Incandescent Electric Lighting/House
House Lighting.
In laying the mains along a street, suitable junction boxes for branch circuits are inserted in the line at points opposite the buildings in which lights are to be used, whence wires of a proper size to carry the current to be used are led into the buildings. Taking one of these branch circuits, or house "Services," for example, we lead it underground through a tube similar to those laid along the street until the wires enter the cellar or basement of the building. Here they are connected to a three-wire cut-out, and are then led to the meter. This cut-out is to provide against a larger amount of current than is necessary for the number of lamps to be used entering the house. The meter is also proportioned in size to the number of lamps employed. After passing through the meter, the wires are led to an elevator shaft, hallway, or suitable space provided in the walls for this purpose, as nearly central as may be, and are carried up to the topmost floor to be lighted. On each floor the wires pass through what is known as a pocket, which is generally a boxed-up space provided with a door for easy access to the enclosure.
In this pocket are arranged a number of cut-outs and switches corresponding to the number of branch circuits to be run to the several rooms on that floor. At this pocket, by turning the proper switch » lights may be turned on in any room before entering it, or the current may simply be turned on, and the lights on that branch be cut in one by one by turning the keys with which each socket is provided.
For large chandeliers, a switch is generally arranged against the walls, at some suitable point in the room by which all the lamps on the chandelier may be turned on at one and the same time.
Arrangements are often provided by which lamps may be turned on in the hall at the front door, and extinguished from the top of the stairs, thus allowing one to have a light before them in whatever part of the house they may choose to go. This is a matter of economy as well as convenience, for it allows of lamps being lit only when and where needed, enabling occupants to use light only in the rooms occupied, while the rest of the house remains in darkness that may be dissipated in an instant at the will of any individual occupant.
Lights outside as well as in are equally under control, and the coming or retiring guest may be lighted to the farthest point of the most extensive grounds without the necessity of the host being in any way exposed to the weather. To crown all, these luxurious conveniences are furnished at a price to place them within the reach of persons of but ordinary means. After the plant is once installed there is only the cost of the light actually used. No leaking taps, or defective joints, no smoke or smell, or dirt— those unpleasant features inherent in all other forms of artificial illumination.
The various devices once placed are likely to last under ordinary usage as long as the householder will probably live to enjoy them; the only exception to this general statement being the lamp itself which, with the proper current for which it is constructed, is guaranteed to last one thousand hours. As the lighting company replace all lamps burned out and, as they control the current to which they are subjected, there is no reason to doubt that their life will be prolonged to the utmost limit consistent with their being burned at their full
"Candle-power," which is that of an ordinary gas jet, from a two-foot burner.
The term candle-power refers to the standard wax candle, which is the unit of illumination adopted in grading electric lights; the lamps commonly used in dwellings being rated as giving a light equivalent to that of sixteen standard candles.
In addition to the large number of advantages possessed by the electric light over all other forms of artificial illumination, it may be said to be far in advance of all others in the readiness with which it may be adapted to all forms of decoration.
It may be mounted in chandeliers, supported in brackets, fixed directly to walls and ceilings in any and every conceivable position, or allowed to hang at the ends of flexible cords. The globes may be of all colors, and the best talent of the civilized world has been levied upon the production of beautifully designed fixtures to receive them, as well as globes, shades, and reflectors to modify the lights and enhance the beauties of its effects. Like the light of the sun, it beautifies all things on which it shines, and is no less welcome in the palace than in the humblest home.
We have endeavored in the preceding pages to state the fact clearly that in the Edison three-wire system of incandescent electric lighting the pressure upon the wires is kept constant. A constant pressure implies a constant current, to measure which the Edison meter has been invented. Mr. Edison is the fortunate possessor of that rare combination of faculties, superior inventive ability, supplemented by unusual business qualifications and, to his intimates, the fact that he has invented a device is a sufficient guarantee of its commercial utility.
The foregoing statement holds good with regard to the Edison meter for the measurement of the electric current supplied to one or more incandescent lamps, and is called up by the fact that upon the introduction of this meter the claim that it was practical in its operations and sufficiently accurate to form the basis for the chains to be made the users of light, was ridiculed by many who would be well pleased had they withheld their opinions till time and use had paved the way for a more just decision upon the merits of the piece of apparatus in question. Time and daily use have proven the Edison meter not only reliable but beyond that, a standard for charges satisfactory both to the furnishers and users of the electric light.
Fig. 25.—Three-wire meter, open.
Its operations are based upon the well-known electrolytic action, which causes two zinc plates immersed in a solution of zinc sulphate to vary their respective weights in proportion to the current passing through them. This will be understood by referring to the cut Fig. 25, which shows a three-wire meter with the front of the case removed.
The cut shows the meter case divided by a partition arranged across its centre, the space above it being occupied by the bottles or jars, containing the zinc plates, immersed in the zinc sulphate solution.
Fig. 26—Meter bottle.
These bottles. Fig. 26, are provided with glass tops, held in place by screw ring, the glass tops having holes in them, through which pass the copper stems of the zinc plates, to engage with the spring clips arranged above the bottles, and serving both to hold the bottles in place and to connect the plates with small wires, leading to the space below the partition. The zinc plates are kept a proper distance apart by hard rubber fittings, which are also arranged to keep the plates from resting upon the bottom of the bottle.
The small wires before mentioned as passing from the clips above the bottles to the lower space of the meter box lead the current to the zinc plates in such a manner that it must pass from one plate to the other through the zinc solution. In doing this the current detaches particles of zinc from one of the plates and transfers them to the other, thus decreasing the weight of the first plate. One ampere, acting for one hour, will deposit a known amount of zinc upon the negative plate in the bottle; and it is by removing and weighing the plates that the amount of current which has passed through the meter is ascertained.
The bottles are arranged in the meters in pairs, two pairs being used in the large sizes of three-wire meter to insure by comparison greater accuracy in determining the amount of current which has passed.
Through the lower space in the meter pass the conductors leading into the house, or rather they pass into the meter box and are secured in binding posts located on each side just within the meter. These binding posts are connected together, by what are termed "Shunt's," in this case, composed of broad strips of German silver, carefully graduated as to their resistance, so the 12241225 of the current passing over the wires will pass through them, while 11225 current will pass through each of the bottles, by means of small wires which may be seen passing up on one side of the meter and down on the other, connecting at both ends to the binding posts of the lower conductor. The upper and lower conductors alone are provided with shunts, the middle or neutral wire having none but passing directly through the meter behind the "Thermostat" the lamp upon which, is arranged between the neutral and upper conductor. The purpose of the thermostat is to prevent the freezing of the zinc solution in the bottles, which it does by the automatic lighting of the lamp upon it; the heat from this lamp being sufficient, in the confined space within the meter, to accomplish the purpose desired. The thermostat, Fig. 27, consists of a block of wood to be secured against the back of the meter. Attached to one end
Fig. 27.—Thermostat.
of this is a lamp socket, one wire from which is attached directly to the conductor leading through the meter, the other being connected to an adjustable metallic screw on the side of the socket. Near this screw is one end of a strip of brass to which is riveted a companion strip of steel, the opposite end being secured to the main block fixed to the back of the meter. From this latter end passes a wire^ which is secured in a binding post located at one end of a piece of metal passing behind the thermostat, to connect the two ends of the neutral wire entering the meter box at opposite sides, together. A lamp having been screwed into the socket, it is ready for operation.
The end of the brass-steel strip, opposite the screw on the lamp socket, is provided with a contact-point which will rest against the end of the screw under proper conditions; that is, when the temperature in the meter falls below a certain point, the brass on the brass-steel strip, contracting more than the steel, will cause the strip to curve, thus bringing the contact piece on its end against the lamp base screw, and, completing the circuit through the lamp, cause it to glow and disseminate the necessary heat.
It is a quality of sulphate of zinc to increase its resistance as it cools, and consequently the resistance of the bottles is ever varying with the change in the temperature about them. As an offset to this seeming defect in the apparatus small spools of copper wire, accurately measured, are placed in the circuits of fine wire leading to the bottles. The conditions which increase the resistance of the bottles, decrease the resistance of the spools; and thus one offsets the other to maintain a constant resistance.
These meters are in use both in this country and abroad in large numbers, and give satisfaction wherever used. They are simple and inexpensive in construction as well as economical and accurate in operation; qualities which have directly influenced their adoption in all the large central stations throughout the country.