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How to GFCI-protect a 3 gang box where each receptacle is on a different circuit.

There's a 3-gang box near my kitchen sink. In it is a light switch, the garbage disposal switch, and an outlet. All of these are on different circuits (with the disposal on a dedicated circuit).

Is there a way to project all of these with a single GFCI, or do I need to replace all three with GFCIs?

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    It would be pretty rare for the disposal to have its own circuit, as pointed out, it’s a small intermittent load. More common is that it shares with the dishwasher. How old is the construction? Are we talking a house built 40,30,20,10 or 5 years ago? Asking because it gives clues about what electrical codes were in force at the time of construction. – Tyson Apr 16 '18 at 14:00
  • @Tyson if its draw is more than 50% of circuit capacity, then it cannot share the circuit with receptacles. (and that receptacle can't be a kitchen countertop receptacle, as they cannot share power with anything but gas ovens and clocks). So the only thing it could share with is other hardwired loads, but those together cannot exceed 100% of circuit capacity (80% for continuous). This can paint you into a corner where you end up needing to dedicate a circuit. – Harper - Reinstate Monica Apr 16 '18 at 16:43
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First, "GFCIs", it sounds like you are talking about the "GFCI + receptacle combo device" readily available all over. While that is one way to provide GFCI protection, it can also be provided by a GFCI device upstream. Any GFCI device can protect all downstream loads. As such, GFCIs come as

  • a GFCI+circuit breaker combo device
  • a GFCI-only device (deadfront, looks like a receptacle but with no holes)
  • a GFCI+receptacle combo device, if having a receptacle on that circuit is allowed there, which in the case of kitchen receptacle circuits, it is not.

So for instance, providing GFCI protection to a switch obviously can't be done by a GFCI+receptacle combo device at the switch location. You need to find an upstream location and install a GFCI device.

You said "GFCI protect your 3-gang box", and it doesn't work that way. Boxes don't get GFCI protection, outlets do. (an "outlet" includes any electrical tap, including hardwired loads such as a light or disposal). This box has a mix of things that do, or do not, need GFCI protection. Lighting generally doesn't need GFCI protection. A disposal may, but putting it downstream of a switch is bad form, as some GFCI devices don't like their power being interrupted. The better location for that GFCI device is upstream of the switch.

Home inspectors are particularly awful about spreading this "GFCIs are receptacles" myth. . If they don't see a "Test" and "Reset" button, they tell you it needs a GFCI there. This is why "GFCI protected" stickers are required on plain receptacles whose GFCI protection is sourced from upstream. Unfortunately, some people consider them unstylish, and tear them off. Get more. You can also make them with a labelmaker, they need not be blue.

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The Outlet, the Garbage Disposal (intermittent usage) , the lights are probably all on the very same Circuit Breaker.

Change out the Circuit Breaker in your panel for something like this {click me}.

  • The kitchen receptacles must be a separate circuit from the disposal and lights, so that guarantees 2 circuits. It is wise to put lighting on a different circuit from other loads, so a usage trip doesn't plunge you into the dark. Three circuits is reasonable. – Harper - Reinstate Monica Apr 16 '18 at 16:29

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