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WShawn 08-01-2008 07:11 PM

GFCI in detached garage question

I got my permits and have started to wire the detached garage/studio I'm building. I'm planning two 20 amp circuits in the garage.

One circuit will have:

-4 outlets along the long south wall and 2 on the back wall
-1 exterior light
-4 hanging fluorescent workshop lighting fixtures

The other circuit will have:

-4 outlets along the north wall and 1 on the back wall
-Garage door opener

I have to protect the outlets with GFCI protection, so the first outlet in each circuit will be a GFCI outlet with the downstream outlets connected to the load terminals of the GFCI. My question is, can I have the lights and the garage door opener connected downstream of the GFCI outlets? The way the garage is configured I'd probably branch the overhead lights from the outlet box that's immediately downstream from the GFCI. Is that okay, or should I run a separate line for the lights and garage door opener?


Shawn Marshall
Portland, Oregon

jrclen 08-02-2008 10:47 AM

Depending on your local code, you can connect the lights and garage door opener either on the line side, before the GFCI, or the load side. It is your choice. I like to connect the lights ahead of the GFCI so if it trips, the lights will remain on.

How will you be running these two circuits? Where will they originate? You are only allowed to install a single circuit from the house to the detached garage. You can get two 20 amp circuits out there by running a multi wire branch circuit, connecting the two hot conductors to a double pole 20 amp breaker in the house and sharing a neutral. You would need a 2 pole disconnect or two switches in the garage to turn them both off. Or you can install a feeder from the house to the garage and install a sub panel in the garage.

Give us more info and we'll help you get this done.

WShawn 08-02-2008 03:27 PM


Thanks for your reply. We have a subpanel installed in the garage which will be connected to a 60 amp breaker in the main panel in the house through an underground conduit running #6 THWN conductors. There will be five circuits coming from the subpanel, 3 to a studio and 2 to the garage.

Logistically I could save some NM-B cable if the garage lights branched off from an outlet downstream of the GFCI outlet, but it's not that much. What I might do is run a separate cable for the lights so they won't go out if the GFCI is tripped but leave the garage door opener downstream of the GFCI.

This earlier post describes the project in more detail:

Since I posted this I dug up the house end of the underground conduit and replaced the turn, and an inspector approved it on Thursday.

Shawn Marshall
Portland, Oregon

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