This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Before the introduction of iron conduits, outletboxes were considered unnecessary, and with a few exceptions were not used, the conduits being brought to the outlet and cut off after the walls and ceilings were plastered. With the introduction of iron conduits, however, the necessity for outlet-boxes was realized; and the Rules of the Fire Underwriter were modified so as to require their use. The Rules of the National Electric Code now require outlet-boxes to be used with rigid iron and flexible steel conduits, and with armored cables. A portion of the rule requiring their use is as follows:
All internal conduits and armored cables "must be equipped at every outlet with an approved outlet-box or plate, "Outlet-plates must not be used where it is practicable to install outletboxes.
"In buildings already constructed, where the conditions are such that neither outlet-box nor plate can be installed, these appliances may be omitted by special permission of the inspection department having jurisdiction, providing the conduit ends are bushed and secured."
Fig. 47 shows a typical form of outlet-box for bracket or ceiling outlets of the universal type. When it is desired to make an opening for the conduits, a blow from a hammer will remove any of the weakened portion of the wall of the outlet-box, as may be required. This form of outlet-box is frequently referred to as the knock-out type. Other forms of outlet-boxes are made with the openings cast in the box at the required points, this class being usually stronger and better made than the universal type. The advantages of the universal type of outlet-box are that one form of box will serve for any ordinary conditions, the openings being made according to the number of conduits and the directions in which they enter the box.
Fig. 48 shows a waterproof form of outlet-box used out of doors, or in other places where the conditions require the use of a watertight and waterproof outlet-box.
It will be seen in this case, that the box is threaded for the conduits, and that the cover is screwed on tightly and a flange provided for a rubber gasket.
Fig. 47. Universal and Knock-Out Type of Outlet Box.
Fig. 48. Water-Tight Outlet Box. Courtesy of H. Krantz Manufacturing Co., Brooklyn, N. Y.
HOUSE FOR CHAS. A. DOUGLAS, ESQ., WASHINGTON, D. C.
Wood, Donn & Deming, Architects, Washington, D. C.
An Interesting Example of an Open-Court Treatment Applied to a Narrow City Lot. Built of Stucco of White Marble Grit, with Wide, Projecting Eaves and Elaborate Supporting Rafters and Beams Stained a Dark Color.
Providing Abundant Light and Air. On Second Floor, over Passageways on Each Side of Court, are Porches upon which Bedrooms Open, Thus Providing Comfort through the Hot Midsummer Nights. The Massing of Flowers and Vines on these Porches at the Parapet Line of the Tile-Covered Eaves, Adds a Most Pleasing Effect. Exterior Shown on Opposite Page.
Figs. 49 and 50 show water-tight floor boxes which are for outlets located in the floor. While the rules do not require that the floor outlet-box shall be water-tight, it is strongly recommended that a water-tight outlet be used in all cases for floor connections. In this case, also, the conduit opening is threaded, as well as the stem cover through which the extension is made in the conduit to the desk or table. When the floor outlet connection is not required, the stem cover may be removed and a flat, blank cover be used to replace the same.
A form of outlet-box used for flexible steel cables and steel armored cable, has already been shown (see Fig. 5.).
There is hardly any limit to the number and variety of makes of outlet-boxes on the market, adapted for ordinary and for special conditions; but the types illustrated in these pages are characteristic and typical forms.
Fig. 50. Types of Floor Outlet-Boxes.