PLAN No. 1191. STEEL CONDUIT WIRING
This is the most expensive, but the safest and best method. In fireproof buildings it is used exclusively, and in some communities wiring of other types is prohibited. Many frame buildings are now being wired with metal conduit, either of the rigid or the flexible type. Rigid conduit is merely wrought iron or steel pipe of the usual trade dimensions, which has been specially treated to prevent its corrosion and to render its interior smooth. Flexible steel conduit resembles metal hose in construction. Metal conduit is installed while the building is under construction, and subsequently rubber-insulated conductors are pulled into it. Usually the conduit is concealed within floors and walls, but it may be supported on surfaces. In concrete construction buildings the conduit is embedded in the concrete, being placed in the forms before the concrete is poured. At outlets where the conductors must be carried from the conduit system to feed lights and switches, steel or cast-iron outlet boxes are connected to the tubes. Pipe tools, such as dies, reamers, hack saws, drills, and bending “hickeys” are used in working conduit.