46 C.F.R. § 111.79-3 Grounding pole.
Title 46 - Shipping
Each receptacle outlet that operates at 100 volts or more must have a grounding pole.
Title 46: Shipping
PART 111—ELECTRIC SYSTEMS—GENERAL REQUIREMENTS
Subpart 111.79—Receptacles
§ 111.79-3 Grounding pole.

