NEC Quiz: Article 354 Answers

by Mark Lamendola

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  1. 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 Nonmetallic Underground Conduit with Conductors (Type NUCC) [354.1, 354.2].

    NUCC is a factory assembly of conductors or cables inside a nonmetallic raceway; the raceway itself is smooth-walled and of circular cross-section.

  2. Article 354 lists five permitted uses [354.10]. 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).

  3. Article 354 lists three prohibited uses [354.12].

    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).

    The third (within a building) 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.

  4. You don't normally use hardware with Type NUCC; that is, you're not mounting it to a wall the way you would mount RMC. You must install Type NUUC using approved methods [354.48, 354.50]. Article 354 also gives explicit commentary regarding bending, bend radii, and number of bends [354.24, 354.26].

  5. You're not assembling this with couplings and connectors, so that's kind of a trick question. But where NUCC enters a box, use bushings and/or adapters that will protect it from abrasion [354.46]. 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 [354.46].

    Really, you should not be installing this wiring method until you have had specific training in the installation methods. For example, a fairly typical installation may involve a large spool on a trailer or motorized platform following behind a motorized trencher. You have to know how to operate the equipment in a manner that doesn't lead to injuring the NUCC or the people installing it. 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.