Size of ground wire

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Old 07-11-06, 12:55 AM
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Size of ground wire

I've heard the general rule for the ground wire when running #8 or #6 in conduit is that it can be one size smaller, is that right? So, for a 4-wire run, I'd use 3 x #8 with a #10 ground?

BUT, then I see that #6 Romex still has only a #10 ground. Why?
 
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Old 07-11-06, 04:02 AM
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There is NO "general rule".
We use Table T250.122, which sizes the grounding conductor according to circuit amperage size.

Up to 30 amps the ground must match the circuit conductors.
For up to 40 & 60 amp circuits the ground size is #10cu.
For up to 100 amp circuits the ground is #8cu.
...and it goes on from there.

Keep in mind, if you upsize the circuit conductors for any reason you must also upsize the ground accordingly.
 
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