This following case supports the need to provide a permanent record to document controller settings/configuration for programmable heating controllers in a manner that can be easily used. Lock-out of unauthorized changes needs to be assured, and configuration should be checked as part of circuit maintenance.

A damaged self-limiting cable in combination with water present in the thermal insulation system resulted in a wet-arcing ground fault. The incident was discovered when plant personnel noticed dense black smoke coming from the thermal insulation system (characteristic of overheated Polyisocyanurate insulation). Ground-fault protection was provided through a programmable heating controller. In this case, the default configuration was changed so that the ground-fault only alarmed. Repeated alarms were interpreted as nuisance alarms associated with system start-up and ignored.