Current setup is a 20A breaker that powers:
- Above counter: 2 gang box with:
- Left side: a switch powering over-sink light
- Right side: a switch for the garbage disposal
- Under sink: A hardwired garbage disposal
Desired/plan:
- Replace the garbage disposal switch with a 20A GFCI
- Install a 15A receptacle below sink (where I'll plug in a button air switch for a plug-in disposal + hot water dispenser)
Nothing wrong with this plan I hope?
I have questions about how to properly wire the GFCI, so that it (I think should) also protect the under-sink outlet.
As I look to install the GFCI, the instructions say:
DO NOT install the GFCI receptacle in an electrical box containing (a) more than four (4) wires (not including the grounding wires) or (b) cables with more than two (2) wires (not including the grounding wire)."
As you can see from the photos, I have 3 cables going into the box. All 3 cables have black/white/ground. Can this be installed and if so what is the correct wiring?
Please let me know if you need more information and I can edit this. In USA.
Best Answer
When UL lists the device, they list the instructions along with it.
The reason for the "DO NOT" instruction is because the instructions in the GFCI device are written for the specific case of one cable in; and 0 or 1 cable out. UL would not approve more complex instructions to handle every case; so the instructions say to get professional help if your case is more complex than the instructions.
The way to wire it is to identify "Always-hot" (which is hot at all times) and true Neutral. Pigtail "Always-hot" to the LINE brass screw. Pigtail Neutral to the LINE silver screw.
GFCI devices have the ability to provide GFCI protection to a downline. If you want to protect downline points-of-use, then for each downline load, hook its Hot wire to LOAD brass screw, and its Neutral wire to the LOAD silver screw. Only do these in pairs - both hot and neutral of any downline.
Note this can get quite confusing where switches are concerned.