A ground fault circuit interrupter (GFCI), or Residual Current Device (RCD) is a type of circuit breaker which shuts off electric power when it senses an imbalance between the outgoing and incoming current. The main purpose is to protect people from an electric shock caused when some of the current travels through a person’s body due to an electrical fault such as a short circuit, insulation failure, or equipment malfunction. Standard circuit breakers shut off power when the current is too high, like 10, 15, or 20 amps, but a mere 0.030 amps through a body can cause paralysis of skeletal muscles and stop the human heart. The GFCI / RCD breaks the circuit when it detects an imbalance of only 0.005 amps.

A circuit breaker protects the house wires and receptacles from overheating and possible fire. A GFCI / RCD protects people and is often found in bathrooms or kitchens where electrical devices are used and people’s bare flesh may be in contact with the floor or metal fixtures which provide an alternate path for current to travel in the case of an electrical fault.