What size ground wire?

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Old 10-24-15, 08:45 AM
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What size ground wire?

I have three 12-2 NM cables pulled into my garage for 3 x 20A circuits. I would like to run THHN from a junction box and use a common ground wire for all three circuits. What gauge wire must I use from the junction box to the panel?
 
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Old 10-24-15, 08:57 AM
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You would use a #12 ground wire.
 
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Old 10-24-15, 08:58 AM
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Attached or unattached garage?
Trying to figure out why your not installing a small sub panel in the garage.
 
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Old 10-24-15, 03:37 PM
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The answer to joecaption's question can extremely important. If the garage is not attached to your house (a separate structure), the NEC allows only one circuit. That circuit can be a feeder to a subpanel feeding multiple circuits withing the garage.

Buildings or Other Structures Supplied by a Feeder(s) or Branch Circuit(s)
225.30 Number of Supplies.
A building or other structure that is served by a branch circuit or feeder on the load side of a service disconnecting means shall be supplied by only one feeder or branch circuit unless permitted in 225.30(A) through (E). For the purpose of this section, a multiwire branch circuit shall be considered a single circuit. (NFPA-70, 2014)
 
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Old 10-25-15, 08:01 AM
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This is an attached garage. Hopefully the image below will help:
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Old 10-25-15, 09:08 AM
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For a 20 amp circuit you need a #12 ground.
 
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Old 10-25-15, 09:33 AM
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I understand 20A = #12. My question is: Must I change the gauge of the ground wire if I'm combining the ground from three separate 20A circuits?
 
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Old 10-25-15, 10:58 AM
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No.... you need to use ONE #12 green wire from the panel to the garage.
 
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Old 10-25-15, 02:22 PM
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You still have not ansewered an important question.
Is the garage attached to the house?
If not there's a whole different set of rules.
 
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Old 10-25-15, 02:26 PM
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This is an attached garage. Hopefully the image below will help:
If you aren't going to read the replies... don't respond.
 
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