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What electrical hazards does a Ground Fault Circuit Interrupter (GFCI) NOT protect against?
Monday, July 9, 2018
The Ground Fault Circuit Interrupter (GFCI) is an important safety device required for electrical circuits in wet areas of a home. GFCI's protect against an electrical shock by tripping within a fraction of a second whenever 6 milliamps or more of the current leaving on the hot wire of a circuit is not returning on the neutral wire. The current that has gone astray is called a “ground fault,” which could cause a shock or even electrocution of a person if the current is flowing through their body, so the GFCI “interrupts” the circuit when this occurs.
A GFCI can be in a receptacle, like in the photo above, integral with a circuit breaker in an electric panel, or installed as a “dead front” GFCI in electrical box by itself.
But here are five unsafe situations that GFCIs do not protect you from:
1) A GFCI does not trip when a person contacts both the hot and neutral wires of a circuit and all the current flows through their body. It does not recognize the problem because no current is leaking from the circuit. While this sounds like a farfetched scenario, we have on numerous occasions come across bare “live” wires at the end of an electrical cable laying half-buried in the insulation in an attic. Inadvertently putting a hand down of the wires while crawling in the attic would be an example of how this situation could happen.
2) Although a GFCI is required to trip within 25 milliseconds, it does not reduce the magnitude of the current. You will still receive a shock for the brief time that it takes for it to shut off the circuit.
3) A GFCI receptacle does not provide protection against too much current flowing through the wires. This is called over-current protection and is provided by a circuit breaker in the electric panel. But GFCI circuit breakers in the electric panel provide both ground fault and over-current protection for the circuits they serve.
4) It does not protect against what is called a “solid short,” where all the current is diverted from its intended route. This could occur between a hot and neutral wire or between two hot wires in a 240-volt circuit. Protection for this problem is provided by circuit breakers.
5) A GFCI does not recognize arc faults, that are typically caused by frayed appliance and extension cords. The hot sparks created by an arc fault have caused numerous house fires. Arc Fault Circuit Interrupters (AFCIs) have been required as part of circuit breakers serving bedrooms for many years, and the requirement has been expanded to most household circuits recently.
None of this is intended to take away from the value of GFCIs for home electrical safety. It’s just that there’s some things they do, and some things they don’t.
Also see our blog post Are Ground Fault Circuit Interrupters (GFCIs) really necessary and worth the trouble?
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