UNIVERSITY OF CALIFORNIA 
 
 COLLEGE OF AGRICULTURE 
 
 AGRICULTURAL EXPERIMENT STATION 
 
 BERKELEY, CALIFORNIA 
 
 THE ELECTRIC BROODER 
 
 B. D. MOSES AND T. A. WOOD 
 
 BULLETIN 441 
 
 November, 1927 
 
 UNIVERSITY OF CALIFORNIA PRINTING OFFICE 
 
 BERKELEY, CALIFORNIA 
 
 1927 
 
FOREWORD 
 
 This bulletin is a contribution of the Division of Agricultural 
 Engineering, University of California, and the Poultry Sub-Com- 
 mittee of the California Committee on the Relation of Electricity to 
 Agriculture. It is the second of a series planned to report the results 
 of investigations conducted jointly by the Agricultural Experiment 
 Station, College of Agriculture, University of California, and the 
 California Committee on the Relation of Electricity to Agriculture. 
 This committee represents the agricultural and electrical industries 
 in California that are working together for the purpose of making 
 available reliable information concerning the use of electricity on the 
 farm, and cooperating with similar committees in other states.* 
 
 E. D. Merrill, Director, 
 California Agricultural Experiment Station. 
 
 * The personnel of this committee for 1926-27 is: 
 
 E. D. Merrill, Dean, College of Agriculture, University of California, 
 
 Berkeley, Chairman. 
 N. E. Sutherland, Pacific Gas & Electric Co., San Francisco, Treasurer. 
 
 B. D. Moses, College of Agriculture, Davis, State Director and Secretary. 
 T. A. Wood, Davis, Field Engineer. 
 
 F. E. Boyd, General Electric Company, San Francisco. 
 
 C. L. Cory, Dean, College of Mechanics, University of California, Berkeley. 
 H. M. Crawford, Pacific Gas & Electric Co., San Francisco. 
 
 J. J. Deuel, California Farm Bureau Federation, San Francisco. 
 
 A. M. Frost, San Joaquin Light & Power Corporation, Fresno. 
 Alex. Johnson, California Farm Bureau Federation, Berkeley. 
 T. H. Lambert, El Monte, Agriculturist. 
 
 B. M. Maddox, Southern California Edison Co., Visalia. 
 
 W. C. McWhinney, Southern California Edison Co., Los Angeles. 
 
 C. Grunsky, California Bailroad Commission, San Francisco. 
 
THE ELECTRIC BROODER 
 
 B. D. MOSES* and T. A. WOOD2 
 
 INTRODUCTION 
 
 ' ' A brooder is a covered and warmed receptacle for the protection 
 of chicks reared without a hen." The heat required can be supplied 
 by the combustion of fuel or by electricity. The universal demand 
 for labor saving devices which are automatically controlled has 
 resulted in the adoption by many farmers of brooders heated by 
 electricity. Statistics indicate that at least five thousand of these 
 units were in use in California in 1926. 
 
 In order to make this type of energy applicable to brooding, heat 
 conservation is necessary. This has been effected in some cases by the 
 use of heat insulation on the hover; in others by curtains around the 
 outer edge of the hover ; and again at other times by crowding chicks 
 together, making use of the body heat. On account of poor ventilation 
 and this crowding, losses have resulted which have sometimes been 
 attributed to the use of electrically generated heat rather than to 
 defects in brooder design and to improper manipulation. 
 
 The purpose of this bulletin is to report results of observations on 
 brooders heated by electricity in actual field operation from the stand- 
 point of general design, mechanical features, power requirements, and 
 heating costs. 
 
 ELECTRIC BROODER REQUIREMENTS 
 
 In the profitable brooding of chicks certain essential requirements 
 have to be met. Some of the more important are : 
 
 1. At least seven square inches of free floor space beneath the 
 brooder should be provided for each chick. 
 
 2. Sufficient heat must be available to maintain a temperature of 
 90 to 95 degrees Fahrenheit two inches above the floor and five inches 
 inside the outer edge of the hover under all weather conditions. 
 
 1 Assistant Professor of Agricultural Engineering and Associate Agricultural 
 Engineer in the Experiment Station. 
 
 2 Field Engineer, California Committee on the Relation of Electricity to 
 Agriculture. 
 
4 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 3. The heating elements should be so arranged as to obtain a 
 uniform distribution of heat and, if possible, to assist in ventilation. 
 
 4. A thermostat for temperature regulation should be provided. 
 
 5. Adequate ventilation is essential to introduce fresh air and to 
 remove the excess carbon dioxide, water vapor, and other impurities 
 as they are formed. 
 
 6. The brooder should be simple and well built. It should be so 
 designed and constructed as to simplify operation, minimize costs and 
 insure satisfactory brooding conditions. 
 
 7. The first cost as well as operating costs must be such as to render 
 the use of the brooder profitable. 
 
 HEAT AND VENTILATION PRINCIPLES INVOLVED 
 
 The temperature of a body is due to the presence of heat in that 
 body, and while there is but one kind of heat of which we have any 
 knowledge, there are three known methods (convection, conduction, 
 and radiation) by which this heat can be transferred from one body 
 to another. 
 
 Convection is the transfer of heat from the source to the absorber 
 by storing the heat temporarily in a carrier substance, such as air or 
 water, and then bodily moving this substance from the source to the 
 cooler heat absorber. For example, a living room is heated by a 
 furnace in the basement. The heat is generated in the basement, is 
 stored temporarily in the air above the furnace, and is allowed or 
 caused to move by convection (air currents) to the living room. 
 
 Conduction is the transfer of heat from one small particle of a 
 substance to the next, by contact of these particles or their near asso- 
 ciation, along the length or breadth of the substance. The fire in a 
 stove, for instance, generates heat, which warms the inner surface of 
 the stove metal. The particles on the inner surface of the metal pass 
 this heat along to the next until the heat appears on the outside sur- 
 face of the stove. The outside surface is not in contact with the heat 
 source but is heated by conduction from a surface which is in direct 
 contact. In gases and liquids, this action is comparatively slow, but 
 in most metals it is much more rapid. The amount of heat transferred 
 depends upon the difference in temperature between the inside and 
 outside surfaces, the thickness of the substance through which it must 
 pass, the area of this exposed surface, and the ability of the substance 
 to transfer heat. 
 
BuL. 441] THE ELECTRIC BROODER 5 
 
 Radiation is the transfer of heat through space by means of vibra- 
 tions in the ether. 3 This is the most common type of heat transfer, 
 since practically all heat upon the surface of this planet comes, or has 
 come, directly or indirectly from the sun by radiation. Heat in this 
 form is transferred with the speed of light, namely, 186,000 miles per 
 second, and requires no material substance for this transfer. These 
 vibrations or waves, do not become sensible heat, until they are 
 absorbed by some substance such as the earth. The amount of heat 
 transferred from the source to the absorber depends upon the size, 
 nature, and surface temperature of the exposed radiating body, upon 
 the distance through which the heat must be radiated, and upon the 
 ability of the cooler body to absorb the heat vibrations. 
 
 Heat reflectors: Radiated heat, like light, can be reflected without 
 great loss if proper reflecting surfaces are used. The amount of heat 
 lost depends upon the surface condition of the reflector, upon the 
 color of the reflector surface, and upon the substance of which it is 
 made. Black, rough surfaces, for instance, will absorb practically all 
 heat rays striking them, while a light polished metal surface may 
 reflect 80 per cent of these rays. The direction of travel of reflected 
 heat rays can be controlled by the use of concave, flat or convex 
 reflectors. The sharpness or abruptness of the concentration or diffu- 
 sion depends upon the radius of curvature of the reflector. By proper 
 reflector designs then, radiated heat can be concentrated within a 
 small area or can be diffused to almost any degree desired. 
 
 Ventilation:* A brooder must be adequately ventilated, since water 
 vapor, carbon dioxide, and other gases given off by the chick tend to 
 accumulate beneath the hover when, for example, curtains are used 
 or ventilation is otherwise more or less restricted. Water vapor has, 
 in some instances, accumulated to such an extent as to result in high 
 mortality to the chicks. 
 
 3 These vibrations or waves exist in nature in various forms. Sound, as an 
 illustration, is transferred through matter by vibrations or waves in the sub- 
 stance surrounding or adjoining the sound source. Heat, light, and electricity 
 require no such material substance for their transfer when in wave form, but 
 are propagated instead with great speed through what appears to be empty 
 space, but which is supposed by physicists to be filled with an immaterial, 
 perfectly elastic, and weightless substance called ether. 
 
 * "Ventilation consists in displacing vitiated air from an apartment and 
 replacing it with fresh air." All the foul air is not displaced bodily at one 
 time, but is diluted by the incoming fresh air until it is suitable for respira- 
 tional purposes. There are two methods of obtaining this ventilation, namely, 
 by "natural" ventilation, in which the air movements are induced by a 
 "thermal" head; and by "mechanical" ventilation, in which the air move- 
 ments are maintained by a power-driven fan. All brooders tested used the 
 natural system. However, in some cases the air flow was intensified by 
 artificial heat which was installed at advantageous points in the system. 
 
b UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 The ability of the brooder air to absorb this water vapor is limited 
 by its temperature, volume, pressure, and humidity. Air which has 
 absorbed all the water vapor possible is said to be "saturated" or to 
 have a "relative humidity" of 100 per cent. If saturated air comes 
 in contact with a surface cooler than this air, its temperature drops 
 and its volume and water absorbing capacity decrease. 5 This causes 
 "condensation" and dew is formed upon the cooler surface. 
 
 Ventilation for the purpose of removing impure air and introduc- 
 ing fresh air affects both the amount of heat used and the quality of 
 chick produced ; but the health of the chick should never he jeopardized 
 in order to save a little heat. The slight cost of the additional heat 
 necessary to secure adequate ventilation is more than offset by the 
 lower mortality of chicks and by the stronger chicks which are 
 produced when all conditions are fully met. 
 
 ECONOMICS OF NEW DEVICES 
 
 Many devices are being developed to reduce brooding costs either 
 by saving heat or by increasing the number of chicks that can be 
 taken care of under the hover. These devices may be in the form of 
 adequate heat insulation, a thermostat switch, or a different type of 
 heating or ventilating system ; and they may effect a saving by reduc- 
 ing the mortality, or by decreasing the amount of heat and of labor 
 required. Before any new brooding device is purchased, the pros- 
 pective customer should determine whether there really will be a 
 saving effected by its use, since the additional money that can be 
 economically invested in any device is limited by the returns which 
 that device will earn. 
 
 NON-GLOWING (BLACK HEATe) TYPES OF BROODERS STUDIED 
 
 The oldest type of electric brooder which seems to be economically 
 successful, in so far as heating costs are concerned, consists of a 
 rather low hover surrounded by curtains and heated by overhead non- 
 
 5 The ability of air to absorb water vapor is doubled for each 27 to 30° F 
 rise in temperature and conversely is halved for each 27 to 30° F drop in tem- 
 perature (within all practical limits of temperatures encountered). Air cannot 
 sustain a humidity greater than 100 per cent. Should a drop in temperature 
 occur to such air, enough vapor condenses out to establish equilibrium again. 
 
 6 ''Black heat'* is a term sometimes applied to the heat from electric 
 heating elements, which operate at a temperature below the glow point; that 
 is, the wire maintains its natural color (see fig. 21). "Convection" brooders 
 are those in which this method of heat transfer predominates. 
 
Bul. 441] 
 
 THE ELECTRIC BROODER 
 
 glowing heating elements (see figs. 1, 2, and sketch No. 1, fig. 3). 
 These heating elements are fastened to the under side of the hover 
 just above the heads of the chicks. The temperature of the air in the 
 brooder is controlled, in so far as the electric heat used is concerned, 
 by a thermostat switch. No definite provision has been made in this 
 type of brooder to induce positive ventilation. When used with a 
 relatively small number of chicks scattered over a large brooder floor 
 area, this early form is fairly satisfactory. 
 
 Pig. 1. — A simple box type, non-glowing or convection electric brooder, 
 using " overhead" heat. Note the use of good electric insulation, an ether 
 wafer thermostat switch, and well designed power leads as well as the 
 simplicity of the hover construction. 
 
 Sketch No. 2 (fig. 3) shows the usual hover employing overhead, 
 non-glowing elements and fitted with a chimney and damper in the 
 apex of the cone. Since warm air tends to rise, this method of con- 
 necting the confined brooder air with the room air, permits the heat 
 generated by the heating elements to escape through the stack, even 
 though the damper is but slightly open. 
 
 Sketch No. 3 (fig. 3) is a further modification of the chimney idea, 
 using a stack which extends down into the brooder, and which may be 
 of one piece or of the telescoping type. The telescoping stack can be 
 adjusted until a place is reached where the temperature difference is 
 
8 UNIVERSITY OP CALIFORNIA EXPERIMENT STATION 
 
 just enough to induce the proper ventilation of the brooder. This 
 device prevents the waste of heat that may occur in the type just 
 mentioned. It depends for its success upon manual control. Failure 
 to adjust the stack for changing temperature and moisture conditions, 
 however, is a source of trouble. The air flows in under the curtain at 
 the edge and out through the stack, an arrangement which leaves the 
 chicks which are near the curtain, in a cool draft. 
 
 U i-AJJJMm 
 
 Fig. 2. — A conical galvanized iron non-glowing or convection type electric 
 brooder, using overhead heat. 
 
 a. Side view showing the low, well constructed conical hover. This brooder 
 can be placed under the dropping board or in other small compartments and 
 allowed to rest on its own legs or it may be suspended from the ceiling by a 
 hook at the apex of the cone. 
 
 b. A view from beneath, showing a good type of electric wiring. The 
 heating elements are wound on asbestos sticks and are fastened to the hover 
 by spring clips. Should the wire on one stick burn out it is easily removed and 
 a new one snapped into place. Note that two heating circuits are connected 
 in parallel, thus assuring some heat should one circuit burn out. 
 
Bul. 441J 
 
 THE ELECTRIC BROODER 
 
 LINE SHETCM NO. 1. 
 HEAT: Blacn, Overhead Heating Elements. 
 
 CONTROL : Thermostat Switch. 
 VENTILATION: Room Cross Currents, Undirected. 
 
 CURTAINS: Two. 
 
 AIR FLOW. J n at One. Side, Out Other Side 
 BROODER FLOOR: Room 
 
 rf T f I \> ft 
 
 LINE. SKETCH Alt 2 
 HEAT: B la CM, Over head Heot inq Elements. 
 
 CONTROL: Thermostat Switch. 
 VENTILATION: Forced, Directed. 
 
 CURTAINS: One. CHIMNEY: At Apex. 
 
 AIR FLOW: In of Curtain, Out Thru Stocrt. 
 BROODER FLOOR: Room. 
 
 MJ. 
 HEAT: B/ach, Overhead Heating Elements. 
 
 CONTROL: Thermostat Switch. 
 VENTILATION: Semi-d, reeled ', Slightly Forced, 
 
 According to Height ofStocJffrom Floor. 
 
 CURTA INS : One . CMIMNE V. Telescoping. 
 
 AIR FLOW: In at Curtain, Out StacK; or In at 
 
 One Side Out Other Side; or Both. 
 BROODER FLOOR: Room. 
 
 HEAT: Blacn, Overhead Heating Elements. 
 
 CONTROL: Thermostat Switch. 
 VENTILATION: Sem.-directed, Slightly Forced, 
 
 According to Height of Hover from Floor. 
 
 CURTAINS: One. FLOOR AIR DUCT: One. 
 
 AIR FLOW: In at Center Air Duct, Out Under 
 
 Curtain; In at One Side, Out Other j or Both. 
 BROODER FLOOR: Room. 
 
 hAs. 
 HEAT: BIocm, Overhead hefting Elements 
 
 CONTROL : Thermostat Switch. 
 VENTILATION: Room Cross Currents, Undirected. 
 
 CURTAINS: One, or Two. 
 
 AIR FLOW: In at One Side, Out Other Side. 
 BROODER FLOOR: False Slatted Floor, Covered 
 
 With Burlap, Standing 2 "above Ffoom Floor. 
 
 HEA T: Blacn Overhead Heating Elements. 
 
 CONTROL: Thermostat Switch. 
 VENTILATION: Forced, Directed. 
 
 CURTAINS: One. AIR DUCT: One, Center. 
 
 AIR DUCT ELEMENT. Slowing Coil. 
 
 AIR FLOW: Jn at Center Air Duct, Out Under 
 
 Curtain. 
 BROODER FLOOR : Room. 
 
 HEAT: Blacx, Overhead heating Elements. 
 
 CONTROL: Thermostat Switch 
 VENTILATION: Room Cross Currents, Undirected. 
 
 CURTAINS: One 
 
 FALSE FLOOR ELEMENT: Blacx heat. 
 
 AIR FLOW: In at One Side, Out Oth tr 
 BROODER FLOOR: Special Heated Floor 
 Standing 4" Above Hoom Floor, A/o Air Duct. 
 
 m 8. 
 
 HEAT: Blacn Overhead Heating Elements. 
 
 CONTROL: Thermostat Switch. 
 VENTILATION: Forced, Directed. 
 
 CURTAINS: One. AIR DUCT: One, or Two. 
 
 FALSE FLOOR ELEMENTS: Blacn heat. 
 
 AIR FLOW: Under False Floor, Up Thru Duct, 
 
 Out Under Curtain. 
 BROODER FLOOR: Special Heoted Floor. 
 
 4-' Above Room Floor. 
 
 Fig. 3. — Line sketches of brooders studied. 
 
10 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 N&9. 
 HEAT: Glowing or BlacK F/oorFfeoflng Elements. 
 
 CONTROL : Thermostat Snitch. 
 VENTI LATION: Semi -directed, Slightly Forced. 
 
 According to Height of Curiam from Floor. 
 
 CURTAINS: One. AIR DUCT: One. 
 
 AIR FLOW : In Thru Tunnel, Out Under Curtain 
 BROODER FLOOR: Room. 
 
 AtPll. 
 
 HEAT: C lowing, Overhead Healing Elements. 
 REFLECTOR: Tin, Concave, 20" Radius, 
 CONTROL : danual. CURTAINS: None. 
 
 VEIV TILA TlON: Cross CWrcn h. Undirected. 
 
 -I 
 
 J 
 
 Hi 10 
 HEAT: Globing or Glac/r Side Floor' Elements. 
 
 CONTROL: Thermostat Snitch. 
 VENTILATION: Forced, Directed. 
 
 CURTAINS: One. 
 
 AIR FLOW: In thru Side Vent, Over Partition, 
 
 Across Brooder, Out Under Curtain. 
 BROODER FLOOR: Room. 
 
 m\I2. 
 HEAT: G/owing, Overhead Heating Elements 
 
 REFLECTOR: Tin, Rt, Vert-,Cene. 
 
 CONTROL : Manual 'r- 7hermostaf Switch. 
 VENTILATION: Cross Currents, Undirected. 
 
 CURTAINS: None. AIR DUCTS: Hone. 
 
 AIR FLOW: As Flowing in Room 
 
 Hi 13. 
 
 HOVER: Same as Used in /V* 12. 
 
 REFLECTOR: Inverted D<shpan Type, Which 
 Is anlmprovement over those used in A/&, 
 J J and 12, Since it Diffuses the Raf some - 
 nhai, Thus fending toTron Out fne 'Hoi Spot " 
 At the Center of the Ho ver. 
 
 N&14. 
 
 HOVER : Same as Used in Rsj2. 
 
 REFLECTOR: Convey, 20" Radius, k/ith 
 Heating Elements JO" Centers, Preferably 
 Three in number. By using Correct ffadius 
 cfCu'rvot^/'e almost any degree of ray dif- 
 fusion can be obtained. 
 
 N&JS. 
 REFLECTOR: Right Inverted Cone. This 
 Typ« should not be used Unless the ratio 
 of height to dioneter is 1 to 4~ or more, 
 since it vitf produce a 'not spot." 
 similar to N BS - II and 12. 
 
 Ate 16. 
 REFLECTOR: Convex Center Portion, 20" 
 to 24" Radius'; Concave Rim, J' to 4" Radius. 
 This Reflector, property designed, rVi/l 
 give even heat distribution and Form 
 no he of 'poc/tet ' nrhcre it meets the 
 hover sides. 
 
 Fig. 4. — Continuation of series shown in figure 3. 
 
Bul. 441] 
 
 THE ELECTRIC BROODER 
 
 11 
 
 Fig. 5. — A conical, galvanized iron, non-glowing or convection type electric 
 brooder, using overhead heat and a chimney of fixed length. The counter 
 balance at the top of the picture is used to adjust the height of the hover 
 from the floor. Note that the curtain is several inches above the floor, thus 
 allowing ample brooder ventilation. 
 
 Fig. 6. — A non-glowing or convection type electric brooder, using overhead 
 heat and a chimney of fixed length. Note the use of good electric wiring 
 practices. The hover is well insulated against heat losses < especially in the 
 central section. 
 
12 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 Sketch No. 4 (fig. 3) shows the usual hover employing overhead 
 non-glowing elements, with the addition of an air duct in the floor of 
 the brooder. The purpose of this air duct is to permit an upward 
 flow of fresh air through the floor into the brooder, thereby forcing 
 impure air out under the curtain. This duct alone does not create a 
 positive air flow and may or may not produce satisfactory ventilation. 
 This type is shown in greater detail in figure 7. 
 
 Sketch No. 5 (fig. 3) shows the usual hover, employing overhead 
 non-glowing elements and equipped with a false floor made of laths 
 tacked to 1% i ncn by 3% inch joists and covered with burlap. The 
 purpose of this false floor is to increase the effective drying surface, 
 since the two sides of the burlap and the lath are exposed to the air 
 flow ; and to make possible the removal of some moisture by a change 
 of burlap. The ventilation of the brooder is not affected to any 
 noticeable degree. 
 
 Sketch No. 6 (fig. 3) shows a heating element installed in the 
 brooder floor air duct to induce a positive, upward flow of fresh 
 air into the brooder, thus forcing the impure air out under the curtain. 
 This heating element is usually of the glowing type and operates at 
 one-half its rated voltage or one-fourth of its rated watts. It is con- 
 trolled by a separate snap switch and is on continuously. The main 
 heat source is still the overhead, non-glowing type of unit shown in 
 sketch No. 4, fig. 3. During the warm part of the day this over- 
 head heat can be cut off and the air duct element left to supply all 
 necessary heat to the chicks. Moisture troubles may develop only 
 under adverse weather conditions, when feeding heavily of milk or 
 when crowding is practiced. Moisture troubles, in this instance, may 
 be due to inadequate ventilation or insufficient heat to supply the 
 necessary heat of vaporization. 
 
 Sketch No. 7 (fig. 3) shows the usual hover employing overhead, 
 non-glowing elements and equipped with a heated brooder floor but 
 using no floor air duct. Heat is transferred by conduction from the 
 lower to the upper surface of the floor, where convection currents 
 are created, which tend to increase the air movements within the 
 brooder. The use of a low hanging curtain restricts the air flow and 
 prevents adequate brooder ventilation unless the hover is raised. The 
 floor temperature did not exceed 80° P during the tests of this type 
 of brooder. 
 
Bul. 441] 
 
 THE ELECTRIC BROODER 
 
 13 
 
 Galvanized Iron Hover 
 Heat Insulation 
 
 Perec fain Insulators 
 Qead 
 
 I 
 
 Power Leeds 
 
 Thermostat Snitch 
 
 Stiver Breaker 
 
 Points 
 
 Curtain 
 
 PLAN 
 Looking Up Prom Beneath Hover 
 
 THE ELECTRIC POULTRY BROODER 
 
 USING 
 
 A LOW GALVANIZED IRON HOVER ,SOME NEAT INSULATION, BLACK 
 
 OVERHEAD HEATING ELEMENTS, A THERMOSTAT SWITCH, CENTER 
 
 FLOOR AIR DUCT A NO CURTAIN. 
 
 VENTILATION: UNCONTROLLED AND SPASMODIC. 
 
 GENERAL DIRECTION OF AIR FLOW: IN THRU 
 
 AIR DUC T OUT UNDER CURTAIN. 
 
 Fig. 7. — Detail of line sketch 4, figure 3. 
 
16 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 Sketch 10 (fig. 4) shows a type which consists of a low flat box 
 about ten inches high (outside measurement), closed on three sides, 
 with a curtain in front. The heating elements are located in a 
 separate side chamber. The heating chamber connects with* the 
 brooder room or outside air from below and with the brooder air 
 from above, the convection currents being led up past the heating 
 elements, over a partition, down across the brooder, and out under 
 the curtain. The ventilation effect is quite positive because of the 
 thermal head developed. From the standpoint of positive brooder 
 ventilation, types 6, 8 and 10 have definite advantages. 
 
 Fig. 10. — An electric brooder using black overhead heating elements, 
 thermostat switch, floor air ducts, curtain, and heated brooder floor. 
 
 Fig. 11. — A simple, homemade, non-glowing or convection type of electric 
 brooder. The hover resting upon its legs with heating compartment, fresh air 
 duct, heating elements, and lid removed to show construction. The heating 
 elements are in series each operating at one-third the rated voltage. 
 
Bul. 441] 
 
 THE ELECTRIC; BROODER 
 
 17 
 
 Other modifications in the convection type of brooder exist, which 
 have not been described and for which no data were taken. As 
 illustrations, figures 11, 12 and 13 are included. 
 
 Fig. 12. — Back view of a homemade rectangular box type, convection, 
 electric brooder. The brooder is closed on three sides with a curtain in front. 
 The air enters the heating compartment through two air ducts (foreground, at 
 lower edge), moves upward past heating elements, over a partition, and out 
 under the curtain. 
 
 Fig. 13. — Bottom view of a homemade brooder floor sometimes used as an 
 auxiliary to insure dry hover conditions. 
 
18 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 SPECIFICATIONS OF NON-GLOWING (BLACK HEAT) ELECTRIC 
 
 BROODERS 
 
 While the following list of parts does not include every item of 
 which a brooder is made, it does include the essentials for the manu- 
 facture of an electric brooder of the "black heat," non-glowing, or 
 convection type: 
 
 1. A rather flat hover to cover the chicks and help retain the heat. 
 It can be made of galvanized iron, lumber, or other materials as 
 desired, care being taken to select a material which will not be injured 
 by the pecking of the chicks and which is easily cleaned and sprayed. 
 If galvanized iron is selected, the hover should be conical in shape 
 and should be about fifteen inches in height. It should have at least 
 three legs about six inches long to support it and a hook at the top to 
 suspend it when necessary. A % 6 -inch iron rod should be rolled into 
 the outer edge to form a bead and give rigidity. If of wood, it can 
 best be made square or rectangular in shape and should be about ten 
 inches high. About seven square inches of floor space per chick 
 should be allowed in designing a hover of any type. (See brooder 
 computations, page 31 for chick capacity determinations.) 
 
 2. Heat insulation of the hover can be in the form of a suitable 
 insulating material applied directly to the hover surfaces, or of a 
 hover jacket filled with air or other insulating material. If the hover 
 is constructed of metal, heat insulation is a very important item. 
 
 3. A curtain of cloth which will not ravel. 
 
 4. For electric insulators, porcelain cleats or knobs should be used 
 every six or eight inches for fastening heating elements to the hover 
 (never use uninsulated hooks or nails) ; porcelain tubes or flexible 
 asbestos tubing, wherever electric wires pass through wood or metal ; 
 and fiber board or similar material under the thermostat and other 
 switches. 
 
 5. A set of electric heating elements, preferably of the non-glowing 
 type. (See table 2, page 32 for resistance wire sizes and lengths. 
 Page 31 for sample brooder design.) 
 
 6. A thermostat switch in the electric circuit to turn heat on or off 
 automatically as required. A good type of ether wafer or bimetalic 
 thermostat is recommended. 
 
 7. A pilot light may or may not be included. Its only function is 
 to indicate if the power is on or off and if the thermostat switch is 
 working properly. 
 
BuL. 441] THE ELECTRIC BROODER 19 
 
 8. A good ventilation system to supply fresh air and to remove 
 water vapor and other impurities from the brooder. 
 
 9. Necessary rubber or asbestos-covered copper wire of correct size 
 for the load to be carried. (See page 33 for wire size calculations 
 and table 1 for wire characteristics.) 
 
 Non-glowing or convection brooders were found in the field in 
 various sizes. In the square or rectangular type they varied from 
 30 inches by 30 inches to 42 inches by 70 inches, and in the round 
 type from 40 inches to 72 inches in diameter. 
 
 OPERATION OF NON-GLOWING BROODERS 
 
 The action of this type of brooder in its most common form is as 
 follows : When the switch is closed the voltage of the electric system 
 forces a current of electricity through the heating circuit. The heating 
 elements in this circuit are made of a wire which offers considerable 
 resistance to the current flow and heat is generated. The amount of 
 heat generated varies directly as the product of the square of the 
 current and the first power of the resistance or in symbols H = K I 2 R 
 where H is the heat generated, I the current flowing in amperes, R the 
 resistance in ohms and K a constant, its value depending upon the 
 system of heat units employed. The air within the brooder becomes 
 heated by contact with the heating elements or by radiation from 
 them, causing the air to expand and move upward and usually out- 
 ward, while fresh and cooler air takes its place. As it moves away 
 from the heating elements the air cools, contracts in volume, and 
 gradually settles toward the floor. A part of this air in time passes 
 out under the curtains and a part returns to the heating elements to 
 repeat its journey. If the heat furnished is adequate and the air 
 paths through the brooder are not too completely restricted, the 
 resulting convection currents set up succeed in accomplishing brooder 
 ventilation. 
 
 The temperature within the brooder continues to rise until the 
 thermostat switch interrupts the circuit. When the air of the brooder 
 cools again to a certain temperature, the thermostat switch closes and 
 electric heating is resumed. 
 
 The use of curtains, insulation and thermostat switches all tend 
 to reduce heating costs. Curtains, however, interfere with ventilation 
 and when used some provision should be made to maintain adequate 
 air replacement. 
 
20 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 Every chick throws off water vapor from its lungs and in its feces, 
 the amount depending first, upon its size or age, second, upon the 
 kind of food, and third, upon the weather conditions, "While the 
 chicks are active about the brooder room and runway, the droppings 
 are scattered so that their moisture content can be absorbed and 
 removed by the room ventilation. However, at night when they enter 
 the hover, the chicks concentrate within a small and often poorly 
 ventilated space yet the amount of water given off by lung and feces 
 and which must be dissipated remains practically the same. Curtains 
 tend to prevent the dissipation of this moisture into the room or out- 
 side air and, as a result, the humidity of the brooder air may rise. 
 The temperature of the hover tends to increase also because of the 
 heat given off by the sleeping chick, and soon reaches a point at which 
 the thermostat switch opens and the electric heat is cut off. With the 
 heat cut off, ventilation is impaired, the air soon becomes saturated 
 and a condition usually called "sweating" follows. "Sweating" on 
 a chick's feathers or upon a window pane in a warm room is due 
 solely to the condensation of water from the saturated warm air upon 
 cooler surfaces. The condensation from the outside air upon the 
 cooler roof of a house might have been called "sweating" instead of 
 dew. The remedy for sweating then is adequate heat to cause the 
 moisture deposits to vaporize and frequent enough brooder air changes 
 to remove this vapor. Adequate ventilation or adequate heat alone 
 cannot economically accomplish the result. The two must work 
 together. 
 
 GLOWING OR "RADIANT"? TYPES OF BROODERS STUDIED 
 
 Some brooders make use of the heat radiated from glowing wires 
 to warm the space occupied by the chicks. They are usually conical in 
 shape with the elements located near the apex. Heat reflectors are 
 used to increase the effect of the heating elements, and some kind of 
 insulating material is used on the surface of the metal of the hover to 
 reduce heat loss to a minimum. (See sketches 11 and 12, fig. 4.) 
 
 . . 7 Qbjects begin to glow, that is emit light which the eye is able to detect, 
 at approximately 400° C (752° F). Up to the point at which they begin to 
 glow they retain their natural color, which is due entirely to reflected light. 
 The color first noted as metals begin to glow is a dull red, which gradually 
 brightens as the temperature increases through blood red, cherry, bright red, 
 salmon, orange, lemon, light yellow, and white. It should be remembered that 
 this color is due to no chemical change in the metal but to the effect of the 
 waves of the radiated light upon the eye. 
 
Bul. 441] 
 
 THE ELECTRIC BROODER 
 
 21 
 
 Fig. 14. — A conical galvanized iron "radiant" or glowing type of electric 
 brooder^ which uses glowing heating elements and a right vertical cone heat 
 reflector. Note the absence of a curtain. The heating elements are located 
 just below the heat reflector in the apex of the cone. By raising the hover 
 slightly and placing the roosts in this heated area as shown, the chicks can be 
 easily taught to go to roost. 
 
 Fig. 15. — A concave cone heat reflector sometimes used in "radiant" or 
 glowing type brooders. A concave reflector concentrates the heat rays toward 
 the center tending to create a "hot spot" on the floor. 
 
22 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 The glowing elements used as the heat source in these brooders 
 radiate heat outward in all directions. Since the chicks can be on the 
 under side only, the heat radiating upward would be of no benefit to 
 them if not reflected. The heat reflector, then, plays a very important 
 part in this type of brooder. Concave and cone reflectors concentrate 
 the rays toward the center, causing a ' ' hot spot " to be formed on the 
 brooder floor. By some, this is considered waste floor space, since the 
 heat is too intense for the chicks to remain in this area. It has the 
 virtue, however, of preventing center crowding and allows a warmer 
 portion of the brooder for those chicks requiring more heat. Also, 
 when a ' ' hot spot ' ' is used, a larger floor area may be available, since 
 the heat may extend out beyond the confines of the hover, sometimes to 
 a distance of eight or ten inches, and chicks have frequently been 
 observed resting comfortably in this area. 
 
 The intensity and size of 'this "hot spot" can be controlled by the 
 height of the reflector from the floor, by the radius of curvature of the 
 reflector by lowering the wire surface temperature, or by screening 
 the rays. Taking advantage of these principles, recent models have 
 adopted improved types of heat reflectors (see heat reflectors, page 
 10), and at least a part of the heat is being controlled by a thermostat 
 switch. Sketch 13 of figure 4 shows the usual radiant brooder 
 equipped with a flat reflector. Since the angle at which the heat rays 
 leave the reflector must equal the angle at which they strike, this 
 reflector diffuses the rays to some extent. The temperature at the 
 center of the hot spot is thus decreased slightly and its area increased, 
 due to this diffusion. 
 
 Sketch 14 (fig. 4) shows the usual radiant brooder equipped with 
 a convex heat reflector. A convex reflector of small radius diffuses 
 the rays very rapidly, while one of greater radius diffuses to a less 
 degree. The radius of curvature should not be less than 20 inches 
 when a hover having a ratio of height to diameter of 1 to 2 is used. 
 
 Sketch 15 (fig. 4) shows the usual radiant brooder equipped with 
 an inverted right cone reflector. With this reflector a good many of 
 the heat rays must suffer double reflection, and some will be converted 
 into heat before they reach the floor. If this type is used, the height 
 of the reflector or cone should be about one-fifth of the reflector 
 diameter. The resulting diffusion of the rays then approaches that 
 of the convex reflector of large radius as described under No. 14. 
 Since a cone is easily formed, this reflector will be very popular, but 
 care should be taken to construct it with proper dimensions. 
 
Bul. 441] 
 
 THE ELECTRIC BROODER 
 
 23 
 
 Fig. 16. — A conical, galvanized iron, il radiant" or glowing type of electric 
 brooder, which uses radiant heating elements and a convex copper heat reflector. 
 Note the heavy bead at the edge which gives the hover rigidity, short legs 
 (not over three inches), thermostat switch and observation door on the side. 
 The hover height should be about one-half the diameter. 
 
 Fig. 17. — A convex copper heat reflector such as that used in the radiant 
 electric brooder. Two heating elements are on the thermostat circuit and two 
 are controlled by a separate switch. This type of reflector diffuses the heat 
 rays, making the complete area under the hover habitable by the chick. 
 
24 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 Fig. 18. — A conical, galvanized iron, "convection" and "radiant" brooder, 
 using electric heat. The heating elements are cast in concrete and have taps 
 for 110 or 220-volt service. The concrete block is hollow at the center and 
 this hollow center compartment is connected to the room air by an air duct 
 at the bottom. The air in the center compartment becomes heated and rises, 
 while new and cooler air takes its place via the duct. The concrete when 
 heated radiates heat into the brooder. It therefore combines the characteristics 
 of both the convection and the radiant brooders. 
 
 Fig. 19. — A conical, galvanized iron, convection type of hover, which uses 
 combination top and center heat. 
 
 a. The hover resting upon its legs, with the center intake opening of the 
 air duct showing at the right. 
 
 h. The hover resting on its side showing the center heating compartment, 
 air duet, reflector^ top heating circuit, porclain knob insulators, and ether wafer 
 thermostat. Some heat is radiated from this center compartment into the 
 brooder and some is reflected downward from the reflector above. 
 
Bul. 441] 
 
 THE ELECTRIC BROODER 
 
 25 
 
 Power Leads from Trans 
 Mas ter Switch and Mam 
 
 Fuse B/ocx, 
 
 [Leads shou/d be largo 
 
 Jo carry mofimum lead 
 
 Heating) 
 
 Farm Power B> 
 (Use heavy Copper.) 
 
 Form fbk/e r Circuits 
 /f**, 1,2,3,4,. etc 
 
 Circuit At'21 /lojter Fuses. 
 (Fuse a/ about 12f % of Full Lead., 
 
 -Master Fuses, 
 (fuse at about lSb% of 
 Fut/ LoadXOpen Main 
 Switch before fusing or Horn- 
 ing on Farm Fouler Bus) 
 
 H//o - rvaft Hour Me ter 
 (Usually Power Company 
 Property) 
 
 Fig. 20. — Electric wiring diagram of a typical farm power layout showing an 
 electric brooder connected to one of the available power circuits. 
 
26 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 The reflector should be made of some metal which will not curl 
 or warp when subjected to the heat from the elements. Tin does very 
 well and when it tarnishes can be given a coat of high heat-resistant 
 aluminum paint. This paint costs very little and increases the 
 reflector efficiency to approximately 80 per cent. Copper, brass, zinc, 
 or other metals can be used but are more expensive. Galvanized iron 
 should not be used since the heat causes the zinc coating to peel off 
 after a short time. 
 
 Sketch 16 (fig. 4) shows a radiant brooder equipped with a com- 
 bination convex and concave reflector. The center portion diffuses 
 the heat rays and the concave rim prevents the formation of a radia- 
 tion heat pocket, where the reflector meets the hover sides. It should 
 be remembered in the construction of this reflector that for best results 
 the hover sides should meet the concave rim at a tangent and that no 
 seams, wrinkles or rough spots should exist on the reflecting surface. 
 A hover 2^2 feet by 5 feet would require a convex reflector about 20 
 inches in diameter located 26 inches above the floor. If the surface 
 has a curvature of approximately 26 inches the heat rays will be 
 reflected uniformly to the floor. 
 
 SPECIFICATIONS OF GLOWING OR RADIANT TYPE BROODERS 
 
 The main parts to the glowing type of brooder are : 
 
 1. A conical, galvanized iron hover to cover the chicks and help 
 retain the artificial heat. It should have a hook at the top to suspend 
 it, at least three legs (about three inches long) to support it, and a 
 % 6 -ineh rod rolled into the edge to form a bead and to give rigidity. 
 Short legs are specified so as to permit the lowering of the hover while 
 the chicks are young or when power fails. The ratio of hover height 
 to diameter should be about 1 to 2. 
 
 2. A heat reflector, preferably that shown under sketch No. 16 
 (fig. 4) with dimensions approximately as listed on page 22. 
 
 3. Adequate heat insulation of the hover. This may be applied 
 directly to the hover surfaces, or may consist of a hover jacket filled 
 with air or other insulating material. 
 
 4. Electric insulators for wiring and fixtures. Porcelain tubes or 
 bushings should be used wherever the wires pass through the hover 
 metal ; porcelain base, screw sockets, or insulated clips, where the 
 elements are attached to the reflector and fiber board or similar 
 material under the thermostat switch and other switches. 
 
BUL. 441] THE ELECTRIC BROODER 27 
 
 5. Electric service connections. Screw sockets or spring connector 
 clips should be used that will carry at least twenty amperes without 
 heating. 
 
 6. Glowing type of electric heating elements. Two or more units 
 should be used with a total wattage equal to the brooder demand. 
 (For brooder calculations see page 31 and for resistance wire size 
 and length, see table 2.) 
 
 7. A thermostat sivitch, preferably of the expanding ether wafer 
 or bimetalic type for temperature control, to be connected into one 
 of the heating circuits. (Not all the circuits.) See figure 20. 
 
 8. Separate wall switches for each heater circuit. (Three heating 
 elements will require three wall switches in addition to the thermostat 
 switch, for ease in control.) 
 
 9. Necessary rubber covered copper wire to bring the power from 
 the supply mains to the hover. It should be of correct size for the 
 load to be carried. (For wire size calculations, see pages 33 and 35, 
 and for wire characteristics, see table 1.) 
 
 10. Necessary asbestos covered copper wire to connect the heating 
 elements under the hover to the rubber covered leads above the hover. 
 Asbestos covered leads should be used wherever the wires are subjected 
 to the hover heat. 
 
 "Radiant" brooders were found in various sizes, from 42 to 72 
 inches in diameter. There is no reason why smaller units could not be 
 used but heating costs per-chick-season increase as the number of 
 chicks per brooder decreases. Again, as in the convection brooder, the 
 five-foot size was the one found to be most commonly used. 
 
 OPERATION OF GLOWING TYPE BROODERS 
 
 As in the non-glowing brooder, the heat in the glowing type is 
 developed by an electric current flowing through heating elements, 
 the length, size, and material of which are such as to cause them to 
 glow. The main heat transfer is by radiation but a slight convection 
 effect results where the air comes in direct contact with the heating 
 elements. 
 
 That portion of the heat which is generated on the under side of 
 the heating element is radiated directly to the floor, but all heat 
 appearing on the upper side must be reflected. This amounts to 
 approximately one-half of the total heat. It does not become useful 
 until the rays are absorbed by the chicks, the floor, or the hover walls. 
 
28 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 
 
 
 
 
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Bul. 441] THE ELECTRIC BROODER 29 
 
 When the temperature beneath the hover rises to a certain point, 
 the thermostat opens one circuit of the heating- system. Should the 
 temperature continue to rise, a wall switch on one of the other heating 
 circuits may be opened or the heat allowed to find its own balance, 
 while the chicks, if necessary, move further out. The radiant heat 
 applied directly to the floor causes any moisture deposits to evaporate 
 into the air and pass from the hover into the room air, there being 
 no curtain to restrict the flow. This automatic removal of moisture 
 by the radiant, curtainless brooder is an important advantage when 
 used by inexperienced poultrymen. Tests indicate that with proper 
 heat control sufficient heat can be obtained to effect proper ventilation 
 and drying without excessive additional cost. No harmful effects 
 upon the chicks from the light of the glowing elements have been 
 reported or observed. 
 
 COMBINATION CONVECTION AND RADIANT BROODERS 
 
 Combinations of the various types of brooders previously described 
 have resulted in units employing both types of heat transfer. This 
 seems to be a logical development, since such a brooder may be able 
 to incorporate most of the advantages of both types and still remove 
 some of their disadvantages. By using both glowing and non-glowing 
 elements as an illustration, the radiant element could be smaller than 
 is now possible, while the thermostat could be installed in the non- 
 glowing circuit thus furnishing a heat "safety factor" and removing 
 the objection that radiant elements burn out when subjected to 
 thermostatic action. 
 
 ELECTRIC BROODER WIRING PRACTICE 
 
 The following suggestions will be found helpful in the construction 
 of an electric brooder and its connection to the power leads : 
 
 1. The wire should be of the correct size and should be properly 
 insulated for the load to be carried and the temperatures encountered. 
 (For wire sizes and current carrying capacities, see table 1.) 
 
 2. The heating elements should develop the proper amount of heat 
 and should be made of high grade resistance wire. (For resistance 
 wire, sizes and lengths necessary to develop specified power, see 
 table 4.) 
 
 3. The brooder power circuit should be properly protected by 
 fuses. (Fuses should not be used with a rating greater than 125 
 per cent of full load.) 
 
30 
 
 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 
 
 
 4. The thermostat switch should be of sturdy construction and 
 positive in operation. The breaker points should be of silver and not 
 less than three-sixteenths of an inch in diameter to avoid burning. 
 A condenser across tlie breaker points reduces the intensity of the arc. 
 
 5. The service connections (sockets or spring clips) should be 
 heavy enough to carry the current at the temperature encountered. 
 This is very important on account of the high air temperatures in 
 which they may operate. 
 
 6. All poor contacts, such as loose screws, poorly spliced wires, and 
 badly formed eyes, must be avoided. 
 
 7. Porcelain or other good insulators should be used at frequent 
 intervals beneath the hover and where the leads pass through the 
 hover material. (Uninsulated hooks or nails should never be used to 
 suspend the elements from the hover.) 
 
 8. Only high grade electrical materials should be used. 
 
 TABLE 1 
 
 Table Giving Resistance, Weight, Current Carrying Capacity, and Voltage 
 Drop for Rubber Covered and Weatherproof Copper Wire 
 
 
 Resist- 
 
 Rubber covered copper wire 
 
 Weatherproof copper wire 
 
 
 
 
 
 
 
 
 
 
 Wire 
 
 ance per 
 
 
 
 
 Voltage 
 
 
 
 
 Voltage 
 
 size 
 
 1000 ft. 
 
 Weight 
 
 
 Maximum 
 
 drop in 
 
 Weight 
 
 
 Maximum 
 
 drop in 
 
 B&S 
 
 at68°F., 
 
 per 
 
 Feet 
 
 safe 
 
 leads per 
 
 per 
 
 Feet 
 
 safe 
 
 leads per 
 
 gage* 
 
 or 20° C 
 
 1000 ft. 
 
 of wire 
 
 current 
 
 100-foot 
 
 1000 ft. 
 
 of wire 
 
 current 
 
 100-foot 
 
 
 
 including 
 
 per 
 
 carrying 
 
 lengths 
 
 including 
 
 per 
 
 carrying 
 
 lengths 
 
 
 
 wire and 
 
 pound 
 
 capacity 
 
 for 
 
 wire and 
 
 pound 
 
 capacity 
 
 for 
 
 
 
 insulation 
 
 
 in 
 amperes* 
 
 maximum 
 currentf 
 
 insulation 
 
 
 in 
 amperes* 
 
 maximum 
 currentf 
 
 18 
 
 6.385 
 
 14 
 
 71.4 
 
 3 
 
 1.92 
 
 16 
 
 62.4 
 
 5 
 
 3.19 
 
 16 
 
 4.015 
 
 18 
 
 55.5 
 
 6 
 
 2.41 
 
 20 
 
 50.0 
 
 10 
 
 4.01 
 
 14 
 
 2.525 
 
 30 
 
 33 3 
 
 15 
 
 3.79 
 
 25 
 
 40.0 
 
 20 
 
 5.05 
 
 12 
 
 1.588 
 
 41 
 
 24.4 
 
 20 
 
 3.18 
 
 35 
 
 28.6 
 
 25 
 
 3.97 
 
 10 
 
 ..9989 
 
 55 
 
 18.2 
 
 25 
 
 2.50 
 
 53 
 
 18.9 
 
 30 
 
 3.00 
 
 8 
 
 ..6282 
 
 76 
 
 13.1 
 
 35 
 
 2.20 
 
 75 
 
 13.3 
 
 50 
 
 3.14 
 
 6 
 
 .3951 
 
 134 
 
 7.5 
 
 50 
 
 1.98 
 
 112 
 
 8.9 
 
 70 
 
 2.77 
 
 5 
 
 .3133 
 
 190 
 
 5.3 
 
 55 
 
 1.72 
 
 135 
 
 7.4 
 
 80 
 
 2.51 
 
 4 
 
 .2485 
 
 220 
 
 4 5 
 
 70 
 
 1.74 
 
 164 
 
 6.1 
 
 90 
 
 2.24 
 
 3 
 
 .1970 
 
 270 
 
 3.7 
 
 80 
 
 1.57 
 
 199 
 
 5.0 
 
 100 
 
 1.97 
 
 2 
 
 .1563 
 
 320 
 
 3.1 
 
 90 
 
 1 41 
 
 260 
 
 3.8 
 
 125 
 
 1.95 
 
 1 
 
 .1239 
 
 365 
 
 2.7 
 
 100 
 
 1.24 
 
 316 
 
 3.2 
 
 150 
 
 1.86 
 
 
 
 .0983 
 
 495 
 
 2.0 
 
 125 
 
 1.23 
 
 407 
 
 2.5 
 
 200 
 
 1.97 
 
 00 
 
 .0779 
 
 600 
 
 1.7 
 
 150 
 
 1.17 
 
 502 
 
 2.0 
 
 225 
 
 1.75 
 
 000 
 
 .0618 
 
 760 
 
 1.3 
 
 175 
 
 1.08 
 
 629 
 
 1.6 
 
 275 
 
 1.70 
 
 0000 
 
 .0490 
 
 925 
 
 1.1 
 
 225 
 
 1.10 
 
 767 
 
 1.3 
 
 325 
 
 1.59 
 
 *From 1925 Electrical Safety Orders, Industrial Accident Commission, State of California, 
 pages 26-27. 
 
 fThe wire length required is twice the distance in feet. Thus, 15 amperes carried 50 feet to a 
 load will require 100 feet of No. 14 wire and will cause a voltage drop of 3.79 volts. 
 
BUL. 441] THE ELECTRIC BROODER 31 
 
 COMPUTATIONS ON THE SELECTION AND DESIGN OF AN 
 ELECTRIC BROODER 
 
 In order to illustrate the method of computing hover size and 
 wiring specifications let it be required to design a "radiant" or glow- 
 ing type electric brooder of 500-chick 8 capacity, to operate on a 110- 
 volt electric circuit. Allowing 7 sq. in. of floor space per chick, then — 
 
 Free area under hover = 500 X 7 = 3500 sq. in. or 24.3 sq. ft. 
 
 If the hover is to be circular its diameter can be found from the 
 
 formula D = J 4 Area • The diameter then = J 4 X 24 - 3 =5.56 
 > 3.1416 M 3.1416 
 
 feet. But if the hover is to be square the length of one side can be 
 
 found from the formula-length of side = VA= V 24lT=4.93 feet. 
 
 The size of the heating elements should next be determined 
 and assuming 2.5 watts per chick, the total wattage of the heating 
 elements = 500 X 2.5 = 1250 watts. 9 
 
 Let it be assumed now that three separate circuits are to be used. 
 The power for each circuit would be 1250 -=- 3 = 416 watts, and 
 by applying the formula for single phase non-inductive electric cir- 
 cuits, Watts = Volts X Amperes, the current through each heating 
 
 416 
 element is found to be Current = -— - = 3.78 amperes. 
 
 Now by referring to table 2 it will be found that No. 27 nickel 
 chrome wire will have a surface temperature of approximately 1472° F 
 when carrying 3.44 amperes and by referring to figure 21 it will be 
 seen that No. 28 wire, slightly smaller than No. 27, begins to glow at 
 about 1150 degrees F. 
 
 s The Poultry Husbandry Division of the University of California recom- 
 mends that not more than 300 chicks be placed in any brooder at one time. 
 This design is carried through for a brooder of 500-chick capacity because it 
 illustrates design features better and because the average brood found in the 
 field during these tests was slightly above this figure. 
 
 9 One thousand watts of electrical power applied for one hour will produce 
 a heating effect equal to approximately 3412 British thermal units (B.t.u.) or 
 800.5 kilogram-calories (kg-cal.). Therefore, 1 watt-hour will produce 3.412 
 B.t.u. or .8005 kilogram-calories. A 600-watt element operating for one hour 
 will then produce GOO X 3.412 B.t.u. = 2047.2 B.t.u., or 600 X .8605 kg-cal. = 
 516.3 kilogram-calories. 1 B.t.u. is equivalent to .252 kilogram-calories and 
 1 kilogram-calorie is equivalent to 3.965 B.t.u. The kilogram-calorie is gen- 
 erally defined as the amount of heat required to raise one kilogram of water 
 from 14.5° C to 15.5° C. The British thermal unit is that quantity of heat 
 used in raising the temperature of one pound of water from 62° F to 63° F. 
 
32 
 
 UNIVERSITY OP CALIFORNIA EXPERIMENT STATION 
 
 After selecting the wire to be used it is next necessary to determine 
 
 the length. This can be found by knowing that the Length required = 
 
 Total Resistance m ., _ . L . . J „ , T 
 
 =r — 7— = — . Table 2 gives the resistance of No. 27 wire as 
 
 Resistance per foot 
 
 3.274 ohms per foot at 68° F or 3.274 X 1.1122 (resistance factor, 
 
 see table 3) =3.6413 ohms per foot at 1472° F. 
 
 It is also known that Volts = Amperes X Resistance and in this 
 
 case the voltage = 110 and amperage = 3.79. Therefore 
 
 110 ■ , , ., ,. ., . „.. 29 
 
 Resistance 
 
 29 ohms and the Length of Wire = 
 
 7.97 
 feet. 
 
 3.79 —*». -, 3 6413 
 
 The safe carrying capacities of various size wires are given in 
 table 1 and the computations for the service wires are similar to those 
 for the heating elements. 
 
 TABLE 2 
 
 Eesistance, Current, and Temperature Characteristics of "Nichrome" 
 
 Eesistance Wire, with Specific Eesistance of 600 OHMS.t 
 
 Per Circular, Mil Foot at 68° F(20° C) 
 
 Wire 
 size 
 
 Diame- 
 ter of 
 wire in 
 inches 
 
 Resist- 
 ance in 
 
 ohms 
 per foot 
 at 68° F. 
 
 20° C. 
 
 Current in amperes necessary to produce the temperatures listed below 
 for straight wire in air, in a horizontal position 
 
 B.&S. 
 gage 
 
 212° F. 
 100° C. 
 
 392° F. 
 200° C. 
 
 572° F. 
 300° C. 
 
 752° F. 
 400° C. 
 
 932° F. 
 500° C. 
 
 1112° F. 
 600° C. 
 
 1292° F. 
 700° C. 
 
 1472° F. 
 800° C. 
 
 1652° F. 
 900° C. 
 
 No. 10 
 
 .102 
 
 .063 
 
 12.3 
 
 22.4 
 
 30.6 
 
 38.0 
 
 44.8 
 
 51.2 
 
 57.0 
 
 63.1 
 
 68.8 
 
 No. 12 
 
 .081 
 
 .100 
 
 8.80 
 
 16.1 
 
 22.0 
 
 27.3 
 
 32.1 
 
 36.8 
 
 40.8 
 
 45.3 
 
 49.4 
 
 No. 14 
 
 .064 
 
 .161 
 
 6 31 
 
 11.5 
 
 15.8 
 
 19.6 
 
 23.0 
 
 26.2 
 
 29.3 
 
 32.4 
 
 35.5 
 
 No. 16 
 
 .051 
 
 .254 
 
 4 54 
 
 8.28 
 
 11.35 
 
 14.1 
 
 16.5 
 
 18.9 
 
 21.0 
 
 23.4 
 
 25.6 
 
 No. 18 
 
 .040 
 
 .412 
 
 3.26 
 
 5.95 
 
 8.13 
 
 10.1 
 
 11.8 
 
 13.6 
 
 15.1 
 
 16.8 
 
 18.4 
 
 No. 20 
 
 .032 
 
 .645 
 
 2.32 
 
 4.27 
 
 5.83 
 
 7.30 
 
 8.53 
 
 9.70 
 
 10.85 
 
 12.0 
 
 13.2 
 
 No. 21 
 
 .0285 
 
 .813 
 
 1.97 
 
 3.62 
 
 4.94 
 
 6.17 
 
 7.23 
 
 8.21 
 
 9.20 
 
 10.2 
 
 11 2 
 
 No. 22 
 
 .0254 
 
 1.031 
 
 1.67 
 
 3.07 
 
 4.18 
 
 5.23 
 
 6.13 
 
 6.96 
 
 7.80 
 
 8.65 
 
 9.46 
 
 No. 23 
 
 .0226 
 
 1.292 
 
 1.42 
 
 2.60 
 
 3.54 
 
 4.43 
 
 5.19 
 
 5.90 
 
 6.61 
 
 7.33 
 
 8.02 
 
 No. 24 
 
 .0201 
 
 1.634 
 
 1.20 
 
 2.20 
 
 3.00 
 
 3.75 
 
 4.40 
 
 5.00 
 
 5.60 
 
 6.20 
 
 6.80 
 
 No. 25 
 
 .0179 
 
 2.060 
 
 1.02 
 
 1.86 
 
 2.54 
 
 3.18 
 
 3.73 
 
 4.25 
 
 4.67 
 
 5.27 
 
 5.76 
 
 No. 26 
 
 .0159 
 
 2.611 
 
 .865 
 
 1.58 
 
 2.15 
 
 2.70 
 
 3.16 
 
 3.61 
 
 3.96 
 
 4.47 
 
 4.88 
 
 No. 27 
 
 .0142 
 
 3.274 
 
 .734 
 
 1.34 
 
 1.82 
 
 2.28 
 
 2.68 
 
 3.06 
 
 3.36 
 
 3.80 
 
 4.13 
 
 No. 28 
 
 .0126 
 
 4.159 
 
 .622 
 
 1.13 
 
 1.54 
 
 1.85 
 
 2.27 
 
 2.62 
 
 2.86 
 
 3.23 
 
 3.50 
 
 No. 29 
 
 .0113 
 
 5.168 
 
 .527 
 
 .960 
 
 1.305 
 
 1.57 
 
 1.93 
 
 2.22 
 
 2.45 
 
 2.71 
 
 2.97 
 
 No. 30 
 
 .0100 
 
 6.600 
 
 .447 
 
 .814 
 
 1.105 
 
 1.33 
 
 1.64 
 
 1.89 
 
 2.08 
 
 2.30 
 
 2.52 
 
 No. 31 
 
 .0089 
 
 8.333 
 
 .378 
 
 .680 
 
 .935 
 
 1.13 
 
 1.39 
 
 1.60 
 
 1.77 
 
 1.95 
 
 2.14 
 
 No. 32 
 
 .0080 
 
 10.313 
 
 .321 
 
 .577 
 
 .791 
 
 .955 
 
 1.18 
 
 1.36 
 
 1.50 
 
 1.66 
 
 1.81 
 
 No. 33 
 
 .0071 
 
 13.098 
 
 .272 
 
 .490 
 
 .670 
 
 .809 
 
 1.00 
 
 1.15 
 
 1.28 
 
 1.41 
 
 1.53 
 
 No. 34 
 
 .0063 
 
 16.623 
 
 .231 
 
 .416 
 
 .567 
 
 .685 
 
 .849 
 
 .980 
 
 1.06 
 
 1.18 
 
 1.29 
 
 No. 35 
 
 .0056 
 
 21.019 
 
 .196 
 
 .353 
 
 .480 
 
 .580 
 
 .720 
 
 .830 
 
 .90 
 
 1.00 
 
 1.09 
 
 No. 36 
 
 .0050 
 
 26.400 
 
 .166 
 
 .300 
 
 .406 
 
 .491 
 
 .611 
 
 .704 
 
 .765 
 
 .850 
 
 .924 
 
 No. 37 
 
 .0045 
 
 32.672 
 
 .141 
 
 .254 
 
 .344 
 
 .416 
 
 .518 
 
 .597 
 
 .650 
 
 .721 
 
 .783 
 
 No. 38 
 
 .0040 
 
 41.240 
 
 .120 
 
 .216 
 
 .291 
 
 .352 
 
 .440 
 
 .507 
 
 .552 
 
 .613 
 
 .663 
 
 No. 39 
 
 .0035 
 
 54.098 
 
 .101 
 
 .183 
 
 .246 
 
 .298 
 
 .373 
 
 .430 
 
 .467 
 
 .517 
 
 .566 
 
 No. 40 
 
 .0031 
 
 73.333 
 
 .085 
 
 .155 
 
 .208 
 
 .252 
 
 .316 
 
 .364 
 
 .396 
 
 .439 
 
 .480 
 
 lengths. 
 
 Adapted from tables by Driver-Harris Company, Detroit, Michigan, 
 tlf a wire of different specific resistance is used, see illustrative problem, page 33, for correct 
 
Bul. 441 
 
 THE ELECTRIC BROODER 
 
 33 
 
 TABLE 3 
 
 "Color-Temperature" Chart tor Metals and "Temperature Correction 
 Factor" for "Nichrome" Resistance Wire at Temperatures Above 
 68° F. An Approximate " Color-Temperature" Chart for all Metals. 
 
 Part "A" 
 
 Color of metal 
 
 Black or 
 natural 
 
 Faint 
 red 
 
 Blood 
 red 
 
 Cherry 
 red 
 
 Bright 
 red 
 
 Salmon 
 red 
 
 Orange 
 
 Lemon 
 
 Light 
 yellow 
 
 White 
 
 Approximate 
 temperature 
 
 Zero to 
 800° F 
 
 800° F 
 
 to 
 1050° F 
 
 1050° F 
 to 
 
 1150° F 
 
 1150° F 
 
 to 
 1300° F 
 
 1300° F 
 
 to 
 1600° F 
 
 1600° F 
 
 to 
 1700° F 
 
 1700° F 
 
 to 
 1800° F 
 
 1800° F 
 
 to 
 1950° F 
 
 1950° F 
 
 to 
 2050° F 
 
 2050° F 
 and up 
 
 "Temperature Correction Factor "t for the Resistance Wire. Used in 
 these Tables, Specific Resistance 660 Ohms per Circular Mil Foot at 
 68° F, 20° C. For Straight Wire in a Horizontal Position in Air. 
 
 Part "B" 
 
 Wire surface 
 
 [68°F 
 
 212° F 
 
 392° F 
 
 572° F 
 
 752° F 
 
 932° F 
 
 1112° F 
 
 1292° F 
 
 1472° F 
 
 1652° F 
 
 1832° F 
 
 temperature 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 [20°C 
 
 100° C 
 
 200° C 
 
 300° C 
 
 400° C 
 
 500° C 
 
 600° C 
 
 700° C 
 
 800° C 
 
 900° C 
 
 1000° C 
 
 Resistance cor- 
 
 
 
 
 
 
 
 
 
 
 
 
 rection factor. .. 
 
 1.0000 
 
 1.0185 
 
 1.0417 
 
 1.0645 
 
 1.0828 
 
 1.0928 
 
 1.0960 
 
 1 . 1022 
 
 1.1122 
 
 1.1257 
 
 1 . 1423 
 
 Adapted from tables published by the Driver-Harris Company, Detroit, Michigan. 
 •(•Illustration on use of "Part B" of Table 3: 
 
 Resistance per foot of No. 25 resistance wire at 68° F., 20° C. is 2.060 ohms. (Table 2.) 
 What is the resistance per foot of this wire at 1472° F., 800° C? 
 Under 1472° F., (800° C.) above, find 1.1122 (Correction factor). 
 
 Therefore, resistance per foot of No. 25 resistance wire at 1472° F. (800° C.) is 2.060X1.1122 = 
 2.2911 ohms. 
 
 Total watts to be delivered by the service wires to each brooder = 
 1250 watts. 
 
 Current flowing to each brooder = 
 
 1250 
 
 11.36 amperes and from 
 
 110 
 
 table 1 it is seen that No. 16 rubber covered wire will carry 6 amperes 
 safely and No. 14 will carry 15 amperes. It is better to be amply safe 
 so No. 14 should be chosen. 
 
 If a wire of different specific resistance than that of table 2 is 
 used, its length can be obtained by multiplying the above length 
 (7.97) by 660 and dividing by the new specific resistance; or, as an 
 illustration, if the specific resistance per circular mil foot is 750 
 instead of 660 ohms, the correct length is obtained by multiplying the 
 
 old length, 7.97, by ^^-=7.02 feet. (This is not an exact solution 
 
 but for practical computations will be found entirely satisfactory.) 
 
34 
 
 UNIVERSITY OP CALIFORNIA EXPERIMENT STATION 
 
 By similar computations, the length of wire necessary to produce 
 this amount of heat in non-glowing heating elements can be deter- 
 mined. (For non-glowing computations the temperature assumed 
 should be approximately 572° F and should not exceed 800° F.) 
 Table 4 lists results of computations on both non-glowing and glowing 
 heat designs and may be used in the design of brooder heating 
 elements without going through the above computations. 
 
 TABLE 4 
 
 Eesistance Wire Sizes and Lengths to Produce ' ' Black Heat ' ' and Glowing 
 Surface Temperatures When Consuming Known Wattages at 110 Volts. 
 For "Nichrome" Eesistance Wire of 660 OHMS Specific Eesistance, 
 Part "A" — Wire Surface Temperature: About 572° F, Non-Glowing 
 
 Required wattage .... 
 
 100 
 
 200 
 
 250 
 
 300 
 
 350 
 
 400 
 
 450 
 
 500 
 
 550 
 
 600 
 
 650 
 
 Amperes at 110 volts 
 
 .909 
 
 1.818 
 
 2.27 
 
 2.727 
 
 3.180 
 
 3.636 
 
 4.09 
 
 4.545 
 
 5.00 
 
 5.454 
 
 5.91 
 
 Resistance in ohms.. 
 
 121.01 
 
 60.51 
 
 48.40 
 
 40.33 
 
 34.60 
 
 30.25 
 
 26.85 
 
 24.19 
 
 22.00 
 
 20.17 
 
 18.62 
 
 Size of wire, B & S 
 
 
 
 
 
 
 
 
 
 
 
 
 gage from Current- 
 
 
 
 
 
 
 
 
 
 
 
 
 temperature chart 
 
 31 
 
 27 
 
 25 
 
 24 
 
 23 
 
 22 
 
 22 
 
 21 
 
 21 
 
 20 
 
 20 
 
 Resistance of wire at 
 
 
 
 
 
 
 
 
 
 
 
 
 68° F, ohms 
 
 8.333 
 
 3.274 
 
 2.060 
 
 1.634 
 
 1.292 
 
 1.031 
 
 1.031 
 
 .813 
 
 .813 
 
 .645 
 
 .645 
 
 Resistance of wire at 
 
 
 
 
 
 
 
 
 
 
 
 
 572° F ohms 
 
 8.870 
 
 3.485 
 
 2.195 
 
 1.739 
 
 1.375 
 
 1.099 
 
 1.099 
 
 .865 
 
 .865 
 
 .687 
 
 .687 
 
 Element length in 
 
 
 feet, at 572° F 
 
 13.64 
 
 17.36 
 
 22.10 
 
 23.19 
 
 25.14 
 
 27.55 
 
 24.50 
 
 27.96 
 
 25.45 
 
 29.35 
 
 27.10 
 
 Part "B" — Wire Surface Temperature about 1472° F ; "Radiant Eeat," 
 
 Glowing 
 
 Required wattage.. 
 
 100 
 
 200 
 
 250 
 
 300 
 
 350 
 
 400 
 
 '450 
 
 500 
 
 550 
 
 600 
 
 650 
 
 Size of wire, B & S 
 
 
 
 
 
 
 
 
 
 
 
 
 gage, Current-tem- 
 
 
 
 
 
 
 
 
 
 
 
 
 perature chart 
 
 35 
 
 31 
 
 30 
 
 29 
 
 28 
 
 27 
 
 26 
 
 26 
 
 25 
 
 25 
 
 24 
 
 Resistance of wire 
 
 
 
 
 
 
 
 
 
 
 
 
 at 68° F, ohms 
 
 21.019 
 
 8.333 
 
 6.600 
 
 5.168 
 
 4.159 
 
 3.274 
 
 2.611 
 
 2.611 
 
 2.060 
 
 2.060 
 
 1.634 
 
 Resistance of wire 
 
 
 
 
 
 
 
 
 
 
 
 
 at 1472° F, ohms .... 
 
 23.373 
 
 9.263 
 
 7.34 
 
 5.747 
 
 4.62 
 
 3.641 
 
 2.903 
 
 2.903 
 
 2.291 
 
 2.291 
 
 1.819 
 
 Element length in 
 
 
 
 
 
 
 
 
 
 
 
 
 feet . . 
 
 5.17 
 
 6.54 
 
 6.59 
 
 7.02 
 
 7.49 
 
 8.31 
 
 9.25 
 
 8.34 
 
 9.59 
 
 8.80 
 
 10.24 
 
 
 
 Note. — Non-glowing wire smaller than No 25 gage is too fine for successful operation in brooders. 
 "Radiant heat" wire, smaller than No. 29, is also impractical for brooder use. Therefore, wattages 
 under 250 are impractical, unless long wire is used or the wire is of extremely high resistance. 
 
 VOLTAGE DROP 
 
 When an electric current flows through a conductor, a drop in 
 voltage occurs along the wire in the direction of flow. This drop in 
 voltage is analogous to the drop in pressure which occurs along a pipe 
 carrying water from a tank or pump. Should this stream of water 
 
BUL. 441] THE ELECTRIC BROODER 35 
 
 be shut off, the pressure in the pipe immediately rises to a value equal 
 to the static head of the system. In a similar manner, when an 
 electric current is interrupted the pressure or voltage across the live 
 terminals of the switch immediately rises to a value equal to the 
 voltage of the system. 
 
 This drop in voltage when a current flows should be kept as low as 
 is economically possible, since it indicates that heat is being developed 
 in the conductor and dissipated into the atmosphere where it can do 
 no good. Usually a voltage drop in excess of 5 per cent will prove 
 uneconomical. 
 
 To illustrate the extent of this loss when long leads are used, it 
 was found during one test that 81.8 amperes were being carried from 
 the meter to the poultry house, a distance of 400 feet, by No. 2 
 weather proof copper wire. The total length of wire necessary then 
 to carry the current to the brooders and back again will be 2 times 
 400 feet or 800 feet. The resistance of No. 2 copper wire at 68° F is 
 (from table 1) .1563 ohms per 1000 feet. The resistance of 800 feet 
 is .8 times .1563 or .1250 ohms. The power lost as heat in the con- 
 ductor was the current in amperes squared times the resistance, or 
 81.8 X 81.8 X .1250 or 836.4 watts. If this current flows 24 hours a 
 day for the three months of the brooding season, the loss will be 836.4 
 (watts per hour) times 24 (hours per day) times 90 (days) or 1,806.6 
 kilowatt-hours. At 2 cents per kilowatt-hour this represents a loss of 
 2 X 1806.6, or $36.13. The drop in voltage from meter to load was 
 836.4 watts divided by 81.8 amperes or 10.2 volts. 
 
 Assume now a voltage drop not greater than 5 per cent in the 
 power leads from this meter to the load, which on the 110-volt circuit 
 will give 110 (volts) times 5 (per cent) or 5.5 volts drop. The power 
 now converted into heat in these leads will be 5.5 (volts) times 81.8 
 (amperes) or 449.9 watts. During the three months of the brooding 
 season, this will amount to 971.8 kilowatt-hours or, at 2 cents per 
 kw-hr., $19.44. The conductor required for a 5 per cent drop in 
 800 feet when 81.8 amperes are flowing will have a resistance of 
 
 449.9 (watts) 
 
 81.8 X 81.8 
 
 (amperes) or .0672 ohms. A thousand feet of this con- 
 
 ductor will have a resistance of - — ^ or .0840 ohms. From table 1 
 
 .0 
 
 the wire having a resistance nearest to this figure is No. 00, which has 
 a resistance of .0779 ohms per 1000 feet. Therefore, if a voltage drop 
 not to exceed 5 per cent is to be allowed, the conductor used should 
 be No. 00 weatherproof copper wire. 
 
36 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
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BUL. 441] THE ELECTRIC BROODER 37 
 
 It should be remembered that this loss in power due to a voltage 
 drop occurs only when a current is flowing through the wire. There 
 is practically no loss when the line is not being used. 
 
 The larger wire will cost considerably more to install, since the 
 same length (800 feet) weighs almost twice as much. Will it be 
 economically sound to make this additional investment in the power 
 leads ? 
 
 The weight of No. 2 weatherproof copper wire required for the 
 800 feet, according to table 1 is 260 X -8 or 208 pounds, while the 
 weight of No. 00 is 502 X .8 or 401.6 pounds. The extra copper then 
 which must be purchased if No. 00 is used is 401.6 minus 208 or 
 193.6 pounds. The cost per pound of this wire will average 25 cents. 
 The additional investment in the line, due to heavier wire, will be 
 193.6 (pounds) times 25 (cents per pounds) or $48.40. 
 
 Applying the reasoning set forth under Economics of New Devices, 
 page 6, the following figures result : If correctly 
 
 As installed installed 
 
 Additional copper costs 193.6 lbs. at 25 cents per pound $48.40 
 
 Additional interest at 6 per cent of one-half value $1.45 
 
 Yearly additional depreciation (10-year life) $4.84 
 
 Repairs, taxes, insurance and overhead, same for both 
 
 Loss due to line resistance $36.13 $19.44 
 
 $36.13 $25.73 
 
 Savings affected by use of larger copper $10.40 
 
 If the transformer bank had been centrally located with respect to 
 the load, as is often possible, a considerable saving in the cost of the 
 wire would have resulted. For best results, the meter should not be 
 more than 200 feet from where the power is being absorbed. 
 
 SAFETY PRECAUTIONS 
 
 In working with any electrical circuit, it is well to remember the 
 following : 
 
 1. Never attempt to work with a "hot" or live circuit. Open the 
 circuit switch or remove the circuit fuses first. While 110 volts will 
 seldom injure one, there are conditions under which it may be 
 injurious. 
 
 2. Consider all electric wires "hot" unless you have opened the 
 circuit yourself or know it to be open. 
 
 3. If a shock is received from the ordinary electrical appliances, 
 determine the cause at once. It generally indicates poor electrical 
 insulation. 
 
38 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 4. Never work with a power circuit when standing on wet ground 
 or wet floors, or when in water. 
 
 5. Never allow the body to become a part of a circuit. The body 
 can form a circuit either to "ground" or to the opposite power "leg." 
 
 6. Always remember that both legs of an alternating current 
 circuit as usually operated are "live." 
 
 7. Fuse the circuits on both legs and fuse for about 125 per cent 
 of full load. These fuses will protect your electrical apparatus and 
 the circuit. 
 
 SUMMARY AND CONCLUSIONS 
 
 The electric brooder is heated with electric heating elements and 
 makes use of radiation, convection or conduction for transfering heat 
 from the elements to the space occupied by the chick. 
 
 When radiation is depended upon as the method of heat transfer 
 and the elements are operated at glowing temperature, the hover is 
 generally three to four feet high, no curtains are used and little or 
 no trouble will be experienced from "sweating." The heating cost 
 at 2 cents per kilowatt-hour will average about 2.5 to 3 cents per 
 chick each 1000 hours. 
 
 For mild climates 2 watts should be allowed per chick and where 
 freezing temperatures are experienced 2.5 to 3 watts should be 
 available. 
 
 Because of the high temperature of the elements there is a slightly 
 greater fire hazard than is found in the ' ' black heat ' ' type. 
 
 In brooders using radiation but equipped with elements that do not 
 glow the hover is low, usually has curtains, and has some special 
 provision for taking care of air replacement. Operation costs are 
 somewhat lower than with the "glowing" type. The heaters should 
 have a capacity of from 1.5 to 2 watts per chick. 
 
 The brooders depending upon convection usually heat some or all 
 of the incoming air, may or may not use curtains, may use either the 
 glowing or non-glowing elements, are comparatively free from sweat- 
 ing troubles, and cost from % of a cent to 1 cent per chick for each 
 1000 hours to heat. 
 
 Due to the tendency of the moisture to condense on the chick's 
 feathers under certain conditions the removal of the tainted air is of 
 prime importance in all types. Some brooders have provision for 
 positive ventilation, others have not. The open or curtainless type of 
 hover requires more heat than the closed or curtain type but it has 
 better ventilation. 
 
Bul.441] 
 
 THE ELECTRIC BROODER 
 
 39 
 
 Seven square inches is the brooder floor area recommended per 
 chick. If a smaller space is used less heat will be required but ven- 
 tilation troubles will probably be greater. The chief difference between 
 brooders lies in the comparative cost and dependability of operation. 
 Those that conserve the heat by means of curtains, crowding or 
 restricted ventilators will cost less but will be less satisfactory than 
 those less careful of the heat but more careful of ventilation. 
 
 In general, brooders using non-glowing coils also use curtains 
 while those using glowing elements do not. 
 
 Table 6 follows, which is a condensed summary of the results of 
 tests conducted by the California Committee on the Relation of 
 Electricity to Agriculture during this investigation. 
 
 TABLE C 
 
 Condensed Summary Electric Poultry Brooder Tests, All Types 1925, 19: 
 Conducted by the California Committee on the Eelation of 
 Electricty to Agriculture 
 
 
 Non-glowing 
 Brooder tests. 
 
 "Radiant" 
 
 or glowing type 
 
 brooder tests 
 
 
 8 
 
 33 
 
 21940 
 
 18121 
 
 3819 
 
 8596.9 
 
 665 
 
 17.4 
 
 .474 
 1.298 
 974 
 4.88 
 .948 cents 
 
 6 
 
 Total number tests run 
 
 16 
 10994 
 
 
 9532 
 
 
 1462 
 
 Total kilowatt-hours consumed 
 
 14810.0 
 687 
 
 Average mortality, per cent 
 
 13.3 
 1.553 
 
 Average connected load per chick, watts 
 
 Average brooding season, hours 
 
 Average brooder area, square inches 
 
 Average cost per cnick, (2 cents per kw.-hr. base) 
 
 1.908 
 1200 
 7.83 
 3.110 cents 
 
 ACKNOWLEDGMENTS 
 
 The writers are indebted to the following poultrymen who have 
 generously cooperated and permitted the study and testing of their 
 electric brooders : L. Bufford, Santa Rosa ; J. J. Burke, Santa Rosa ; 
 H. Cook, Santa Rosa; F. Ehrlick, Santa Rosa; J. O. Freisinn, Santa 
 Rosa; P. Randolph, Santa Rosa; M. Schulz, Santa Rosa; E. O. Hussey, 
 Petaluma; D. B. Walls, Petaluma; Grace N. Johnson, Healdsburg; 
 P. Mothorn, Healdsburg; and E. S. Williams, Sebastopol. The follow- 
 ing have also assisted in numerous ways : M. W. Buster, Specialist in 
 Agricultural Extension ; J. W. Felt, Great Western Power Company, 
 Santa Rosa; W. W. Shuhaw, Pacific Gas & Electric Company, Santa 
 Rosa, and the Poultry Husbandry Division of the University of 
 California. 
 
12n?-ll,'27