What size ground wire?
#1
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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?
#4
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)
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)
#10
This is an attached garage. Hopefully the image below will help: