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NEC Quiz: Article 440 Answers

by Mark Lamendola

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  1. Because EMT uses compresion-style fittings, you must run an EGC of the wire type within the EMT [440.9].

  2. The ampere rating of the disconnect for a hermetic compressor motor must be at least 115% of the nameplate rated-load current or the branch-circuit selection current (whichever is greater) [440.12(A)(1)].

  3. Locating it on the panel is almost certainly the worse choice in all circumstances. And if the panel in question is an acess panel, locating it there is prohibited [440.12(B)(1)].

  4. Its ampacity must be sufficient for all of the loads you intend for it to carry [440.34]. Be sure to refer to 440.32 or 440.33, for single compressor-motor applications and multiple motor applications, respectively. For example, if you are installing a residential heat pump that also has a 15A convenience receptacle on the same supply conductors then you would size the heat pump part per 440.33 because you have the compressor motor and the fan motor (more than one motor) on those conductors.

  5. Yes, in fact you are required to. The OCPD must have sufficient time delay to permit starting the unit. Because these units often start under load, the delay may be considerable.