There are a number of metal and nonmetallic raceways in common use. Conduit is a subcategory. Electrical Metallic Tubing (EMT), a familiar sight in commercial and industrial facilities, plays a minor role in residential wiring, where it is used only when enhanced protection is needed. EMT is the common thin-wall tubing joined with set crew connectors or, for outdoor use, compression fittings.
Because of the thin wall, it is not to be threaded in the field. Instead, pipe and fittings slide together easily, making for a quick and user-friendly installation in contrast to the heavier cousins, Intermediate Metal Conduit (IMC) and Rigid Metal Conduit (RMC), both of which are threaded.
Technically, EMT is not conduit. It is tubing or raceway. Nevertheless, electricians commonly speak, when using it, of running conduit. A simple installation is quite easy, but when it becomes more complex, specialized skills are needed. All bends are to be smooth, uniform and of sufficient radius so the pipe does not kink or lose cross-sectional area. If this happens, it will be difficult if not impossible to pull the conductors. Consequently, a bender, manual or machine-powered for larger sizes, must be used.
The bending od EMT is part science and part art. There are a great variety of bends, serving different purposes and configurations.
A basic principle is that the conduit should always run close to the finish surface, never taking a shortcut through space. Making the installation conform to an irregular building configuration can be quite a challenge, and there is planning involved in making runs come out right. Difficult jobs sometimes require trigonometric calculations. Where multiple runs must make angle turns, multi-shot bends, different for each pipe as the radius changes, are needed to get a good finished appearance. The idea is to start with simpler projects such as straight parallel runs terminating in box offsets.
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