NEC Quiz: Article 427 Answers

by Mark Lamendola

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  1. They are to be considered a continuous load [427.4]. If you use a controller to turn them on and off every couple of hours, that does not change the characterization.

  2. Ensure that equipment is physically guarded, isolated, or thermally insulated. The reason is to protect people who may come into contact with it [427.12]. You can't get around this requirement by declaring a section of pipe (or whatever) to be "unlikely" to be in contact with a person. People do stupid things. If there is any risk of contact, follow the requirement.

  3. The danger is that, since the vessel isn't serving as a heat sink for the equipment, the equipment can overheat. So you must provide a means of preventing overtemperature, unless the design of the heater assembly precludes overheating [427.15].

  4. You use a dual-winding transformer with a grounded shield between the primary and secondary windings [427.26].

  5. Yes, the controller must open all ungrounded conductors. And you cannot use a controller as the disconnect means unless it can be locked in the OFF position [427.56(B)].