Construction-site power: GFCIs on temporary 120-volt outlets, or a written assured grounding program with tests

OSHA’s construction electrical standard requires ground-fault circuit interrupters on 120-volt, single-phase, 15- and 20-ampere receptacles that are not part of permanent wiring, or an assured equipment grounding conductor program with written procedures, a competent person, daily inspections, periodic tests and records.

Source facts

29 CFR 1926.404(b)(1) requires employers to use either ground-fault circuit interrupters or an assured equipment grounding conductor program to protect employees on construction sites. All 120-volt, single-phase, 15- and 20-ampere receptacle outlets that are not part of the building’s permanent wiring and are in use by employees must have approved GFCIs, except receptacles on small two-wire portable or vehicle-mounted generators rated 5 kW or less whose circuit conductors are insulated from the frame.

An assured equipment grounding conductor program must cover all cord sets, receptacles not part of the building and cord-and-plug equipment, with a written description available at the jobsite and one or more designated competent persons. Each cord set, plug, receptacle and cord-and-plug tool must be visually inspected before each day’s use, and damaged equipment may not be used until repaired.

Equipment grounding conductors must be tested for continuity and correct terminal attachment before first use, after repairs, after any incident that may have caused damage, such as a cord being run over, and at least every 3 months, or every 6 months for fixed cord sets and receptacles not exposed to damage. Test results must be recorded by logs, color coding or other effective means and be available on the jobsite.

Applicability

Use this for temporary power on construction sites, including extension cords and portable tools used during installations. Michigan employers follow MIOSHA, whose standards must be at least as effective as OSHA’s; check the state rule.

DSE recommendation

DSE recommends plugging every tool and extension cord on a construction site into GFCI-protected power and keeping cords and tools in a documented inspection program either way. Inspect cords and plugs before each day’s use, pull damaged cords from service immediately, test portable GFCIs before use, and mark inspected cords with the current period’s color.

Verification

During site visits, check that temporary outlets in use are GFCI-protected, that cords carry the current inspection color or log entry, and that no damaged cords are in service.

Official reference

OSHA — 29 CFR 1926.404, Wiring design and protection. Reviewed October 19, 2026.