62 Modern Commercial Wiring
Copyright Goodheart-Willcox Co., Inc.
Figure 5-7. Service-entrance cable can be used for general
indoor wiring as well as at the service entrance. A—Type SE
cable. B—Type USE cable is used for underground applications.
Protective
outer jacket
Reinforcement
tape
Insulated
neutral
conductor
Insulation
Type SE
Conductor
Bare
equipment
ground
A
Protective
outer jacket
Reinforcement
tape
Concentric
neutral
Insulation
Conductors
Type USE
B
Figure 5-8. Types AC and ACL cable are also commonly
referred to as BX cable.
Antishort
bushing
Interlocked
metallic armor
Type USE is basically the same as type SE except the
outer jacketing is better suited for direct burial. It is
highly moisture and corrosion resistant. Type ASE has an
armored jacket, which provides additional protection.
As already noted, service-entrance cable can be used
for interior wiring or for service-entrance cable between
the utility supply and main service disconnect. When it is
used for interior wiring, the grounded neutral conductor
must be insulated, with the following exceptions:
• When used as a feeder between two buildings.
• When used as the circuit conductor or branch
wiring to clothes dryers, counter-mounted cook-
tops, ranges, and ovens.
Service-entrance cable may not be used for interior
wiring of buildings of any type exceeding three stories high.
Armored cable (AC and ACL)
Type AC or ACL (often called “BX” cable) is used in
both dry and wet locations, but is not permitted to be
buried, see Figure 5-8. This type of cable, once commonly
used in many applications, has some limitations for
commercial use. It may not be used in places of assembly,
studios, movie theaters, hazardous locations, commercial
garages, areas with vapors and corrosive agents, lifts,
cranes, hoists, elevators, or battery rooms.
Armored cable can be used in the following situations:
• As flexible connections to motors or vibrating
equipment (up to 24″ length).
• As fixture whips (up to 6′ length).
• In dry locations.
• Concealed behind walls (may be fished behind
walls in old work).
• Exposed along wall surfaces.
• Where exposed to weather or moisture (type
ACL only).
Armored cable must be properly supported at inter-
vals of 4′ - 6″ and within 12″ of terminal boxes or fittings.
When routing BX cable through wall, floor, or ceiling
members, the member must be drilled through the center
or notched and covered with a metal plate to protect the
cable from nails. The cable can be run along the sides of
studs, joists, or rafters without further protection. Guard
strips made of 1 × 1 or 1 × 2 stock are used to protect BX
or AC cable when it is run along attic floor joists.
CAUTION
Antishort insulating bushing must be placed between
conductors and the outer armor wherever the cable
is cut. The bushings protect the conductor insulation
from any sharp edges on the cut armor.
Nonmetallic-sheathed cable (NM, NMC, and UF)
Often referred to as Romex, nonmetallic-sheathed cable
is frequently used as the preferred wiring method in small
commercial establishments, as well as in resi-dential struc-
tures. This cable is made up of two to four insulated conduc-
tors plus a green insulated or bare grounding conductor with
an overall nonmetallic sheath. See Figure 5-9.