Abstract – Historically, Class A ground-fault circuit
interrupters (GFCIs) have been responsible for a
substantial reduction in residential electrocutions. Yet,
they have not had much success in industrial
applications because of the limitation on system voltage
(maximum 240 V) and the 6 mA maximum allowed
leakage current. As a result, industrial personnel
protection has been lagging its residential counterpart.
UL realized this gap and defined new GFCI classes to
specifically address personnel protection in industrial
applications. The new UL 943C defines the requirements
of special-purpose GFCIs that can be used on systems up
to 600 V and allows for a leakage current of 20 mA. This
paper describes the UL 943C requirements and the newly
defined GFCI classes. The difference between equipment
ground-fault protection devices (EGFPDs) and GFCIs are
also addressed. Finally, the application of a Class C GFCI
in a pulp and paper plant is described.