GFCI Wiring w/Three Wire Cable

[bobimhoff]

Hey everyone - looking for help with a simple question. I'm installing a GFCI outlet under my sink for my garbage disposal.

The line coming in is a three-wire cable, and the load going out is a two-wire cable. The grounds are already pigtailed together - I know I'll connect that to the ground. I'm thrown off a bit by the red wire. It isn't hot, only the black wire (A) on the line is.

I hope the diagram makes it easy to describe. If the red wire wasn't there, I would think to wire it as follows:

1A, 3B, 2F, 4E, 5D

How should I go about wiring this outlet? Where should the red wire go?

 

[Reach4]

I would cap the red wire with a wire nut.

Regarding hot vs white (neutral) for the GFCI, usually the neutral screws are silver color, and hot is goldish. I think that may be what your photo shows.

Your downstream outlets should get a “GFCI PROTECTED” label. https://www.ncosfm.gov/electrical/4064d2-gfci-stickers/open

 

[Sponsor]

 

[bobimhoff]

Thanks for the response - only issue is that if I do it that way, the garbage disposal will be on regardless of the switch position. Previously, with a standard outlet, the two black lines were capped together with a wire nut, and the red wire was connected as the line. This doesn't seem to work with the GFCI, however.

 

[wwhitney]

If you had a working always-powered normal receptacle, and you replace it with a GFCI, using only the LINE terminals on the GFCI, matching which wire goes to the side of the receptacle with the wide plug (neutral) and which goes to the side of the receptacle with the narrow plug (hot), the GFCI will work properly unless it is defective.

I infer that the reason you have 3 conductors on the incoming power cable is that switched power for the garbage disposal is routed through this box. So the 3 wires are neutral (white), always hot (black or red), and switched hot (red or black, respectively).

Cheers, Wayne

 

[Reach4]

Thanks for the response - only issue is that if I do it that way, the garbage disposal will be on regardless of the switch position. Previously, with a standard outlet, the two black lines were capped together with a wire nut, and the red wire was connected as the line. This doesn't seem to work with the GFCI, however.

Is the red wire hot when you flip the switch?

 

[bobimhoff]

Is the red wire hot when you flip the switch?

Yes, when switched the red is hot.

 

[wwhitney]

Yes, when switched the red is hot.

So then if the "load" is the garbage disposal, the connectivity should be:

D-5
B-3-E
C-F
A-1

That will make the garbage disposal switched (no GFCI protection), and the GFCI receptacle constantly powered.

Cheers, Wayne