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Section 2 Installation
Copyright Goodheart-Willcox Co., Inc.
Nonmetallic
Sheathed Cable
Nonmetallic sheathed cable (NM) has two or
more insulated conductors wrapped in a strong
plastic or braided outer sheath. Often included
is a bare copper ground wire, Figure 4-12. NM is
the easiest and, in many areas, the most popular
system to install. NM is easily cut to length with
cable cutters. A cable ripper is used to split the
outer jacket from the point where the wires will
be exposed to the end of the cable. Place the
cutting tooth in the center of the cable about 8”
from the end. Squeeze the ripper closed to pierce
the jacket and pull it to the end of the cable. Use
a knife to carefully cut the jacket completely off
the cable. See Figure 4-13.
Nonmetallic Sheathed Cable: Types NM, NMC, and NMS — Article 334
Locations Allowed
Type NM: Normally Dry
Type NMC: Moist, damp, or corrosive
Type NMS: Normally Dry
Sizes
14 AWG
through
2 AWG
Maximum Mounting Distance
12″
4 1/2′
nonmetallic sheathed cable (NM): A cable with 2 or
more conductors and a ground all within an outer
jacket, suitable for use in most residential installations
except where conduit is required. NM is called Romex
in the trade.
Clamp type of connector
(2 screws)
Setscrew type of connector
cannot be used on
aluminum-armored cable
Inspection tab of
anti-short bushing
is exposed
Steel AC
Figure 4-11. The setscrew connector cannot be used on aluminum AC. The clamping connector can be used on
steel or aluminum AC. Always read the cable manufacturer’s installation instructions for any restrictions.
History Brief
Romex®
Type NM cable is referred to almost univer-
sally as Romex, regardless of which company
makes the cable. Originally developed by
General Cable in Rome, New York, in 1922,
NM cable is now made by many different
companies.
Pro Tip
Color-Coding
Generally, nonmetallic sheathed cable
(NM) is color-coded. The color of the outer
jacket identifi es the wire size: white for 14
AWG, yellow for 12 AWG, and orange for 10
AWG. Always measure the wire to be sure of