A set of plans, including elevation and details, if any, and show ing decorative treatment of the various rooms, should be obtained from the Architect. A careful study should then be made by the Architect, the Owner, and the Engineer, or some other person qualified to make recommendations as to illumination. The location of the outlets will depend : First, upon the decorative treatment of the room, which determines the aesthetic and architectural effects; second, upon the type and general form of fixtures to be used, which shoula be previously decided on; third, upon the tastes of the owners or occupants in regard to illumination in general, as it is found that tastes vary widely in regard to amount and kind of illumination.
The location of the outlets, and the number of lights required at each, having been determined, the outlets should be marked on the plans.
The Architect should then be consulted as to the location of the centers of distribution, the available points for the risers or feeders, and the available space for the branch circuit conductors.
In regard to the rising points for the feeders and mains, the fol lowing precautions should be used in selecting chases: 1. The space should be amply large to accommodate all the feeders and mains likely to rise at that given point. This seems trite and unnecessary, but it is the most usual trouble with chases for risers. Formerly architects and builders paid little attention to the requirements for chases for electrical work; but in these later days of 2-inch and 2i-inch conduit, they realize that these pipes are not so invisible and mysterious as the force they serve to dis tribute, particularly when twenty or more such conduits must be stowed away in a building where no special provision has been made for them.
2. If possible, the space should be devoted solely to electric wiring. Steam pipes are objectionable on account of their temperature; and these and all other pipes are objectionable in the same space occupied by the electrical conduits, for if the space proves too small, the electric conduits are the first to be crowded out.
The chase, if possible, should be continuous from the cellar to the roof, or as far as needed. This is necessary in order to avoid unnecessary bends or elbows, which are objectionable for many reasons.
In similar manner, the location of cut-out cabinets or distributing centers should fulfil the following requirements: 1. They should be accessible at all times.
2. They should be placed sufficiently close together to prevent the cir cuits from being too long.
3. Do not place them in too prominent a position, as that is objectionable from the Architect's point of view.
4. They should be placed as near as possible to the rising chases, in order to shorten the feeders and mains supplying them.
Having determined the system and method of wiring, the location of outlets and distributing centers, the next step is to lay out the branch circuits supplying the various outlets.
Before starting to lay out the branch circuits, a drawing showing the floor construction, and showing the space between the top of the beams and girders and the flooring, should be obtained from the Archi tect. In buildings of iron or steel construction, it is almost the invariable practice, where the work is to be concealed, to run the conduits over the beams, under the rough flooring, carrying them between the sleepers when running parallel to the sleepers, and notch ing the latter when the conduits run across them (see Fig. 31). In wooden frame buildings, the conduits run parallel to the beams and to the furring (see Fig. 32); they are also sometimes run below the beams. In the latter case the beams have to be notched, and this is allowable only in certain places, usually near the points where the beams are supported. The Architect's drawing is therefore necessary in order that the location and course of the conduits may be indicated on the plans.
The first consideration in laying out the branch circuit is the number of outlets and number of lights to be wired on any one branch circuit. The Rules of the National Electric Code (Rule 21-D) require that "no set of incandescent lamps requiring more than 660 watts, whether grouped on one fixture or on several fixtures or pendants, will be dependent on one cut-out." While it would be possible to have branch circuits supplying more than 660 watts, by placing various cut-outs at different points along the route of the branch circuit, so as to subdivide it into small sections to comply with the rule, this method is not recommended, except in certain cases, for exposed wiring in factories or mills. As a rule, the proper method is to have the cut-outs located at the center of distribution, and to limit each branch circuit to 660 watts, which corresponds to twelve or thirteen 50-watt lamps, twelve being the usual limit. Attention is called to the fact that the inspectors usually allow 50 watts for each socket connected to a branch circuit; and although 8-candle-power lamps may be placed at some of the outlets, the inspectors hold that the standard lamp is approximately 50 watts, and for that reason th°-^ is always the likelihood of a lamp of that capacity being used, and their mspec tion is based on that assumption. Therefore, to comply with the requirements, an allowance of not more than twelve lamps per branch circuit should be made.