Wed 21 Jan, 2015 07:44 pm
How does a GFCI breaker work, and how is it wired?
A Ground Fault Current Interruptor is wired as any other circuit breaker.
It opens automatically if the difference is greater than the rated default current, i.e. 30 mA.
GFCI breakers work on a differential current measurement between the hot and grounded circuit conductior or neutral on a three-wire 120/240 from a single-phase source. On a single pole GFCI breaker if there is a 10amp load and that 10amps is returning on the grounded-circuit conductor the differential is zero so the breaker does not trip. If some current (5ma for people protection and 30ma for equipment like snow melt) leaks from the circuit on the load side of the breaker, the breaker trips. This is not to be confused with the overload protection the breaker provides which is much higher based on the breaker ampere rating.