If a product has a three-prong grounding type plug, is a GFCI necessary?
GFCIs are necessary even if the product has a third wire ground. GFCIs provide more sensitive protection to consumers against electric shock hazards. With grounding systems, if ground path degradation occurs, the high resistance could limit the current flow to ground below that required to trip the circuit breaker or blow the fuse. This would lead to a shock hazard if a person contacted energized exposed metal parts.