CALIFORNIA AGRICULTURAL EXTENSION SERVICE CIRCULAR 14 September, 1927 SELECTION AND CARE OF ELECTRICAL EQUIPMENT USED IN DAIRY MANUFACTURING A. W. FARRALL PUBLISHED BY THE COLLEGE OF AGRICULTURE UNIVERSITY OF AGRICULTURE Cooperative Extension work in Agriculture and Home Economics, College of Agriculture, University of California, and United States Department of Agriculture cooperating. Dis- tributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. B. H. Crocheron, Director, California Agricultural Extension Service. UNIVERSITY OF CALIFORNIA PRINTING OFFICE BERKELEY, CALIFORNIA 1927 Digitized by the Internet Archive in 2011 with funding from University of California, Davis Libraries http://www.archive.org/details/selectioncareofe14farr SELECTION AND CARE OF ELECTRICAL EQUIPMENT USED IN DAIRY MANUFACTURING A. W. FAKRALLi The use of electrical energy has become general in California. A recent questionnaire survey, conducted by the author, showed that more than 92 per cent of the 900 dairy manufacturing plants of Cali- fornia use electricity for power. It is also estimated that 65 per cent of the farms of California use some type of electrical equipment. 2 In addition, there are a large number of dehydraters, preserving fac- tories, and canning works, which use electrical machinery. A demand has arisen from many of these sources, particularly from the dairy manufacturing plants, for more information regarding the selection, care, and operation of electrical equipment, as applied to dairy conditions. In order to provide this information and thereby assist the operator in making the most efficient use of his equipment, this publication has been prepared. Much of the data were collected from the viewpoint of dairy manufacturing, but applications may easily be made to cover conditions in general agriculture, such as pumping, lighting, and other general purposes. DEFINITION OF ELECTRICAL TERMS A knowledge of the meaning of the terms which are in frequent use in connection with electrical equipment, is necessary for the understanding of this publication. Voltage is the term which applies to the electrical pressure in a system. The direction of flow of current is always from a point of high to one of low pressure. The terminals of a generator or battery might be thought of as the high and low pressure points. If no volt- age is present no energy will flow, or if the electrical pressure is the same for both terminals no current will flow. Lowering of the voltage causes a reduced current flow in a system and raising it causes an 1 Junior Agricultural Engineer in the Experiment Station, Division of Dairy Industry and Agricultural Engineering Cooperating. 2 Data from Committee on the Relation of Electricity to Agriculture. 4 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClRC. 14 increased flow. Electrical equipment is made to operate on a given voltage, which should be used to secure best results. Ordinary com- mercial voltages are 110 volts for lighting and 220 volts for power, although in the larger power units, 440 or even 2200 are used. A given amount of energy may be transmitted over a high voltage system with less loss than when low voltages are used. Thus if a motor draws 1100 watts from the line, it will require = 5 amperes of current when used as a 220-volt line. If it is used on a 110-volt line the amperage will be — 10 amperes. The loss in energy through a line having 3 ohms resistance will be 5 2 X 3 = 75 watts in the case of the 220-volt line, while on the 110-volt line it will be 10 2 X 3 = 300 watts. There is a further advantage in using the higher voltage when possible in that the drop in voltage when using a given size of wire for a given load, is less than when a low voltage Fig. 1. — Voltmeter for measuring electrical pressure. The illustration also shows' a trouble lamp, which can be used instead of a voltmeter to determine pressure, although not accurately. is used. Many instances are on record where a motor which was situated some distance from the transformer did not operate satisfac- torily on 110 volts, but did when the line and motor were changed to operate at 220 volts. Voltage may be measured by means of a voltmeter (fig. 1) which is connected directly across the circuit. A trouble lamp (fig. 1) equipped with a 220-volt lamp may also be used for determining volt- ages, roughly. If the lamp shines bright, the line voltage is probably 220 volts, while if it shows dim, it is very likely 110 volts. Amperage refers to the rate of flow of a current of electricity. One ampere is the amount of current which will be forced through a resistance of one ohm by a pressure of one volt. The amperage requirement of a circuit is important mainly because it determines the 1927] ELECTRICAL EQUIPMENT USED IN DAIRY MANUFACTURING 5 size of wires and the size of fuses which must be used. A large wire should be used for carrying a large current. Table 1 shows the allow- able carrying capacity of various sizes of copper wire, according to the National Board of Fire Underwriters. The watt is the unit for the measurement of electrical power. One horsepower is equivalent to 746 watts. The kilowatt (abbreviated kw., or K.W.) equals 1000 watts. TABLE 1 Allowable Carrying Capacity of Wires B. & S. gage Rubber insulation Varnished cloth insulation Other insulation 18 Amperes 3 Amperes Amperes 5 16 6 10 14 15 18 20 12 20 25 25 10 25 30 30 8 35 40 50 6 50 60 70 5 55 65 80 4 70 85 90 3 80 95 100 2 90 110 125 1 100 120 150 125 150 200 00 150 180 225 000 175 210 275 200 240 300 0000 225 270 325 The kilowatt-hour (kw-hr.) is the standard commercial unit for measurement of electrical energy, commonly spoken of as "power," although incorrectly. It represents the amount of energy expended by 1000 watts flowing for one hour, or say 500 watts flowing for two hours. Kilowatt-hours equal kilowatts times hours. Direct current flows always in the same direction, as from the poles of a dry battery. Alternating current (A.C.) flows first in one direction and then in the other. It starts from zero and gradually builds up to the maximum voltage, flowing in one direction; then it decreases in strength down to zero and builds up to a maximum voltage, flowing in the opposite direction, after which it gradually decreases in strength until it again reaches zero value. This complete set of changes is called a cycle. Standard alternating current makes 60 of these com- CALIFORNIA AGRICULTURAL EXTENSION SERVICE [Cmc. 14 plete cycles every second and is therefore called 60-cycle current. Alternating current is used largely today, because its voltage may be easily changed by means of transformers, enabling it to be carried long distances at high voltage with small loss. The phase of an alternating current circuit is important since it determines the type of motor used, and the general wiring scheme. One, two and three-phase systems are the most common types. One might consider phase as meaning circuit. In a single-phase system, there is just one main circuit or path in which the current can travel to the generator and back, while in a three-phase there are three Ll L2 L3 LI L2 6 A 3-Phase Single-Phase Fig. 2. — A three-phase system has three separate circuits acting as a unit, while the single phase has only one. Ll, L2, and L3 indicate conductors. Loads may be placed at points A, B, and C. primary circuits, and the main current surge is in each one suc- cessively. The sum of the currents in any two circuits at a given instant is equal and opposite that in the other one. If one lead wire is broken it immediately kills two phases leaving only one still operating at full capacity. This is known as "single-phasing." This is what happens after one fuse of a 3-phase motor has burned out. Single- phase current may be obtained by "tapping into" any two wires of a 3-phase system. Three-phase systems are very generally used for power circuits, because the energy can be transmitted more economic- ally, and also because the rugged 3-phase induction motors may be used. I 927 ] ELECTRICAL EQUIPMENT USED IN DAIRY MANUFACTURING 7 Single-phase current is used for lighting and for small power circuits. Figure 2 illustrates the two systems. Power factor is defined as the ratio of the watts (which is the measure of true power being used) to the product of volts and amperes. Thus if in a circuit, a wattmeter read 6000 watts, while a voltmeter read 220 and an ammeter 30, the power factor would be = 90 per cent. The most economical power factor is unity or 100 per cent, since the lower the power factor, the larger the cur- rent that must be handled by motors and wires in order to develop a certain power. Low power factor results in heating of motors, voltage drop and loss of energy. It is to the interest of a plant owner, to keep the power factor as near unity as possible. The principal cause of low power factor is operation of induction motors at light load. Synchronous motors have the ability to raise the power factor of a system, and are often employed with this purpose in mind. TYPES OF MOTORS AND THEIR OPERATION Types of Motors. — The motors most commonly used in dairy manu- facturing plants are of five general types, as follows : The single-phase motors are generally used in the smaller sizes, below one-half horsepower, because of the ease with which they may be connected to the line. They are also used in some places in larger sizes, where 3-phase current is not available. They are usually heavier and more expensive for their power than 3-phase motors. They are also slightly less efficient and are more difficult to protect from moisture. The repulsion-induction single-phase motor uses a wound rotor and lias a commutator and brushes. These must be kept well fitted, clean, and properly adjusted or they will cause sparking, especially during the starting period. This type of motor has a good starting torque, and is used on many iceless ice cream cabinets. The split-phase motor, in addition to the regular armature wind- ing, employs a small starting winding of high-resistance wire, which is in operation during the starting period and which is thrown out of service by a centrifugally operated switch after the motor has reached its normal speed. This type of motor does not ordinarily have as good starting torque as the repulsion-induction type. The 3-phase squirrel-cage motor as usually constructed, consists of a stationary part called the stator, which holds the windings and 8 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClEC. 14 supports the bearings, and a rotating part in which the conductors are a series of copper or aluminum bars. These are welded or cast together in the shape of the traditional squirrel cage, hence the name. This type of motor is simple, rugged and very efficient, is easily water- proofed, and has practically constant speed under varying loads. For these reasons, it has become very popular and has given good satis- faction in actual use. The parts of this type are shown in figure 3, unassembled. The double-wound squirrel-cage motor is a new development, which allows the motor to be started directly on the line, in sizes up to 50 horsepower without the use of a starting compensator. The 3-phase wound-rotor type motor has windings in the rotor as well as on the stator, and ordinarily uses brushes and slip rings. It has the ability to start a heavier load with less voltage disturbance on the line than the squirrel-cage type ; for this reason, it is used where it is necessary to start a very heavy load frequently. A further advan- tage of this motor is that its speed can be varied considerably by means of a special type of controller. The disadvantages are that it is not quite as efficient as the squirrel-cage type, that it is not as strong mechanically or electrically, that it requires more upkeep, and that it cannot easily be made water proof. The synchronous motor is so constructed that it operates at con- stant speed at all loads. It has the ability, if properly adjusted, to increase the power factor of the line. Since an auxiliary direct cur- rent exciter must be used in conjunction with this motor, it is custom- ary to use it only in the larger sizes. It is often used for driving refrigeration machinery. Characteristics of Motors. — Every motor has certain individual characteristics which are typical of its action. Some of these are start- ing ability, speed, torque, power factor, heating, and capacity for doing work. The starting characteristics of a motor are dependent upon the design, but all are similar in that they draw a very heavy current from the line at this period of their operation. A large motor, if thrown directly upon the line, may cause a serious drop in voltage, flickering of lights, or even burning out of fuses. Motor starters, which reduce the starting voltage, are sometimes used in order to overcome these troubles. Double wound squirrel-cage type motors have recently been developed, which are greatly improved in this respect, and may be thrown directly upon the line without serious effect. J 927 J ELECTRICAL EQUIPMENT USED IN DAIRY MANUFACTURING Reference Letter Description A Stator, complete. Give Spec. No. of stator coil stamped on part number name plate. B Stator spider without punchings, wind- ings, and terminal board. C Stator coil. Give Spec. No. stamped on part number name plate. D Set of stator punchings. E Stator end connection. F Stator flange. G Stator wedge. H Terminal board, complete. I Terminal board. J Terminal for terminal board lead. K Terminal lead. L Cap screw for terminal board. M Terminal bushing. N Bolt and nut for terminal. O Outside space block. P End shield. Q Bolt fastening end shield to stator. R Dust guard. S Pipe plug for end shield. T Drain plug for end shield. U Oil gauge, complete. V Cap for oil gauge. Reference Letter Description W Nipple for oil gauge. X Elbow for oil gauge. Y Bearing lining. Give Cat. No. stamped on part number name plate. Z Oil ring. Aa Set screw for bearing lining. Ba Oil well cover, complete. Ca Screw for oil well cover. Da Sliding Base, complete. Ea Belt tightener carrier. Fa Belt tightener screw. Ga Base clamp. Ha Guide washer for sliding bar. la Bolt fastening stator to sliding bar. Ja Nut for la. Ka Sleeve for belt tightener screw. La Nut for belt tightener screw. Ma Rotor, complete. Na Shaft, bare. Oa Fan Pa Cap screw fastening fan to flange. Qa Lock washer for Pa. Ra Key for pulley. Sa Pulley. Ta Name plate. Ua Conduit terminal box, complete. Fig. 3. — Parts of a three-phase squirrel-cage type motor, of General Electric Co.) (Courtesy 10 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClRC. 14 The torque (tork), or turning effort of a motor, is its ability to rotate its shaft. This ability is greater on a 1200 R.P.M. motor than on an 1800 R.P.M. motor of the same horsepower. It is measured in pound-feet and is illustrated as follows : If a motor has a torque of 10 pound-feet, it has the ability to exert a pull of 10 pounds on the rim of a pulley which is one foot from the center of the shaft, or 5 pounds on the rim of a pulley which is 2 feet from the center. The starting torque varies with the type of motor. This point should be given special consideration in some types of service, as for example, that of starting a heavy refrigeration machine. With single- phase, repulsion-induction motors, the setting of the brushes greatly affects the starting torque. The pull-out torque is the point at which the motor will stop on account of too great a load, and is usually from two to three times the normal full-load torque. Low voltage causes a considerable decrease in torque. The speed of an alternating current induction motor is deter- mined by the number of poles it has, and by the frequency or cycles per second of the circuit on which it is used. A four-pole motor on a 60-cycle circuit has a synchronous speed of =1800 R.P.M. -^ i ^ -r^ ™ 120 X frequency Formula R.P.M. = ^ § — r ^- number or poles The speed of an alternating-current motor may be changed by reconnecting the windings so that there are a different number of poles, or by placing it on a line of different frequency. If a 60-cycle motor of 1200 R.P.M. is operated on a 50-cycle circuit, its speed will be reduced to approximately five-sixths of its rated speed. The R.P.M. of variable speed alternating-current induction motors is changed by means of a controller, which shifts the connections, making a different number of poles. The power factor of a motor is affected very largely by its size and design and by the load carried. A well loaded motor usually has a good power factor, while one carrying only a quarter load, for example, has a low power factor. This causes a lowering of the power factor on the whole electrical system and may result in overheating the other motors on the line. Large motors, as a rule, have a higher power factor than small ones. Overloads cause low power factor similar to underloads. Heating of motors is a subject of great importance, because it is most often the first sign of trouble, and because it is also the factor which determines the safe limit of load that a motor will carry. I 927 ] ELECTRICAL EQUIPMENT USED IN DAIRY MANUFACTURING 11 Motors are rated as 40 degree and 50 degree motors, meaning that they will develop their rated horsepower continuously, with a tem- perature rise of not more than the respective number of degrees centi- grade above atmospheric temperature. 1° Centigrade equals 1.8° Fahrenheit. If a 40° motor is operated in an atmosphere of 70° F the maximum temperature of its windings should not exceed [40 X 1.8] -f- 70 = 142° F. Under similar conditions, 50° motor would have a temperature not exceeding 160° F. A 40° motor is generally built larger or with a better ventilating system than a 50° motor, and in general, it has a greater overload capacity. The proper ventilation of motors is of great importance in keeping them from overheating. All hoods or covers should be ventilated. Any localized heating of the motor is usually a sign of trouble and should be looked after immediately. A rough method of determining when a motor is overheated is as follows : If the hand cannot be held on the motor winding or stator for twenty seconds, the motor is too hot. A more accurate method is to place the bulb of an ordinary thermometer down into the stator winding against the coils and read the maximum temperature. Low power factor, overloading, poor ventilation, low voltage, and defective windings are frequent causes of overheating. Determining the Load for Motors. — Proper loading of motors is one of the greatest factors in their economical and successful use. Overloading is expensive and dangerous, because of likelihood of burn- ing out the motor windings. Underloading is expensive because of greater first cost of equipment, such as motor, wire, and switches, and because of lower efficiency of the motor. With many motors, a differ- ence of from 4 to 8 per cent in efficiency is found between full and half load. Smaller loads result in much lower efficiency. The average motor has the ability to carry momentary overloads of 100 per cent without injury. The limit of load is really deter- mined by the heating of the motor. In a system in which there is low power factor, or low voltage, a motor will not carry as great a load as under normal conditions. Motors operating in warm places or where ventilation is poor, are also limited in the load they may safely carry. It is the average load, such as is shown in figure 4 and not the peak load, which determines the heating of the motor, and therefore, the amount that may be safely carried, provided that it is not large enough to stall the motor at the peak load. 12 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [CIRC. 14 In all cases where there is doubt, it is advisable to check the actual requirements of a machine before determining the size of motor to buy. It is always better to use a motor that is too large rather than one that is too small. Protection from Moisture. — Moisture has been called the greatest enemy of electricity. This is especially true in creamery work. Since water is a good conductor of electricity, its presence causes shorts or 3 — «—«—« ^^^^™«— ■ — —J* P«BMM>M»^d ^. ~"^^~"" — — — CL CD Maximum load O X 1 Average load 4 6 Minutes Q 10 Fig. 4. — The average load and not the peak load usually determines the heating, and therefore, the size of motor which must be used. grounds in electrical equipment, and careful attention should be given to avoid these difficulties. It is impossible to make the ordinary open type motor entirely waterproof, although many 3-phase motors will withstand considerable moisture. It is advisable to use hoods or shields over motors and other electrical equipment. A good type of hood is shown in figure 5. This hood allows ventilation, which is very important, in keeping the motor cool. There are motors built which have especially protected windings enclosed in a waterproof substance. Some of these are giving very good service under actual commercial conditions. Motors completely enclosed are sometimes used, but the special problem with them is that of overheating. This type of motor is sometimes connected to an external ventilating system and is thus kept cool. I 927 ] ELECTRICAL EQUIPMENT USED IN DAIRY MANUFACTURING 13 The location of the motor on a raised block, or in a place where it will not be subject to contact with streams of water, will prevent much trouble from moisture. It is good policy to dry motors thoroughly once a year, and then spray them with a good insulating and waterproof paint, being par- ticularly careful to cover the windings. Sometimes a waterproof putty is used to cover the windings, but with this material, care must be taken not to close too many air passages, and thus effect poor ventilation and consequent overheating of the motor. Selection of Motors. — In the selection of motors a number of features should be given special attention. Perhaps the first of these should be selection of a motor of proper size, i.e., one which will handle the load under all normal conditions, and one which has sufficient starting torque to bring the load up to speed quickly. The second consideration should be that of ruggedness and reliability. A motor should be of as simple construction as possible and should have great mechanical and electrical strength. The 3-phase squirrel-cage type of motor is an example of a strong, rugged con- Fig. 5. — Ventilated motor hood, for protection of motor. Ventilator near top of hood allows circulation of air about the motor. struction, in which there are no delicate parts to break or get out of adjustment. Its ability to resist moisture, if the motor is to be subject to moist conditions, is next in importance. A fourth consideration should be the reliability of the company manufacturing it. Repairs and service should be available within reasonable distances. It is well to make use of the manufacturer's services for any specific problem which may present itself. Motor Troubles. — It is impossible in a publication of this type to cover each trouble for each particular type of motor, and therefore they will be discussed only generally. Trouble with motors is usually shown by one of the following manifestations. 14 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClRC. 14 Failure to start may be caused by lack of proper voltage, blown fuses, broken wires, too great loads, improper connections, a starting device which is out of order, a switch not entirely closed, or improper brush setting. Overheating may be caused by overloading, low voltage, high volt- age, poor connections, worn or poorly lubricated bearings, short- circuits, grounds, lack of ventilation, low power-factor, or a burned- out fuse. Burning out of fuses may be caused by overloading, tight belts, low voltage, grounds, short circuits, or any of the troubles given under overheating. Sparking at the commutator may be due to dirty, worn, or poorly- fitting commutator and brushes ; to improper setting of brush-holder ; or to grounds, shorts, or open circuits within the rotor winding. Lack of power may result from low voltage, poor connections, worn or dry bearings, one fuse out on a two or three-phase motor, or to too tight a belt. Testing and Repair- of Motors. — Some of the more common methods of testing and repairing are given below. Before working on electric circuits always turn off the power at the main switch before attempt- ing to touch the "live" parts. It may even be desirable to remove the fuses in exceptional cases, to prevent unauthorized persons from turning on the power while work is being done on the system. Standing on a dry board or rubber mat, together with the use of rubber gloves, will minimize the danger of shock. Ordinary rubbers or rubber boots on the feet will also tend to prevent shocks. Severe shocks are caused by the current flowing through one's body, and the current will not flow unless the body is connected to both sides of the circuit at the same time. It should be remembered that the ground as well as the wire may form one side of the circuit. Play safe turn off the power at the main switch before attempting to work on the system. A trouble lamp connected to the motor winding as shown in the diagram, figure 6, will light if there is a ground. Water soaked motors usually show grounds, as indicated above, and must be dried out before they will operate properly. Three common methods of drying are employed. The first method is to place the motor in an oven and bake it for twelve hours at a tem- perature of 150°F, or to hang it above a gas jet for the required length of time in order to allow it to become heated sufficiently to evaporate the moisture. 1927 ELECTRICAL EQUIPMENT USED IN DAIRY MANUFACTURING 15 The second method is to block the rotor and apply a reduced voltage to the motor terminals, allowing the heat which is generated to dry the motor. This method is used on large motors, which are difficult to move. It requires close attention on the part of the operator to prevent excessive heating and the burning out of the motor. /^\^^Troub\e lamp v r IIOV. Moior terminals Fig. 6. — Testing for ground. Lamp will light if motor winding is grounded. Fig. 7. Fig. 8. Fig. 7. -Measuring the stator-rotor clearance of a motor. The sectional model shown in the cut is for demonstration use only. Fig. 8. — Removing bearing sleeves. A third method is to blow heated air through the motor by means of a fan. Bearings of electric motors are of two general types, those using balls or rollers and those using the plain sleeve. When bearings become worn, there, is danger of the rotor rubbing on the stationary part, and for this reason, the clearance between rotor and stator should be measured occasionally. This is done by inserting a thin, tapering gauge through slots provided in the end bells of the motor. The accompanying cut, figure 7, shows the 16 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClRC. 14 method. The clearance should be practically the same on top and bottom and on each side of the motor. The ball-bearing assembly can usually be removed by loosening the retaining bolts, and then driving it out with a wooden block and mallet. Care should be taken in replacing the bearing sleeve to drive straight, as otherwise it may become sprung out of shape. Bearings of plain type usually employ a ring oiler. Before an attempt is made to drive out the sleeve, it is necessary to loosen the retaining screw and also to lift up the oil ring so that it does not catch on the sleeve holder. Figure 8, illustrates the method of removal of sleeve type bearings. The care of brushes and commutators consists mostly of keeping them clean and well fitted. Cleaning is accomplished by brushing with a soft brush and gaso- line. If the commutator is rough, it may be smoothed by holding a piece of fine "00" sandpaper against it by means of a block, while the rotor is turned or by placing it in a lathe and taking a very light cut. This latter procedure is recommended if the commutator is out of round or is badly pitted. After the commutator is smoothed off, the brushes may be fitted to it by placing a band of "00" sandpaper around the commutator, rough side out, in contact with the brushes, and rocking the com- mutator and sandpaper back and forth. The mica used for insulating one section of the commutator from another, sometimes projects above the surface and causes sparking. It should be cut down so that its edge is below the surface. This is best accomplished by means of an undercutting machine or on a lathe, but may be done in an emergency with a broken hack-saw blade, which has been ground off to the required thickness. A commutator should have a smooth, glassy, chocolate brown appearance. Centrifugal switches on split-phase motors may have corroded or burned points and an occasional smoothing and brightening will aid in keeping them in good working order. Lubrication of Motors. — The lubrication of electric motors calls for a light, free-flowing mineral oil, which can work in between sur- faces where there is small clearance. A dynamo oil or medium auto oil is satisfactory. Large motors may use a heavier-bodied oil. Ball- bearing motors use a specially prepared grease or vaseline. It is very desirable to have a regular schedule for inspection and lubrication of bearings. 1927] ELECTRICAL EQUIPMENT USED IN DAIRY MANUFACTURING 17 LIGHTING Proper Illumination. — Good illumination may be denned as a uniform, non-glaring light, free from shadows and of sufficient inten- sity that the work may not be handicapped. The best light for all except cold storage rooms is sunlight ; for this reason, provision for an abundance of natural light through windows or sky lights is recommended. Sufficient light is conductive to more efficient use of labor, to better health of workers, and to more sanitary conditions. The proper intensity of artificial lighting for dairy plants, as recommended by illuminating engineers, has been set at a value of four to eight-foot Fig. 9. — Two rooms furnished the same amount of light. Note degree of illumination due to light and dark colored walls. candles. A more simple method of arriving at the proper illuminat- ing value, is to allow 1.5 to 2.0 watts lamp capacity per square foot of floor area, with light colored rooms and ceilings of medium height. Figure 9 illustrates the marked effect of the color of walls upon the lighting intensity of two rooms, each supplied with the same amount of light. This is of special importance in refrigeration rooms, where the heat produced from the electric lamp causes loss of refrigeration. The. selection of the proper type of fixture is of importance. For factory conditions, the porcelain enameled type of reflector has gen- erally been found to be good ; it has high powers of reflection, is not fragile, is easily cleaned, and is inexpensive. The standard R.L.M. dome reflector is a good type. The special moisture proof fixture with extra glass cover is also good, under conditions of high moisture or in the presence of corroding vapors. 18 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClEC. 14 TABLE 2 Effect of Voltage on Electric Lamps* Lamp voltage Circuit voltage Per cent normal voltage Per cent normal illumination Per cent normal life 110 95 35 181 112 97 91 140 115 115 100 100 100 117 101 106 79 120 104 116 57 125 108 133 32 * Data supplied by National Lamp Works— General Electric Co. Efficiency of Electric Lamps. — The illuminating efficiency of elec- tric lamps and the length of life, are greatly affected by the operating voltage. The normal life of an electric lamp is 1000 hours. As shown in Table 6, the illuminating powers of a lamp are increased by an increase in the voltage, but at a considerable sacrifice in length of life. Main I A k Pilot, light 7b motor Fig. 10. — Wiring diagram for pilot light. The Pilot Light. — There are many places about the creamery where it is desirable to have a signal for indicating when current is flowing to lights or equipment as reminders to the workmen. In many plants considerable energy is wasted by failure to turn off electricity at the proper time. To overcome this trouble it is possible to install I 92 ?] ELECTRICAL EQUIPMENT USED IN DAIRY MANUFACTURING 19 in a conspicuous place a pilot light of low wattage, such as that shown in the diagram, figure 10. The lamp will always be lighted when the main switch is turned on. HEATING AND PROCESSING Electrical energy is used successfully for heating where it is not too expensive, where it saves a considerable amount of labor, and where it offers better control of temperature than other methods. It Fig. 11. Fig. 12. Fig. 11. — Home-made open type electric heater. Fig. 12. — Immersion type electric heater. may require a longer heating period than oil or coal, but by proper arrangement of the schedule, it will usually be found to be sufficiently rapid. Types of Electric Heaters. — There are a number of different types of heaters available. One is the plain open resistance type, in which resistance wire is wound around a porcelain or asbestos composition core, or is merely stretched between insulated binding posts or grids. Another is the immersion type, which is made of a resistance wire housing. The open type, figure 11, is used for heating air, while the immersion type, figure 12, is used for heating liquids. With the latter the current must not be left on when the heater is not sub- merged, lest it burn out or its life be shortened. With some makes, it is possible to renew the burned out element at nominal cost. 20 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [Circ. 14 Some elements are so connected that several different heats may be had by adjustment of a switch. Cost of Electrical Heating. — The cost of heating with electricity is usually determined by the power rate and the efficiency of the installa- tion. Electric heating units are 100 per cent efficient, and if proper insulation is used with them, a higher over-all efficiency can usually be obtained, taking all factors into consideration, than when coal or oil is used. From one kw-hr. there are produced 3412 B.t.u., while from one pound of coal about 13,000 B.t.u. are produced. (B.t.u. — British thermal unit — is the unit of heat, representing the amount of heat necessary to raise one pound of water 1 degree Fahrenheit.) The following table shows the comparative cost of energy alone for coal, oil, TABLE 3 Comparative Approximate Cost of Heat Energy from Different Sources Cost per unit of fuel Efficiency of heater in per cent Heat units available Heat units for $1.00 Coal $10.00 per ton 70 13,000 B.t.u. per lb. 1,820,000 Oil $2.10 per bbl. 72 18,500 B.t.u. per lb. 2,125,700 Electricity 1.5c per kw-hr. 100 3,412 B.t.u. per kw-hr. 227,667 and electric heating. The over-all cost of heating should include items such as labor, interest on investment, and depreciation. Oftentimes the question of cleanliness is a factor that must be considered. AUTOMATIC CONTROL OF EQUIPMENT Many operations, such as starting and stopping of machinery, control of temperature, and processing in general, are easily handled by automatic electrical control. One of the advantages is that of being able to control from a distance. The controlling mechanism may operate from a combination of a thermostat which operates by temperature change ; from a pressure switch which operates from changes of pressure and from a time switch which operates from changes of time. It may also operate from any one of the above. The relay is used where large currents are to be handled. Magnetic valves, such as shown in figure 13, are used for handling liquids and gases. Magnetic switches may be con- trolled by means of a push button station, located some distance from the switch. This makes possible a saving in wire, and enables the switch box to be installed in a dry place on the wall. 1927] ELECTRICAL EQUIPMENT USED IN DAIRY MANUFACTURING 21 r>c-> Fig. 13. — Magnetic value used for controlling the flow of liquids such as brine or water passing through pipe lines. (Courtesy Taylor Instrument Co.) ELECTRIC WIRING Wiring Regulations. 3 — The safety regulations of cities and states require that certain conditions be complied with in the installation of electrical wiring, and these should always be consulted before laying out a piece of work. Care should be taken not to overload small lines by attaching large electrical appliances to them. Continued over- loading will cause heating and gradual failure of the insulation. Wires should be large enough to carry a considerable overload without heating and without causing serious voltage drop. Rubber covered wire is used for inside and weatherproof for outside work. The latter is much more brittle and more difficult to bend. Rubber covered wire with white or striped covering may be secured, and has the advantage of being easily traced as one side of a circuit, if black wire is used for the other side. It is also cleaner to handle than the black wire. All wiring should be in metal conduit or pipe. The rigid type should be used in creameries where possible, because it is more nearly waterproof than is the flexible. The latter type is often used for temporary rewiring work, or for installation where there is small danger of water collecting, or where it is difficult to bend the rigid type to the proper shape. The armored cable figure 14, having one, two, or three conductors is very often used for temporary lines, or on portable machines, such as tube cleaners, or ice stackers. In connec- 3 See Industrial Accident Commission of the State of California. Electric safety orders. 1925 ed., California State Printing Office, Sacramento, Calif. 1925. 22 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClRC. 14 tion with the proper kind of plugs or quick attachment devices, this cable is very convenient. Flexible cords having one, two, or three conductors are also used in connection with portable machinery. Electrical Connections. — Good electrical connections are important from the standpoint of safety and reliability, if one is to have the best service from his electrical equipment. They should be large enough to carry the load safely, should be well insulated, and should have sufficient mechanical strength not to sag or break. I %4 i C D Fig. 14. — A, flexible armored cable. B, flexible conduit. C, lugs. D, tubular connectors. All connections should be well bolted together or soldered. All bolted connections should be made with copper lugs (fig. 14), soldered to the ends of the wires and then bolted together. Temporary con- nections can be made very satisfactorily with tubular connectors (fig. 14). The tightening of screws holds the wire firmly in place. The insulation should consist of first a layer of rubber insulating tape wound on the half-lap ; second, a layer of friction tape, also wound on the half-lap ; third, a coat of good insulating paint to give a desirable finish, and make the connection waterproof. Switches and Starters. — The simplest starting device is a plain, enclosed, single-throw switch, with an externally-operated handle for throwing it off and on. This switch is sometimes made in the double- throw type with one set of fuses for starting, and another for running. The latter type of construction is preferable because it gives the motor better protection, if small fuses are used on the ''running" side. The magnetic switch is made to be operated from a push button station or by a hand-operated lever. This type of switch has the 1927] ELECTRICAL EQUIPMENT USED IN DAIRY MANUFACTURING 23 advantage that it automatically opens the circuit when the power goes off or the voltage becomes too low. A thermal overload relay or a magnetic relay is used for protection of the motor from overloads. Where motors larger than 7% hp.* are used, it is customary to use a starter with a small transformer or resistance built in. This starter serves to reduce the voltage applied to the motor and thus prevents an excessive current being drawn from the line. FUSING AND PROTECTION OF CIRCUITS The proper fusing of electric lines is of great importance, for the fuse is to the electric line, what the safety plug is to the steam boiler. A fuse contains a small strip of metal, which melts out when a cur- rent greater than its rating in amperes is passed through it. This breaks the circuit and stops the flow of electricity. The practice of Mg. 15. — Common types of fuses. A, plug; B, cartridge; C, time-limit; D, renewable cartridge. "bridging" burned out fuses with pennies or nails or wires is very dangerous, and may be compared to that of substituting a steel plug in the place of a fusible plug in a steam boiler. The protection is gone, and the result may be a burned out motor, a burned out line, or possibly a fire. Types of Fuses. — Four types of fuses, as shown in figure 15 are ordinarily used on motor and lighting circuits. The one marked A is the ordinary plug fuse, which is used mostly in lighting circuits, and is made in sizes up to 30 amperes. B is the plain cartridge, such as is used on lighting and motor circuits, in sizes up to 400 amperes or more. C is a time-limit fuse, which is used mainly on motor cir- cuits. While this fuse will not burn out on a momentary overload like the ordinary fuse, if the overload continues for considerable time, it will burn out and protect the motor. The fuse is easily renewed by replacing a small link. D is a renewable-link cartridge fuse, which has practically the same characteristics as the plain cart- * See Double wound squirrel cage motor, page 8. 24 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClRC. 14 ridge fuse. It has the advantage also of having a renewable link, which when burned out, can be replaced at a nominal cost. Fuses should be of such a size or amperage that they will carry no more than the maximum, safe, carrying capacity in amperes of the line, motor, or device which is to be protected. Extra long fuses are used on lines operating at 440 volts or above. There are special conditions which must be overcome by fuses selected for motors. The latter draw for only a short time, a starting current so heavy that it would burn out a fuse small enough to afford protection against a continuous running overload. If plain fuses are used, two sets are usually installed, one of about 200% of the motor Fig. 16. — Thermal over-load relay. (Courtesy General Electric Co.) name plate amperage for starting, and another of from 115 to 125% of name plate amperage for running. If time limit fuses are used, they are usually of about 110% of the name plate amperage of the motor. For example, if a motor used 15 amperes of current at full load, the fuse should be 110% of 15 amperes, or 16.5. The nearest commercial size should be used. Types of Relays. — Overload-relays are electrical devices, which take the place of fuses in the motor circuit. They are of two general types. The thermal overload-relay, figure 16, opens the motor circuit, by means of a small blade, made of two dissimilar metals, and which bends to one side when heated by the current to a certain predeter- mined temperature. It is reset by pushing a trip or plunger. The magnetic overload-relay opens the circuit by the action of a plunger, which is raised by the pull of a magnet, when the prede- termined current value is exceeded. The adjustment of the relay is important, as is also the keeping of oil in the dashpot. Magnetic overload relays should be adjusted to operate at about 115 to 125% of the name plate amperage of the motor. 1927] ELECTRICAL EQUIPMENT USED IN DAIRY MANUFACTURING 25 POWER TRANSMISSION Types of Drive. — The most common methods of drive are by direct connection to the motor shaft, or by silent chain drive, belt, friction, or gears. No one method can be said to be best for all conditions, as the size and nature of the load, as well as sanitary considerations, may influence the selection of a particular method. In general, the elimination of belts and chains which throw oil and dirt about a creamery is desirable from the standpoint of cleanli- ness. A gear set or enclosed chain running in oil is, next to the direct- connected unit, the most desirable. There are places where there is plenty of space for a belt drive, and where the ease of installation justifies its use. If certain heavy loads must be carried, a belt will slip and protect the machine or motor from possible injury in starting or at peak loads. There is considerable controversy over the question of group and individual drives. The group drive is lower in the first cost, and if a certain group of machines are always operated at the same time, it is often the logical method. However, there is the disadvantage of hav- ing line shafts and counter shafts, which must be considered from the sanitary standpoint, as well as that of safety. If a machine is operated alone, it is better to use individual drive. Adjustment of Drive. — There is considerable importance attached to the adjustment of any form of drive. Chains must be kept neither too tight nor too loose, or they will wear and consume power needlessly. Gears and belts must be run under the same conditions. Tight belts place a great strain upon bearings. The short center belt drive with idler is gaining in popularity and gives very good service, at the same time conserving floor space. The proper alignment of pulleys is important. Belts which are held in place by guides, sticks, or any other such means are wasteful of power and wear rapidly. Leather belts may be kept soft and pliable by frequent applications of a small amount of neatsfoot oil, while other types of belts require a special dressing, recommended by the manufacturer. Speed of Pulleys and Gears. — The speed of pulleys and gears may be calculated as follows: Diameter of Driver (inches) X R.P.M. = Diameter of Driven (inches) X R.P.M. 26 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClBC. 14 (a) Diameter of driver multiplied by its R.P.M., divided by diameter of driven, gives K.P.M. of driven. (b) Diameter of driver multiplied by its R.P.M., divided by R.P.M. of driven, gives diameter of driven. (c) In the case of gears, the same general formula may be used, by substituting the number of teeth in the place of "Diameter" in the formula. Problem : Given : A pulley ten inches in diameter and having a speed of 100 R.P.M. drives a second pulley at 200 R.P.M. Find the diameter of the second pulley. Solution : Use formula (b) as shown above. Diameter of driver times its diameter in inches, divided by R.P.M. of driven equal diameter of driven. 100 X 10 -f- 200 = 5. Therefore, the diameter of the driven pulley must be 5 inches. PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION No. 275. The Cultivation of Belladonna in California. 276. The Pomegranate. 277. Sudan Grass. 278. Grain Sorghums. 279. Irrigation of Rice in California. 283. The Olive Insects of California. 294. Bean Culture in California. 304. A Study of the Effects of Freezes on Citrus in California. 310. Plum Pollination. 312. Mariout Barley. 813. Pruning Young Deciduous Fruit Trees. 319. Caprifigs and Caprification. 324. Storage of Perishable Fruit at Freez- ing Temperatures. 325. Rice Irrigation Measurements and Experiments in Sacramento Valley, 1914-1919. 328. Prune Growing in California. 331. Phylloxera-Resistant Stocks. 335. Cocoanut Meal as a Feed for Dairy Cows and Other Livestock. 339. The Relative Cost of Making Logs from Small and Large Timber. 340. Control of the Pocket Gopher in California. 343. Cheese Pests and Their Control. 344. Cold Storage as an Aid to the Mar- keting of Plums. 346. Almond Pollination. 347. The Control of Red Spiders in Decid- uous Orchards. 348. Pruning Young Olive Trees. 349. A Study of Sidedraft and Tractor Hitches. 350. Agriculture in Cut-over Redwood Lands. 352. Further Experiments in Plum Pollina- tion. 853. Bovine Infectious Abortion. 354. Results of Rice Experiments in 1922. 357. A Self-mixing Dusting Machine for Applying Dry Insecticides and Fungicides. 858. Black Measles, Water Berries, and Related Vine Troubles. 361. Preliminary Yield Tables for Second Growth Redwood. 362. Dust and the Tractor Engine. 363. The Pruning of Citrus Trees in Cali- fornia. 364. Fungicidal Dusts for the Control of Bunt. 365. Avocado Culture in California. 366. Turkish Tobacco Culture, Curing and Marketing. 367. Methods of Harvesting and Irrigation in Relation of Mouldy Walnuts. 368. Bacterial Decomposition of Olives dur- ing Pickling. 369. Comparison of Woods for Butter Boxes. 370. Browning of Yellow Newtown Apples. 371. The Relative Cost of Yarding Small and Large Timber. 372. The Cost of Producing Market Milk and Butterfat on 246 California Dairies. 373. Pear Pollination. 374. A Survey of Orchard Practices in the Citrus Industry of Southern Cali- fornia. 375. Results of Rice Experiments at Cor- tena, 1923. 376. Sun-Drying and Dehydration of Wal- nuts. 377. The Cold Storage of Pears. 379. Walnut Culture in California. 380. Growth of Eucalyptus in California Plantations. 381. Growing and Handling Asparagus Crowns. BULLETINS No. 382. 383. 385. 386. 387. 388. 389. 390. 391. 392. 393. 394. 395. 397. 398. 399. 400. 401. 402. 403. 404. 405. 406. 407. 408. 409. 410. 411. 412. 413. 414. 415. 416. 417. 411 419. 420. 421. 422. 423. 424. 425. 426. 427. •12; Pumping for Drainage in the San Joaquin Valley, California. Monilia Blossom Blight (Brown Rot) of Apricot. Pollination of the Sweet Cherry. Pruning Bearing Deciduous Fruit Trees. Fig Smut. The Principles and Practice of Sun- drying Fruit. Berseem or Egyptian Clover. Harvesting and Packing Grapes in California. Machines for Coating Seed Wheat with Copper Carbonate Dust. Fruit Juice Concentrates. Crop Sequences at Davis. Cereal Hay Production in California. Feeding Trials with Cereal Hay. Bark Diseases of Citrus Trees. The Mat Bean (Phaseolus aconitifo lius). Manufacture of Roquefort" Type Cheese from Goat's Milk. Orchard Heating in California. The Blackberry Mite, the Cause of Redberry Disease of the Himalaya Blackberry, and its Control. The Utilization of Surplus Plums. Cost of Work Horses on California Farms. The Codling Moth in Walnuts. Farm-Accounting Associations. The Dehydration of Prunes. Citrus Culture in Central California. Stationary Spray Plants in California. Yield, Stand and Volume Tables for White Fir in the California Pine Region. Alternaria Rot of Lemons. The Digestibility of Certain Fruit By- products as Determined for Rumi- nants. Factors Affecting the Quality of Fresh Asparagus after it is Harvested. Paradichlorobenzene as a Soil Fumi- gant. A Study of the Relative Values of Cer- tain Root Crops and Salmon Oil as Sources of Vitamin A for Poultry. The California Poultry Industry; a Statistical Study. Planting and Thinning Distances for Deciduous Fruit Trees. The Tractor on California Farms. Culture of the Oriental Persimmon in California. Poultry Feeding: Principles and Practice. A Study of Various Rations for Finishing Range Calves as Baby Beeves. Economic Aspects of the Cantaloupe Industry. Rice and Rice By-products as Feeds for Fattening Swine. Beef Cattle Feeding Trials, 1921-24. Cost of Producing Almonds in Cali- fornia; a Progress Report. Apricots (Series on California Crops and Prices). The Relation of Rate of Maturity to Egg Production. Apple Growing in California. Apple Pollination Studies in fornia. The Value of Orange Pulp for Milk Production. The Relation of Maturity of Cali- fornia Plums to Shipping Dessert Quality. Cali- and No. 87. Alfalfa. 117. The Selection and Cost of a Small Pumping Plant. 127. House Fumigation. 129. The Control of Citrus Insects. 136. Melilotus indica as a Green-Manure Crop for California. 144. Oidium or Powdery Mildew of the Vine. 157. Control of the Pear Scab. 160. Lettuce Growing in California. 164. Small Fruit Culture in California. 166. The County Farm Bureau. 170. Fertilizing California Soils for the 1918 Crop. 173. The Construction of the Wood-Hoop Silo. 178. The Packing of Apples in California. 179. Factors of Importance in Producing Milk of Low Bacterial Count. 190. Agriculture Clubs in California. 199. Onion Growing in California. 202. County Organizations for Rural Fire Control. 203. Peat as a Manure Substitute. 209. The Function of the Farm Bureau. 210. Suggestions to the Settler in California. 212. Salvaging Rain-Damaged Prunes. 215. Feeding Dairy Cows in California. 217. Methods for Marketing Vegetables in California. 220. Unfermented Fruit Juices. 228. Vineyard Irrigation in Arid Climates. 230. Testing Milk, Cream, and Skim Milk for Butterfat. 231. The Home Vineyard. 232. Harvesting and Handling California Cherries for Eastern Shipment. 234. Winter Injury to Young Walnut Trees during 1921-22. 235. Soil Analysis and Soil and Plant Inter-relations. 236. The Common Hawks and Owls of California from the Standpoint of the Rancher. 237. Directions for the Tanning and Dress- ing of Furs. 238. The Apricot in California. 239. Harvesting and Handling Apricots and Plums for Eastern Shipment. 240. Harvesting and Handling Pears for Eastern Shipment. 241. Harvesting and Handling Peaches for Eastern Shipment. 243. Marmalade Juice and Jelly Juice from Citrus Fruits. 244. Central Wire Bracing for Fruit Trees. 245. Vine Pruning Systems. 247. Colonization and Rural Development. 248. Some Common Errors in Vine Prun- ing and Their Remedies. 249. Replacing Missing Vines. 250. Measurement of Irrigation Water on the Farm. 252. Supports for Vines. 253. Vineyard Plans. 254. The Use of Artificial Light to Increase Winter Egg Production. CIRCULARS No. 255. 256. 257. 258. 259. 261. 262. 263. 264. 265. 266. 267. 269. 270. 272. 273. 274. 276. 277. 278. 279. 281. 282. 283. 284. 285. 286. 287. 288. 289. 290. 291. 292. 293. 294. 295. 296. 298. 299. 300. 301. 302. 303. 304. 305. 306. 307. 308. 309. Leguminous Plants as Organic Fertil- izer in California Agriculture. The Control of Wild Morning Glory. The Small-Seeded Horse Bean. Thinning Deciduous Fruits. Pear By-products. Sewing Grain Sacks. Cabbage Growing in California. Tomato Production in California. Preliminary Essentials to Bovine Tuberculosis Control. Plant Disease and Pest Control. Analyzing the Citrus Orchard by Means of Simple Tree Records. The Tendency of Tractors to Rise in Front; Causes and Remedies. An Orchard Brush Burner. A Farm Septic Tank. California Farm Tenancy and Methods of Leasing. Saving the Gophered Citrus Tree. Fusarium Wilt of Tomato and its Con- trol by Means of Resistant Varieties. Home Canning. Head, Cane, and Cordon Pruning of Vines. Olive Pickling in Mediterranean Coun- tries. The Preparation and Refining of Olive Oil in Southern Europe. The Results of a Survey to Determine the Cost of Producing Beef in Cali- fornia. Prevention of Insect Attack on Stored Grain. Fertilizing Citrus Trees in California. The Almond in California. Sweet Potato Production in California. Milk Houses for California Dairies. Potato Production in California. Phylloxera Resistant Vineyards. Oak Fungus in Orchard Trees. The Tangier Pea. Blackhead and Other Causes of Loss of Turkeys in California. Alkali Soils. The Basis of Grape Standardization. Propagation of Deciduous Fruits. The Growing and Handling of Head Lettuce in California. Control of the California Ground Squirrel. The Possibilities and Limitations of Cooperative Marketing. Poultry Breeding Records. Coccidiosis of Chickens. Buckeye Poisoning of the Honey Bee. The Sugar Beet in California. A Promising Remedy for Black Measles of the Vine. Drainage on the Farm. Liming the Soil. A General Purpose Soil Auger and its Use on the Farm. American Foulbrood and its Control. Cantaloupe Production in California. Fruit Tree and Orchard Judging. The publications listed above may be had by addressing College of Agriculture, University of California, Berkeley, California, 12m-9,'27