An ELCI is similar to a residential GFCI (ground-fault circuit-interrupter). The circuitry inside the device measures the incoming and outgoing current flow. If it senses a problem with the ground, whether due to a damaged or severed wire or an incorrectly connected piece of equipment, it shuts off the power within a fraction of a second.
The PGFM series operates in tandem with an Airpax™ LEL series, UL 489 listed circuit breaker, with shunt trip and auxiliary switch manufactured by Sensata Technologies.