Electrical: What is a GFCI or GFI Breaker or Outlet and why might it trip when used with an electric kiln?
What is a GFCI or a GFI Breaker or Outlet?
- A 'GFCI' or Ground Fault Circuit Interrupter, sometimes called a 'GFI' or Ground Fault Interrupter, is part of either an outlet or a circuit breaker.
- It is typically required for added safety on any circuit that may come in contact with water, like outdoors, the kitchen, or the bathroom.
- A GFCI measures the amperage on both the hot and the neutral wires in a 120-volt circuit, or it measures the amperage on both hot wires in a 240-volt circuit.
- If there is more than about a five milliamp difference (5 thousandths of an amp difference) between the amperage readings of the wires, the GFCI acts like a circuit breaker and shuts the power off.
Why might it trip when used with an electric kiln?
- In a kiln, the firebrick is not a perfect insulator, so a tiny bit of the current leaks from the elements to the safety ground and unbalances the current in the two hot wires.
- The resistance of the brick goes down as the temperature goes up, so the kiln may be able to start a firing, but the GFCI would probably trip as the temperature goes up.
- Above 1700°F is when the firebrick has a significant drop in resistance.
- Due to the nature of the firebrick in a kiln, GFCI-protected circuits are not recommended for use with the power circuits in electric kilns. If you must have a GFCI outlet, we suggest hard-wiring the kiln to a fused disconnect switch or circuit breaker.
