The heat tape and heating panels must have a grounded conductive coating. Note that in previous codes, this covering was required to be metallic, but in the 2002 code it was changed to permit nonmetallic conductive coatins to be used. See 427.23. GFP was required even when the heat trace had a grounded metallic covering. The GFP is required because resistance heating can fail in a manner that will produce enough heat to start a fire without pulling enough current to open the overcurrent protective device.