Ground-fault protection in construction job trailers

February 16, 1993
Mr. Philip P. Mercuris
Director of Safety
Master Builders of Iowa
[Recipient address omitted]
Dear Mr. Mercuris:
This is in response to your December 22 letter requesting an interpretation of an Occupational Safety and Health Administration (OSHA) ground-fault protection for a construction job-site trailer.
With regard to whether GFCI's or an assured grounding conductor program is required for receptacles inside a construction job-site trailer, (reference National Electrical Code (NEC), Section 550-4), please be advised that although such trailers are permanently wired in accordance with the National Electrical Code still require, for certain interior receptacles, ground fault circuit interrupter protection for personnel (NEC Section 550-8(b)). However, as stated in your letter, all exterior receptacles and any interior receptacles used with cord sets running outside the trailer would not be considered a part of the permanent wiring. In such cases, either a GFCI or an assured grounding conductor program would be required in accordance to 29 CFR 1926.404(b).
If we can be of any further assistance, please contact me or Mr. Dale Cavanaugh of my staff at (202) 219-8136.
Sincerely,
Roy Gurnham, P.E., Esq. Director
Office of Construction and Maritime
Compliance Assistance

[Requester letter reproduced on OSHA page; omitted here.]