Ground wire size


Old 02-07-11, 05:50 PM
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Ground wire size

Over the years, I have noticed that on some romex type wire and some extension cords have a ground wire that is smaller then the load wires.
I always thought it was correct to have the same gauge wires.
When is a smaller ground wire ok?
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Old 02-07-11, 06:35 PM
Tolyn Ironhand's Avatar
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Many cases you may have a ground wire smaller that the other conductors. If you have a code book (or you might find it on the net) go to table 250.66 or 205.122. You will find that as the conductor size or amperage goes up the ground wire can lag behind. This is because it is figured that the ground wire will only carry current for a very short amount of time compared to the other conductors.

As far as the cords you mentioned, they were likely engineered that way and passed the UL listing process.
Old 02-07-11, 06:56 PM
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Thanks---That makes sense-----Now I know
Old 02-07-11, 07:18 PM
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Back zen, the ground wire was premitted to be 2 number sizes smaller than the conductors.

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