Figure 5-52. - Running threads.
include EMT, rigid, and flexible conduit installed in specific locations. The exceptions for each type are outlined in the NEC©. All types of conduit must be reamed after they have been cut. Conduit threaded in the field must be threaded with a die that has a 3/4-inch taper per foot. When threaded conduit enters a box or fitting, a bushing must be used to protect the conductor insulation from being cut or tom. Also, for those types that use threaded couplings, running threads, as shown in figure 5-52, are not to be used for connection at couplings. Running threads weaken the conduit and may come loose. Threaded couplings and connectors used with any type of conduit must be made up tight. Couplings or connectors that are to be buried in concrete or masonry have to be the concrete-tight type; those to be installed in wet locations have to be the raintight type.
Conduit must be supported by straps or hangers throughout the entire run. Figure 5-53 shows how straps are fastened on different types of surfaces. On a wooden surface, nails or wood screws can be used to secure the straps. On brick or concrete surfaces, first you just make a hole with a star or carbide drill and then install an expansion anchor. Use an expansion tool to force the anchors apart, forming a wedge to hold the anchor in the hole. Then secure the strap to the surface with machine screws attached to the anchor. On tile or other hollow material, secure the straps with toggle bolts. If the installation is made on metal surfaces, you can drill holes to secure straps or hangers with machine or sheet metal screws.
Figure 5-53. - Conduit support fastening.
Table 5-5. - Nonmetallic Conduit Support
CONDUIT (Inches) MAXIUM SPACE BETWEEN SUPPORTS (Feet))
1/2 -1. . . . . . . . . 3
1 1/4 - 2 . . . . . . 5
2 1/2 - 3 . . . . . . . 6
3 1/2 - 5 . . . . . . 7
6 . . . . . . . . . . . . . . . . . 6
The number of supports needed depends on the type of conduit being used. Holes, or notches, in framing members may serve as supports. EMT and IMC require supports within 3 feet of each outlet box, junction box, cabinet, or fitting, and every 10 feet thereafter. Rigid metal conduit must also be supported within 3 feet of a box, but the distance between supports may be increased as the size of the conduit increases if the run is straight and is made up with threaded couplings. The distance between supports on direct vertical runs of rigid conduit from machine tools, and the like, may be increased to 20 feet if threaded couplings are used and the riser is supported at each end.
Rigid nonmetallic conduit must be supported, as shown in table 5-5. In addition, it must be supported within 3 feet of each opening.
Flexible metal conduit and liquidtight flex must be supported at intervals not to exceed 4 1/2 feet and within 12 inches on each side of every outlet box or fitting. Exceptions to this rule are runs of 3 feet or less where flexibility is needed or 6 feet where light fixtures are being connected.
When you run conduit from one point to another, you often need to make more turns than the NEC© allows in a single run (360° of bends). When this larger number of turns is the case, you can use a fitting called a conduit body. Conduit bodies are often referred to by their brand names, such as Condulet or Unilet. A conduit body is a portion of a conduit system that provides access to the system through a removable cover to the interior of that system at a junction of two or more sections or at a terminal point. An important point to remember is that all Condulets must be accessible after construction is completed. Figure 5-54 shows some of the more common conduit bodies and covers.Continue Reading