.S5 P5 Copy 1 ^^ PURDUE UNIVERSITY PUBLICATIONS OF THE ENGINEERING DEPARTMENTS Vol.. in MAROH, 1919 ELECTRIC RANGES BY C. W. PIPER No. 1 BULLETIN NO. 2 ENGINEERING EXPERIMENT STATION The formal organization of the Engineering Experiment Sta- tion of Purdue University was approved by the Board of Trustees on February 28, 1917. Its function, as set forth at that time, is to conduct researches in the field of engineering, to cooperate with engineering societies in pursuing industrial investigations; and to publish and distribute the results of its work in the form of bulletins. The board of management consists of the dean and official heads of the four engineering schools, the dean acting as director. Bulletins will be issued from time to time setting forth the results of scientific investigations conducted in the laboratories of the university by members of the station staff. Circulars of information, containing compilations of facts and data gathered from reliable sources will be published as occasion demands. The cooperation of engineering societies, of public commissions and of individual manufacturers in research of general interest, will be welcomed by the board of management. All communications should be addressed to DIRECTOR OF ENGINEERING EXPERIMENT STATION Purdue University, Lafayette, Indiana. BULLETIN NO. 2 ENGINEERING EXPERIMENT STATION ELECTRIC RANGES BY C^ W. PIPER, Instructor in Electrical Engineering PURDUE UNIVERSITY LAFAYETTE, INDIANA MARCH, 1919 1 CONTENTS Page List of Figures 3 Preface 4 Introduction 5 Electric Ranges 9 Electric Oven Tests 9 Results of Oven Tests 13 Baking Tests 16 Results of Baking Tests 17 Miscellaneous Observations 22 Surface Burners 22 The Relative Cost of Baking ' 28 Electric Range Data „. 30 The Advantages of Electric Ranges 33 Points to be considered in selecting an Electric Range 35 Description of Ranges , 37 Conclusions 40 Index ; 41 LIST OF FIGURES No. Page 1 Range No. i. Open type heating units 6 2 Range No. 2. Surface burners, porcelain type. Oven heat- ing units, open type y 3 Range No. 3. Surface burners, enclosed type. Oven heat- ing units, open type 8 4 Oven preheating and cooling curves, empty 9 5 Oven cooling curves, oven empty 10 6 Oven preheating and cooling curves, oven full 11 7 Open-door characteristic, oven No. 3 12 8 Open door characteristic, oven No. 6 12 9 Oven preheating and cooling with temperature indicator curve 14 ID Oven radiation 1 5 1 1 Oven radiation 16 12 Biscuit baking test 18 13 Biscuit baking test 18 14 Cake baking test 19 15 Cake baking test 19 16 Bread baking test 20 17 Bread baking test 20 18 Meat cooking test 21 19 Meat cooking test 21 20 Porcelain type surface burners 23 21 Hot plate tests 23 22 Open coil reflector type surface burner 24 23 Hot plate efificiencies 25 24 Hot plate efficiencies '. 26 25 Semi-enclosed type surface burner 27 26 Enclosed type surface burners 28 2^ Comparative costs of operating ranges 30 28 Daily load curve — Monday 32 29 Daily load curve — Wednesday 33 30 Range No. 4. Surface burners, porcelain type. Oven heat- ing units, enclosed and open type 34 31 Range No. 5. Heating units, enclosed type 36 32 Range No. 6. Surface burners, porcelain type. Oven heat- ing units, porcelain and open type 37 33 Range No. 7. Surface burners, semi-enclosed type. Oven heating units, enclosed and open type 39' PREFACE The object of this bulletin is to present the characteristics of the different types of electric ranges, also data on the cost of baking with electricity. The work was conducted by Mr. C. W. Piper, Instructor in Electrical Engineering, and Mr. H. W. Asire, Research Assistant, Engineering Experiment Station, under the direction of Professor C. Francis Harding, Head of the School of Electrical Engineering, Purdue University. The Home Economics Department, under the direction of Pro- fessor Mary L. Matthews, co-operated extensively in the opera- tion of the ranges and offered valuable assistance and advice in connection with the cooking tests. The following students assisted at different times with the work as a part of their theses : Miss Helen Virginia Hendey, Messrs. R. B. Stein, E. W. Tatman, E. H. Crosby, J. M. Naylor and K. A. Rarick. The work was made possible through the courtesy of the Hot- point Electric Heating Company, Ontario, Cal. ; Rutenber Electric Company, Marion, Ind. ; Standard Electric Stove Company, Toledo, Ohio ; Hughes Electric Heating Company, Chicago, 111. ; Estate Stove and Range Company, Hamilton, Ohio ; Westinghouse Electric & Manufacturing Company, East Pittsburg, Pa., and the Globe Stove and Range Company, Kokomo, Ind. ELECTRIC RANGES INTRODUCTION The year 1890 or 1891 may be taken as the date which marks the first practical attempt to make electrically heated cooking ap- paratus. In the early days there were many technical difficulties to be surmounted by the pioneers in electric cooking but these have been gradually overcome. In 1891, Mr. H. J. Downing, one of the pioneers and founders of the Downing Radiant Heat Company, exhibited electric cookers and heaters, at the Crystal Palace Electrical Exhibition. In 1895, Col. R. E. Crompton read a paper before the Society of Arts on the use of electricity for cooking purposes. He also showed a large variety of cooking appliances and their uses. The American engineer and manufacturer have made rapid advances and contributed many valuable ideas in the electric cook- ing field, from as early as 1896. Mr. A. F. Berry placed on the British market, in 1908, the "Tricity" cooker. The design was quite similar to the oven of to- day. Many thousands of these cookers are now in daily service and are generally giving satisfaction. The progress of electric cooking in America has been retarded for several reasons, chief of them being the high cost of the ap- paratus and of the energy. However, the advantages of cooking with electricity are fast being recognized. There are now on the American market many types of electric cooking apparatus, some quite novel in conception and design. Com- plete equipments for electric cooking have been placed and are now in use in hotels, hospitals, colleges, convents, schools, club buildings, restaurants and other large establishments in America, England, Canada, Australia and other countries. Railways, large steamships and war vessels are using electricity for cooking as well as for lighting and motor power. Each step from cooking by the open fireplace, to the coal stove, gas and electric range has been marked by the use of more expen- sive fuel, greater heat efificiency. better temperature control, and more satisfactory food. There are three reasons for cooking food : 1. To make it more digestible. 2. To improve its appearance and flavor. 3. To sterilize it and so arrest or prevent chemical change. Usually all three results are attained as in baking bread, w^here the raw starch is cooked to a more digestible form, the yeast plant is killed, preventing the bread from spoiling and the attractiveness is increased manv fold. Fig. 1. Range No. 1. Open type heating units. The electric fireless cooker range is well adapted for obtaining the above results. It has close temperature control which makes slow, thorough baking possible and produces more digestible food. A quick rise in temperature provided at will gives a nice even brown in a few minutes. The use of electricity for cooking will become even more popu- lar as the cost of energy is reduced. ' The energy rates throughout the country are in general so high that electric cooking is possible only to those who can afford luxuries, and until the rates are re- duced for cooking purposes, electrically heated stoves will be barrefl for the kitchen of the average family. I^^^^^^BII ^^■M It i ^1 f ig^ <0 1 ^^^H^^^^^^H R Fig. 2 Range No. 3. Surface burners, porcelain type. Oven heating units, open type. It has been found that at three cents per kilowatt-hour the housewife who operates a modern electric range can cook as eco- nomically as one who uses a gas range and pays one dollar per thou- sand cubic feet of gas. In analyzing the prices at which current is offered for electric cooking in the United States, the interesting fact is revealed that in the Eastern and Western States, the rates average less than four cents per kilowatt-hour, while in some central locali- ties where water power is available or coal is cheap, energy is sup- plied for as low as two cents per kilowatt-hour. Fig. 3. Range No. 3. Surface burners, enclosed type. Oven heating units, open type. The comparison and conclusions drawn in this bulletin are based upon the rate of three cents per kilowatt-hour which is the flat rate advised by the National Electric Light Association. 9 THE ELECTRIC RANGES The ranges used for this investigation were : Globe Electric Range Serial No. Ei Westinghouse Electric Range Style No. 240603 Estate Electric Range No. 84 Hughes Electric Range Style No. 50 Standard Electrie Range Model No. 601 Hot Point Electric Range Model D Rutenber Electric Range No. 1058 The order in which these ranges are given above has nothing to do with the numbers by which they are referred to later. These stoves represent the best types of modern American electric ranges. All are of the cabinet design, except range No. 7, OVENS PREhE^TINC, AND Coolltte, ttApry .S 1.0 1.6 Fig. 4 which has its oven below the surface elements. The detailed des- cription of the ranges will be found at the end of the bulletin. ELECTRIC OVEN TESTS The ranges were tested under conditions such as are found in the home, except, that rated voltage was impressed upon each range 10 and kept constant while in the home the voltage is somewhat var- iable. The temperatures of the ovens were measured by calibrated copper-advance thermocouples, and milli-voltmeters. The thermo- couples were placed as near the center of the ovens as conditions would permit. The tests were divided into six classes as follows: 1. Preheating and cooling with ovens empty. 2. Preheating and cooling with three pounds of water in each oven. 3- 4- 5- Temperature indicator calibration. Open door test. Oven insulation tests. Baking tests. 500 4SO t 400 iu X X l5 350 (0 Ul (5 300 z ? 250 s: E f^ 200 z > 150 W^ ^ Ov£/V COOLWG CUH-V£3 Ovens Ep)ptY V^ N, \ ^ \ V x\ ^ \ ^\ \ \ \\ \^ \ V \ ^ <" ■^Ai- L \ \ ^ N, ^J V ^ ^ ^ \, \ ■v \ •^ ;;^ \ \ \ N *^^ ■"~^ ~^ ^ \ \, "^ \'l ■^ ^ \ , ^"^-^ c: ■^ \ ^ ^ \ \. ^ -^ ~^ ^, ■^ ^ ^ ^ ^ \j -- ^ ^ .Z A 6 .8 (.0 1.2 1.4 16 Time /n Hours Fig:. Of the various tests the preheating and cooling tests with empty ovens will be first considered as they determine the time and energy II required to bring the ovens up to baking temperatures. These were made by supplying maximum current input to the empty oven. When the temperature reached 500° F. the current was turned off and the oven allowed to cool at its natural rate. Power input in watts and temperature readings were observed at five minute inter- vals. Curves of these tests will be found in Figs. 4, 5, and 9. The tests with water in the ovens were made by placing a wide top pan containing three pounds of cold water in the cold oven and heating until the water boiled. These tests were made to determine the time and energy required to heat the ovens when baking starts at room temperature. Two thermocouples were used in each oven. One measured the oven temperature and the other that of the water. The placing of water in the oven tended naturally to in- crease the preheating time and to decrease the cooling rate. The results of these tests are given in Figs. 6 and 9. 360 I z l5 400 n c to & 320 z u 5 240 K e. r ^ 160 z > 80 ^ OvtN PRtHtAflNC AKD COCH-INC CodVCS OvtN CONTAININS 3 1-Ba Wateh HtATtO TO Boil-lN« ^, ^ / X \ / A ^ \ / A \ \\ s s. // y\ K n\ \ ^ > // ^ \ \ \ \ \ ^N^ j 'A / \ s \ "i: N ^ 1 i/i / \ V ^ S^ ^ ^ ===== III y ^^^ "X ^ ^ fl / K. -^ :::^ Jfe.£___^ If ^~~~~- -^ ^ ' - 1 c 5 1,0 I.S 2.0 Z.5 Time in Hours Fig. 6 While conducting the preheating tests, the performance of the oven door temperature indicators was observed. These thermome- ters all had about the same lagging characteristics as the one shown in Fig. 9. The temperature decrease and consequent loss of energy due to opening the oven doors, for short periods, was determined. The ovens were brought up to the desired temperature and at inter- vals of two minutes and three quarters the doors were opened for 12 600 y- w X z kJ K 500 y y 2 400 D I kl 5 300 <)£ UJ F zoo z w 6 /oo c ( ^ \ ^ /J V ^' \. / A ^, ' tr '^r^ \ 5 Opcn Door Cha«acteri3t»c OvtN No. 3 > £ 4 6 8 to la 14- TlMt. IN MlHOTE-5 Fig. 7 y I r ( ) \ A / \ y \ u5 V3 y y S -500 D z y D 400 CL r ^ 300 z UJ > ,0 200 V y' V / \ v / \ 1 — \ Open Door Characteristic OvELN No. 6 \ 1 D 2 4 6 8 »0 12 1 Tint IN Minutes 4 riff, s 13 three quarters of a minute. All readings were taken at the time of opening and closing the doors. During the entire test the power input in watts was maintained constant. Figs. 7 and 8 show the cooling effect of open oven doors. The heat insulation property of the oven walls, was obtained by adjusting the power supplied to the oven to a definite value and allowing the oven temperature to rise until it became constant. The time required for this varied from ij^ to 7 hours. Fig. 10 shows the radiation from each oven throughout its working temperature range. RESULTS OF OVEN TESTS Preheating (ovens empty) : The energy input during the pre- heating run was a maximum for each oven except No. 5. This range was run on medium, so as to have the watts input approxi- mately the same as the other ovens. This caused its preheating time to be increased. It will be noted that Range No. 3 with its small oven and large heating units became hot the quickest, reaching 500°F. in nine minutes. Range No. 5 which has a heavy steel lining, heated most slowly. However, credited to this range is a slow cooling rate, while No. 3 cooled most quickly. The cooling rates taken from the previous tests are shown on Fig 5. Here it is noted that range No. 6 was the slowest to cool. The general oven dimensions and appearance would not indicate that its cooling rate should be superior to all others. Preheating (ovens filled): The eft'ects produced by water in the ovens were quite noticeable (Fig. 6). In three instances it- altered the position of the curves. Peaks of the curves for ovens No. I and No. 3 were shifted toward the others. The general ten- dency seemed to be to group the curves more closely, only par- tially overcoming, however, the domiijant oven characteristics. Open Door : The characteristic curves for opening doors show that oven No. 3 cooled quickly. During the three quarter minute of open door, an average temperature decrease of 75°F. oc- curred. In the following two minutes, when the door was closed the temperature increased 50°F., there being 25° net loss in tem- perature. Oven No. 4 corresponds very closely to that of No. 3, the total drop for the test being 7o°F. Ranges No. 5 and No. 6 main- tained a constant heat, even though their temperature was about 100° higher than No. 3, that is, the two minute period during which the doors were closed, was sufficient to allow the oven to recover the heat lost, while the doors were open. The ovens lined with heavy material cool more slowly, when the doors are open, than the small ovens constructed of lighter weight material. 14 Temperature Indicator: The oven temperature indicators have a tendency to lag behind the oven temperature changes. Fig. 9 shows a characteristic indicator temperature curve. They register less than the true oven temperature because the oven door tem- perature is lower than the temperature of the air inside the oven. The most satisfactory indicator tested was that on range No. 7, which followed closely the oven temperature changes. Its calibra- tion closely approximated actual tempera^tures expressed in de- grees Fahrenheit. T 2 ^ SOO I WJ i 400 D z J \ OvtN PREHCATINS AND CoOLIM€ CuRVCJ No 1- Oven No 1 EM»n-Y No Z- OvtW No. 1 COMTAIMINfi 3 LBS. WATtd Ko.3-OvEN No. 1 Empty, TEMPttrA-ajRt as iNOICATtO BY Oven THtRMOHtTtH. K / \ M y V p\ \ \ 1 \ K A i 3 S! ^ 200 5 6 100 i • ( %< \' «., \ ^^^ ^^ N. Vi ^ V rT^ >«. >T. ■^ ^ ^-o ^ ■■^ 3 .4 8 1.2 1.6 2.0 2.4 Z.8 3.Z TiMCL IN Hours Fig. 9 Oven Insulation : Ranges No. i and No. 4 required the great- est amount of energy while range No. 6 consumed the least. The other ranges consumed about the same amount of energy. The oven of range No. i has thin walls and a poorly fitting door, and the losses are great through the thin non-insulated bottom to the warmer oven. The oven of range No. 4 is large, but the reason for the loss of heat in this oven could not be determined by inspection. The door catch was of poor design and possibly the heat insulating material of the walls was not of the bqst quality. The construction of the oven of range No. 3, with the glass door, would indicate high losses but due to its small size, and large heating units, the temperature increased rapidly. 15 The excellent heat retaining property of oven No. 6 is prob- ably accounted for by the oven walls being well insulated and the door fitting close, as the ventilation permitted very little heat to escape. In the determination of the efficiency of the oven the volume must be considered as well as its temperature. The curves in Fig. II represent the energy loss per cubic foot of oven space. The 1600 lAOO 1200 1000 y. 600 3 (L z *> V- 600 i 4<>0 [EGO O 1 Oven fKAOiATioN Heat Supplied « Heat Lost / J Ty /. / / / / // / / / / // V/ // # / / } / // y /I .^> // / / / / A f ^ / / r;; ^ 7 y / ^' /• z' y A 0. ^ y ^ 4 ^ y ^ ^ D lOO ZOO 300 AOO SOO 600 700 Oven Tcmpcrm-ure. in DeeREZi Fahrejaheit 8C o Fig. 10 ordinates are derived by dividing the watts input by the volume of each oven expressed in cubic feet. This gives the economic per- formance of each oven. Oven No. 3 has the maximum loss per cubic foot of contents, as would be expected from its construction. The other ranges fall in order as indicated by the cooling rates pre- viously discussed. i6 BAKING TESTS The foods chosen were those consumed regularly in the home. They were selected ^yith respect to the time required for baking. Biscuits require but a short time, bread and cake bake in about an hour, while meat consumes several hours.. 600 700 600 5-500 400 30O b ZOO / / Oven Radiation HtAT Supplied* Heat Lost / / m / / / / / / ./ > / / /// / / // / / ^ / / / / /\ / / / 6 ^ / r / /y / > / r ,/" y / 4 f\ f ,.' > y ) V^ ^ ^ y ^ / <%■ ^ y /( ^ f- ^ y' A W ^ ^ 4 zoo 300 400 500 ' 600 OvcH Temperature, in Decrees Fahrehheit Fig. 11 The same perspn prepared the biscuits, cake, bread and meat, attended to their insertion and removal f roni the ovens and inspected their progress during baking. This method allowed those conduct- ing the test to devote their entire time and attention to the many necessary instrument observations, and made for uniformity of manipulation. 17 BISCUITS The biscuits were baked in the ovens at an approximate tem- perature of 45o°F. Observations were recorded at intervals of two minutes. The baking extended over a period of ten to twelve min- utes. One batch of dough was prepared, from which a pan of six biscuits was placed in each oven. This made, the tests uniform and a comparison of results possible. Five tests were conducted in each oven. CAKE Three cake bakings were run in each oven, each cake taking about sixty minutes at an approximate temperature of 35o°F. BREAD The bread baking was conducted in a similar manner to the foregoing tests, one batch of dough being prepared from which an equal amount was placed in each oven. The bread was in the oven for approximately seventy-five minutes, at a temperature of 375 °F. MEAT One meat roasting test was conducted in each oven. The roast was started at a temperature of approximately 475 °F. During the three hours required to prepare the meat, the temperature was al- lowed to decrease to about 300° F. RESULTS OF BAKING TESTS The results of the baking tests are given in Figs. 12 to 19. The continuous curves are for the oven temperature. Any adjustment of the control switch, or opening and closing of the oven door causes a lagging increase or decrease of the oven temperature ; hence a gradual rise or fall in the temperature curve. The oven tem- perature for the bread and meat should decrease slowly as baking progresses as indicated in the curves. The adjustment of the control switch produces an immediate in- crease or decrease of the power input, which is represented by the dotted line and accounts for its irregularity. When the oven is being used as a fireless cooker the power is turned off. During the baking some of the ovens require a large amount of power, while others use very little and often were operated as fireless cookers. Range No. 5 was operated as a fireless cooker most of the time. The first test was started at the point marked "No. i in" and baking continued until the point marked "No. i out." The second test was prepared and started at the point marked "No. 2 in," thus the baking continued throughout the tests. 1 1 J c c J Biscuit Baking "Test Oven No 1 2i 600 * ji i 1 .__. ... 1 1 1 -_ 1 T. 1- £ I 500 z 1 1 1 1 1 ~ ^ 1 1 1 1 z r ^ t 1 1 ^ k^ \ I 1 > ^ ^, 1 1 — S^ X >16y 00 J ^ i-^ ^ 1 1 1 ^ S l-Z ul ^° f £ / 1 1 1 1 1 1 / 1 r 1 .... i". 1 r' T ""*" P 1 / / 1 1 1 1 1 1 I g ^ / 1 1 V 1 1 ; 6 4 100 / •X 1 1 / 1- J Fig. 13 1.2 600 H Z 10 ^ 500 X if > ^ 5 — Biscuit Baking Test Oven No 3 ^ 3 C ' 3 « » 1 ^ A . ■N . 1 .6^300 t ^ S 0. /\ 1 \ ^ / L J T 1 ^ i 1 i X y .Z lOO < / 1 1 / 1 1 > IOZO3O4O9D«07D8O00lC TiMt IM HlHUTtS >o Fig. 13 19 !; .8 s , Cake Bakin6 Test J OvtN No. Z 1 i 1 N Si ^ 1 ar i "S jl f1 ' ! jj I y \ L ^ 1 / \ I if """^^-Saa s ' ' ^ ^ --- .^ SOQ ' "fl /[ /] It / 1 i. 1 — 1 — ' j 1 I 1 1 *" """" .--•i. •*::' ii'J- """ ._) L_ "" ~ ■■"■ ~~ _ J Fig. 14 ZA 600 b io 5 JOO > 16^400 \ p Cake Bakins Te3T Oven No 7 \ 1 <: L T ._. n rj j r 1 1 1 5 1 1! 1 1 t /^ 1 1 1 1 / N ^ > . r" KU StSL t <^ , _ / /! ■f 1 1 1 1 / 1 I j[ 1 1 1 1 / 1 1 1 1 1 1 4 5100 / 1 1 1 ! f L_ __. -\ 11 j -S 1.0 1.6 £.0 IS 3.0 t.5 Time in Hours Fig. 15 20 2 4 600 I 2 Z 50O K 2 > 16 ul 400 C It - o •^12 300 1 1 u -■8 1- 200 z 4 ,5 lOO Bread Baking Test Oven No 4- — 6 o $ • T 1 1 1 1 1 1 1 [ i 1 ■ z z 1 -\ 1 1 ^ 1 1 V r \ ^ J 1 ^ 1 V TeripeRATuRe. >i 1 ^^ '1 1 1 f 1 ■^ J 1 1 ] h ' 1 1 1 1 1 1 / 1 1 1 1 1 / L. J-- . J?' -OWA TTS — 1 — I — — . --- ii ^_ -— -— — — LJ ._. ■1 ' 1 "■ "a 5 1.0 1.5 ZO Z5 3.0 3 5 40 TiMEL IN Hours Fig. 16 ,,_ ■ V Bread Baking Test Oven No. 5 24 600 1- X ao J 500 X z t - d Z i r" 1 r-^ 1 ^• — -l 1 Lr- ^ S l6lj 4O0 l' ^ 1 < o / 1 \ s > 1 /" V / ^ \ O 1.2 - 300 .8 t 200 r t^ r . u .4 > lOO O y /' 1 ^ \ i/ \ / \ V, z / 1 < / ^ ^ / ^ ^ ,/ / 1 1 / j ' / 1 1 •il I 1 o o < 1 Ii > > 1. 3 I 5 2 o e 5 3 o 4 5 4 4.' Fig. 17 21 Z4 600 1- I ^o55oo a: X z i O 1.6 y 400 ^ iZ u 300 O 8^200 > o A lOO |o z Meat Cookins TtsT Oven No 2 ■"h \ \ ' . — . . ^ SMPf.(V>T-.i«<^ '" 1 L 1 1 L — — T .- — 1 5 5 1.0 I.S Z.O Time in Hours 2.5 _3.0 a5 rig. 18 24 6oo )- Z.O 1 500 u c a if ^ 1.6 ^ 400 O ac ID Q f f f i f .8 S! 200 - 1 Meat Cooking Test Oven No. 6 -— » 1 1 ^ A V ^ t- / 1 \ ^ 2»Pf / 1 ... 1 JflT, i&E^ L 1 1 / 1 ^ UJ Aq lOO G / / 1 1 L — VATT 3 __. __. __. — -- — -n 1 1 C 5 10 1.5 2.0 2.5 3.0 3. Time in Hours s Fig. 19 22 MISCELLANEOUS OBSERVATIONS The method of operating the ranges was similar in every case. Individual taste, difference in ovens and variation in voltage ; of the supply circuit, all tend to produce a variable time temperature i curve. Thus the curves given for the time and temperature of bak- ' ing Figs 12 to 19 are only suggestive. Ovens No. i and No. 2 required more heat than the others. It was probably because their radiation was great and their loss of heat large when doors were opened. It did not increase the cost of operat- ing materially, as it takes a very short time to get the ovens hot. The oven of range No. 3 was just large enough for the small size roaster, and so shallow that the bread almost touched the top coil. i When roasting meat, this was the only oven in which steam con- ' densed and ran out around the door. This condensing might have been caused by the cool glass in the oven door. In oven No. 4 the food had to be turned so as to brown evenly, probably because of improper location of the heating coils. Oven No. 5 was steam tight and held heat longest, but upon opening the oven door, the fumes of the fat from the roasting meat, and the intense heat were very disagreeable to the face and eyes. The flavor of the meat roasted in this oven was not nearly as good as the other roasts, due to the tight oven, not permitting the vapor to escape. The ovens after being heated, did not need both the upper and i lower coils energized, the lower coil only being used most of the 1 time. The upper coil was used only when baking was nearly com- i plete. so as to give the desired brown to the food. j During most of the baking operations, the ovens could have ' been operated partially as fireless cookers. They are so constructed ■ as to economize in power in that way. The current also might have been turned off a few minutes before the food was entirely cooked and finished as in a fireless cooker. The better one understands the ranges, the more economical will their operation become. i SURFACE BURNERS I I Four types of surface burners were studied. • Ranges Nos. 2, 4 and 6, were equipped with moulded porcelain I burners. These are round flat porcelain plates with deep grooves in their upper surfaces to receive the heating coils. This type of burn- i er transfers the heat more by conduction than by radiation. ' The open coil reflector burner on Range No. i has the coils i mounted in a steel frame, supported with porcelain bushings in truss construction. A bright reflector is located underneath to as- sist in concentrating the heat upon the cooking utensils. The heat is transferred to the vessel principally by radiation and convection. 2.^ Fig. 21). Porcelain type surface burners. too h -^ -^ T^ ^ p3 5=- / /' / y' /■ y / ^ ' /^ X' Jf \0, / y A u X ,/ / X c I ^ (60 UJ u (t (* u Q /40 2 lU f c t" (DO 5 1 SO / / / '/ / / 4 ^ 'A 0' ^ / 1 / f / /■ // p ^ ^ 1 / / /^ / / / 1 / / A V / 1 J / / // V / ', / / / // V / / / A / /, V / / / / ^ / / / // / / ^ ^ ^/ / Hot PcATt TtsTa 3 L«& Vl^TtR Ht/«TtP TO BoH-irtO & E.VA(»o««TtD. // / / y ^ y y ^ ^ ^ 5 lo IS t^ e.5 T/MC IN Minutes Fig. 21 The semi-enclosed unit of range No. 7 is of the moulded porce- lain construction. The element is separated from the vessel by a cast steel grating. Heat must be carried largely by convection for about three quarters of an inch to the grating, then by conduction to the utensil. 24 The enclosed or iron-clad unit has its coils entirely within a steel jacket, which presents a smooth surface to the vessel. Ranges Nos. 3 and 5 have this type of surface burner. They are very efficient with metal ware, as the heat is transferred directly by conduction. Fig. 22. Open coil reflector type surface burner. SURFACE BURNER TESTS The tests were conducted under laboratory conditions such as constant voltage and the elimination of cool air currents from the room. A known amount of water was evaporated and the input noted. A vessel was selected that would just cover the hot plate. This was a dark granite straight side pan, eight inches in diameter and six inches high, with a bulge upward in the bottom, of about three-eighths of an inch. Three pounds of water were used in each test and evaporated down to the ton of the bulge. The weight of the remaining water, subtracted from the three pounds,- gave the amount evaporated. The change of temperature was noted at five-minute intervals up to the boiling point. The temperature increased rapidly to 205°F. and very slowly from this point to 2i2°F, It was difficult to determine the exact time that the water arrived at the boiling point. Due to this fact no calculations have been made involving the boiling point. Efficiencies have been calculated for the total boil- 25 ing period and for the first eight minutes of the heating period. Fig. 21 shows the time required to heat three pounds of water to the boil- ing point on each of the seven ranges. The thermal efficiency was obtained by comparing the British thermal units absorbed by the water, with the British thermal units put into the burner. The following relations are stated in order that the method of determining the thermal efficiencies may be evident. Hot Plate, EFFicieNciE.s BY ElVAPORATlON OF WaTER a 9 < Z Z Z (T VO ^ 1 1 > t^ u '. z -^ ) 1 . - ^ i 1 1 30 Fig. 33 To raise the temperature of one pound of water one degree Fahrenheit, one British thermal unit is required. To evaporate one pound of water at 2i2°F. requires the absorp- tion of 969.7 British thermal units. One kilo-watt-hour is equivalent to 3415 British thermal units. The efficiencies as shown in Fig. 23, were obtained by adding to the product of the temperature change and total weight of water, the British thermal units obtained by the product of 969.7 and the weig'ht of water evaporated, expressed in pounds. This sum was then divid- ed by 3.415 times the watt hours used. 26 T == Temperature of water at start of test. T' = Temperature of water at end of test. W = Total weight of water in pounds. W' = Total weight of water evaporated in pounds. WH = Watt hours put into the burner. (T— T) W + 969.7 \\" 3.415 (W.H.) = Efficiency The efficiency at the end of the first eight minutes, at a point below the boiling temperature on each range, was obtained in a simi- lar manner. Fig. 24 shows the hot plate efi^iciencies for three pounds of water heated for eight minutes. 100 90 &0 O 60 u Oi. 50 3 L Hot Plate ELpncieNaes -bsl Watelr Heated for & Minutes \c 5 ^° 't r- d ^ Z c Q c 1 2 1 t - c 0^ - in ^ n c 2 I 5 CO 1 ■ d ^ 1 4.0 Fig. 24 THE BURNERS The grooves of the moulded porcelain burner form deep pockets in which the food lodges. This has to be burned or' dug out to pre- vent the burner from becoming hot in spots and being damaged. The open-coil reflector burner, to maintain its high efficiency depends upon the reflector being kept brig'ht. Particles of food drop through and lodge upon the reflector. This, together with the intense heat, cause a loss of reflecting properties which lowers the efficiency rapidly. ^7 The semi-enclosed burner is very difficult to keep clean. The enclosed burner is expensive to operate for short periods and takes more time and energy for heating. The radiant reflector type is most efficient in the laboratory where conditions are under better control and where the reflector can Fig. 2.5. Semi-enclosed type surface burner. be kept bright by frequent changes. With burners such as this in the home, the efficiency might soon drop below that of the porcelain type. The porcelain burner maintains a high efficiency without much attention. For long periods of heating the iron-clad and semi-enclosed units are best adapted and are very efficient. 28 THE RELATIVE COST OF BAKING The following tables give the results of the various tests upon the seven electric ovens. The three cent kilowatt-hour rate was used in computing the costs. l"ig. 2'>, EiK'losed type surface liurners. BISCUITS ove Preheating Preheating Number of lo. watt hours time min. tests I 558 15 4 2 547 12 4 3 891 50 3 4 929 20 4 5 1677 38 5 6 1075 21 5 7 961 25 4 V. H. to Percent Total Total bake of total w.h.pre- cost w. h. to heating cents bake & baking 178 24 736 2.2 194 26 741 2.27 128 12 1019 3-0 III 10 1040 3-1 150 8 1827 5-4 116 9 1191 3-5 137 12 1098 3-3 Oven No. i cost less for biscuits, while No. 5 proved to be the most expensive. The heating units in oven No. i were of the open type and the ventilated oven was lined with bright aluminum. The heat units of No. 5 were of the enclosed type, imbeded in heavy cast steel. The oven was lined as No. i but was not ventilated. Biscuit baking is a short process, requiring but twelve minutes. It is evident that ovens constructed as that of No. i with the open type heating unit are the most economical for short period baking, owing to their quick preheating characteristic. 29 CAKE stove Preheating Number Watt-hours Percent of Total watt Total No. watt hours of tests to bake total w.h. hours preheat- cost to bake ing & baking cents I 558 3 885 61 1443 4-3 2 547 3 356 39 903 2.7 3 891 3 322 24 1303 3-9 4 929 3 458 33 1387 4-1 5 1677 4 326 16 2004 6.0 6 1075 4 360 25 1435 4-3 7 961 3 412 30 1375 4.1 Oven No. 2 was a little cheaper for cake baking than oven No. i. Thei r construction is similar. Oven No. K was again the most expensive. BREAD Stove Preheating Watt hours Percent total Total watt Total cost No. watt hours to bake w.h. to bake hours preheat- ing & baking cents I 558 576 51 1 134 3-4 2 547 346 35 893 2.6 3 891 362 39 1253 3-7 4 929 591 39 1520 4-5 5 1677 32 2 1710 S-i 6 1075 288 21 1363 4.0 7 961 423 30 1384 4-1 Three bread baking tests were run in each oven. They were similar to those of the cake. The time required was about the same in both cases, being seventy-five or eighty minutes. The small input for bakin, to oven No. 5 was due it its use as a fireless oven most of the time. MEAT Stove Preheating Watt hours Percent total Total watt Total cost No. watt hours to bake w.h. to bake hours preheat- ing & "baking cents I 558 2224 81 2782 8.3 2 547 1315 71 1862 5-5 3 891 1 169 57 2060 6.1 4 939 1299 58 2228 6.6 5 1677 499 23 2177 6.5 6 1075 143 12 1218 3-6 7 961 1974 67 2935 8.8 The longer baking tests. such as with the meat, rather reverse the conclusions derived from the short tests. Oven I No. I was best for short baking periods, while it was about the most ex- pensive for cooking of long duration. The heavy enclosed type of 30 heating unit and ovens of the type of No. 5 were found to be the cheapest for long periods of baking. They are the most expensive for quick baking. The comparative costs of operating the electric ranges are given in Fig. 2^/. The energy required to preheat the ovens is large as compared with that put into the ovens for baking. Thus the quantity of food could be increased for larger families without the same proportion- ate increase in cost. CoHPAnATivt Cost or OPtWATIMG rtANaC * MtAT - N ■< ifl IB h- & bbooaod i X z X X X X DISCU1T6 CAKt - N « ■« wi « 1 ( b « b b 6 '. 1. t X i X -i 5HE.AO - w ifl ^ in « r- it i 6 6 . 7 z "» 7 ;■ ■* ■» 3 r - to »i < m i» t i _ 1 1 o X 9 Fig. 27 An oven selected for the home should be one suitable for short baking periods as with few exceptions food prepared in the home requires less than oue hour for baking. It should have a well insu- lated, light aluminum lining and adjustable ventilation. Open type heating units are most desirable. Service such as restaurants, hotels, clubs, etc., where the ovens will be in service for long periods and quite frequently, the heavy cast steel enclosed, heating unit would be by far the most -economical. ELECTRIC RANGE DATA The cost of operating the electric range in the home, together with the characteristic range load curve, have been studied by sev- eral of the large power companies, so as to make the proper adjust- ment of energy rates. ■ 31 Mr. Henry Wallsmith, Hartford City, Indiana, in his report* to the American Gas & Electric Company, shows some very inter- esting facts in regard to electric range performance for different size families and homes. The rate paid for electricity is a combination cooking and lighting rate ; lighting rate eleven cents per K. W. H., cooking rate six cents per first ten K. W. H., and all excess consumption three cents per K. W. H. Size of Number of Time Range Light Total Total Net Range family rooms month & day k.w.h. k.w.h. k.w.h. bill bill 2 6 I-I4 to 2-21 36 II 47 $2.29 $1.19 2 ■ 6 3-24 to 4-24 71 II 82 3.26 2.16 3 7 1-22 to 2-21 112 20 132 5.06 3.06 5 6 3-22 to 4-22 54 58 112 4.24 1.56 5 8 2-23 to 3-24 lOI z^ 133 5-31 2. II 7 lO 2-21 to 3-21 108 51 159 6.53 1.43 7 10 12-22 to 1-22 167 57 218 8.30 2.60 The Pacific Power & Light Company reports'' a detailed inves- tigation into the cost of cooking by electricity. The results obtained from the investigation indicate that the average family can cook electrically for about $3.00 per month with energy selling at 3.6 cents per K. W. H. The company has a total of 201 electric ranges con- nected to its lines. The average monthly number of ranges in service was 161, with a yearly cost for operating each range of $30.60. The average monthly bill was $2.55 net. The company has deducted from the total, all the minimum charge bills and their earnings and finds that the average bill now is $3.13 a month. This is a more accurate ex- pression of the cost of electric cooking, because the minimum charge bills do not indicate that the ranges were really used to their best advantage. A New England Power Company which has sixty ranges con- nected to its lines, and a rate of three cents per K. W. H., reports* an average cost of eighty cents per month per person as a fair cost of preparing meals electrically. The cost of baking electrically as presented by this bulletin can not be stated in terms of cost per person per month as this in- cludes cooking with both surface burners and ovens. * N. E. L. A. Bulletin t Electrical World. Januarv. 1919 t N. E. L. A. Bulletin 32 CHARACTERISTICS OF RANGE LOAD The opinion of many engineers is that the peak of the range load occurs at the same time as the station peak and that the maxi- mum range demand will be a large percentage of the range con- nected load. Mr. R. B. Snyder of the Milwaukee Electric Rail- way & Light Company, in his analysis of the electric range load found several conditions which are interesting to note.* The demands upon the gas supply for the average city, where most of the homes use this fuel for cooking, occurs at the noon hour. These are the consumers who will eventually use electricity, so their maximum demand will no doubt be at the same hour. to 15 «) 1" O J i s Daiuy Load Curve. Monday / i \ k A r\ M- A / r^ u J \ \ _jL \ ^ / A r H \ 4 » a K) 12 2 4- 6 £ A.M. (nooh) P.m. J Fig. 28 4 The demand from the apartment buildings seems to be of a different character. The average daily load for an apartment with twenty-two electric ranges in service, gives the curves of Figs. Nos. 28 and 29 with the peak in the evening from 5 p. m. to 6:30 p. m. The distribution of electric ranges between ordinary homes and apartment buildings results in a distinct advantage to the com- pany furnishing the power supply. With the range load thus divided, two peaks occur in the range load curve, instead of a single one. These peaks appear at from 11 :30 A. M. to i :oo P. M., and from 5:00 P. M. to 6:30 P. M. Electrical World, April 14, 1917 33 The curves indicate further that the demands for each week day was about the same. The maximum was 22 K. W., with Sunday a minimum of 9 K. W. The total connected load was 98 K. W. The maximum demand for a group of twenty-five ranges will not exceed fifteen percent of the connected load. The maximum de- mand for a single range may averge 40 to 60 percent of its rating. The average daily consumption per person over a period of ten days was 1.18 K. W. H., including lights. This shows the average consumption to be well below i K. W. H. per person per day. zo 15 J 2 s Daiuy Load CuRVt WtONCSDAY r f A \ \ 1 \ f / f '\ ^ J ^A / ^ °< & 8 K> *Z 2 A.M. {.r*oorcelain type, enclosed and open t.vpe. Oven heating vmits. gases. It can be easily regulated to produce a steady even heat at any desired temperature, by the upper and lower heating units having three controls each, giving eighteen different oven temper- atures. The automatic attachments which can be placed upon electric ranges are desirable as well as economical. The clock, thermastat, 35 and fireless cooker arrangement enable one to place the meal in the oven at their convenience, setting the clock and thermostat with the knowledge that the energy will be turned on at the proper time and continue until the oven is of the desired temperature, then the ther- mostat will stop the current flow and the meal will be prepared by the fireless cooker method at the proper time. Five principal reasons have been paramount in the delay of the general public in taking up electric cooking. They may be enumerated as follows : 1. High first cost including purchase price and installation. 2. Anticipated high operating cost. 3. Satisfaction with present method of cooking. 4. Loss in disposition of old equipment. 5. Slightly longer time for cooking. All these reasons are rapidly being overcome. Central sta- tions are doing their utmost to cheapen installations by introducing low prices and deferred payments. POINTS TO BE CONSIDERED IN SELECTING AN ELECTRIC RANGE The desirable characteristics as developed during the tests are indicated below. Most of the ranges tested met these requirements very well. In general an electric range should be : Attractive in appearance; Easy to clean ; Provided with heating units separately controlled. Surface burners should have : Porcelain heating units ; Heating units of diflferent sizes. The oven should be : Quick heating ; Ventilated ; Of convenient height and size; Designed to give uniform browning of foods. The heating elements should be easily removable for repairs or cleaning. The moulded porcelain types of coils are desirable as they heat quickly and one can tell readily when the current is on. Open coils are best for the oven. Surface or hot plate elements of different diameters are de- sirable. Such elements accommodate cooking vessels of different sizes and thus save much energy. The oven should be non-rusting, well insulated, and provided with a substantial, close-fitting door. The steam tight oven is not 36 desirable because food will not brown until extra energy is used to eliminate the moisture. Ovens raised from the floor are more convenient. The glass door is more economical, because there is less necessity for opening the door, resulting in loss of heat. The glass is, however, liable to be broken when hot, by a little cool air striking it. Pyrex glass used in the door would probably remedy this defect. Fig. 31. Range No. 5. Heating units enclosed type. A right hand oven with a door that opens down is most conven- ient. The oven should have a dependable thermometer or temperature indicator. Each element should be individually fused and should have a separate switch. This would prevent the whole or a large portion of the stove being rendered inoperative by accident to a single unit. Ample capacity in burners is to be desired, so that delays may be reduced to a minimum. The inside dimensions of the oven should be about eighteen inches wide, twelve inches high, and sixteen inches deep. DESCRIPTION OF RANGES The size of the oven as stated represents the size of the largest receptacle it will accommodate and not the outer dimensions given by some of the manufacturers. The four surface burners of range No. i are of open construc- tion and of different diameters. The oven is eighteen and one-half Fig. 32. Range No. 6. Surface burners, porcelain type, porcelain and open type. Oven heating units, inches wide, ten inches high, and eighteen inches deep, with two large open heating units, each taking 1200 watts. The oven is ventilated. 38 There is no heat insulation between the bottom of oven and warm- er oven which is just below. The door does not fit tightly and opens downward. There is a metal thermometer in the door. Range No. 2 has three surface burners of moulded porcelain of the same diameters. The oven is eighteen inches wide, fourteen inches high and twelve inches deep, with two large open heating units, each consuming 1250 watts. The oven is well insulated and ventilated. The door fits tightly and opens downward. There is a metal thermometer in the door. The two surface burners of Range No. 3 are enclosed, both being eight and one-half inches in diameter. The oven is nineteen inches wide, ten and one-half inches high and twelve inches deep, provided with two large open heating units using 1000 watts each. It is well insulated and ventilated. The door, with glass panels, opens from the side. The oven is equipped with a metal temperature in- dicator and automatic clock current control. Range No. 4 has four surface burners of open porcelain. Three are six and one-half inches in diameter, one eight and one-half inch- es in diameter. The oven is eighteen and one-half inches wide, fifteen inches high and twelve inchest deep, with two large heating elements. The upper one is open and the lower one enclosed, both together taking 2500 watts. The oven is not ventilated. The door is poorly fitted and opens downward. There is a metal thermometer in the door. The surface burners of range No. 5 are enclosed, one eight inches in diameter and three, six inches in diameter. The oven is eighteen inches wide, twelve inches high, and eighteen inches deep, with two large enclosed heating units, taking 3500 watts total. The oven is well insulated but not ventilated. There is a mercury ther- mometer in the door. Range No. 6 has three surface burners of the open type. One is nine inches in diameter, the other two, seven and one-half inches in diameter. The oven is fifteen inches wide, thirteen inches high and eighteen and one-half inches deep, with two large heating units, taking 1000 watts each. The upper heating unit is of open construc- tion, the lower, porcelain construction. The oven is ventilated, and equipped with a metal thermometer and automatic clock current con- trol. The door fits tightly and opens from side. Range No. 7 has three surface burners that are of the semi-en- closed type. One is six inches in diameter, — the other two are eight inches in diameter. The oven is eighteen inches wide, ten inches high and seventeen inches deep, with an open type upper heating unit and enclose lower unit, each using 1250 watts. It is well insulated and ventilated. The door fits well and opens downward. There is a metal thermometer in the door. 39 Fig. 33. Range No. 7. Surface burners semi-enclosed type. Oven heating units, enclosed and open type. 40 CONCLUSIONS The modern electric range has improved ventilation, resulting in more efficient application of heat. The surplus moisture is car- ried off and but little heat escapes. Meat, bread, cakes, and pies brown evenly to any degree on top, bottom and sides. There is no need of matches. There are no odors from gas or smoke. The kitchen is not hot. There is no fire to use up the air in the room. There is no scouring of pots and pans, so much time and labor are saved. The electric oven is always ready and does its work with econ- omy, cleanliness and little supervision. The main obstacle which tends to restrict the use of electric ranges seems to be their price and the high rate of electric energy. If the rates were lowered, so that the operating expense would be the same as for other fuels, the added advantages of more leisure time, less labor and clean, sanitary methods would be obvious. These advantages should be taken into account when considering electric ranges, together with the fact that the insurance rate is usually reduced where gas is not taken into the home. Statistics* show that there are more homes in the United States already which are supplied with electric current, than are supplied with running water. Thus it seems that further publicity and the introduction of special cooking rates will bring about the general use of electricity for cooking purposes. The electric range is just beginning to receive the recognition which it deserves, being superior both to the coal and the gas range. A far higher percentage of the heat energy is absorbed by the food in the cooking and baking operations and very little goes into the kitchen to make it uncomfortably warm in hot weather. The uniform results that can be obtained with the electric oven and the hot plates are appreciated by those who have used both gas and electric ranges. * Encyclopedia Britannica INDEX Page Advantages of electric ranges - - - 33 Baking tests 16 biscuits - 17 bread 17 cake 17 meat 17 Baking curves discussion 17 Baking costs 28 biscuits 28 bread 29 cake A 29 meat - 29 Biscuit baking, test 17 cost • 28 Bread baking, test 17 cost - 29 Cake baking, test 17 cost - -- 29 Characteristics of range loads 32 Conclusions 40 Cooking of foods, purpose 6 Cooking curves, discussion, oven 17 Cost of baking 28 Curve discussions 17 baking -17 heat insulation of oven 14 open door 13 preheating ovens empty 13 preheating ovens filled 13 surface burner 24 temperature indicator 14 Efficiencies of, ovens 15 surface burner 25 Insulation of oven, test 14 Introduction 5 Meat baking, test 17 cost 29 Observations, miscellaneous 22 INDEX Page Open door, test 11 discussion of curves 13 Oven, efficiencies 15 lieat insulation 14 tests 9 Preface - 4 Preheating, ovens empty, test 10 ovens filled, test 11 discussion 13 Ranges, data 30 description 37 desirable characteristics ^ 35 load characteristics 32 selecting 35 tested .- : I. 9 Surface burners 22 description 22 discussion 23 efficiencies 25 tests 24 Temperature indicators ;... 14 Testing, baking 16 efficiencies of oven 15 efficiencies of surface burner 25 heat insulation of oven walls 13 open door testing of ovens -.. 11 ovens 9 preheating ovens empty -- 10 preheating ovens filled 11 surface burners 24 %-