In the prelude to the questions, we gave away the fact this is a nonmetallic
conduit. What we didn't give away is the particular type. This is Reinforced
Thermosetting Resin Conduit (Type RTRC) [355.1, 355.2].
RTRC is a rigid
nonmetallic conduit of circular cross section. It has integral couplings,
similar to those in the PVC used for plumbing.
355 lists seven permitted uses [355.10]. Basically, you're going to use it where
you would otherwise use a metallic raceway but corrosion is a limiting factor.
That's why, for example, you'd use it in a cinder fill. It is suitable for
direct burial, if you follow the minimum cover requirements for Rigid Nonmetallic
Conduit (see Tables 300.5 and 300.500).
355 lists five prohibited uses [355.12].
One of those is in hazardous locations;
that's because plastic and static electricity tend to be ready playmates.
A second is for the protection of the conduit itself (where exposed).
A third (in theaters and similar locations) is a small consolation to the
fact the highly toxic material the raceway is made of is, well, highly toxic.
On the Wireville site,
Frank Bisbee has covered the fact that the European Union far more widely limits
the use of highly toxic materials in electrical installations. And not just in
conduit but also as an electrical conductor insulating material. The Europeans
have really objected to the use of Teflon, another outrageously toxic material
that you should avoid using unless you have absolutely no other choice. And it's
likely you will always have another choice.
You can't use it to support luminaires, and you can't use it where the
temperature may exceed 122 DegrF (unless it's listed for a higher temperature.
install Type RTRC using approved methods. Article 355 gives explicit commentary regarding
bending, bend radii, number of
bends, and other facets of installation [355.24 - 355.48].
Couplings and connectors
are integral to the conduit (though you can also attach couplings and connectors
to cut conduit). Where RTRC enters a box, use
bushings and/or adapters that will protect the wires from abrasion [355.46]. If the box,
fitting, or enclosure provides the equivalent protection of a bushing and/or
adapter, then you don't have to add more bushings and/or adapters [355.46].
Really, you should not be installing this wiring method until you have had
specific training in the installation methods. If you are
the project engineer, factor the necessary training into your budget so your project
doesn't incur rework costs and lost time accidents.