Chapter 4 Wiring Systems
97
as if it was nonfl exible conduit, but it has the
advantage of bending without using tools. There
are special couplings, locknuts, and bushings
for attaching FMC. The wire is fi shed through
as with other conduit.
Intermediate Metal Conduit: Type IMC — Article 342
Locations Allowed
Dry
Wet
Corrosive
Sizes
1/2″
through
4″
Maximum Mounting Distance
3′
10′
intermediate metal conduit (IMC): Conduit with walls
thicker than EMT but thinner than RMC. Has many
advantages over RMC because it is lighter in weight
and has more room inside for pulling wires.
fl exible metal conduit (FMC): Metal corrugated tubing
that provides a fl exible conduit.
Greenfi eld: A common name for FMC.
liquidtight fl exible metal conduit (LFMC): This con-
duit is FMC with a waterproof outer coating and
special fi ttings to maintain its watertight integrity.
Figure 4-30. Flexible metal conduit (Greenfi eld) is
similar to armored cable without the wires.
Flexible Metal Conduit: Type FMC — Article 348
Locations Allowed
Dry
Sizes
1/2″
through
4″
Maximum Mounting Distance
12″
4 1/2′
Pro Tip
Intermediate Metal Conduit
The internal diameter (ID) of IMC is larger
than that of the equivalent trade size of RMC;
therefore, there is more room for pulling wires
and calculating conduit fi ll.
Flexible Metal
Conduit (Greenfi eld)
Flexible metal conduit (FMC) is a spiral-
wrapped metal conduit similar to the outer
armor in AC. See Figure 4-30. FMC is often
called Greenfi eld because it was invented by
Harry Greenfi eld. FMC is routed and attached
Code Alert
Section 348.60
Where used to connect equipment where
fl exibility is required after installation, an equip-
ment grounding conductor shall be installed.
Where fl exibility is not required after installa-
tion, FMC shall be permitted to be used as an
equipment grounding conductor when installed
in accordance with 250.118(5).