Rule 1721. All 120-volt, single-phase 15 and 20 ampere receptacle outlets used for construction operations, which are not a part of the permanent wiring of the building or structure and which are in use by an employee, shall have approved ground fault circuit interrupters for personnel protection. A receptacle on a 2-wire, single-phase portable or vehicle mounted generator rated at not more than 5 kilowatt, where the circuit conductors of the generator are insulated from the generator frame and all other grounded surfaces, need not be protected with ground fault interrupters.
Mich. Admin. Code R. 408.41721