The original light switches had the ground spliced at the back and not connected to the switch. I am replacing the switch with a new 15a rated light switch and spliced a 14g ground (I just cut a new from a spare cable I had) and spliced with the rest of the grounds.

I don't know if this is to code. Namely, a 15a breaker having 12g wiring (this is on the whole house and the breakers look original from the 80s). Then me putting a 14g ground from a light switch that is rated for 15a.

  • Code mentions minimums allowed. Having 12 or 10 gauge wire just costs more but is allowed, if the device will take 10 gauge. It does not work the other way, you cannot have 14 gauge wire on 20 amp breaker(ground might be an exception). Larger is allowed, smaller(than code minimums) is not.
    – crip659
    Oct 19, 2023 at 17:37

1 Answer 1


You need to use #12 pigtails for #12 circuit conductors.

NEC 250.122(B) Increase in Size. If ungrounded conductors are increased in size for any reason [except temperature or conduit fill code sections] equipment grounding conductors, if installed, shall be increased in size proportionately...

The ugly part is "for any reason". I can't create a logic argument that concludes "no reason".

Might be worth noting 404.9(B) allows grounding of snap switches installed in metal boxes by metal screws, even without the switches being marked self grounding. A strict interpretation of 250.122 would still require #12 ground wire if switch has a ground wire.

  • For reading clarity "[except temperature or conduit fill code sections]" replaces text of code sections that address those adjustment factors. Oct 19, 2023 at 18:39
  • Regarding metal box, I had a similar argument with an inspector, I had an existing EMT conduit with #12 20A ground, added #10 30A circuit and the inspector made me pull out the #12 ground wire or replace it with #10 even though the ground wire was redundant. Oct 19, 2023 at 18:40
  • 1
    If understand this correctly, in plain English, I have to use a #12 ground (pigtails look like any bare #12 ground) because the existing cables are #12 regardless of the fact that the breaker is 15a. right?
    – Michael
    Oct 19, 2023 at 19:56
  • Yes that is the NEC requirement, and that is a section so rarely objected to that it is unlikely to have an exception adopted locally. Oct 19, 2023 at 20:07
  • @NoSparksPlease do you have any idea when that requirement was introduced into the NEC? I have some old black #14 "romex" in my house which has a #16 bare ground wire alongside the #14 ungrounded pair. Probably built/installed sometime around 1965.
    – brhans
    Oct 19, 2023 at 20:59

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