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 High Density
Polyethylene Conduit (HDPE) [353.1, 353.2].
Polyethylene is a type of plastic made from petroleum. It's inexpensive
(if you discount the costs of the oil wars, environmental damage, etc.) and is
widely used. It is also highly toxic, both in normal
condition (you can smell its toxic fumes wafting off of products made from it)
and egregiously so when burned. Try to avoid using it anywhere that humans are
likely to spend much time.
353 lists six permitted uses [353.10]. Even though these are permitted, you
should avoid using HDPE when another (nonplastic) type of material is suitable for the
conditions and application.
353 lists five prohibited uses [353.12]. One of those is in hazardous locations;
that's because plastic and static electricity tend to be ready playmates. Two
of the other prohibited uses are for the protection of the conduit itself (where
subject to temperatures above 122 DegrF and where exposed). But
the other one, within a building, is a small consolation to the
fact this highly toxic material 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.
Article 353 doesn't explicitly say so, you have to
install HDPE as a complete system, using the appropriate listed hangers, clamps,
fittings, and so forth. Pay close attention to the MDS and product labels.
Article 353 does give explicit commentary regarding bend radii and number of
bushings, couplings, connectors, brackets, etc., listed for use with HDPE (not
stated in subsection 353.42 because there isn't one; see 353.28, 353.30, and
Really, you should not be installing this wiring method until you have had
specific training in the installation methods and safety features. If you are
the project engineer, factor that training into your budget so your project
doesn't incur rework costs and health liability baggage.