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#220351 10/27/19 10:04 PM
Joined: Mar 2004
Posts: 814
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BigB Offline OP
Member
These are online instructions for a 40 amp EV charger. Note the sentence in the red box.

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A
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12 AWG ground on a 40 amp breaker is what is allowed in T250.122.

Joined: Mar 2004
Posts: 814
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BigB Offline OP
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Originally Posted by ampherder
12 AWG ground on a 40 amp breaker is what is allowed in T250.122.


I see that now, I wasn't aware it had changed

Joined: Jul 2004
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G
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I understand table 250-.122 may be confusing to read but it says
Rating or Setting of
Automatic Overcurrent
Device in Circuit Ahead
of Equipment, Conduit, etc.,
Not Exceeding
(Amperes)

20 12ga copper
60 10ga copper

I read that to say if you exceed 20a and do not exceed 60a you are in a #10.
Just as a sanity check, what size is the ground in a 10ga or 8 ga cable ... 10ga


Greg Fretwell
Joined: Mar 2004
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BigB Offline OP
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OK yes that makes sense. They made it a bit confusing when they took out the 30 and 40 amp columns just because we were so used to seeing those numbers included but when you think about it they weren't necessary when the higher amperage columns jump from conductor size to conductor size with no repetition. So the instructions for the EV charger are incorrect.

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G
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Yes the OP was right and the EV instructions were wrong.
They made the change in format to T 250.122 in the 2011 cycle but the rule didn't change.


Greg Fretwell

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