 ELECTRICAL TABLES AND DATA Platinum, cu. ft., 1340 ; cu. in., 0.718. Porcelain, cu. ft., 150 ; cu. in., 0.087. Salt, cu. ft., 60; gal., 8.04. Sand, cu. ft., 105; cu. yd., 2835. Silver, cu. ft., 653 ; cu. in., 0.377. Slate, cu. ft., 184; cu. in., 0.109. Sulphur, cu. ft., 125. Tantalum, cu, ft., 1040; cu. in., 0.60. Tar, cu. ft., 62.5; gal., 8.33. Tin, cu. ft., 455 ; cu. in., 0.263. Tungsten, cu. ft., 1175 ; cu. in., 0.68. Water, plain, cu. ft., 62.5; gal., 8.33. Wood OCO/, VU.. JUL., 1 1/ , ash, cu. i :t., 46 ; per 1000 ft., 3850 butternut, * ' 28 ; " 2330 cedar, ^ ' 38 3165 chestnut, * ' 39 ; " 3250 cypress, ' ' 35 ; " 2915 elm, * ' 36 ; " ♦ 3000 fir. ' 35 2915 hemlock, ' ' 27 2250 hickory, ' ' 55 4600 lignum vitae, ' ' 81 6750 mahogany ' ' 36 3000 maple, * ' 50 ; " 4560 oak, ' ' 47; ; " 3915 pine, white, ^ ' 25 2275 pine, yellow, ' ' 45 3750 poplar, ' ' 24 ; " 2200 redwood, ' ' 30 2740 spruce, ^ ' 28 ; " 2330 walnut, ' ' 41 ; " 3400 Zinc, cu. ft., 420; cu. in., 0.243. ELECTRICAL TABLES AND DATA 281 Contents of Barrels or Round Containers = 2i\ersige diameter squared x height x 0.7854. If measurements are taken in inches 2)2 xi7x 0.000454 = eu. ft. D^x if X 0.0034 =gal. 2)2 X if X 0.000425 -bu. If cubic contents are known in feet, multiply by 7.58 to obtain gallons, and by 0.936 to obtain bushels. To obtain cubic yards divide by 27. Welding. — From 30 to 60 H. P. per square inch area of weld to be made are used. This is the power required to be delivered to welder. The greater the capacity the shorter will be the time required to make a weld. In some cases only a few seconds are required. Wire Calculations. — This division contains the following tables: A table of carrying capacities of copper and alumi- num wires. A table showing carrying capacities of different combinations of wires. Table for determining the total wattage of groups of lamps or other devices usually rated in watts. Tables for calculating the amperage per H. P. of motors at various efficiencies and power factors. Tables showing maximum H. P. allowed on wires according to N. E.C. rules and carrying capacities. Tables for determining proper size of wire for a certain loss in voltage; copper and aluminum wires, direct current, and 60 and 25 cycles. Tables to facilitate determining the most economical conductors. Various tables showing physical properties of cop- per, aluminum, copper clad, german silver and steel wires. Tables showing outside diam^eters of wires and cables. 282 ELECTRICAL TABLES AND DATA TABLE LXXXXVIII Table of Allowable Carrying Capacity of Wires. B. & S. Rubber ' Insulation Other Insulations Circular Gauge Copper Aluminum Copper Aluminum Mils 18 3 2 5 4 1624 16 6 5 10 8 2583 14 15 12 20 17 4107 12 20 17 25 21 6530 10 25 21 30 25 10380 8 35 29 50 42 16510 6 50 42 70 59 26250 5 55 46 80 67 33100 4 70 59 90 76 41740 3 80 67 100 84 52630 2 90 76 125 105 66370 1 100 84 150 126 83690 125 105 200 168 105500 00 150 126 225 189 133100 000 175 147 275 231 167800 0000 225 189 325 273 211600 Circular ' Mils • 200000 200 168 300 252 300000 275 231 40Q 336 400000 325 273 500 420 500000 400 336 600 504 600000 450 378 680 571 700000 '500 420 760 639 800000 550 462 840 705 900000 600 504 920 773 1000000 650 546 1000 840 1100000 690 580 1080 901 1200000 • 730 613 1150 966 1300000 770 646 1220 1024 1400000 810 680 1290 1083 ^ 1500000 850 714 1360 1142 1600000 890 748 1430 1201 1700000 930 781 1490 1251 1800000 970 815 1550 1301 1900000 1010 848 1610 1352 * 2000000 1050 882 1670 1402 ELECTRICAL TABLES AND DATA 283 Carrying Capacities of Different Combinations of Wires. — Owing to the relatively different radiating surface of wires of different sizes the carrying capacity per circular mil is not the same for all wires, and where wires of different gauge number are to be con- nected in parallel this must be taken into account. In the following table this is done and the carrying ca- pacity of smaller wires at the current density allowed for the larger wires is given wherever the horizontal and vertical lines pertaining to any two wires cross. The number found at this place indicates the am- perage the smaller wire will have with the larger wire fully loaded. The figures are based on the carrying capacities given by the National Electrical Code. To find the proper wire to reinforce another which has been overloaded: Select the horizontal line pertain- ing to the larger wire and follow along this line until a number about equal to the necessary additional amperes is found. At the head of the vertical column in which this number is found will be found the gauge number of the proper wire to be used. 284 ELECTRICAL TABLES AND DATA TABLE LXXXXTX Table Showing Combined Carrying Capacity of Different Wires — Eubber Insulation Amps. B.&S. 14 12 10 8 6 5 4 3 15 12 20 00 000 0000 15 20 25 35 50 55 70 80 90 100 125 150 175 225 14 12 10 8 6 5 4 3 2 1 00 000 0000 275 300000 325 400000 400 500000 10 15 8 13 12 11 11 10 9 8 7 7 6 7 6 5 5 25 22 35 20 31 17 27 18 28 16 25 14 22 12 19 12 19 11 18 10 17 11 17 9 15 8 13 8 13 50 44 55 70 45 55 39 50 64 35 45 56 31 39 49 31 39 49 30 37 47 27 34 43 28 35 44 24 30 38 21 26 33 21 26 33 80 71 90 63 80 62 77 59 74 54 69 56 76 48 61 43 54 42 53 100 98 125 94 118 87 108 89 112 77 68 67 96 85 84 150 138 175 141 178 225 122 154 194 109 137 172 106 134 169 Amps. B&S. 20 25 30 50 70 80 90 100 125 150 200 225 275 325 400 500 600 14 12 10 8 6 5 4 3 2 1 00 000 0000 300000 400000 500000 Other Insulations 14 12 10 8 6 5 4 3 2 1 00 000 0000 20 15 25 11 19 12 19 10 17 10 16 10 16 12 12 11 12 11 6 10 6 10 5 8 5 8 5 8 30 31 50 27 44 25 40 25 40 19 31 19 31 18 29 19 31 17 28 17 27 16 25 14 22 13 20 12 20 70 64 80 64 80 50 63 50 63 47 59 49 62 44 56 43 54 40 51 35 44 33 41 31 40 90 80 100 78 99 125 74 94 118 150 79 99 125 157 200 70 89 112 141 178 225 68 86 109 137 173 218 64 81102 128 162 204 55 70 88 112 140 177 52 66 83 104 132 166 50 63 80 100 127 160 275 258 223 209 202 325 282 264 255 ELECTRICAL TABLES AND DATA 285 TABLE C Table for determining total wattage required for incandescent lamps or other devices usually rated in watts. To find total wattage add all numbers found where lines pertaining to number of lamps and wattage of same cross. ' Number ■» of Watts lamps 1000 750 500 250 150 100 60 40 25 2 2000 1500 1000 500 300 200 120 80 50 3 3000 2250 1500 750 450 300 180 120 75 4 4000 3000 2000 1000 600 400 240 160 100 5 oOOO 3750 2500 1250 750 500 300 200 125 6 6000 4500 3000 1500 900 600 360 240 150 7 7000 5250 3500 1750 1050 700 420 280 175 8 8000 6000 4000 2000 1200 800 480 320 200 9 9000 6750 4500 2250 2700 900 540 360 225 10 10000 7500 5000 2500 1500 1000 600 400 250 15 15000 11250 7500 3750 2250 1500 900 600 375 20 20000 15000 10000 5000 3000 2000 1200 800 500 25 25000 18750 12500 6250 3750 2500 1500 1000 625 30 30000 22500 15000 7500 4500 3000 1800 1200 750 35 35000 26250 17500 8750 5250 3500 2100 1400 875 40 40000 30000 20000 10000 6000 4000 2400 1600 1000 45 45000 33750 22500 11250 6750 4500 2700 1800 1125 50 50000 87500 25000 12500 7500 5000 3000 2000 1250 55 55000 41250 27500 13750 8250 5500 3300 2200 1375 60 60000 45000 30000 15000 9000 6000 3600 2400 1500 65 65000 48750 32500 16250 9750 6500 3900 2600 1625 70 70000 52500 35000 17500 10500 7000 4200 2800 1750 75 75000 56250 37500 18750 11250 7500 4500 3000 1875 80 80000 60000 40000 20000 12000 8000 4800 3200 2000 85 85000 63750 42500 21250 12750 8500 5100 3400 2125 90 90000 67500 45000 22500 13500 9000 5400 3600 2025 100 100000 75000 50000 25000 15000 10000 6000 4000 2500 110 110000 82500 55000 27500 16500 11000 6600 4400 2750 120 120000 90000 60000 30000 18000 12000 7200 4800 3000 130 130000 92500 65000 32500 19500 13000 7800 5200 3250 140 140000 105000 70000 35000 21000 14000 8400 5600 3500 150 150000 112500 75000 37500 22500 15000 9000 6000 3750 286 ELECTRICAL TABLES AND Dx\TA TABLE CI Table showing wattage capacity of different wires. 110 Volts— —220 Volts— —440 Volts- Eubber Other Rubber Other Rubber Other Ins. Ins. Ins. Ins. Ins. Ins. 14 1650 2200 3300 4400 6600 8800 12 2200 2750 4400 5500 8800 11000 10 2750 3300 5500 6600 11000 13200 8 3850 5500 7700 11000 15400 22000 6 5500 7700 11000 15400 22000 30800 6050 8800 12100 17600 24200 35200 4 7700 9900 15400 19800 30800 39600 3 8800 11000 17600 22000 35200 44000 2 9900 13750 19800 27500 39600 55000 1 11000 16500 22000 33000 • 44000 66000 13750 22000 27500 44000 55000 88000 00 16500 24750 33000 49500 66000 99000 000 19250 30250 38500 60500 77000 121000 0000 24750 35750 49500 71500 99000 143000 200000 22000 33000 44000 66000 88000 132000 300000 30250 44000 60500 88000 121000 176000 400000 35750 55000 71500 110000 143000 220000 500000 44000 66000 88000 132000 176000 264000 If system is balanced use columns 220 volts for 3-wire 110-volt systems and column 440 volts for 3-wire 220 volt systems or for such voltages direct. Tables for calculating amperage of motors with various efficiencies, power factors systems and voltages. RULE FOR FINDING AMPERES In top part of table select numbers found where lines pertaining to efficiency and power factors cross and find same number in middle table. In same line under proper system will be found the number of amperes required for 1 H. P. at 110 volts. In bottom table select divisor pertaining to higher voltages, di- vide amperes by this and multiply by number of H. P. The result will give the total number of amperes re- quired. The efficiency of small motors is always much less than that of larger motors. ELECTRICAL TABLES AND DATA 287 TABLE CXI ll Efficiency o d .95 .90 .87J .85 .82i .80 .75 .70 .65 .60 .55 .95 .90 .86 .83 .81 .78 .76 .71 .67 .62 .57 .53 .90 .86 .81 .79 .77 .74 .72 .68 .63 .59 .54 .50 .85 .81 .77 .74 .72 .70 .68 .64 .60 .55 .51 .47 .80 .76 .72 .70 .68 M .64 .60 .56 .52 .48 .44 .75 .71 .68 .66 .64 .62 .60 .56 .53 .49 .45 .41 .70 .67 .63 .61 .59 .58 .56 .53 .49 .46 .42 .39 Amperes for 1 H. P. at 110 Volts Direct Direct current Two Three current Two Three or s. phase phase phase or s 5. phase ) phase phase .39 17.4 12.5 10.0 .66 10.3 7.3 5.9 .41 16.5 11.9 9.6 .67 10.1 7.2 5.9 .42 16.1 11.6 9.3 .68 9.9 7.1 5.8 .44 15.4 11.1 8.9 .70 9.7 7.0 5.6 .45 15.1 10.8 8.7 .71 9.6 6.9 5.5 .46 14.7 10.5 8.6 .72 9.5 6.8 5.4 .47 14.4 10.3 8.4 .74 9.2 6.6 5.3 .48 14.1 10.2 8.2 .76 8.9 6.4 5.1 .49 13.8 9.9 8.0 .77 8.8 6.3 5.1 .50 13.6 9.7 7.8 .78 8.7 6.2 5.0 .51 13.3 9.5 7.6 .79 8.6 6.1 5.0 .52 13.0 9.4 7.5 .81 8.4 6.0 4.8 .53 12.8 9.2 7.4 .83 8.2 5.9 4.7 .54 12.6 9.0 7.3 .84 8.1 5.8 4.6 ,55 12.4 8.8 7.1 .85 8.0 5.7 4.6 ,56 12.1 8.7 7.0 .86 7.9 5.7 4.5 .57 11.9 8.5 6.8 .90 7.5 5.4 4.3 .58 11.7 8.4 6.7 .92 7.4 5.3 4.3 .59 11.5 8.3 6.6 .93 7.3 5.2 4.2 .60 11.3 8.1 6.5 .94 7.2 5.2 4.2 .61 11.1 8.0 6.4 .95 7.1 5.1 4.1 .62 10.9 7.8 6.3 .96 7.0 5.1 4.1 .63 10.7 7.7 6.2 .97 7.0 5.0 4.0 .64 10.6 7.6 6.1 .98 6.9 4.9 4.0 Voltages 110 220 440 550 650 1100 2080 2200 Divisor 1 2 4 5 5.9 11 18.9 20 288 ELECTRICAL TABLES AND DATA CO i o Eh « u Eh W be OQ O o H CO bJD^ ;-• fl o o -M '"5 t>. M 1— 1 M o ^•3 5Q s^ 13 Q o • i-H o ^ O CO a o GQ Eh WfH -rt^ <^. ^ '^ ^ •go Ih r-H 1-1 CO T:tH "^DOrr* ci*^ lot-h »— I o^'-i'-icvico l> o h4 Ci '^. ^. ^. ^. KS » r^ »6 "^ ^* <^* ^* ^CO ^ r-l •' QO JZj r-H T-l C! : <^. »; o6 Tt^* Oi* rH* lO l>- Gi O T^i Ol r-\ T-i r-\ iq o iq iq o t-* t>.* CO* lO CO IC t^ rH lO CO »— I rH Cvl Oq C\l iq o iq o Oi oo* 00* t^ h-I CO Oi rH CO t^ lO r-\ 1-i r-i r-\ o Lq iq o o CO 05 CO* CO O O rH tH t>- CO »-H rH rH rH rH iq o o o »q CO O CO* O* CO CO 00 Oi cq o M ic ^. R *^. ^ J^. '^. ^. ^. , •^. "^ '^. '-'^. R CY5* CO O CO CO •^ th cq CO "^ lO lO lO o 1 o fC; (-; CO CO CO CO *- Jrj rH rH eg CO "S^* cq ^. ^. 0^^. -^ d "<** ^ ^ ^ ^ i2 s^ ^! Cq ^ ^. ^ <^ •^PQp^' (^-TtH* ^* t^d O H? Tij ^ O Tt^ CO CI 2 d »^* "^ Q'^* <=^' Q^' C^ ,-1 rH (^ O ^. ^, ^. cq T^H lO* CO Ci CO* 'S^! ^. '^. ^. ^ 6 . CO CO iO b- CO CO* Oi t>. 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(T) 0) >^ .r-i n bC ;3 o --^ .5§ W SI OG .rH o p.g C ^ © .2 ^ ELECTRICAL TABLES AND DATA 289 O :3 P P O ^ o 3 O O CO CO 00 QO Ci t— ' ^ CO CO CI o o o o o o I— '-<100C0ClO CTOClOtO^^ OOOOOO OOOOOlCl!^ - C5- (D Hi o p p CD CTQ o CD ^ CD p o CD HH < p O Pi Ci o:» cji ^ t-i c;i o o o tNO k-J l_l O CO (» o o o o o o o o o o o o o o o hP^ H+i^ CO CO CO Ci o o o I— I ^— ' I— I ^ Oi CJT o o o o o o o o o o o o o o o COCOOlOOOtO rf^CiOOOOO OOOOOO OOOOOO p ^ o J. >^ CO DO to t—' I— I p 4^ CO hP^ 00 CO o bi CO o C5 CO to to to )__i I— 1 ^-i to ^ O CO CO oo to 4^- Ci CO O h-i C5 C5 05 O Ci CO (-i O O CO CO CD (— I ^ CO CO 4^ O Hf^ CO DO I— k O CO OOOOOO OOOOOO OOOOOO OOOOOO OOOOOO O O CO CO 00 00 OO DO ;^rf^ bOCO^^^I— 'OO ^ ^ C5 Cl CI rfik j0 CO to DO h-i O CO ;_a O I— ' Oi t— ' ^ DO ^ CO Oi CO 4^ 4^ O Oi 05 Oi en en cji Oj CO o 00 en CO ^ 4^ CO 4^ CO CO O O CO CO 00 00 4^ I— » -q CO CO e;i 00 o CO en -n| cm en en 4^ 4^ 4x 4^ 4^ ^ 00 Oi CO o O CO C5 O CO O OO 00 -q ^ 05 Oi Ci I— I Gi DO Oi I— ' O CO 05 O Oi CO 4^ 4^ CO CO CO CO CO O 00 05 4^ l-» t-i CO 00 --:i en CO Oi Oi Oi <:j\ z:\ ^ 00 4^ t— ' ^ CO 00 Oi QO (-» en DO CO Oi 05 cji en en 4:*. 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F *3 rH rH rH rH eg eg CO CO CO rtH 10 CD ^d c3 ^"^t-. eg 00 Gi CD eg Gi 1-i^ CO rH t- rj^^ LO CD rH -P-^ - (^ rH* eg* eg co* 10* cd t-* Oi* 0* rA H^* CD* Gi* i6 Cvf rA CD* 16 "5 ..N S w i—\r-ii—ir-i rH eg eg CO CO '^ 1— i © C3 -^r^ bo 1=1 ^rH eg 00 CD 10 rt^ CO eg rH 000000 .1-i r-{ r-\ 000000 M 000000 *? 00000 eg 02 p "^ S h-i 10 10 »o CO Tr^ LO 10 ^o • XS^eg eg CO 10 t^ 00 '0 Ci eg Lt) eg t- eg o*;2 ^ t i-\ r-\ T-^ c^ a• 00 Gi Cvj 10 t- eg t- ci T-i r-i r-{ rH eg eg eg CO tH ELECTRICAL TABLES AND DATA 291 tfx 00 to to to I— » o to ^ o to ^ O en Ol O C71 o^ Gi 0\ o o o o o o o o o o o o o o hfi^ CO CO to o o to ^ o o on CI CO to o o o o o o o o o o o o o o o o o CJ! to O O 00 •a w co^oicototo .C:^' Ol 05 00 o to ht^ 8= H CO Ul o 5* on? CD ^ i35 h^- en CO O CO to oi o o CO to to to (-1 l-» CO 00 to o 00 en c^tOtOOOOOrf^ OOtOOitOOOO p ^ (-' h-i s ^ CD ^ fD CO I— I CD Gi "^l O^ en to p ^ CO to h^ bo to 05 to o • bo to *rf^ o:> en rfx ^p». CO CO '^<^<^

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LO LO L'^ LO O ^ O fn r-l rH i-H oq CO O >q LO LO q tq q LO LO! o Co' rtn' oq' O CO l>-* t>.* CD* LO CD* c^ tH Tj- LO <^ t^* t>. c; ^ CO t- o -M g r-. > r— ( rH 1— ,-H 'OrO •^ C M ^'^ ^'^ '-'^ ^ ^ § i? 05 r^ Ci ^* Ci C: 00 Lo o q Lo q O LO LO LO q > B oc' oo' 00 oq' t>.* CD O* ci oc* t:H W3 »f C^ rH Cq Cvl Tt" :0 t^ 00 c; oq -^ c: 01 CD r- c^ ^ d 1—1 rH 1— oq 01 CO oq ^ _^. LO LO LO LO O ^ ^ Ci T:tH* Th ci ^ Ph tH ^ (M CO TlH q o LO q q TJ-* co' oc oo' QO' l: q oi !>.* LO LO O r- O* CD mder pro] ;he gauge P lO ^ t- 00 c^ Ol Tt t- Ol Ci ^ . k. 1-1 oq rH . m M ^ ^ «^ ^ ^ ^ ^ cm' LO* OC ^* CO f^^ ,- r-H .-H CO tH o T^ Tf q q o ?d' oq' oo' CO* oc t:h q oq q '^* O* r-' CO !>.* lO LO! CD t^ Ci oq Tf t- O CO U y^ r— r- Ol rH I-- -w O o -M 3 rt _; cvi Tf o o oq rj^^ q q rH tH rt co' o cd' oq' q CD oq Th 00 oc CO* ci o -*' pq d c CO Tti O LO O t- c; o Tt- oq . P J . CC CO O Cq 00 ^ 2 "^ ^^* c: co' c: th oc xH T+H q o oq o oc oo' t>.* oc Th CD* CD* q cc oq >d Tt* o ol ^ ' £ O ^ r-, C<] CO O CD t^ t>. Oi rH LC t- ^ LO CO P ^ d iH ^— r~ oq oq oq cp ^ % ^4 CD o ^ o cq (-^ T— LO c: t^ o ^ ^ »-i m ^ C\J CO oq 00 00 tH rjH co' -** Ol O CO O -D 2S" t-* oq Tf oq t>.' d CD CO C ••s rt^ O CD t^ t>. Ci ^ CO t- LO o o O .p- Q ^^ r- r- rH o . c M M o ^ 2 ^ C<] 00 T}^, CD CO ,a o ^* !>.' ci iri rA o oq oq q QO Ifi oo' r-' ci Cd' M^. 01 oq* o 00 CD CO Ld r-' CO* ■^ 02 o . g>; O^ r^ eg oq oq CO CO rti CD t^ CO O C5 < CO -2 c 2 t^ -j ^ Cvl CO o ^ ; M HH TJ^ o t>^ «-i' Lo oq oq q oq oq l>.* — -* LO' co' rA O X oi -D q Ol tH Tf* d oq* B^ i'i > ^* 00 00 00 ^ -^ r-H oq oq oq CO ^ oq oq q oq CO Tt rj^ oq LO t- -D5 00 Tt q P ^ II g < o Mains 5.8 7. 7.8 9. 9.8 11. 3.8 19. 9.6 27. -A id cj oi 00 oc* 00* t-* t>.* i>I b£p H o CO CO CO -^ lO t- 00 O oq rH r- rr rH cS o P5 c^ th -^^ oq oq yJ. 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CO rH oq Tt' Ci rf' TJ-* ci S Ph 1 r~l ^H ^H rH oq oq CO Tt CO 1— i "^ rr t_ CJ T ^ fcJD w Tf oq o CO ^ i^ T*H CO oq 1-1 o o o o o e ^ O ^ rH r^rH o o o o 03 a o o o " «+H P *? « o o o ro o O o oq «§g ^ 02 J ^S.J O LO O O O <-, o O lO O g O O O] o iH r~i rH O lO LO LO) O = i3t^ cq oq CO iQ t^ O Ol t^ Ol o o '-+2 o o >>?^ oq oq oq CO CO e^ •^ t P.^- IC O lO lO o ^ o o o o ri^ t- 00 Qi o "•^ tH lO o »o lO o 'p C/2 r^ C ^ cTj ^ f-i oq oq CO LO) oq LO t- oq O H Eh UPi 1— 1 r-l rH oq oq .^ ELECTRICAL TABLES AND DATA 293 O 3 CD CO O tA CD CO 3 g § 3 O !S3 ^ ^ o Hi tb ? P ^ P -^ Oi Oi OiV\ CJ CO Ol o cn o o o o o Oi ^^ ►^. CO to O Cl o to ^ o o o en en M O O O 00 oi 00 o to rfi. o o o o o • to O to to O 00 to to to I— » M to I— ' o OO -. O Oi rfi. 4^ rfi. CO CO en CO o ^1 rfi. C^ to 00 05 rf^ •^i Oi a OJ (in I— » ^ to ^:i to C5 C^ rf^ to tf^ •^ Ci Oi en tn i-» -^ CO 00 h;^ Ox cn en en o k-» O CO CO 00 to en 00 o to en e;i o o o ci en en h;^ ^;^ •<1 4^ I— ' -^l CO o o o o o OO 00 -:5 -^I Ci CO 4^ 00 I— I en en Ot o en en f^i. CO (-1 o -q Q3 CO CO ^ 00 00 j;^ a ^ o *»> CO CO o:) CO I— ' • *- Ci to 00 to to CO to to to i-» KwS 1-' GO 4^ O -:« i\i^^ to O 00 4^ to t^P o rf^ ^^^ CO CO to OV • o o o o o l"" I" en en CO CO CO en o o e;^ cji CO CO en o en ►^' CO Co: or 00 o CO 'hh 2! en o o • o CO to to S3W2 t-* en I-* 1^:5 S oen en i^g" o 4^ CO CO ps* ^ CO I— ' Mm o o o • Q CD CD g s td o <1 294 ELECTRICAL TABLES AND DATA Tables for Calculating Drop in Voltage, — The drop in voltage in a direct current circuit is always equal to IR^ while in an alternating current circuit it is equal to IZ. These formulae are, however, not well suited for use when the problem is to find the proper wire to be used where the loss is determined upon. That portion of the following tables devoted to direct currents consists simply of one column of fig- ures in which are given the conductances of the vari- ous wires. That part of the tables used for alternating current circuits gives the admittances of the various wires under different circumstances. The losses in voltage which form the basis of the following tables have been calculated from the formula : \/[{Exp.f.) + {IR)Y+[{Exr.f.) + {IX)]' = E^ where E stands for voltage to be delivered at end of line ; p. f, for power factor of load ; I for current in amperes; R for ohmic resistance of line; r. /. for re- active factor ; X for reactive volts in line, and E^ for the e. m. f . necessary at the starting point to deliver E at the end of line. The ohmic resistance and the react- ive volts can be taken from Tables CIX and CX and the power factor (cosine of angle of lag) and reactive factor (sine of angle of lag) from Table CXI. To obtain the loss in volts it is necessary to subtract E from E^, Referring to Figure 34, which illustrates the common method of figuring drop in voltage for alternating current circuits, the losses for which the tables are calculated are equal to the difference be- tween the lines A and B. Having thus briefly outlined how the line losses, used as the basis of the following tables have been derived, we may now proceed to explain the tables and the method of their use. ELECTRICAL TABLES AND DATA 295 Since, according to a transposition of Ohms law, E I Tl 11 — =it it follows that -^7 = -77. In other words ^ or 75 I hi K K /j give ns the conductance or admittance which in con- nection with the current / will consume the voltage E. The numerical value of conductance or admittance in any line equals the number of amperes which can be transmitted over that line at a loss of one volt. This conductance for direct currents and admittance for alternating currents has been tabulated in the follow- ing pages. Hence, if we divide the current to be trans- Figure 34, mitted by the volts we wish to lose we shall obtain the value of the conductance or admittance which is necessary to cause this loss. The basis of the table is a line of 100 feet in length, which represents 200 feet of wire of a two-wire line. In order to find a wire which shall give us any desired loss, we need then merely to find what that loss is to be per 100 feet of line, and divide the amperes to be transmitted by this loss; then trace down the column describing the con- ditions (direct current or separation of wires) until we come to a number which about equals the one previously found. In connection with three-phase systems, if great accuracy is required, it will be neces- sary to divide the volts to be lost by 0.86 before pro- ceeding with the rest. 296 ELECTRICAL TABLES AND DATA In order to facilitate the calculations, the tables, CXII to CXIII, have been added. Table CXII gives the average value of amperes per H. P. with various voltages, and table CXIII shows the value in actual volts per hundred feet run of 1 per cent loss with the distances and voltages given. If the loss to be allowed over any distance and with any of the voltages given is stated in per cent, we need merely to multiply the number found where distance and voltage cross by the number of per cent to find the number of volts to be lost per 100 feet. Example: We have 50 H.P., three-phase, 60 cycles, at 1000 volts, to transmit a distance of 2200 feet, with 24-inch separation, at a loss of 5 per cent. What size of wire must be used? Fifty H.P. three phase at 1000 volts equals 35 amperes. (See Table CXII.) For a voltage of 1000 and a distance of 2200 feet the number with which we must divide our cur- rent for one per cent is .451. (See Table CXIII.) This multiplied by the percentage of loss, 5 = 2.255, and this, in turn, divided by 0.86, gives us 2.62, with which we divide our amperes, 35, and obtain 13.3 as the admittance required. Tracing downward in table CXIV under the proper separation, 24 inches, we find the number 14.2 as the nearest, and this indicates a No. 5 wire. The same plan is used for direct cur- rent, and the conductances are given in column D. C. If larger wires are indicated, the conductances of the larger wire are in proportion to the circular mils for direct current. 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d> d> <6 d> c6 <6 c^ d> d> d> d> d> O m Ph T; Q. on ;^ cm O OO CO kO rt^ CO CM rH O O OOOOOO OOOOOOO '2 S ^■^'^'■^'^ oooooooooooooo « o°3 ooooooo>oooooo Hr-) . 000000)000000 ^^03 »ooiooc)OOir:)Ooo '^ cqcoco-^iocot^t^oooso ELECTRICAL TABLES AND DATA 299 TABLE CXI Power and Reactive Factors for Different Angles of Lag or Lead CD g P s Power Factors Cosine (^ Reactive Factors Sine ^ bX) (73 P o Power Factors Cosine Reactive Factors Sine ^ £ S P o Power Factors Cosine (^ d > CO as o WPh 1 .999 .017 31 .857 .515 61 .485 .875 2 .999 .035 32 .848 .530 62 .469 .883 3 .998 .052 33 .839 .545 63 .454 .891 4 .997 .070 34 .829 .559 64 .438 .899 5 .996 .087 35 .819 .574 65 .423 .906 6 .994 .105 36 .809 .588 66 .407 .914 7 .992 .122 37 .798 .602 67 .391 .921 8 .990 .139 38 .788 .616 68 .375 .927 9 .988 .156 39 .777 .629 69 .358 .934 10 .985 .174 40 .766 .643 70 .342 .940 11 .982 .191 41 .755 .656 71 .326 .946 12 .978 .208 42 .743 .669 72 .309 .951 13 .974 .225 43 .731 .682 73 .292 .956 14 .970 .242 44 .719 .695 74 .276 .961 15 .966 .259 45 .707 .707 75 .259 .966 16 .961 .276 46 .695 .719 76 .242 .970 17 .956 .292 47 .682 .731 77 .225 .974 18 .951 .309 48 .669 .743 78 .208 .978 19 .946 .326 49 .656 .755 79 .191 .982 20 .940 .342 50 .643 .767 80 .174 .985 21 .934 .358 51 .629 .777 81 .156 .988 22 .927 .375 52 .616 .788 82 .139 .990 23 .920 .391 53 .602 .799 83 .122 .992 24 .914 .407 54 .588 .809 84 .105 .994 25 .906 .423 55 .574 .819 85 .087 .996 26 .899 .438 56 .560 .829 86 .070 .997 27 .891 .454 57 .545 .839 ' 87 .052 .998 28 .883 .470 58 .530 .848 88 .035 .999 29 .875 .485 59 .515 .857 89 .017 .999 30 .866 .500 60 .500 .866 300 ELECTRICAL TABLES AND DATA ^ rt^-^^^^"^ COOrHCOTj^t^ COOOrHOQCO Cd^hii 1—1 C^i o Oi *OCgTt^Q0C<]C0 OtHOOCOOO S ^ 5J CD CO 1—1 rH O ,2^ ^ c« ^ _ CJ OOOOi— lO OOC^Thti— lt>. ^ L_| O O O O Ci rH O Tft O 00 t- i-H g p r-li— ICg^t^lOOi TtlOOi-HOQ'"^ CO CM CO l>- (M -4^ >> COmS^'^'^'^ ^ OOOOOO Ot--:HOOCOLO rri '"' "H '^ r*^ /— «v _J 0,T _^ »/^ ,— \ >— » ^j_. /-^v /-rf-i r>r\ /Win CC z,,'^ OrHC^TflOO Ort^OiOOOOCO ^ S ^ Oi— l^qTt^COO eOOOi-HCqrt^ § ^ g -^ • ; • •^- cN o ^ . "^ ^ H S • • • •^- . t^ .-r*-..^^.^^ P3 OOi— lOaiOQOOa i-tO"— iCsiCOrft l-l O T^ tj ^^ Q O t^ rtH 00 00 O o lO O O >0 O |-IlJ-=.OOflOiOT-lC\IOOlO ^ w^ ^ £5 •••-•-• 5- ^O S.*t^^t^l«CD ^ r^'r^ ^ ^ '^ ^ *^0-HCQrJiT-ICO O^ ^'^^. '^^. ^ ^O OC^TtHOOOO PocOCvlrJHCOO Ph S^,.-TflI>-COOqr-l . lOCQTttOOCOO OOOrHT* Hi ^ ^ ® bo Ot^'^ OCiOOCOCOUD OCOCOt^t^Ttt OOCOt^O(M COCOt^TtHi— ICO COOrHC^TtiCO Co " fe c^"^^. '>:<»'^. g o ococof^icot- s. ?^.Ol0C\lTHr-l o CDIOOO^O Ot-THOiCOCD Li tt^ '"' rd Cvl »0 i-H Ol Cq O lO O rH eg Tt^ CO < p GQ 1—1 eg CO »o be 5=! -g i^ O O Oi b- "^ rtH tH ^ ^Oh 00 Oi ^ '-^rH'cg r*H*coo ^'^. '-l^. ^. 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CO TjH CO tH TjH CD CO CD CD rH 00 LO Ci LO C^^ P^ tdO O d I 'C • C^ ^ r-I CO* LO* l>^ Cv] lO* Ci* Tt^* O t>^ CD* CD OO* Cq LO* rt^* rj^* LO* O* J C^IJ-^Sm "^"tf THTH^-^C^IC0C0T:^L0CD00CiO1-1G^lC0 P-i 0) "^^ c t- ^ n ^ W S ^ Ci CO O Oq T^^ LO LO CO Oq r-'^ LO t-*^ t>; Ci CO rH rH 00 iq « +j -M -M ^ ^ 2 O rH CO* L:J t>.* Cv] LO Ci T^* O* 00* l>^ OO* rH* CD rt^* t:^^ I>-* 00* ci cC,„^ 03-i. T-lT-tr-lCqCOCO'^LOt^OOOrHCvlCOLO •=PSh<15*^^C ^^ ^ ^ ^ ,-H ^ M^iDlZ^J^'^rt, . LO LO t- oq r>. CO c Q rH* CO* iO* t-* Cv] LO Ci* rt^ ^* Ci* Ci* Cvl* 00* 00* ; ; ; \ ' '^^a^ ^. ^^"^ THrHrHCqCOCOTHCDt-Ci ', '. . . I .* cm" LO* ci T^* o OO ci rH OO* CO* o 00* oq iO r-^ W d ^'^-^ K ^ CDj^ Q rH rH rH Cq CO CO ^ CD t^ Ci rH CO CD CO CO fe-M'-a^^w^ h^-^r/^ rtHoqooocDLOr^cooqrHOOoooooOo iiSp^^^aS^ £5^ OqcOCO^^ •S^ 0^2 ^.ti O . ■^<»m«w ^*^!^ ^ tiC . OLO OOOOOO LOOOLOIOIOOOOOO O^-ii CZ , . Cr^CvlOQCOlOt-OOCiOOqLOOC^qt^OqLOOLOOO pflS^^S"^ O °? 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'"I "^ '"1 tA 1-5 CO* TtH !>: d CM* LO* d -rtH* 2 t^ '^O ^* rt^* CM* rH QO rH ^ ^ ^ csj (^ CO CO TtH o CO t- 00 00 O cooi'^oioiococxjcoa:'^'^'^'^'^*^^"'*^'^ ^ rt* CO rt^* |>: d CM* ^* O* TH r^ 90 t^ CO t^ LO* d LO* O T_lr- Ir-lCMCM^'^^^^'-^OOcJSi— I CO tH LO ^ O 00 CO C5 ^- O 05 I t- LO tTj ^jj . . ^ i_,j T-n CO 00 Ci Cvl ^. ^. 00 CO O^ C5 . ^ . ^ -. tH iH* CO 10 |>: d CM LO* d LO r:^ 50 00 O Ci Ci rH rH O ^rHrHCMCM<^^^^^*^^<^'^ "rtHLO^'~'Oi— I .^^^ -^ CO Gi '"1 O O rH b-; Ci Oq CO ^ ^. *R '^. ^ r-i r-i ^ »0 00 d CM* lO* tA LO* £^ 2 ITI I^ ' rH tH rH CM CM ^ ^ *^ ^ • COLO^~'LOLOOOOOO'^'^^'^'~''^ CM C? ^. O^ OD O T^ S 00 S ^. 00 : d CM* LO* d LO* r;:^ ^ f^ f^ pi ^ ^ ^ ^ rHrHrHCM^'^^^^'-'^OOOrHT^ •- 0) u •-' y ^ -^ ^ ^H ^ ^ o P , :5 c^ o .. 0)*^ cut! W) -M tH 3 3 o r 2:! cr o j? ^ ft (V«M P* GQ .go ^ OS . ;^CMOoOCOOr^COCq.HOOOOOOOOO 0000000 000000 l::) o 10 o o CM CO CO TtH LO LOCMOit^CO'rtlLOCOOOOirHCO'rhlCOQOO'rH CM CM '^ COOOCOt^OSCOt^CMO LO LOCOt-OOOCM^"^=^^O^^c-GN^ ,_l^-_('~''~'CMCM(MCOCO"^ CMt-^1^Cq^Cit-COTt^»£5«^t:-OiCq^HCMCOCO ^rHCMCMT^^L0C0t-00OCM^00OC0L0l>.C0 rHrHiHriCMCMCMCMCO ELECTRICAL TABLES AND DATA 305 Economy of Conductors. — Any system of electrical conductors may be designed with reference to any of the following conditions : 1. The conductors may be designed for minimum first cost, regardless of waste or quality of service. 2. The conductors may be designed for the best possible service regardless of cost. 3. The conductors may be designed for a minimum cost of generating plant. 4. The conductors may be designed for maximum general economy of operation and installation ; i. e., to yield the most profitable results in the long run. 5. The conductors may be designed for a minimum first cost of generating plant and conductors. The first problem is solved by selecting the smallest wire allowed, either by heating limitations, or mechan- ical considerations. The second problem is solved by selecting very large wires, thus reducing the loss to any desired minimum. The third condition is fulfilled by selecting such large wires that the generator will not be called upon to deliver much waste power. The fourth problem has heretofore required some very extensive and elaborate calculations, but with the tables following, these have been reduced to a minimum and can be made in a few moments. This is, moreover, a subject which has been very much neglected, especially in connection with short runs such as are used inside of buildings, or to connect one building with another. The general practice has been to figure on a loss of from 2 to 5 per cent, or to dis- regard all question of economy and work from the standpoint of minimum first cost entirely. It must be understood that a certain loss in elec- trical transmission is unavoidable, and that the nearer we approach to an efficiency of 100 per cent the more copper proportionately will be required to reduce the 306 ELECTRICAL TABLES AND DATA remaining loss. For instance, if we have a certain wire causing a loss of 10 per cent, by adding another wire just like it we reduce our loss to 5 per cent ; by adding two more similar wires we reduce the loss only 2^ per cent more, and by adding four more wires of the same size we gain only 1^ per cent more. In other words, the original wire was capable of trans- mitting 90 per cent of our energy; two wires 95 per cent, four wires 97^ per cent, and eight wires 98f per cent. That under such circumstances it is easy to spend more in trying to save the energy than it is worth, is evident. It has been shown by Sir Wm. Thompson and others that the most economical loss is that at which the annual value of the energy lost equals the interest charge on the cost of line construc- tion necessary to save it. In making calculations on this subject we need have nothing to do with the total length of line, or even the total cost of the line; we need be concerned only with the difference in cost between installing any convenient length of the small- est wire permissible, and that of substituting a larger wire. In some cases this may cause no other expense except that of the larger wire, in other cases it may be necessary to reconstruct the whole line in order to make room for larger wires. The basis of the following tables is found in the proposition and formula below : R 1000 X c 1000 X c j xl^xpxh the maximum capital which may economically be invested to substitute a larger wire in place of the smallest permissible wire where : R equals the resistance of the smallest wire con- sidered, r the resistance of the larger wire to be considered, ELECTRICAL TABLES AND DATA 307 c the interest rate applicable (governed by the num- ber of years line is to remain in use), / the current to be transmitted, p the rate per K. W. and h the number of hours / is used per year. In connection with this formula we need not con- sider the whole length of line, but may take any con- venient portion of it ; therefore, in these tables a run of 100 feet (200 feet of wire) is taken as the basis of all calculations. The rate of interest applicable in this formula is the following : If line is to be in use only one year it must pay a dividend of 106 per cent ; two years, 56 ; three years, 40; four years, 32; five years, 27; six years, 24; seven years, 21^ ; eight years, about 20, and nine years, 18| per year. * In table CXVIII the values have been calculated for all of the wire sizes given, / ^ can be easily calculated and p and h can be found, for many values thereof, in table CXIX. The figures in table CXVIII have all been carried out to seven decimal points in order to simplify the comparison of small wires with the larger ones, and also to obtain greater accuracy. In most cases, however, when comparing small wires, it will not be necessary to use the full figures, and one or more figures at the right may be dropped. In using the tables it will be best to first find the quantity (I^xpxh), as this is fixed in any given problem. Next determine the smallest wire permis- sible, either on account of safety rules, mechanical considerations, or perhaps because it is already in- stalled. Note the number given in horizontal line in which the B & S gauge number is found and under the column pertaining to the number of years line is to remain in servidfe ; from this number subtract the corresponding number pertaining to some larger wire and with the remainder multiply the quantity I p h 308 ELECTRICAL TABLES AND DATA previously determined. This will give us the sum in dollars which may economically be invested to substi- tute the larger wire in place of the smaller. Bear in mind that this is only for a length of run of 100 feet. Example : We wish to find whether it will be profit- able to substitute a No. 6 wire in place of a No. 14 carrying a load of 15 amperes, the rate per K. W. being 3 cents, the current to be used 1000 hours per year, and the line assumed to remain in use five years, at the end of which time it will be worthless. Three cents times 1000 hours gives us $30.00; this multiplied by 225 (I^) gives us 6750. We now subtract .0002944 (No. 6) from .0018229 (No. 14), which leaves us (omitting the last three decimals) .0016; multiplying 6750 by this, we have 10.8, which is the number of dollars we may spend to install a No. 6 instead of a No. 14 wire. The difference in cost between a No. 14 and a No. 6 is from about ten to twelve dollars, not figuring the cost of supports. The foregoing calculations are assumed to be made from the standpoint of an engineer who connects onto an established system and who is responsible only for the actual loss in watts occurring on his part of the line. Sometimes, however, a line must be laid out from the central station, and the point then is not only the wattage loss, but also the loss in generator capacity. In this connection the length of the line is the principal consideration, and it becomes a ques- tion whether it is cheaper to provide a certain excess capacity in the generator and allow this to be lost in a small transmission line, or to provide a heavier line and use the generator pressure more economically. In lines of this character boosters are usually resorted to to regulate the pressure. The standard central station l^ystem usually soon evolves into an interconnected system of wires in which no accurate calculations on loss can be made. ELECTRICAL TABLES AND DATA 309 o <^ oo -«q Oi oi 4^ CO 00 m>coo oooooooo • o^;;:^ OOOOOOOOO fto cS- ^j oooooooooo • t; o- c H ooooooooooo '-'•-'•-' r/5 "^ ^c1^ ooooooooooooi— »iNDCorfi>.c;iaiOootOhf^ r'' 2 3oa> p w 3 ii ;z^ oooooooooooooooooooooo c a- ■ o oooooooooooooooooooooo t^ Bpoq^S* oooooooooooooooooooooo^-* S^:::*^^ OOOOOOOOOOOOOOOOOOh- 1|— 'C04^ m ffi^3 CDOOOOOOOOt— 'I— 1|— itOtOCO(4^Cl^l— 'OOCX) m fif^nr^^ tototNOtooococnai*OH^h^ooco:o^i^i'X>cnQoOi— lo hJ o3"^„s» otooiooco^o^rf^cooQo^ioiwtoc^oootocoo S.^::-3^ •^r+S 3 3* oooooooooooooooooooooo ^^ S, 2, 5 r: c oooooooooooooooooooooo *^ S.?D^3 oooooooooooooooooooooo"^ mpcm!^ OOOOOOOOOOOOOOOOI-»l— 'tsOCOOiCO o Ks — ^'"'m OOOOOOOh- 'I— 'tN^t^OCO^+^Ol^lQOI-'^^tOO-<^^^ M p^p2na corfi^h*i^oics^coto-qtoooa«oio:>ocDtof-icoooQo hJ ►^='33 oo^^^o:>coc^^tf^o;<:DO^t^^^Oh-l*qtoGi:D^oooo5 oq ^crq 3- ^ ^ p "3 O O O O O O O O O O O O O O O O O O O O O O (V3 Ms^ofD oooooooooooooooooooooo. O^m'irv oooooooooooooooooooooh-i^ ►irr-Ssi 0000000000000001— ki—'i—'Cocn^i to o _52. 000001— 'I— 'I— 't0C0C0Cr»0i^Ots0Cn00H-*OO^l P 3 a'<»'^ C10:)0'm^00C04i>-00h-' "-1 c 5-^5 2.^ ^^^oo50lOoc^^^D^oc^o^oo'^oo^•<^CJToa^o » g- ^'d^ jy CO 3 — r^ oooooooooooooooooooooo ^fi. ^33^- t-3 oooooooooooooooooooooo-, S^o^ *i^ ooooooooooooooooooooot-i^ o'^ci^^ ►**• 000000000000001— 'I— 'K-ktocooicooi^ *^<2 s* bd tr2.^5 tr^ OOOOh- 'I— 'I— 'tOCOCOrf^Oi^lCOtOClCDh^^COCOCDOOP .^,, .^ Oi^OOCOI-^COOL\DI-^OCOtOOOQOCOa5^QOI— 'OOOOO^ o^^O §• Li O0l^-^wo^^CJ^l^0l^0c:lrf^01^^-'Q0l^0l— 'O0ooto-OOihfi'h^^Oi*>O^CQ 3fl>^f5 oooooooooooooooooooooo -f. ia"S-o OOOOOOOOOOOOOOOOOOOOOO ^-^ SS.P* 3 000000000000000000001— 'i>D^ 3"m2- OOOOOOOOOOOOt-il— 'h-itOtOCOOlQOCOl— I CD o O ot— kk-ki— 'I— 't— 'totorf^ciCiOoocooiOaiCotOKp^coi—i m Pi5.5trp ooooiN3>4^^t>Dco>— 'tNDOncodcocnQotOi— 'tooooo t-^ '^B)?::^ ^ooocr^aiC^l-la5-<^a^ooooorf^oWQocot^o:o^f^ cq ^^^ S-v* oooooooooooooooooooooo .<| S* 5* ^ 3 ^ oooooooooooooooooooooo, ®^^r, :^ ooooooooooooooooooooi— 'to^ c:^'^ — m oooooooooooot-'i-'i-'tocNDcoaicoaico o mC)^— S- CDK- It— il— •!— 'h- 'tOCO*ootooico^tNOOiaiOiCQ ^^-z. -. S53^o oooooooooooooooooooooo (V> oooooooooooooooooooooo,, M-.- OOOOOOOOOOOOOOOOOOOh-^l— itO^ ^ ^^O* oooooooooooooooooooooo,, v-^^CDd OOOOOOOOOOOOOOOOOOOh-^l— itO^ ^ ^^ OOOOOOOOOOO^-'I— 't— 'iNStOCOrf^OiOOoi O ja3S^ OtOCOCni-qi— iCSOlOOOCDI— '^lOOOlNOQOI— kCOQ0CO-<| >-t ' t^- 2 r* C5I— 'I— »l— 'OitO^qOOQlO^OOObOaiOCnOlOtCOl— k|— 'Oi '^ C. ^^ 'OtT'm'S" OOOOOOOOOOOOOOOOOOOOOO CO "< '^ ^, OOOOOOOOOOOOOOOOOOOOOO,,, <^cr' 0)0000000000000000001— 'I— 'tO^ ' ' ' OOOOOOOOOOOI— 'I— 'I— 'bOtOCOi4^a50^-l ^ I— iK-»l— »l— »l— 't0tN0C0aiO00OC0Cih-'05C0t0-<|-qOl— I P I— ktOCOOiOOtNOOO- ^TtHOOCvjCOOrt^OOCvlCDOOOO ^ «H ^H ►^^ p^ p P p p p p p p O O p p p t^ ^ S Jn O^ CO CO as CQ ^d 06 rH ^* b^ o' id o d W t>^ o '^ rHr-HrHCqcqCsJOOr^COOi ^ i "-^ I ^ g ro<^ Hniooiqo^^piooiooiopp g ^j M ^ c\I id i>^ d c^* ^' t-' o' cq id t-* o' id 00000 o' 0000000 O 3 ;-l O ci (M* co' id c:i id ^ a cSrt ppppopppppppp H . '^ rH c4 CO* rjH id d i>I GO oi o* id o* d ►^ rH rH cq CO in ^iqp>opiopiopiqpp '^ * rH rH* cq' OQ CO CO* TjH* TjH* id !>•* d id rtU -H rH § J3 ^ ^ 0000000000000 r r 0000000000000 3 ^rHcqco'^io;oi>'QOOioiooo Q M rH 1-H cq CO ^ ELECTRICAL TABLES AND DATA 311 TABLE CXX Copper Wire Table Bureau of Standards, Washington, D. C. Working Table, International Standard Annealed Copper American Wire Gauge (B. & S.) Diam Gauge in No. Mils .. ^ Cross Section ^ Circular Square 1 Mils Inches ^Ohms per 25° C (=77° F) 1000 Feet-^ 65° C (=149° F) Pounds per 1000 Feet 0000 460. 212 000. 0.166 0.0500 0.0577 641. 000 410. 168 000. .132 .0630 .0727 508. 00 365. 133 000. .105 .0795 .0917 403. 325. 106 000. .0829 .100 .116 319. 1 289. 83 700. .0657 .126 .146 253. 2 258. 60 400. .0521 .159 .184 201. 3 229. 52 600. .0413 .201 .232 159. 4 204. 41 700. .0328 .253 .292 126. 5 182. 33 100. .0260 .319 .369 100. 6 162. 26 300. .0206 .403 .465 79.5 7 144. 20 800. .0164 .508 .586 63.0 8 128. 16 500. .0130 .641 .739 50.0 9 114. 13 100. .0103 .808 .932 39.6 10 102. 10 400. .008 15 1.02 1.18 31.4 11 91. 8230. .006 47 1.28 1.48 24.9 12 81. 6530. .005 13 1.62 1.87 19.8 13 72. 5180. .004 07 2.04 2.36 15.7 . 14 64. 4110. .003 23 2.58 2.97 12.4 15 57. 3260. .002 56 3.25 3.75 9.86 16 51. 2580. .002 03 4.C9 4.73 7.82 17 45. 2050. .001 61 5.16 5.96 6.20 18 40. 1620. .001 28 6.51 7.51 4.92 19 36. 1290. .001 01 8.21 9.48 3.90 20 32. 1020. .000 802 10.4 11.9 3.09 21 28.5 810. .000 636 13.1' 15.1 2.45 312 ELECTRICAL TABLES AND DATA TABLE CXX— Continued Gauge No. Diam. , in Mils f Cross Section v Circular Square Mils Inches ^Ohms per 25" C (=77° F) 1000 Feet-^ es'-c (=149° F) Pounds per 1000 Feet 22 25.3 642. .000 50o 16.5 19.0 1.94 23 22.6 509. .000 400 20.8 24.0 . 1.54 24 20.1 404. .000 317 26.2 30.2 1.22 25 17.9 320. .000 252 33.0 38.1 0.970 26 15.9 254. .000 200 41.6 48.0 .769 27 14.2 202. .000 158 52.5 60.6 .610 28 12.6 160. .000 126 66.2 76.4 .484 29 11.3 127. .000 099 5 83.4 96.3 .384 30 10.0 101. .000 078 9 105. 121. .304 31 8.9 79.7 .000 062 6 133. 153. .241 32 8.0 63.2 .000 049 6 167. 193. .191 33 7.1 50.1 .000 039 4 211. 243. .152 34 6.3 39.8 .000 031 2 266. 307. .120 35 5.6 31.5 .000 024 8 .335. 387. .0954 36 5.0 25.0 .000 019 6 423. 488. .0757 37 4.5 19.8 .000 015 6 533. 616. .0600 38 4.0 15.7 .000 012 3 673. 776. .0476 39 3.5 12.5 .000 009 8 848. 979. .0377 40 3.1 9.9 .000 007 8 1070. 1230. .0299 ISTotfi. l.^-The table is based on the international standard of resistance for copper, which takes the fundamental mass resistivity = 0.15328 ohm (meter, gram) at 20° C, the corre- sponding temperature coefficient = 0.00393 at 20° C, and the density = 8.89 grams per cc at 20° C. The temperature coefficient is proportional to the conductivity, whence the change of mass resistivity per degree C is a constant, 0.000597 ohm (meter, gram). Note 2.— The values given in the table are only for an- nealed copper of the standard resistivity. The user of the table must apply the proper correction for copper of any other resistivity. Hard-drawn copper may be taken as about 2.7 per cent higher resistivity than annealed copper. Note 3. — Ohms per mile, or pounds per mile, may be ob- tained by multiplying the respective values above by 5.28. Note 4. — For complete tables and other data see Circular No. 31 of the Bureau of Standards. Bureau of Standards, Washington, D. C, 1914 ELECTRICAL TABLES AND DATA 313 tso o caocnooooooooooo t>'^2 oooooooooooooo ti!^^ oooooooooooooc:) orr^ CDOOOC^OOOOOOOOO ^ o oooooooooooooo ^"^ o >^ • td o b b b o o o o o o o o o p b If •i ^-^ 1— ' 1— k 1— k o o o o o o o o o o ^D CO (— k o CO 00 00 ^^ ^q Oi o^ en Ol e;i o -a o M^ 00 00 CO CO ^ f-k -1 CO CO CTi CO 3'; o o h- k o o o CO rf^ rf^ CO 00 CO 1 W o b b b b b b b b b b b b p b 1000 65 (=14 *-< «rh •-< h- k h- k h- k h- 1 1— k 1— k o o o o o o o o rf^ OO CO to t— k o CO 00 oo ^ ^ 05 Oi a:» CO "H^ c^ 00 1— » ^4^ ^+^ ^+^ ZJ} 00 CO • o o p p p p p p p p p p -1 3 2 >^ h-l 1— k 1— k h-k h-k s Standard Concentri Stranding t. Number Diam. O of of Wires, D Wires in Mils in CO o td o^ Oi Oi C5 o CO CO CO o to LO l\0 to to H> h-l H-k H-* 1— k 1— * 1— k 1— k H-k h-k ^ ^ ^ ^Cl ^ trh P 1—* to to 1— ' to 1— » o 1— k 1— k 1— I 1— k to 1— k lO 1— k 1— k h-k 1— k h-k h-k to h-» to £3- P M 00 I— k 4^ oo CO .^ CO h^ oo to Ol CO to en OQ •-< b b\ 00 b b bo h\ b \^ LO • b » 1— ' h-i 1— k 1— k 1— k t— » 1— k l-A 1— k (— k (—* h-k h-k h-i o o 1 — k 1— k lO to CO CO rf^ i4^ Cil C( en c^ p 0) C5 o lO OI o Ci 1— k Oi 1— k Ol o hl^ o CO ^ to w CO LO CO CO o^ i^ LO p th oo p h-k * CD ^- o P- 1— k 1— » t— ' h-k t— I 1— k 1— k h-l h-k h-l Soc S-3 3 o o CO o CO CO to lO to to 10 o C7i en o CJS h-^ t— ' 1— k h- k ^ ^q ^1 ^ ^ o CO o CO CO w cr a> (T) X CD o 1 r/i -• ►i 1— ' 1— ' 1— k )— k ^-k 1— ' h-k h-k h-k bleC itran Dia f Wi in M CO o o o CO CO o o o CO o o o o Ci CO to .^ CO ^ h- k o-i oo -. iq C ^ CO O l>^ TtH rA t— * O l6 r-i lO O '^* lO b-* O CO* b-* ci fe ^orOiOCiO^CiOCOCOCOCDCOCOcOCOCOCOCOtHrH 'Or-';:: •r!CkHr-IOO'^CiCO^rtlCqoOrHO>LOOOOOOCOC\l(MO ^rt^COOiCOCvJOSLOi— It^CvJQOcOt^Cvlt^rHt^COCiCO O :3p;s:;<^<3iCi<^O^OOQOl^L^COC::)LOkOrt('^COCOCslCM i^ ;q.s ^ r^ o ho c d ^ o ■-" £ .h "" ^. "^. '"l ^. ^. ^. ^. *^. '^. *^ ^. '^l *^. ^ C 'H d > ^ "^* O b-* CO* Gi* »o' CD* O* tH* t^ O* Cvl* iO •J 'g^Q^^.S '^ ^rA ^ ^ O C ooooooco(^^coooTHcdo6loco H -S^§t-<^CDr-tOOOTtHCiTtHOOCvlt^LOT-Hi— ICQlLOOCO rq O ^o ^COi— lOrHt^lOCOCgOCSt^COlOT^COCqcgrH fcH .»>- C)IC2'~I'— I'— 11— iCvJCvlCvlCvJCOCOirflrJHlOt^CSrHTtHQOCO ©•©T? OOOOOOCI^oOOdCDCDOCDi—li— ItHCQ O II U 0) _ P, r roU lOrtlTjHCO«OCOCOOOOOOrHCriOqi-H P3o?-COTtllOCOCiCii— l'^l-CDCDCOq O OOOOrHC^CO ►^' ^- ■ 000 2j^ O dOOC>C^CDOCD(OCJOCDOOO (e-riS OOOOOOOO OOOOOOOC^t-rHCO i3o''5 00000000 oooooqoococDcocooq 02*^'^ OiOO»oOlOOlO OiOOlOi— ICOCOCDOOCDIQ u oot^i>.cocoioiO'«ti Tt^cocooaca1— if-ii— I ELECTRICAL TABLES AND DATA 315 CO to ^ N O 63 O <} O CD V- o p p ■ ■ 00 a ^ ^- - a> i^ w MCD^ ^QTQ 2.- o o B H< p P • - !:-• Hs tr ^ p t3- O . , P c Hs ft) O o O O O t?j O *Qo ti-p ^ 00 » B ?o!^p o "^ p.^ B- O B P o B Ol Oi '^ Hi POO o ^ M. u3\y p CD C^ ►5^^ c^- CO M. CD '^ O s. p ^ ♦-^ '^ -*• P S "^ ^ "as-;:' ^^g.g.g' 5^^^g^2"3 -^«^ "^^ O ^CD B g o g- Mg-g-g.^ ^B ^^ ^ CO is- p. C* ^ p ^ ^ o p 3^ 5* orq B- o 2 (t> .^ pj SS'^ 3 2. CD 2^ HH i-i« . ft) :^ ^ sT B CD H CD W p OD CO O CD Hv CD B o to S B ° M. B CD CO Ct) t-" p B CD CD 2 Cl OO CO O O O O O O i-'torocorfi.i-^:;"OT Ci(oc:»co(— » f^f^N* P o o oo -q Ci en Hf^ c:> cri h^^ Ci t—' «— » rf^ CO o CO bo .. .^ to Ol I^OT Oi CO II o --1C1 Hfi>. CO to iLciS CJiCO^q^q CO iu^^'^ en CO CO O CO O °tTJ Ot C5 00 O to g^ C t-i rf^ t-i INO CO "^ 3 b CO b • • r g' -q ^1 ~q ^1 ^ >^ Ol Oi Oi ^q OO hP». h-* OO -q b *a» to bo bo 5 ^ c >-i M>^ fh (D D' P M fD 3 O ^P p;:;opo. ^p^o era o M M f-» to to KP*. Oi OO O CO Oi rfi> hf^ C5 t\0 CO CO CO CO CO to CO CO rfx ^^ CO (U) ; 26250 .180 A 24.1 128. 47.0 .63720 ELECTRICAL TABLES AND DATA 317 TABLE CXXIII Aluminum Company of America Weight of Aluminum, Wrought Iron, Steel, Copper and Brass Wire. Diameters determined by American (Brown & Sharpe) Gauge. Water at 62° Fahrenheit, 62.355 lbs. per cubic foot. Drawn "WVought Steel Copper Brass Iron is 2.8724 times heavier than : " 2.9322 " *' '* " 3.3321 '• '• 3.1900 " Drawn Aluminum. No. of Gaug' Size of each e No. Inch Weight of Wire per : Ft. per lb. Alumi- Alumi- Wro't num num lion Steel Feet Lbs. Lbs. Lbs. 1000 Lin Copper Lbs. eal Feet Brass Lbs. 0000 .46000 5.185 192.86 553.97 565.50 642.68 615.21 000 .40964 6.539 152.94 439.33 448.45 509.32 487.92 00 .36480 8.246 121.28 348.40 355.65 404.20 386.94 .32486 10.396 96.18 276.30 282.02 320.50 306.83 1 .28930 13.108 76.29 219.11 223.68 254.20 243.35 2 .25763 16.529 60.50 173.78 177.38 201.60 192.98 3 .22942 20.846 47.97 137.80 140.67 159.86 153.02 4 .20431 26.281 38.05 109.28 111.57 126.78 121.37 5 .18194 33.146 • 30.17 86.68 88.46 100.54 96.26 6 .16202 41.789 23.93 68.73 70.15 79.72 76.32 7 .14428 52.687 18.98 54.43 55.56 63.23 60.53 8 .12849 66.445 15.05 43.23 44.12 50.14 48.00 9 .11443 83.822 11.93 34.28 34.99 39.77 38.07 10 .10189 105.68 9.46^ I 27.18 27.74 31.53 30.18 11 .090742 133.24 7.505 21.56 22.01 25.01 23.94 12 .080808 168.01 5.952 I 17.10 17.46 19.83 18.99 13 .071961 211.86 4.720 13.56 13.84 15.73 15.06 14 .064084 267.17 3.743 10.75 10.98 12.47 11.94 318 ELECTRICAL TABLES AND DATA TABLE CXXIII— Continued Size of No. each of No. Gauge Inch Ft. per lb. Alumi- num Feet ^T\"eight of Wii Alumi- Wro't num Iron Lbs. Lbs. re per 1000 Lineal Feet-^ Steel Copper Brass Lbs. Lbs. Lbs. 15 .057068 336.93 2.968 8.526 8.704 9.890 9.468 16 .050820 424.81 2.354 6.761 6.903 7.843 7.508 17 .045257 535.62 1.867 5.362 5.474 6.220 5.955 18 .040303 675.67 1.480 4.252 4.342 4.933 4.723 19 .035890 851.79 1.174 3.372 3.443 3.912 3.755 20 .031961 1074.11 .9310 2.672 2.730 3.102 2.970 21 .028462 1356. .7382 2.121 2.165 2.460 2.355 22 .025347 1707.94 .5855 1.682 1.717 1.951 1.868 23 .022571 2153.78 .4643 1.333 1.361 .547 1.481 24 .020100 2715.91 .3682 1.058 1.080 1.227 1.175 25 .017900 3424.66 .2920 .8388 .8563 .9731 .9316 26 .015940 4317.78 .2316 .6652 .6791 .7716 .7387 27 .014195 5446.63 .1836 .5276 .5385 .6120 .5858 28 .012641 6868.13 .1456 .4183 .4270 .4853 .4645 29 .011257 8657.5 .1155 .3317 .3386 .3849 .3683 30 .010025 10917.0 .0916 .2631 .2686 .3052 .2922 31 .008928 13762.8 .0727 .2087 .2130 .2421 .2318 32 .007950 17361.1 .0576 .1655 .1693 .1919 .1837 33 .007080 21886.7 .0457 .1312 .1340 .1522 .1457 34 .006304 27622. .0362 .1040 .1062 .1207 .1155 35 .005614 34807.3 .0287 .0825 .0842 .0957 .0916 36 .005000 43878.9 .0228 .0655 .0668 .0759 .0727 37 .004453 55245. .0181 .0519 .0530 .0602 .0577 38 .003965 69783.7 .0143 .0413 .0420 .0478 .0457 39 .003531 88028.2 .0114 .0326 .0333 .0379 .0363 40 .003144 110980. .0090 .0259 .0264 .0300 .0287 Specific gravity Wire. . . 2.680 7.698 7.858 8.930 8.549 Wt., per cu. ft., Wire.. 167.111480.000 490.000 556.830 533.073 ELECTRICAL TABLES AND DATA il9 C7I rf*' CO to 1— » o o o o o o o o o o Di Gauge No. 1— ' 00 to o to to CO to to GO CO CO to CO Oi o o ameter in Mils o") CO h^ Ol CO >-i to M ^ Oi o o o o o o Oi oo o Ci CO Oi rf^ ^q o o o o o o o CO Oi CO OO to o o o o o o o o o to g (73 - * * ' * * * rn o p > O P P o o o b b b M 1— ' i-i B C2 y tf IND CO h^ o\ Oi OO o CO Oi CTp - s Oi to 1— ' to Ol to Ol to 05 to o CD o >; O OO CO 1— ' --< 02 3 ^ bi h^ CO to to J-J M M b Oa 5- Hj CD o M O rf!^ 00 to CO o CO 1— ' to 00 o 1-* OO o P P P M M <~- CO 5* c-^ o M t— I 1— I h-l M O rrj to o Mi <1 04) CO rf^ CJ -:l CO to OJ CO 'ound per OO Fe QfQ GQ O 00 00 b CO b to ^ pi ^ O O P- (D cn GQ Oj <-»• "^ o o P Ci W • 00 o >— k to pi ^ M to CO a CO en |4^ N— «' O? CO Ol CO ^ o en to to •d CO »^ o 00 CO to •-i— 100 COOrt< 05»0(M t^«D'^ COCOON t-ItHtH iq t- o lO lO o Ci t^ CD ^00 05 i>.' t-* oi •^ CO CQ ^ J^ t>- Tt^ ic CO o a; r-l CO O b- CO Oi CD lO . CM QO CD CO TtH 05 LO CO oq 1—1 O o O o o w -O !>•* CO TTl ci lO co' oi r-i o C CO cq 1—1 P o Q. .s O X X CO 0) ?^fc '-i -1 ^. Ph o lO lO b' o iq io CQ 05 l> O CD 00 O t^ l>; CD* riH CO 0) 00 t^ TtH rH CO j: ao ^ oc o O TtH CO CD b- 1-! Ci Tfl O CD (M 1—1 (M CO Ti^ Oi t- OO Ci CO 00 od cq rA (M Oi 1-1 c\i iq CO lO CD* CO* o:> 00 CO ^ rH Ci iH rH* O* iq CM t- O* co' CD in i-» CO Tt^ Oi CD t^ lO '^J< o iq TtH rH* CD CO (M (M CO ^-g CD tH O 03 m b o CD CO (M 1—1 1—1 O O O lO t^ CO -^ ^ O OO CD 1— I O O o o o CO 1— ( iO o o CO CM CO o o CD CO -lO O *^ CO to (— 1 o CO 00 ^1 C5 en M^ g t— ' h-i 1-1 »-l M >-i to g^. 3 T) CO CO ^ rf^ o\ Cl p -— I 1— 1 >— > to CO CO en Oi ^1 o to as o ai to o a£ CD to c« CO Cl 1—1 p p p p t— k ••^1 p to 4^ p .^ p O CO h\ ^1 bo b en bo (— ' to ^ CO O b b b .^ b b b b b b b b b b b b o O o o o (^ o o o o o o ^^ o o o o o ^Wri O o o o o o o o o o o o o o o o o o o o o o o o 1— I o 1—1 o to o to o CO III ^ O o (— ' 1— » M to CO CO h^ o ^ CO to o\ o en k-i O^ > . td -C| CO to on CO k^ 1— » CO CO to 00 CO Oi 00 o to ^ CO fP -Q ^ CO Gi c; 00 to tf^ Ci Oi CO en ^ CO J W o l-« (— ' M M >< ^q oo o 00 Ci o\ ►f^ CO to to 1—1 1—1 1— ' IND o oo en 00 4^ to CO Ci 1— » as 00 O 00 Oi en 4^ M O p p 00 (— ' p 00 p p CO CO ►^ p .^ ^ p to • • * * * >f^ b H-i h-1 o 1-1 ^ 3 O "TJ ri- »^^ b b b b b b b b b b b t— I h-i h-1 to to CO o i— » 1— » »~i to to CO hf^ en - to to CO .^ en ^ p 1—1 4^ 00 00 o o\ -:i CO >— ' rf^ 00 oo CO ^1 b CO 4^ bo 00 CO oo ^ 3* oo CO to ^ ^ Ol ^ en LO 00 »— ' en CO 3 M CO ►^ ;22 ELECTRICAL TABLES AND DATA o o O 09 (i 0> Pi ^ O M o o I' 0) tn p, oj CO ri-^ iq <:d 00 o co b-^ rH t>. Tj^ CO TiH Oi r>. O Oi a rH rH r-i Csi ci CO TjH lO ;D CX) rH CO* 6 P^ Ph o a o o O C3 0) O cad ^"^ k)^ a ^ lOt^lOC-(^JlOIOt^lO Oq O CO t^ rH t>. TtJ CO T^^ Oi t>. Ci l>. C\] b- ITD 00 * rn rH r-i OQ Cvl CO* "^* »0 «© 00* O CO* !>•* rH t^ t1^ rH rH rH C^ C^ CO t^COTHt^^r^r^TJ^COOOt^rt^OOr^lOlOCO Ci C>1 lO Ci Tt^^ rH Ci Oi C<1 OO Oi lO CD b- 00 TJ^ 00 * T-i rA r-^ (M* Co' CO* '<:*^ ^ t-* oi Cl0C0Q0t>.rH0000OTtl0^ 5-^ 00»OCq^b-rHTt^GriL'^CvlC5t>-CDTjHC0C0(MrH M OOOCDO^COCOCMrHrHrH •« ft^ OOkOOOOOOOOlOOt^OLOi-HrHCM 0) ^2 OCOQOt^COOOJCDCTOOrtHCviasOOCDlOT^CO > O Q O CO CD O TtH Tji CO C\i Oq rH rH rH a oooooooooooooooooo l>- '^ ~" '"^ '^ " — .- -- - -- Oi'^CvllO'^COJ-OCMrHCOCDrHCDcOOOOCO rHt-10CMO00CDlQ^C0CQClLOOOOOOOC\10000Cvlir"OCD Ot— lThlOOTt^OCDCOrHait^i;Dr+irt'COC\lC\lrH lOT^COCvlOqcqrHrHrH ^^^-^^J^-M^Mr-i tH '"1 "^. ^ TjH CD O^^ 00 CO Cvl !>. lO ^ 00 00 Tt^ iC CD OS O CD* OO* Oi Od CO* 00* l6 rH* TtH* (M* lO jf'l>-l>-CQ rH rH rH ;^ a)'dOOlOOOlOOOrH00^1^"^THC-rt^OOCO(MO:»sJiO^Oi^C.CO ^^r, Z^ '^ '^ ^ '^ Oi ^ ^ ^ CQ CO O^ r-i r-{ T-i O w CO CvJ rH rH T— I o ^^2'^'~^^<^'*^-'^'^t-QC)<^OrH01C0'^ OOO ^HrHrHrHrH o o o . • . . . , , . i . . • , • 'i' rHrHC^CvlCOTtHlOt^CirHTtiOOCOaiCDCD ^ rHrHrHOQCqcOTtH *^ ^ Gi lCOi'>:+^b-Ot^C- CD rA rA Od Oa* CO* T^* lO* CD 00* O* Cvf CD* O* lO* Cvl* o* ^ rHrHrHG^CQCOr^lO O a

oj . u d bo ^ ELECTRICAL TABLES AND DATA 323 o o o o o o OT ^f»>^^ooooC50^4»'Co^^MOooo ^n o /^^ 2 p p QO CO p to ►;- Ol to rf^ Cl Ci vfi' O r-i QO p,"^ o p ^-^ ox ^ ^ ^ § sr. <^ o <^ p o ^ ® 2. h-il-il— 'h-'tOtOCO^^OT^So -d 5 tOCOh^^^UtOiOtOOtOOCOCO^C^OOtOirt '^0 -^J ZL O005t4i'a50toi-'<:7<^h4^^-ObOWOoP3 2s (.. i-iKJtotocov^i^C5^^i— '^^ooco;c<:;1 jr-d 5; "* *-^ OOltOCiCOOOrf^t— 'OOOl^l— 'O^^'d *"^ ,^ H-( tOh-'^QOO^QOOOOOCOCX)0~>J*0 00^2^Tl i? 1 -^ I > ^ 5 5* C tl l-'|_it0t0C0CJ?<3i'^lC£)b0C7JCD4^OQ0H ^ oaihii.oo*^tohi^cc^C5aiooai^i-i^ p ,-^ »-«• . pj <; 2 (-il-*i-*l-'tOtOOOh^Ol-q22 ^2 ~ tOCO(lnCl^OtOOlOOh^^COCX)^OtOP^>Ti K^^ j/j rfx W O pO H^ Ci ^1 01 OO 01 OO Ct CO w to & o -5 ^ jr • O *--». «> i ^ g ^ o o j^ ^-iK-it_i(_itN0Co^f^C7?Ci-q'o^ ts* M bococno:^h-'coo^oo:>i-»ootoc:>t3 j <^ ^ oicacotocatocnrf^cDoas^too^o) r? /3 a> "d ^ w ^ o O f-J >-« to to CO CO ^ ° 5" ^ Q, Mh-'tOCOCOaiCiOOtOtOCaOC'll— '00{o2 S hJi r^ to^io:)!— '^os^h-'oco^icoocoi-i CL^ ^ ^ •^IQOOOOOJOCOOOI— 'CiaiH-kOi— 'I— ' i^^^ p o )_il_i|_itOtOCO^^. ^ |_i|-_itoCOCOCn^OOOCOC5H-'CiCOO 2 coooc»to«r>o^-*Oioi^^cnaitoci x oc;iocncaoooiooooooo ii 324 ELECTRICAL TABLES AND DATA TABLE CXXVII 18% German Silver Kesistance Wire. Weight Resistance Lbs. No. per per B.&S. Diam. Area 1000 Ft. 1000 Ft. Ohms Gauge 1 Ins. C. M. at 75° F. Bare Per Lbi .325 105,625 1.95 302 .00645 1 .289 83,521 2.53 239 .01025 2 .258 66,564 3.22 190 .0163 3 .229 52,441 4.14 150 .0259 4 .204 41,616 5.18 119 .0412 5 .182 33,124 6.55 95 .0656 6 .162 26,244 8.28 72 .1042 7 .144 20,736 10.47 59 .1657 8 .128 16,384 13.22 47 .2635 9 .114 12,996 16.68 37.6 .4189 10 .102 10,404 20.8 29.2 .6663 11 .091 8,281 26.2 23.7 1.059 12 .081 6,561 33.2 18.8 1.684 13 ,072 5,184 42 . 14.8 2.619 14 .064 4,096 53 11.7 4,258 15 .057 3,249 67 9.3 6.773 16 .051 2,601 84 7.45 10.768 17 .045 2,025 107 5.73 17.121 18 .040 1,600 136 4.57 27.216 19 .036 1,296 168 3.7 43.281 20 .032 1,024 222 2.93 68.838 21 .0285 812.3 270 . 2.32 109.45 - 22 .0253 640.1 340 1.83 174.03 23 .0226 510.8 425 1.46 276.78 24 .0201 404.0 540 1.15 439.95 25 .0179 320.4 680 .91 699.72 26 .0159 252,8 864 .72 1,112.4 27 .0142 201.6 1,076 .58 1,768.8 28 .0126 158.8 1,370 .46 2,811.9 29 .0113 127.7 1,700 .365 4,473 30 .010 100.0 2,180 .286 7,011 31 .0089 79.2 2,750 .266 11,306 32 .008 64.0 3,400 .183 17,980 33 .0071 50.4 4,300 .144 28,581 34 .0063 39.7 5,480 .113 45,465 35 .0056 31.4 6,920 .090 72,261 36 .005 25.0 8,700 .071 114,933 37 .0045 20.2 11,000 .058 182,742 38 .004 16.0 13,850 .046 291,270 39 .0035 12.2 17,550 .035 462,000 40 .003 9.0 22,200 .026 887,250 ELECTRICAL TABLES AND DATA 325 The composition commonly known as German Silver is that containing 18% of nickel. Its resistance varies some- what in different lots, and according to temper, and is approximately 21 times that of copper. 30% German Silver Wire has a resistance approximately 28 times that of copper. TABLE CXXVIII Properties of Galvanized Telephone and Telegraph Wires. Based on Standard Specifications. American Steel and Wire Co. --2 wt. in lbs, ^ 3 03 Per t^^ 1000 Per <:tS feet mil© Approximate breaking strain in lbs. Res. per mile (Latent Ohms) at 68° F.. 20° C. Ex. B.B. B.B. steel Ex. B.B. B.B. steel 340 115600 313 1655 4138 4634 4965 2.84 3.38 3.93 1 300 90000 244 1289 3223 3609 3867 3.65 4.34 5.04 2 284 80656 218 1155 2888 3234 3465 4.07 4.85 5.63 3 259 67081 182 960 2400 2688 2880 4.90 5.83 6.77 4 238 56644 153 811 2028 2271 2433 5.80 6.91 8.01 5 220 48400 131 693 1732 1940 2079 6.78 8.08 9.38 6 203 41209 112 590 1475 1652 1770 7.97 9.49 11.02 7 180 32400 87 463 1158 1296 1389 10.15 12.10 14.04 8 165 27225 74 390 975 1092 1170 12.05 14.36 16.71 9 148 21904 60 314 785 879 942 14.97 17.84 20.70 10 134 17956 49 258 645 722 774 18.22 21.71 25.29 11 120 14400 39 206 515 577 618 22.82 27.19 31.55 12 109 11881 32 170 425 476 510 27.65 32.94 38.23 13 95 9025 25 129 310 347 372 37.90 45.16 52.41 14 83 6889 19 99 247 277 297 47.48 56.56 65M 15 72 5184 14 74 185 207 222 63.52 75.68 87.84 16 65 4225 11 61 152 171 183 77.05 91.80 106.55 326 ELECTRICAL TABLES AND DATA TABLE CXXIX Approximate Outside Dimensions of Wires and Cables The table below is for tlie use of those who wish to esti- mate carrying capacities of conductors without cutting into insulation or shutting down a plant. The figures given are thought to be an average for voltage up to 600. Weather- proof dimensions are for minimum thickness allowed by N. E. C. Eubber Covered Weatherproof Lead Covered S •4^ ^ -M -4^ IS ® ^ -M ss h ■■-> CO © ^^ o O Qj 0) ®fa 1i s ^3 B 3 a O 0) •^o s ^5 %^ T^ d f^ t-, •^ o 03 h i: ^ o c3 r^ >H -M '6^ o^ ^s ft s^ ^s 5 6^ ^S 2000000 2y8 64%4 7200 156/^4 55764 7008 2%4 6*3/64 11300 1750000 2ii2 62%4 6300 14%4 535/6, 6190 22/64 625/64 10225 1500000 1% 5''%4 5550 1*7'64 513/64 5375 169'64 66/64 9100 1250000 1% 5S2/64 4700 135/,4 4-'%4 4500 15%4 53^/64 7950 1000000 13%4 45?'64 3900 12%4 42764 3675 13%, 5%4 6280 950000 131/64 44664 3750 135/64 455/64 6050 900000 12%4 436/64 3575 12%4 4%4 3330 133/64 4«/64 5800 850000 12Tf,4 43%4 3400 133/64 4*6/64 5580 800000 12%4 423/64 3250 11%4 35%4 3000 13%4 44%4 5350 750000 12%4 41764 3000 11%4 353/^1 2800 12%4 43%4 5110 700000 120/64 4%4 2850 11%4 3^764 2650 126/64 42%4 4880 650000 11%4 41/64 2835 12%4 42%4 4640 600000 11%4 336/64 2575 1764 335/64 2250 12%4 41764 4385 550000 11%4 3^764 2325 12%4 41*/64 4150 500000 1%4 33%4 2130 1%4 325/64 1900 11%4 359/64 3480 450000 1%4 32%4 1925 61/64 263/64 1700 112/64 3*764 3225 400000 1%4 31%4 1735 5%4 25764 1550 110/64 3*1/64 3000 350000 6%4 3%4 1525 5%4 2*%4 1350 15/64 325/64 2750 300000 60/64 25%4 1360 5%4 235/64 1175 11/64 31%4 2480 250000 5-/64 251/64 1185 4%4 228/64 985 61/64 8 2230 225000 W%4 dUU o%4 X °%4 •''/64 A 'y64 3%4 34/54 37/g4 260 33/54X62/64 85^4X67/54 ^ -7B4 31/64 30/64 3%4 215 82/54 X 59/54 38/54 X 63/54 5 27/64 39/54 3%4 35/64 185 89/54 X 56/g4 82/54X59/64 6 26/64 29/64 27/54 89/54 150 29/54X54/54 39/54X56/54 8 23/54 26/64 24/64 27/54 100 27/54X49/54 28/54X5754 10 22/54 25/54 2%4 24/64 75 25/54X45/64 26/64X48/54 12 29/54 23/64 21/64 24/54 60 24^4 X 43/54 24/54 X 44/54 14 19/54 22/54 20/54 23/54 45 2%4X 41/64 23/64X41/64 Weights given are thought to be average weights; duplex wires weigh nearly double the amounts given. 328 ELECTRICAL TABLES AND DATA TABLE CXXXI Approximate Weight and Diameters of Rubber Covered Lead Encased Cables Sir igle Conduct or to 600 Volts Dup! lex Con duetor Wt. per "Wt. per B. &S. Diameter 1000 ft. Diameter 1000 ft. 0000 5%4 1600 5%4X 10^64 2900 000 51/64 1400 5%4 X 9%4 2600 00 4%4 1250 ''%4 X 9%4 2300 4%4 1100 "/64 X Wei 2000 1 S%4 900 3%4 X 6%4 1700 2 3%4 750 3%4X 6^64 1400 4 2%4 500 3%4 X 5%4 1100 6 26/fi4 400 2%4 X 5%4 800 8 2%4 300 22'fl4 X 4%4 600 10 2y64 275 21/64 X 3%4 500 12 1%4 175 1%4 X 31/64 350 14 1%4 150 18/64 X 3%4 300 ELECTRICAL TABLES AND DATA TABLE CXXXII 329 Sths. 16ths. 32nds. 64ths. Mils. 8ths. 16ths. 32nds. 64ths. Mils. 1 2 3 4 5 6 7 8 9 10 11 12 .. 13 15.6 31.2 46.9 62.5 78.1 93.7 109.3 125. 140.6 156.2 171.8 187.5 203.1 218.7 234.3 250. 265.6 281.2 296.8 312.5 328.1 343.7 359.3 375. 390.6 406.2 421.8 437.5 453.1 468.7 484.3 500. 33 34 35 36 37 38 39 40 41 42 43 44 % 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 515.6 1 17 531.2 546.8 1 2 9 18 562.5 578 1 3 19 593 7 609 3 1 2 4 . . . . 5 10 20 625. 640 6 5 21 656.2 671.8 3 6 11 22 687.5 703.1 7 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 23 718 7 734 3 2 4 8 6 12 24 750. 765.6 9 25 781 2 796 8 5 10 13 26 812.5 828 1 ii.. 27 843 7 859 3 3 6 12 7 14 28 875. 890 6 ..13.. 29 906 2 921 8 7 14 15 30 937.5 953 1 .15.. 31 968 7 984 3 4 8 16 8 16 32 1000. INDEX TO TABLES PAGE Aluminum and copper wire comparison 8 Arc lamp data 10 Armored cable data 11 Belting data 19 to 23 Bus bar data 27 Centigrade and Fahrenheit comparison 32 to 33 Center of distribution data 30 Conduit size recommendations 35 to 37 Conversion, inch to decimals 329 Cutout locations 25 Cutout dimensions 44 to 47 .Electrolysis 57 to 58 Economy of conductors ^ 309 to 310 Economy of motors 163 to 164 Elevator H. P. requirements 67 Fusing currents 80 Fusing transformers 77 Fuse wire 78 to 79 Gauges, comparison of.- 82 to 83 Guying 172 Heating , 97 to 100 Illumination 105 to 114 Insulator dimensions 118 to 121 Lamp renewals 117 Logarithms 126 Machinery, power determination for 160 Magnet calculations 61 to 65 Melting points 131 Meters, maximum demand 140 Motor speeds, a. c 145 Motor wiring tables 287 to 293 Nails, dimensions of 165 Overhead const, data 170 to 175 Panel board dimensions 178 to 180 Pumping 183 to 185 Reciprocals of numbers 187 to 190 Reflectors 191 330 ELECTRICAL TABLES AND DATA 331 PAGE Ropes 200 to 201 Screw data 205 Sign hanging 208 to 210 Sign letters 207 Sparking distances 215 Switches, dimensions of 224 to 231 Terminals, dimensions of 237 to 238 Transformer distribution 256 Transformer efficiency 258 Trolley losses 260 Ventilation 271 to 274 Wires, aluminum 316 to 321 calculations 285 to 309 carrying capacity N. E. C 282 '' *' combined 284 *' '' underground 265 to 268 copper 311 to 315 copper clad 322 to 323 German silver 324 mains and branches 222 outside dimensions of 326 to 328 quantity required 218 reactances and resistances 278, 297 to 299 sag and breaking strain 170 telegraph and telephone 325 i Books That Really Teach you the things you want to know, and in a simple, practical way that you can understand Our illustrated catalogue, which will be sent you free upon request, tells all about the Practical Mechanical Books for Home Study that we publish. There are popular priced books on the operation of trains and station work, prac- tical mechariical drawing and machine designing, pattern making, electrical railroading, power stations, automobiles, gas engines, electrical wiring, armature and magnet winding, dynamo tending, elementary electricity, wireless telegraphy and telephony, carpentry and architecture, concrete con- struction, plumbing and heat- ing, sign and house painting, amusements, etc., etc. No matter what your ambi- tion or desire for knowledge may^ be, we publish books written by authorities in their different lines that will give you just the traim'ng and information that you want and need. Write today for this up-to-date and complete illu8* trated catalogue and popular price list. It is f ree« FREDERICK J. DRAKE & CO. PUBUSHERS OF SELF-EDUCATIONAL BOOKS 10 6 Michigan Avenue CHICAGO FREDERICK J. DRAKE & CO.'S PRACTICAL MECHANICAL BOOKS FOR HOME STUDY Price. Titles. Cloth. Lea, Air Brake Practice, Modern — Dukesmith. Illustrated 1.50 . . . Air Brake, Complete Examinations, West- inghouse and New York 2.00 Air Brake, Westinghouse System 2.00 Air Brake, New York System 2.00 American Homes, Low Cost — Hodgson. Il- lustrated 1.00 Architectural Drawing, Self - Taught — Hodgson. Illustrated 2.00 Architecture, Easy Steps to — Hodgson. Il- lustrated 1.50 Architecture, Five Orders — Hodgson. Il- lustrated 1.00 Armature and Magnet Winding — Horst- mann & Tousley 1.50 Artist, The Amateur — Delamotte 1.00 Automobile Hand Book — Brookes. Illus- trated 2.00 Automobile, The Mechanician's Catechism — Swingle 1.25 Blacksmithing, Modern — Holmstrom. Il- lustrated 1.00 Boat Building, for Amateurs — Neison. Il- lustrated 1.00 Bricklayers' and Masons' Assistant, The 20th Century — Hodgson. Illustrated.. 1.50 Bricklaying, Practical, Self - Taught — Hodgson. Illustrated 1.00 Bungalows and Low Priced Cottages — Hodgson 1.00 Calculation of Horse Power Made Easy — Brookes. Illustrated 75 Carpentry, Modern. 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Electric Railroading — Aylmer-Small. Il- lustrated 3.56 Electro - Plating Hand Book — Weston. Illustrated 1.00 1.50 Elementary Electricity, Up To Date — Aylmer-Small 1.25 ... Estimator, Modern, for Builders and Architects — Hodgson 1.50 ... Examination Questions and Answers for Locomotive Firemen — Wallace. Illus- trated 1.50 Examination Questions and Answers for Marine and Stationary Engineers — Swingle. Illustrated 1.50 Elevators, Hydraulic and Electric — Swin- gle. Illustrated 1.00 . . . Electrician's Operating and Testing Manual — Horstmann & Tousley. Illus- trated 1.56 Farm Engines and How to Run Them — Stephenson. Illustrated 1.00 ... Furnitur'^ Making, Home — Raeth. Illus- tratec 60 ... Gas and Oil Engine Hand Book — • Brookes. Illustrated 1.00 1.50 Hand Book for Engineers and Electri- cians — Swingle. Illustrated. Pocket Book Style 3.00 Hardwood Finishing, Up-to-date — Hodg- son. Illustrated 1.00 ... Horse Shoeing, Correct — Holmstrom. Il- lustrated 1.00 ... Hot Water Heating, Steam and Gas Fit- ting — Donaldson. Illustrated, 1.50 ... Heating and Lighting Railway Passen- ger Cars — Prior 1.25, . . . Locomotive Breakdowns, with Questions and Answers — Wallace. Illustrated 1.50 Locomotive Fireman's Boiler Instructor — Swingle 1.50 Locomotive Engineering — Sv/ingle. Illus- trated. Pocket Book Style 3.00 Machine Shop Practice — Brookes. Illus- trated 2.00 ... Mechanical Drawing and Machine Design — Westinghouse. Illustrated.. 2.00 ... Motorman, How to Become a Successful. Aylmer-Small. Illustrated 1.50 Motorman's Practical Air Brake Instruc- tor — Denehie 1.50 Modern Electric Illumination, Theory and Practice — Horstmann & Tousley. Illustrated 2.0C Millwright's Practical Hand Book — Swij>- gle. Illustrated ^.00 ... Modern American Telephony In All Its Branches — Smith. Illustrated ^m Price. Titles. Cloth. Lea. Operation of Trains and Station Work — Prior. Illustrated 1.50 Painting:, Cyclopedia of — Maire. Illus- trated 1.50 ... Pattern Making and Foundry Practice — Hand. Illustrated 1.50 Picture Making for Pleasure and Profit — Baldwin. Illustrated 1.25 ... Plumbing, Practical, Up-to-Date — Clow. Illustrated 1.50 ... Railway Roadbed and Track, Construc- tion and Maintenance of — Prior. Illus- trated 2.00 Railway Shop Up-to-Date — Haig. Illus- trated 2.00 . Sheet Metal Workers' Instructor — Rose, Illustrated 2.00 . Signist's Book of Modern Alphabets — Del- amotte 1.50 . Sign Painting, The Art of — Atkinson... 3.00 . Stair Building and Hand Railing — Hodg- son. Illustrated 1.00 . Steam Boilers — Swingle. Illustrated 1. Steel Square, A Key to — Woods 1.50 . Steel Square, Vol. I — Hodgson. Illus- trated 1.09 . Steel Square, Vol. II — Hodgson. Illus- trated 1.00 . Steel Square, A B C — Hodgson 50 . Steel Construction, Practical — Hodgson. Illustrated 50 . Storage Batteries — Niblett 50 . Sho' Cards, A Show At — Atkinson and Atkinson 3.00 . Stonemasonry, Practical, Self-Taught — Hodgson. Illustrated 1.00 . Telegraphy Salf-Taught — Edison. Illus- trated , 1.00 . Telephone Hand-Book— Illus- trated 1.00 . Timber Framing, Light and Heavy — Hodgson 2.00 . Toolsmith and Steel Worker — Holford. Illustrated 1.50 . Turbine, The Steam — Swingle. Illustrated 1.00 . Walschaert Valve Gear Breakdowns and How to Adjust Them — Swingle. Illus- trated 1.00 . Wiring Diagrams, Modern — Horstmann & Tousley. Illustrated 1.50 Wireless Telegraphy and Telephony — V. H. Laughter 1.00 Wood Carving, Practical — Hodgson. Illus- trated 1.50 THE RED BOOK SERIES OF TRADE SCHOOIi IVIANUALS By F. Maire ^<5 mo., Cloth, Illustrated. Price, each, $0.60 Exterior Painting, Wood, Iron and Brick. Interior Painting, Water and Oil Colors. Colors, What They Are and What to Expect ^.-om Them. Graining and Marbling. Carriage Painting. The Wood Finisher. Fredenck J. Drake & Company^s CATALOGUE OF Standard Up-to-Date Hand Books on the following Subjects: Dialogues, Recitations, Tableaux, Ctiarades, Pantomimes, Mock Trials, Monologues, Drills, Marches, Minstrel and Entertainment Books, Magic, Palmistry, Hypnotism, Black Art, Electricity, Speakers, Poultry, Letter Writers, Dream Books, Fortune Tellers, Popular Dramas, Photography, Etiquette, Dancing, Etc., Etc., Etc., Etc. Each book in this list is the work of a com- petent specialist, and will be found reliable, practical and thoroughly un-to-date. Any Book Advertised in This Catalogue Sent Postpaid, on Receipt of Price. FREDERICK J. DRAKE & CO.