NEC Quiz: Article 362 Answers

by Mark Lamendola

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  1. In the prelude to the questions, we gave away the fact this is a type of tubing. But of course the name gives that away also. What we didn't give away is its defining characteristics (though we did mention some of them). As the name tells us, it's also non-metallic.

    Electrical Nonmetallic Tubing (ENT) [362.1, 362.2] is an unthreaded, nonmetallic, corrugated raceway of circular cross section. Run your bonding jumper inside your ENT.
     

  2. Article 362 lists nine permitted uses [362.10]. That would seem rather wide open, but the factors mentioned in the prologue above serve as limiting factors to the conscientious specifier. And if you read these permitted uses carefully, you see each one has a longish description with qualifying (limiting) conditions imposed.
     

  3. Article 362 also lists nine prohibited uses [362.12]. If you look at that list, it totally makes sense because of the nature of this tubing. For example, it doesn't seal so you can't use it in a battery room where gases could enter the tubing if you did install it there. And item number 7 on that list is worth a closer look. Why is this not permitted in theaters and similar locations (except as provided by 518.4 and 520.5)? Because, as noted in the prologue, it's highly toxic and even more highly toxic when burned. Theaters and similar locations have a high occupancy density, and that means during a fire many people will be breathing the smoke of whatever is burning. The toxicity of PVC is why it (along with highly toxic Teflon) is banned as a wiring method in many other countries. The substitute material often isn't much better, but at least it's not toxic PVC.

 

 

  1. You must install ENT using approved methods. Article 362 gives explicit commentary regarding bending, bend radii, number of bends, trimming, supporting, securing, and other facets of installation [362.24 - 362.42]. Something many installers overlook is the fact that each run of ENT can have a maximum of 360 degrees of bends in it between pull points [362.26]. You see this limit on other raceway, also. It's there because when you go beyond this limit then pulling wire requires excessive tension on the wire (no matter how much lube you use). With ENT, it's a good engineering practice to limit the total to 270 degrees. Why this limitation? Because ENT presents extra friction compared to, say, EMT. With EMT, you have smooth walls but ENT is corrugated. EMT also has "catching points" at those connectors; try to limit it to about 300 degrees of total bends between pull points.

    An easy way to accomplish the limitation is to just install a pullbox or a suitable fitting halfway through the run.

  2. You can make joints between lengths of tubing (and connectors) using only methods approved for use with ENT [362.48].