Chapter 4 Wiring Systems
93
Electrical
Nonmetallic Tubing
A newer type of plastic corrugated raceway
called electrical nonmetallic tubing (ENT) is
now recognized for general use by the NEC
under Article 362. It is fl ame retardant and
is resistant to moisture and chemical atmo-
spheres. ENT can be used in almost any
building or dwelling regardless of height and
can be concealed behind walls, above ceilings,
or embedded in concrete. Being lightweight
and fl exible, ENT is easy to handle. The various
connectors, couplings, and fi ttings are attached
with snap-locks or plastic bonding cement.
Installation varies and should be performed
according to the manufacturer’s instructions.
See Figure 4-25.
There are some restrictions and limitations
on the use of ENT:
• Not for hazardous material
• Cannot be left exposed, with some exceptions
• Not to be used as supportive means
• Not permitted for direct burial application
• Not for voltage exceeding 600 V
Electrical Nonmetallic Tubing: Type ENT — Article 362
Locations Allowed
Dry
Wet
Corrosive
Sizes
1/2″
through
2″
Maximum Mounting Distance
3″
3′
History Brief
“Smurf”
ENT is referred to in the trade as “smurf
tube” or simply “smurf”. The distinctive blue color
found on most, but not all, ENT is the reason for
this nickname. Smurfs were bright blue cartoon
characters that were popular in the early 1980s.
electrical nonmetallic tubing (ENT): Plastic corrugated
tubing that provides a fl exible conduit. Also called
smurf because one type of ENT is a bright blue color,
like the Smurf cartoon characters.
Electrical nonmetallic
tubing (ENT)
Connector
Nonmetallic
box
Figure 4-25. Electrical nonmetallic tubing is a corru-
gated plastic tube that is easy to handle and install.
(Carlon, Lamson & Sessions)