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Code Q&A: Receptacles on a Construction Site

Your most pressing National Electrical Code (NEC) questions answered


Q. What are the Code rules regarding receptacles installed on construction sites?

A. All receptacles used for temporary installations must be of the grounding type, and the receptacle grounding terminal must be connected to an equipment grounding conductor in accordance with 250.146 and 406.4. On a construction site, receptacles aren't permitted to be placed on a branch circuit that supplies temporary lighting [590.4(D)(1)], as shown in the Figure. This requirement is necessary so that illumination is maintained, even when the receptacle's GFCI-protection device opens.

All 15A and 20A receptacles installed in a wet location of a construction site must be within an enclosure that's weatherproof when an attachment plug is inserted. For other than one- or two-family dwellings, the outlet box hood must be listed for "extra-duty" use if supported by grade, and all nonlocking-type 15A and 20A, 125V and 250V receptacles in a wet location must be listed as weather resistant [406.9(B)(1) and 590.4(D)(2)].

Exposed plastic surface material of weather-resistant receptacles must have UV resistance to ensure that deterioration from sunlight doesn't take place, or that it's minimal. In testing, receptacles are subjected to temperature cycling from very cold to very warm conditions, and then subjected to additional dielectric testing. The rapid transition from the cold to warm temperatures will change the relative humidity and moisture content on the device, and the dielectric test ensures that this won’t create a breakdown of the insulation properties.

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