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