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
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
1/2 -1. . . . . . . . .
1 1/4 - 2 . . . . . .
2 1/2 - 3 . . . . . . .
3 1/2 - 5 . . . . . .
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
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.