Can a GFCI damage a garbage disposal?

Let's find out what's under the hood of a typical GFCI receptacle or circuit breaker...

A great question from this SubStack

Hey Mike,

Can an outlet protected by a GFCI cause any harm or shorten the life of an appliance (say a garbage disposal) plugged into this outlet? - Steven

Hey Steven,

No, it can't create any damage. A GFCI is basically a latching relay with a sensing circuit that trips the relay off if there's more than 5 milliamperes of difference between the outgoing line current and the returning neutral current. The rest of the time the GFCI does nothing to the supply voltage or current.

How it works

As you can see from the diagram above, a GFCI outlet just passes the incoming power through to the load. And if the sensing circuit determines there’s a current imbalance over 5 milliamps it opens the contacts. This is just like flipping a switch to OFF, so there’s nothing happening inside the GFCI that can damage appliances like a garbage disposal (or whatever).

A GFCI breaker works the same way

But unlike a GFCI receptacle, a GFCI breaker also includes a thermal / magnetic circuit breaker. And just like an GFCI receptacle, until there’s a current imbalance it’s just passing current, just like any standard circuit breaker. But if there’s more than 5mA of current balance, the breaker is flipped OFF.

Let’s play safe out there… Mike