Basics of electrical conduit
Jan 13th, 2022 at 06:09 Electronics Bareilly 242 views
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All the rules for bending conduit are applicable to bending EMT. EMT is much easier to bend than RMC, where the next size larger bender is needed due to the greater outside diameter.
Many jobs involving a single 90° bend are quite simple and require no advanced knowledge or expertise. A fundamental principle in all EMT Electrical Conduit installations is that the pipe should conform closely to the wall or ceiling finish surface. In other words, do not allow the raceway to take a shortcut through open space in a building interior. Nor, generally, should a diagonal route be taken even if that would reduce the amount of raceway and wire required.
To make an interior corner, use a bender, forming a uniform 90° sweep. To make an exterior corner, use a conduit fitting such as a 90° conduit body with removable cover, to facilitate conductor installation.
The NEC specifies that each individual raceway run is to be installed as a complete system including end terminations prior to pulling in conductors. The NEC also states that conductors are to be pulled through the equivalent of no more than four 90° bends between terminations and/or open pull points. This figure is true for all sizes of conduit. There is no limit to the distance of the run.
Quite often a conduit run consists of a straight stub between boxes. To simplify the installation, you can postpone tying down one of the boxes until after the pipe is terminated. Another common, simple job involves running pipe from a box to an interior corner, known in the trade as a brick wall, where a conduit bend is needed. You can leave one or both legs long, then mark and cut them to fit after the bend is made. Alternately, and more elegantly, use the standard deduction for a given size conduit. For half-inch conduit, the deduction is five inches. For 0.75-in. conduit, the deduction is six inches. For IMC Electrical Conduit the deduction is eight inches. Usually the deduction is stamped on the bender.
Mark the conduit, minus the deduction for the conduit size. Put the conduit in the bender with the mark on the Rigid Electrical Conduit aligned with a mark on the bender, usually an arrow called the B mark.
