Q. We have a heat tape system installed on a metal roof. The heat tape has arced against the metal before, and we are concerned we will burn the place to the ground. Someone told us to use a GFCI on the circuit, and someone else told us not to. Does the NEC offer any guidance here?
A. Yes. Fixed outdoor electric deicing and snow-melting equipment must have ground-fault protection of equipment (GPE), unless the equipment uses mineral-insulated, metal-sheathed cable embedded in a noncombustible medium [426.28]. This GPE protection is different from a GFCI because it trips at a higher current value (30mA as opposed to 5mA).