I’ve read that the same gauge wire must be used throughtout a circuit. Does that include the grounding wire of a receptacle or switch?
We have 12-gauge wire left over from a kitchen remodel. The receptacles and switches I’ve been replacing use 14-gauge wire. Is it safe to use 12-gauge for the grounding wires?
Janet
Replies
The real restriction is that wire must be "protected" by a breaker that is sized for the smallest wire in the circuit. This means that if there is any #14 wire in the circuit the breaker can be no larger than 15A (aside from some special cases). There is disagreement (based on how the inspector reads the code) as to whether it's OK to mix wire sizes in a circuit. And much of this restriction doesn't apply to ground wires -- they're permitted to be smaller in some circumstances.
But I can't imagine any inspector objecting to using #12 ground wire in a #14 (15A) circuit, so long as the wire fits the fittings.
I hadn't known the reason behind the restriction, but it reminds me of an experiment I did as a kid. I took the foil-covered paper from a pack of cigarettes and cut strips that narrowed in the middle. Held the ends of a strip to each end of a "dry cell" (that's what they were called back then) and watched the strip burn up, always starting at the narrowest part. Back then I did the experiment for fun without thinking about the science, but the wiring code makes more sense now.
Janet
Bigger is OK
For your smaller circuits, you are required to have a 'full size' ground wire. that is, the ground wire cannot be made smaller than the circuit conductors.
Nothing says it can't be larger.
Good to know, thanks. I didn't want to waste the leftover wire.
I did find one switch that had a 16-gauge grounding wire. Don't know if that was incorrect, but it didn't matter since I was replacing the whole thing anyway.
Janet
The #16 ground was likely legal at the time. Originally, ca 1950 or so, grounds were not required at all. Then, maybe until 1965 (rough guess) the ground could be smaller than the other wires. For wires larger than about #6 it's still the case that the ground can be one size smaller, but for regular household wiring the ground must be the same minimum size as the rest. (Remember, a "smaller" wire gauge number indicates a larger wire.)