Two ways to protect workers
29 CFR 1926.404(b)(1)(i) makes the employer protect construction-site employees with either ground-fault circuit interrupters under (b)(1)(ii) or an assured equipment grounding conductor program under (b)(1)(iii). GFCIs are not the only route; the program is the alternative.
These ground-fault rules are in addition to all other equipment grounding conductor requirements of Subpart K. They do not replace those requirements, they do not waive them for cord-and-plug equipment, and they are not limited to circuits that lack a grounding conductor. The assured program in fact tests the equipment grounding conductor's continuity and attachment, so it assumes the conductor is there.
Which receptacles need a GFCI
Under 1926.404(b)(1)(ii), a receptacle needs GFCI protection only when every one of these is true:
- 120 volts
- single-phase
- rated 15 or 20 amperes
- not part of the permanent wiring of the building or structure
- in use by employees
Check each condition in turn. A 120-volt, 20-ampere receptacle on a spider box is covered. A 240-volt single-phase receptacle fails the 120-volt condition. A 120-volt, 30-ampere receptacle fails the 15/20-ampere rating. A 208-volt, three-phase receptacle fails both voltage and single-phase.
The generator exemption
The same paragraph exempts receptacles on a generator, but only when all of these hold at once:
- a two-wire, single-phase generator
- portable or vehicle-mounted (both qualify, not vehicle-mounted only)
- rated not more than 5 kW
- circuit conductors insulated from the generator frame and all other grounded surfaces
The common error is stopping at the 5 kW rating. A 5 kW, two-wire, single-phase portable generator whose circuit conductors are bonded to the frame fails the insulation condition, so its 120-volt, 20-ampere receptacles still need GFCIs. A two-wire, single-phase generator above 5 kW is not exempt either; there is no "any rating" version of this exemption.