PERIODIC TESTS

Rule 17.—Each watt-hour meter shall be tested according to the following schedule and adjusted whenever it is found to be in error more than 1 per cent., the tests both before and after adjustment being made at approximately three-quarters and one-tenth of the rated capacity of the meter. Meters operated at low power-factor shall also be tested at approximately the minimum power-factor under which they will be required to operate. The tests shall be made by comparing the meter, while connected in its permanent position, on the consumer’s premises with approved, suitable standards, making at least two test runs at each load, of at least 30 seconds each, which agree within 1 per cent.

Single-phase, induction-type meters having current capacities not exceeding 50 amperes shall be tested at least once every 4 months and as much oftener as the results obtained shall warrant.

All single-phase induction-type meters having current capacities exceeding 50 amperes and all polyphase and commutator-type meters having voltage ratings not exceeding 250 volts and current capacities not exceeding 50 amperes shall be tested at least once every 12 months.

All other watt-hour meters shall be tested at least once every 6 months.

Rule 20.—Request Tests.—Each utility furnishing metered electric service shall make a test of the accuracy of any electricity meter upon request of the consumer, provided the consumer does not request such test more frequently than once in 6 months. A report giving the results of each request test shall be made to the consumer and the complete, original record kept on file in the office of the utility.

Electric Batteries.

—Electric batteries are composed of electric cells that are made in two general types: the primary cell, in which electricity is generated by the decomposition of zinc; and the secondary cell or storage cell in which electricity from a dynamo may be accumulated and thus stored. Electric cells are the elements of which electric batteries are made; a single electric cell is often called a battery but the battery is really two or more cells combined to produce effects that cannot be attained by a single element.

Both primary and secondary batteries form a part of the household equipment but the work of the secondary battery is used more particularly for electric lighting, the operation of small motors and for other purposes where continuous current is required. It will, therefore, be considered in another place.

Primary batteries are used to operate call-bells, table pushes, buzzers, night latches and various other forms of electric alarms besides which they are used in gas lighters, thermostat motors and for many special forms, all of which form an important part in the affairs of everyday life. Primary battery cells for household use are made to be used in the wet and dry form, but the dry cell is now more extensively used than any other kind and for most purposes has supplanted the wet form.

Formerly all primary cells were made of zinc and copper plates placed in a solution called an electrolite, that dissolved the zinc and thus generated electricity, the electrolite acting as a conductor of the electricity to the opposite plate. In later electric cells the copper was replaced by plates of carbon and from the zinc and carbon cell was finally evolved the present-day dry cell. When the use of electric cells reached a point where portable batteries were required, a form was demanded from which the solution could not be lost accidentally. The first electric cells in which the electrolite was not fluid was, therefore, called a dry cell. These cells are not completely dry. The electrolite is made in the form of a paste that acts in the same manner as the fluid electrolite and is only dry in that it is not fluid.

Fig. 254.—Electric dry cell.

Fig. 255.—Details of electric dry cell.

In construction the dry cell is shown in Figs. 254 and 255, the former showing its exterior and the latter exposing its internal construction. The container is a zinc can which is lined with porous paper to prevent the filler from coming into contact with the zinc. The zinc further is the active electrode, the chemical destruction of which generates the electricity. The parts enclosed in the container are: a carbon rod, which acts as the positive pole; and the filler, composed of finely divided carbon mixed with manganese dioxide and wet with a solution of salammoniac. The composition plug, made of coal-tar products and rosin, is intended to keep the contents of the can in place and prevent the evaporation of the moisture. Binding posts attached to the carbon rod and soldered to the can furnish the + and-poles.

In the action of cell, the salammoniac attacks the zinc in which chemical action electricity is evolved. The electricity is conducted to the carbon pole through the carbon and the salammoniac solution which in this case is the electrolite. In the dissolution of the zinc, hydrogen gas is liberated which adds to the resistance of the cell and thus reduces the current. The presence of the hydrogen is increased when the action of the cell is rapid and the decrease in current is said to be due to polarization. The manganese dioxide is mixed with the filler in order that the free hydrogen may combine with the oxide and thus reduce the resistance. This process is known as depolarization. The combination between the hydrogen and the oxide is slow and for this reason the depolarization of batteries sometimes require several hours. Dry cells are usually contained in paper cartons to prevent the surfaces from coming into contact and thus destroying their electrical action.

The best cell is that which gives the greatest amount of current for the longest time. Under any condition the working value of a cell is determined by the number of amperes of current it can furnish. The current is measured by a battery tester such as Fig. 257. The + connection of the tester is placed in contact with the + pole of the cell or battery and the other connection placed on the-pole. The pointer will immediately indicate the current given out by the battery. A new dry cell will give 20 or more amperes of current for a short time but if used continuously the quantity of current will be reduced by polarizing until but a very small amount is generated. A cell that indicates less than 5 amperes should be replaced. If short-circuited, that is if the poles are connected without any intervening resistance, a large amount of current will be given but the cell will soon wear out and possibly be ruined. A cell should, therefore, never be allowed to become short-circuited. The voltage of a cell is practically continuous and should be from 1.5 to 1 volt. It is quite possible that a cell may possess its normal voltage and yet deliver little current; the voltage of a cell does not indicate its working property. In order to be assured of active cells they should be tested at the time of purchase with an ammeter.

The moisture in the paste of a cell is that which forms the circuit between the zinc and the carbon elements. If the paste has dried out its resistance is increased and the cell generates little current. The voltage of such a cell may be normal while the amperage is very low. Cells in this condition may be revived by adding moisture to the paste as a temporary remedy. This may be accomplished by puncturing the can with a nail and adding water. A solution of salammoniac may be used instead of water and the cell soaked to accomplish the same purpose; this, however, is only a temporary expedient.

Temperature influences the working properties of an electric cell in pronounced manner. The moisture contained in the cell is composed of ammonium chloride and zinc chloride and consequently the resistance of the cell increases with the fall of temperature; the effect of the resistance thus added is a decrease in the flow of current. Batteries should be kept in a temperature as nearly as possible that of 70°F. The battery regains its normal rate of discharge when the temperature is restored.

The normal voltage and amperage for a given make of cell is practically the same for all. The size of the cell does not in any way influence the voltage. Small cells and large cells are the same. The large cells are advantageous only in that they give out a greater number of ampere-hours of energy. All batteries are rated in the number of ampere-hours of current they are capable of furnishing. The ampere-hour represents an ampere of current for one hour. On this basis all batteries are rated for the total amount of energy they are capable of producing. If the battery is worked at a high current, its life is short; if however, it is discharged at a low rate, its life should be long. In all cases the product of the number of amperes and the number of hours constitute the ampere-hours of energy produced.

Battery Formation.

—For ordinary household work as that of operating doorbells, etc., the cells which form a battery are joined in series, that is the positive or carbon pole of one cell is joined to the zinc or negative pole of the next. The cells so connected are placed in circuit with the bell and push button. If by accident the two cells of a battery are joined with both carbon poles or both zinc poles together the battery will give out no current because the voltage is opposed.

Fig. 256.—Battery combinations.

In the use of batteries for ignition as for gasoline engines, automobiles, etc., the arrangement of the cells has frequently a decided influence on the effect produced. In Fig. 256 A is represented four cells joined in series, that is the carbon or + poles are joined with the zinc or-poles, alternately. Connected in this manner if each cell gives 1.5 volts the battery will give 4 × 1.5 = 6 volts; the current, however, will remain as that of a single cell. If the cells singly give 20 amperes, the battery will give 20 amperes. When cells are connected in this form the current passes through each cell in turn and is as much a part of the circuit as the wires. Should one of the cells be “dead”—that is delivering no current—it will act as additional resistance and the current is reduced.

When joined in multiple or parallel connection as in Fig. 256 B, in which all similar binding posts are connected, the effect is decidedly different. In the multiple connection all of the zincs are joined to act as a single zinc and all of the carbons are likewise joined and act as a single carbon. In such a combination the voltage will be that of a single cell 1.5 volts, but the amperage will be four times that of a single cell or 80 amperes.

The diagrams and following descriptions of possible combinations were taken from a bulletin on battery connections issued by the French Battery and Carbon Co.

By combining the series and multiple connections, as shown in Fig. C, both the voltage and current can be increased over that delivered by one cell. Referring to the figure, it is seen that in each of the two rows of four cells the cells are connected in series. This would produce 6 volts and 20 amperes for the series of four which may now be assumed as a unit, so that the two rows can be imagined as two large cells, each of which has a normal output of 20 amperes at 6 volts. Now by connecting the similar poles of two such large cells they are in multiple and we get an increased current or 40 amperes and 6 volts, which is the capacity of the eight cells connected as shown in the figure. This is commonly designated as a multiple-series battery.

Fig. 256 D illustrates a multiple-series connection made in a different manner, but which produces the same voltage and current as the above mentioned. In Fig. D, two cells at a time are connected in multiple, and these sets are then connected in series. The capacity of each set of two is 40 amperes at 1½ volts, and as these four sets are connected in series the total output of the eight cells combined is 6 volts and 40 amperes, the same as that produced by the connections shown in Fig. C.

Fig. E shows the multiple-series connection illustrated in Fig. D, applied to twelve cells in which four sets of three cells each are wired in series, the three cells of a set being in multiple so that the capacity of a set is 1½ volts and 60 amperes. By connecting the four sets in series as shown, the total capacity will be 60 amperes at 6 volts.

The use of the series-multiple connection is a distinct step forward in dry-cell use. The arrangement of cells shown in Figs. C or D is better than the arrangement in Fig. A, in just the same way that a team of horses is better than a single horse. One horse pulling a load of 2 tons may become exhausted in one hour, but two horses pulling that same load may work continuously for six hours. It is true that in Fig. C there are twice as many cells used as in Fig. A, but the eight cells in Fig. C will do from three to four times as much work as the four cells in Fig. A. In other words, while more cells are used in the multiple-series arrangement, the amount of service per cell is greater and the service is, therefore, cheaper in the multiple-series arrangement.

Some battery manufacturers sell their batteries put up in boxes, the cells being connected up in multiple-series and surrounded by pitch or tar to keep out the moisture. This has certain advantages as well as certain disadvantages. One of the objections to this method of putting up dry cells is that if by any chance one cell out of the eight or twelve which are buried in the pitch is defective it will run all of the cells down, and being buried offers no means of detection or removal. It is not possible to guarantee absolutely that a weak cell will not be occasionally included in a large number, so dry cells may be expected to vary to some degree among themselves.

It is interesting to know the effect of one weak cell on a series-multiple arrangement. If, for example, in Fig. C or Fig. D, the dotted line connecting (a) and (b) be used to indicate a cell which is partly short-circuited by internal weakness or external defect the result is as follows:

In the arrangement shown in Fig. C, where one cell of the upper four is short-circuited, the lower four will discharge through the upper four even though the external circuit is not closed; that is, one short-circuited cell will cause a run-down in all of the cells. In Fig. D, however, one short-circuited cell will influence not the entire set but the other one to which it is directly connected. There is thus seen to be an advantage in the arrangement of Fig. D and Fig. E, over the arrangement in Fig. C.

In making connections between cells insulated wire should be used, or special battery connectors are preferably employed. The ends of the wires or connectors and the binding posts must be scraped clean so that good electrical connection can be made between the two, and the knurled nuts should be screwed tight into place. Care must also be taken that the pasteboard covering around the battery is not torn. This would allow contact between the zinc containers, and thus short-circuit the cells. The batteries should be placed so that the zinc cans and the binding posts of any cell do not come into contact with any other cell. Vibration might cause enough motion for the brass terminal to wear through the pasteboard of the neighboring cell and make contact with the zinc can.

Different classes of work require different amounts of current at different voltages and by choosing the proper combination of series, multiple, or series-multiple connections practically every requirement can be fulfilled. For electric bells, telegraph instruments, miniature lights, toy motors with fine wire windings, etc., series connection is recommended for the reason that the resistance of the external circuit is high and a large voltage is necessary. For spark coils, magnets and toy motors with large wire windings, multiple or series-multiple connection of batteries should be used as a high voltage is not required.

For some work, gas-engine ignition especially, it is economical to have two complete sets of batteries, either of which can be thrown into the circuit at will, so that while one set is delivering current the other is recuperating. It has been estimated that by using two sets of batteries, properly connected to give the desired current, the life of each set is increased about four times. Thus it is seen that a saving of 50 per cent. is effected in the cost of the batteries.

Battery Testers.

—The “strength” of a cell is determined by the amperes of current it is capable of producing; therefore, a meter that will indicate the amount of current being produced is used to test the current strength of the cell. Battery testers are made to indicate voltage or amperage and sometimes the instrument is made to indicate both volts and amperes. As explained above, the voltage of a cell is not a true indicator of its strength. The ampere meter or ammeter, as it is termed, is the proper indicator of the strength of the cell.

Fig. 257.—Battery tester.

The common battery tester does not always give the exact number of amperes of current, but it indicates the relative strength which is really the thing desired. When the current from an active cell is once shown on the dial of the tester, any other cell of the same intensity will be indicated in like amount.

Electric Conductors.

—Covered wire for carrying electricity is made in a great variety of forms and designated by names that have been suggested by their use. These wires are made of a single strand or in cables, where several wires are collected, insulated and formed into a single piece. Cables may contain any number of insulated wires.

The sizes of wires are determined by a wire gage. In the United States the B. & S. gage is used as the standard for all wires and sheet metal. The gage originated with the Brown & Sharp Mfg. Co. of Providence, R. I., and has become a national standard by common consent. The numbers range from No. 0000 to No. 60. The size of wire for household electrical service ranges from No. 18 which is 0.04 inch in diameter to No. 8 which is 0.128 inch across. The carrying capacities in amperes of wires, as given by the Underwriters’ table of sizes from No. 8 to No. 18, are as follows:

Wire
gage No.		Rubber
insulation,
amperes		Other
insulation,
amperes
83550
102530
122025
141520
16610
1835

Lamp Cord.

—The flexible cord used for drop lights, connectors, portable lamps, extensions, etc., is made of two cords twisted together or two cords laid parallel and covered with braided silk or cotton. The conductors consist of a number of No. 30 B. & S. gage, unannealed copper wires twisted into a cable of required capacity. The conductor is wound with fine cotton thread over which is a layer of seamless rubber, and the whole is covered with braided cotton or silk. Lamp cord is sold in three grades, old code, new code, and commercial, which vary only in the thickness and quality of rubber which encloses the conductor.

The new code lamp cord is identical with the old code form except that it is required by the National Board of Fire Underwriters to be covered with a higher quality of rubber insulation than was used in the old form. The commercial cord is not recognized by the National Board of Underwriters. It is practically the same as that described but does not conform to the tests prescribed for the new code cord.

The sizes of the conductors enclosed in the lamp cord are made equal in carrying capacity to the standard wire gage numbers. The sizes ordinarily used are No. 18 and 20 gage but they are made in sizes from No. 10 to No. 22 of the Brown & Sharp gage.

Portable Cord.

—This is a term used to designate reinforced lamp cord. The wires are laid parallel and are covered as with a supplementary insulation of rubber. The additional insulation and the braided covering assumes a cylindrical form. The covering is saturated with weatherproof compound, waxed and polished.

Annunciator Wire.

—This wire is made in the usual sizes and covered with two layers of cotton thread saturated with a special wax and highly polished. As the name implies it is used for annunciators, door bells and other purposes of like importance.

Private Electric Generating Plants.

—The conveniences to be derived from the use of electricity were for many years available only by those who lived in distributing areas covered by commercial electrical generating plants. Except in towns of sufficient size to warrant the erection of expensive light and power systems or along the lines of electric power transmission, current for domestic purposes was not obtainable.

Within a comparatively few years there have been developed a number of small electric generating systems that are suitable for supplying the average household with the electric energy for all domestic conveniences. The combination of the gasoline engine, the electric dynamo and the storage battery have made possible generating apparatus that is operated with the minimum of difficulty and which supplies all of the electric appliances that were formerly served only from commercial electric circuits.

An electric generating system is commonly termed an electric plant. It consists of an engine for the development of power, a dynamo for changing the power into electricity and—to be of the greatest service—a storage battery for the accumulation of a supply of energy to be used at such times as are not convenient to keep the dynamo in active operation.

Such a combination, each part comprised of mechanism with which the average householder is unfamiliar, seems at first too great a complication to put into successful practice. Such, however, is not the case. The operation of small electric generating plants is no longer an experiment. Their general use testifies to their successful service. The working principles are in most cases those of elementary physics combined with mechanism, the management of which is not difficult to comprehend. Such plants are made to suit every condition of application and at a cost that is condusive to general employment.

In a brief space it is not possible to enter into a detailed discussion of the gasoline engine, the electric dynamo, and the storage battery with the various appliances necessary for their operation; it is, therefore, intended to give only a general description of the leading features of each. The manufacturers of such plants furnish to their customers and to others who are interested detailed information with explicit instructions for their successful management.

The first private lighting plants were made up of parts built by different manufacturers and assembled to form generating systems with little regard to their adaptability. A gasoline engine belted to a dynamo of the proper generating capacity supplied the electricity. Neither the engines nor the dynamos were particularly suited to the work to be performed, yet these combinations were sufficiently successful to command a ready sale. The energy thus generated was accumulated in a storage battery from which was taken the current for a lighting and heating device. Besides the generating and storage apparatus there is required in such a system, a switchboard, to which are attached the necessary meters and switches that are required to measure and direct the current to the various electric circuits.

Foresighted manufacturers, comprehending the probable future demand, began the construction of the various parts, suited to the work and the conditions under which they were to be employed. The manufacture of apparatus, designed for the special service and composed of the fewest possible parts, has reduced the operating difficulty to a point of relative simplicity. Experience in the use of a large number of these plants has revealed to the maker the course of many minor difficulties of operation and the means of their correction. The mechanism has been improved to prevent possible derangement and to simplify the means of control, until the private electric plant is successfully employed by those who have had no former experience with power-generating machines.

Fig. 258.—Household electric generating plant.

As an example of the private electric plant Fig. 258 shows the apparatus included in a combined engine, dynamo and switchboard, connected with a storage battery. The relative size of the machine is shown by comparison with the girl in the act of starting the motor. This plant is of capacity suitable for supplying an average home with electricity for all ordinary domestic uses. A nearer view of the generating apparatus is given in Fig. 259 in which all of the exterior parts are named. An interior view of the generating apparatus is given in Fig. 260, in which is exposed all of the working parts. The right-hand side of the picture shows all of the parts of the gasoline engine that furnishes the power for driving the generator. This is an example of an air-cooled gasoline engine in which the excess heat developed in the cylinder is carried away by a drought of air. The air draft is induced by the flywheel of the engine, which is constructed as a fan. The blades of the fan, when in motion, are so set as to draw air into the top of the engine casing and exhaust it from the rim of the wheel. The air in passing takes up the heat in excess of that necessary for the proper cylinder temperature. This form of cylinder cooling takes the place of the customary water circulation and thus eliminates its attending sources of trouble. In principle the engine is the same as is employed in automobiles and other power generation.

Fig. 259.—Combined motor, electric generator and switchboard.

On the left-hand side is seen the dynamo and switchboard. The dynamo armature is attached to the crankshaft of the engine by which it is rotated in a magnetic field to produce the desired amount of electricity. The brushes, in contact with the commutator, conduct the electricity as it is generated in the armature, which after passing through the switchboard is made available from the two wires at the top of the board marked “light and power wires.” These wires are connected with the storage battery and also to the house circuits through which the current is to be sent.

Fig. 260.—Details of motor, electric generator and switchboard.

Referring to the switchboard of Fig. 259, the three switches and the ammeter comprise the necessary accessories. The starting switch is so arranged that by pressing the lever a current of electricity from the storage battery is sent through the dynamo. The dynamo acting as a motor starts the engine. When the engine has attained its proper speed its function as a dynamo overcomes the current pressure from the battery and sends electricity into the cells to restore the expended energy, or if so desired the current may be used directly from the dynamo for any household purpose. The box enclosing the switch contains a magnetic circuit-breaker so constructed that when the battery is completely charged the switch automatically releases its contact and stops the engine.

The “stopping switch” at the right of the board and the “switch for light and circuit” on the left are used respectively for stopping the engine and for opening and closing the house circuits.

The meter performs a multiple function, in that it shows at any time the condition of charge in the storage battery, the rate at which current is entering or leaving the battery and also acts to stop the engine when the battery is charged. At any time the pointer reaches the mark indicated in the picture, the ignition circuit is automatically broken and the engine stops. The fuses on the board in this case perform the same function as those already described.

Storage Batteries.

—These batteries have already been mentioned as secondary batteries. They are sometimes called electric accumulators. The electricity is stored or accumulated, not by reason of the destruction of an electrode as in the primary cell but by the chemical change that takes place in the plates as the charging current is sent through the cell. When the battery is discharged, the current from the dynamo is sent through the battery circuit in the reverse direction to that of the discharge and the plates are restored to their original condition. The action that takes place in charging and discharging is due to chemical changes that take place in the plates and also in the solution or electrolyte in which the plates are immersed.

There are two types of storage batteries, those made of lead plates immersed in an acid electrolyte and the Edison battery which is composed of iron-nickel cells immersed in a caustic potash electrolyte. The former type is most commonly used and is the one to be described.

The lead-plate cell illustrated in Fig. 262 shows all of the parts of a working element. The plates are made in the form of lead grids which when filled to suit the requirements of their action, form the positive and negative electrodes. The negative plates are filled with finely divided metallic lead which when charged are slate gray in color. The positive plates are filled with lead oxide. When charged they are chocolate brown in color. In the figure there are three positive and four negative plates which together form the element, then with their separators are placed in a solution of sulphuric acid electrolyte. The separators are thin pieces of wood and perforated rubber plates that keep the positive and negative plates from touching each other and keep in place the disintegration produced by the electro-chemical action of the cell.

The unit of electric capacity in batteries is the ampere-hour. The cell illustrated will accumulate 80 ampere-hours of energy. It will discharge an ampere of current for 80 hours. If desired it may be discharged at the rate of two amperes for 40 hours, or four amperes for 20 hours, or at any other rate of amperes and hours, the product of which is 80. The number of ampere-hours a cell will accumulate will depend on the area of the positive and negative plates; large cells will store a greater number of ampere-hours than those of small size.

The cells, no matter what size, give an average electric pressure of 2 volts.

The plates are joined by heavy plate-straps connecting all of the positives on one end and all of the negative kind on the opposite end. To insure rigidity the two sets are secured to the rubber cover by locknuts. In this cell the plates are suspended from the cover. The plate terminals are made of heavy lead connectors that when formed into a battery are joined together with lead bolts and nuts.

Fig. 261.—Hydrometer for testing storage battery electrolyte.

The electrolyte is a solution of pure sulphuric acid in distilled water and on its purity depends, in a great measure, its action and length of life. The electrolyte is made of a definite density which is expressed as its specific gravity. When fully charged the electrolyte will test 1220 by the hydrometer. That is, it will be 1.220 heavier than water. When discharged it will test by the hydrometer 1185. This means that in discharging the density has been reduced to 1.185 that of water. The chemical change in the electrolyte is, therefore, an important part of the charge and discharge of the cell. The density of an electrolyte may be determined by a hydrometer such as Fig. 261. This is an ordinary glass hydrometer such as is used for determining the density of fluids, enclosed in a glass tube, to which is attached a rubber bulb. The point of the tube is inserted into the opening at the top of the cell and the electrolyte drawn into the tube by the reopening of the collapsed bulb. The density is then read from the stem of the hydrometer.

The Pilot Cell.

—In order to make apparent this density of the electrolyte without the necessity of its measurement with a hydrometer, one cell of the battery is provided with a gage as that of Fig. 262. This is an enlargement of the end of the jar in which floats a hollow glass ball of such weight that it will at any time indicate by its position the relative density of the solution. When the cell is charged the ball stands at the top of the gage and indicates a density 1220; when discharged it is at the bottom and expressed by its position a density of 1185. The electrolyte densities are the indicators of the conditions of charge. The ball by its position shows at a glance the quantity of electricity in the battery.

The voltage usually employed in household electric plants is that of a battery composed of 16 cells. Since the normal voltage of a storage cell is 2 volts such a battery joined in series is 32 volts. This voltage for the purpose fulfills all ordinary conditions and is generally employed. A battery of 16 cells, of 80-ampere-hour capacity, will deliver current of 1 ampere for 80 hours at 32 volts intensity. A 20-watt lamp on a 32-volt circuit requires 2⁄3 ampere for its operation. The battery will, therefore, keep lighted one such lamp for 96 hours, or four 20-watt lamps may be lighted continuously for 24 hours, or eight lamps for 12 hours, before recharging.

Aside from its ability to supply the required light for the average home, it furnishes energy sufficient for heating a flat-iron or other heating apparatus, to operate motors for pumping water, driving a washing machine or any other of the domestic requirements.

Such plants are made in sizes to suit any condition of requirement. In large establishments a larger motor generator and battery will be necessary with which to generate and store the required electricity but in any case suitable apparatus is to be obtained to meet any requirement of light, heat or power developed.

Fig. 262.—Electric storage cell.

National Electrical Code.

—The details governing the size, the manner of placing and securing wires in buildings is included in the regulations published by the National Board of Fire Underwriters as the National Electric Code. Likewise the mechanical construction of all apparatus dealing with electric distribution is definitely specified so that manufacturers furnish reliable materials for all requirements. In the specifications for furnishing buildings with the use of electricity, descriptions are made of the desired types and styles of the switches and various other fixtures to suit the requirements.

Electric Light Wiring.

—In the equipment of a house for the use of electricity, the wiring, together with distributing panel, the various outlets, receptacles, switches, and other appliances that make up the system, is of more than passing consequence. In the construction of the electric system it is important that the wires and their installation be done in a manner to meet every contingency.

The following descriptions for electric house wiring were taken from a set of specifications published by the Bryant Electric Co. as applying to buildings of wood frame construction. The specifications serve as explanations for the appliances required in an ordinary dwelling. The specifications are for the least expensive form of good practice in wiring for frame buildings. They would not be permitted in large cities where further protection from fire is required and where more rigid rules are demanded by the Board of Fire Underwriters.

1. System.—The circuit wiring shall be installed as a two-wire direct current or alternating system. Not more than 16 outlets or a maximum of 660 watts shall be placed on any one circuit, allowing 110 watts for each baseboard plug connection or extension outlet and 55 watts for each 16 candlepower lamp indicated at the various wall and ceiling outlets on plans. All wiring shall be installed as a concealed knob-and-tube system.

The type of wiring is designated as a two-wire direct or alternating current system in order that there shall be no doubt as to the method of wiring to be used. There are other methods that might be employed that need not be discussed here.

The 16 outlets mentioned are intended to cover all lamps or plug attachments that are to be used for heaters, fans, motors, or any other electric device. The 660 watts at 110 volts pressure will require 6 amperes in the main wires of the circuit, which is the maximum current the wires are intended to carry. This does not mean that 110-watt lamps might not be used but that no single circuit shall carry lamps that will aggregate more than 660 watts.

The concealed knob-and-tube system mentioned is illustrated in Figs. 263 and 264, in which the wires which pass through joists and studding are to be insulated by porcelain tubes and those wires which lay parallel to these members are to be fastened to porcelain knobs which are secured by screws to the wood pieces to prevent any possibility of coming into contact with electric conducting materials.

Fig. 263.—Manner of securing wires by the knob-and-tube system for ceiling outlets.

2. Outlets.—At each and every switch, wall, ceiling, receptacle or other outlet shown on plans, install a metal outlet box of a style most suitable for the purpose of the outlet. All outlet boxes must be rigidly secured in place by approved method and those intended for fixtures shall be provided with a fixture stud, or in the case of large fixtures, a hanger to furnish support independent of the outlet box.

Outlet Boxes.

—For the safe and convenient accommodation of switches, receptacles or other connections in the walls and ceilings of a building, outlet boxes are used as a means of securing the wire terminals to the receptacles. These boxes are made in a number of forms for general application. One style is shown in Fig. 265. The boxes are made of sheet steel and arranged to be secured in place with screws. The box is further provided with screw fastenings to which the switch or receptacle may be firmly attached.

Fig. 264.—This shows the knob-and-tube system of securing the wires in partitions and the manner of fastening metal “cut out” boxes; for switch, attachments, plugs, etc.

3. Installation of Wires, Etc.—All wires shall be rigidly supported on porcelain insulators which separate the wire at least 1 inch from the surface wired over. Wires passing through floors, studding, etc., shall be protected with porcelain tubes, and where wires pass vertically through bottom plates, bridging, etc., of partitions, an extra tube shall be used to protect wires from plaster droppings. Wires must be supported at least every 4 feet and where near gas or water pipes extra supports shall be used. All porcelain material shall be non-absorptive and broken or damaged pieces must be replaced. Tubes shall be of sufficient length to bush entire length of hole. At outlets the wires shall be protected by flexible tubing, the same to be continuous from nearest wire support to inside of outlet box. Wires installed in masonry work shall be protected by approved rigid iron conduit which shall be continuous from outlet to outlet.

The method and reasons for supporting the wires described above are as have already been mentioned under item 1. The reason for extra supports near gas pipes and water pipes is as a precaution against the possibility of short-circuiting.

Fig. 265.—Outlet box.

4. Conductors.—Conductors shall be continuous from outlet to outlet and no splices shall be made except in outlet boxes. No wire smaller than No. 14 B. & S. gage shall be used and for all circuits of 100 feet or longer, No. 12, B. & S. gage or larger shall be used. All conductors of No. 8 B. & S. gage or larger shall be stranded. Wires shall be of sufficient length at outlets to make connection to apparatus without straining connections. Splices shall be made both mechanically and electrically perfect, and the proper thickness of rubber and friction tape shall be then applied.

Continuous conductors are required because of the possibility of defects in the joints of spliced wire.

5. Position of Outlets.—Unless otherwise indicated or directed, plug receptacles shall be located just above baseboard; wall brackets, 5 feet above finished floor in bedrooms, and 5 feet 6 inches in all other rooms; wall switches, 4 feet above finished floors. All outlets shall be centered with regard to panelling, furring, trim, etc., and any outlet which is improperly located on account of above conditions must be corrected at the contractor’s expense. All outlets must be set plumb and extend to finish of wall, ceiling or floor, as the case may be, without projecting beyond same.

6. Materials.—All materials used in carrying out these specifications shall be acceptable to the National Board of Fire Underwriters and to the local department having jurisdiction. Where the make or brand is specified or where the expression “equal to” is used, the contractor must notify the architect of the make or brand to be used and receive his approval before any of said material is installed. Where a particular brand or make is distinctly specified, no substitution will be permitted.

7. Grade of Wire.—The insulation of all conductors shall be rubber, with protecting braids, which shall be N.E.C. Standard (National Electrical Code Standard).

8. Outlet Boxes.—Outlet boxes shall be standard pressed steel, knock-out type and shall be enameled.

9. Local Switches.—Local wall switches shall be two-button flush type completely enclosed in a box of non-breakable insulating material with brass beveled-edge cover plate finished to match surrounding hardware.

Fig. 269 shows the various forms and grades of switches that there are on the market. The screws which attach the plate to the switch enter bushings that are under spring tension thereby preventing defacement of the plate by overtightening of the screws. Single-pole is to be used where the load will not be in excess of 660 watts; double-pole to be used where the load is more then 660 watts or where for any other reason it is desirable to break the current at both wires. Three-point switches are to be used when a light or group of lights is to be controlled, as hall lights that may be lighted or extinguished, from either the top or at the bottom of a stairway. Four-point switches are to be used between and two, three-point switches to control additional lights. Where two or more switches are placed together an approved gang plate is to be provided which designates the use of each switch. Where indicated on the plan, clothes closets shall be equipped with automatic door switch to connect the light when the door is open.

10. Pilot Lights.—Switches controlling cellar, attic and porch lights shall have pilot lamp in parallel on the load side of the switch. The switch in Fig. 3 requires for its installation a two-gang outlet box. The ruby bull’s-eye which covers the lamp is practically flush, extending from the wall no further than the buttons of the switch.

Pilot lights are intended to indicate the operation of other lights or apparatus that cannot be directly observed.

The term bull’s-eye applies to a colored-glass button covering a miniature lamp which burns whenever a light is used which is apt to be forgotten and allowed to burn for a longer time than necessary.

11. Plug Receptacles.—Plug receptacles shall be of the disappearing-door type, with beveled-edge brass cover plate finished to match surrounding hardware (see Fig. 266). In this receptacle the doors are pushed inward by the insertion of the plug and upon its withdrawal close automatically, effectually excluding dirt and concealing the live terminals. It is the latest and best plug receptacle obtainable.

Plug receptacles are the attachments for the terminal pieces of plugs, which temporarily connect portable lamps, electric fans or other devices, they are made in many forms.

12. Wall and Ceiling Sockets.—One-light ceiling receptacles shall be of a type to fit standard 3¼-inch or 4-inch outlet boxes. Wall sockets shall be of the insulated base type. Sockets in cellars shall be made entirely of porcelain and of the pull type. All lamp sockets used in fulfilling these specifications shall have an approved rating of 660 watts, 250 volts.

13. Drop Lights.—Drop lights shall consist of the necessary length of reinforced cord supported by an insulated rosette with brass base and cover; the latter to cover 4-inch outlet box, and furnished with a key socket complete with a 2¼-inch shade-holder. Each drop cord shall have an adjuster.

14. Heater Switch, Pilot and Receptacle.—Heating device outlets shall be equipped with combination of switch, pilot light and receptacle with plug and spare pilot lamp.

15. Service Switch.—The service-entrance switch shall be 30 amperes, porcelain base with connections for plug fuses.

Installation of Service Switch.—Service switch shall be installed in a moisture-proof metal box with hinged door.

Panel Cabinet.—The distributing panel cabinet shall be of steel not less than No. 12 gage reinforced with angle iron frames, which shall be securely riveted in place. Cabinet shall be larger than panel to give at least 4-inch wire space around panel and shall be given at least two coats of moisture-repellant paint.

Distributing Panel.—The distributing panel shall consist of two-wire 125-volt branch cutouts, two-wire 125-volt porcelain-base panel-board units, two-wire 125-volt porcelain-base deadfront panel-board units. The distributing panel shall be surrounded with an ebony asbestos or slate partition ½ inch thick which will form a wire space around panel.

Fuses.—All fuses for branch circuits shall be not more than 10 amperes capacity. The contractor shall furnish the owner with 150 per cent. of required number of 125-volt plug-type fuses for complete installation.

Panel Trim and Door.—The panel trim and door shall be of steel, with brass cylinder lock and concealed hinges, all furnished under this contract. A directory of circuits and outlets served by panel shall be enclosed in glass with metal frame, mounted on inside of panel door.

Hardware.—All hardware furnished under this contract shall match in quality and finish other adjacent hardware.

Three-way Control.—The nearest outlet at top and bottom of all stairs and in entrance hall shall be controlled by three-way switches located on separate floors where directed.

Electrolier Control.—Wherever there are ceiling outlets for fixtures having three or more sockets controlled by wall switches three wires shall be run between the switch box and the outlet to permit the use of electrolier switches.

Dining-room Circuit.—Furnish and install in dining-room, where indicated on plans, an approved floor box containing an approved 25-ampere plug receptacle. The wires connecting this receptacle to the center of distribution shall be No. 10 B. & S. gage. Furnish and deliver to whom directed an approved multiple-connection block consisting of three individually fused plug receptacles. The connection between the plug receptacle and this block shall be made by means of 10 feet of No. 10 B. & S. approved silk-covered portable cord with an approved 20-ampere cord connector 2 feet from the multiple block.

House Feeders.—The size of the feeder from the service switch to the panel board shall be figured in accordance with the National Code rules for carrying capacity, allowing for all circuits being fully loaded. The feeder shall be of sufficient size, however, to confine the drop in voltage with all lights in circuit to 1 per cent. of the line voltage.

Service Connection.—Make extension of house feeder overhead to lighting company’s mains and make all connections complete to the satisfaction of the light company and the architect. Furnish and install the necessary frame or backboard for meter.

Call Bells.—The contractor shall furnish, install and connect all push buttons, bells, buzzers and annunciators, as shown on plans or therein described. All wiring shall be cleated in joists, studs, etc., with insulated staples. Damp places, metal pipes of all descriptions, flues, etc., must be avoided and wire fastenings must be applied in such a way that insulation is not damaged. No splices shall be made where same will not be accessible at any time after completion of building. Wires shall not be smaller than No. 18 B. & S. gage and shall be damp-proof insulated. Bells, buzzers, buttons, etc., shall be of approved make. Push button for main entrance door shall be provided with ornamental place with approved finish. Push button in dining-room shall consist of combination floor push, with necessary length of flexible cord and approved portable foot push. Furnish and install where directed three cells of carbon cylinder battery in a substantial cabinet.

Burglar Alarm.—Furnish and install complete burglar alarm system consisting of the necessary wires, window springs, door springs, night latch cutout for front door, bell, batteries, cabinet, interconnection strip, etc., and everything required for a complete open-circuit system. Each window sash and door throughout the building shall be equipped with contact spring of approved make and all springs on same side of building on each floor shall be wired on one circuit and terminated on single-pole knife switch on interconnection strip. The interconnection strip shall be located as directed and shall have cutout switches for each circuit as well as a double-pole battery switch. The battery shall consist of at least three dry cells in suitable cabinet placed where directed and both positive and negative leads shall be carried direct to interconnection strip. The burglar-alarm wires shall be not less than No. 16 B. & S. gage, insulated and installed as specified for call bells.

Intercommunicating Telephones.—Furnish and install an intercommunicating telephone system complete with all telephone sets, wiring, batteries, etc. All wires to be cables containing one pair of No. 22 B. & S. gage conductors for each station and a pair of No. 16 B. & S. gage conductors for talking and ringing battery respectively. Each pair of wires shall be twisted and all pairs shall be twisted around each other to eliminate cross talk and inductive noises. The wires shall be silk insulated, with a moisture repellent of beeswax or varnish and the whole covered with a lead sheath at least 1⁄64 inch in thickness. Where cables terminate in outlet boxes they shall be fanned out and laced in an orderly manner and secured to connecting terminals, one of which shall be provided for each wire. Install where directed in an approved cabinet at least four cells of dry battery each, for talking and ringing purposes.

Installation of Interphone Cable.—Intercommunicating cables shall be supported with pipe straps and liberal clearance shall be observed where near steam or other pipes.

Automatic Door Switch.

—Where indicated on the plan, clothes closets shall be equipped with automatic door switch to connect the light when the door is open.

Fig. 266 is placed in the door frame in such position that electric contact is made by release of the projecting pin as the door is opened. When the door is closed, the pin is depressed and the light is extinguished

Plug Receptacles.

—Plug receptacles shall be selected from the styles shown in Figs. 267,a, b, c or d.

Fig. 266.—Automatic door switch.

Fig. 267,a is the disappearing-door type with beveled-edge brass cover plate finished to match surrounding hardware. In this receptacle the doors are pushed inward by the insertion of the plug and upon its withdrawal close automatically, effectually excluding dirt and concealing the live terminals. It is the latest and best plug receptacle obtainable.

Fig. 267,b is of the Chapman type with beveled-edge brass cover plate finished to match surrounding hardware. In this receptacle the doors open outward but are flush whether the plug is in or out.

Fig. 267.—Styles of plug receptacles.

Fig. 268.—Heating-device receptacles.

Fig. 267,c is of the screw-plug type with beveled-edge brass cover plate finished to match surrounding hardware. By many this is preferred for apartment use as it will receive any style of Edison attachment plug.

Fig. 269.—Service switches.

Fig. 267,d is of the removable-mechanism type with beveled-edge brass cover plate finished to match surrounding hardware. The mechanism of this receptacle is exchangeable with the mechanism of the double-pole switch as shown in Fig. 270,c.

Heater Switch, Pilot and Receptacle.

—Heating-device outlets shall be equipped with combination of switch, pilot light and receptacle with plug and spare pilot lamp. Figs. 268,a, b, c and d, represent various forms from which selection may be made. All are adapted for the same purpose and differ only in mechanical arrangement.

Fig. 270.—Local wall switches.

Service Switch.

—The service entrance switch may be selected from the three styles shown in Figs. 269,a, b, and c.

Fig. 271.—Pilot lights.

Fig. 272.—Wall and ceiling sockets.

Fig. 269,a is composed of a 30-ampere porcelain base with connections for plug fuses.

Fig. 269,b is a slate base with connections for cartridge fuses.

Fig. 269,c is a slate base with connections for open-link fuses

Local Switches.

—Local wall switches may be selected from the various styles shown in Figs. 270,a, b, c, d and e.

Fig. 270,a is the two-button flush type completely enclosed in a box of non-breakable insulating material with brass beveled cover plate finished to match surrounding hardware.

Fig. 273.—Drop-light attachments and lamp bases.

Fig. 270,b is a two-button flush type with brass beveled-edge cover plate finished to match surrounding hardware.

Fig. 270,c is of the removable-mechanism type with brass beveled-edge cover plate finished to match surrounding hardware.

Fig. 270,d is the single-button flush type with brass beveled-edge cover plate finished to match surrounding hardware.

Fig. 270,e is the rotary-flush type with brass beveled-edge cover plate finished to match surrounding hardware.

Pilot Lights.

—Switches controlling cellar, attic and porch lights may be either Fig. 270,a or b.

Fig. 270,a requires for its installation a two-gang outlet box. The ruby bull’s-eye which covers the lamp is practically flush, extending from the wall no further than the buttons of the switch.

Fig. 270,b is installed in a single-gang box. The lamp extends through the plate and is protected by a perforated cage which extends about an inch from the plate.

Wall and Ceiling Sockets.

—One-light ceiling receptacles may be selected from the types shown in Figs. 272,a, b, c, d and e.

Fig. 272,a is of a type to fit standard 3¼-inch or 4-inch outlet boxes.

Fig. 272,b is of the small concealed-base type.

Fig. 272,c is of the large concealed-base type.

Fig. 272,d is of the insulated-base type.

Fig. 272,e is of the porcelain-base type.

Sockets in cellars shall be made entirely of porcelain. Those in bathrooms shall be entirely of porcelain and of the pull type.

Drop Lights.

—Drop lights shall consist of the necessary length of reinforced cord supported by either brass or porcelain bases. Each drop cord to have an adjuster. Figs. 273,a, b, c, d, e, f, g, illustrate the various styles. Fig. 273,h is a shade holder to be used with the drop lights.

INDEX