Not to hijack, but I have similar question. We want to install exterior GFCIs on our garage (forgot during build, we have one on back of house and 2 on porch but they're too far for charging battery on tractor, etc.). Have 20A circuit for interior garage receptacles and 1 dedicated for freezer. Electrician did not use conduit - ran all the 12/2 (and 14/2 for lights) up in trusses, then down through holes along studs where (plastic) outlets are located. I want to pull off one outlet in back of garage, would be easy to take out a couple of staples, pull wire up, drill new hole and run it down a few feet over for new exterior box. Then to save wire I was hoping to run either straight through a couple of studs (as is done in interior house wiring) or *down*, put the holes low in studs, and then up a couple of feet to new box. If I ran straight across I would put in conduit. If I ran down to sill plate, would it need to be in conduit? Or, do I have to run *up* and over like all the other wiring in garage? Walls are just studded out, no insulation or drywall (except shared wall with house). We may finish them at some point.

With some exceptions, the metal conduit serves a the equipment ground so there is no need for a ground wire. In that scenario you need to use self grounding devices in firm contact with the metal junction box or use a short pigtail from the device to the box. Of course, if you are a belt and suspenders kind of guy, you can run a separate ground wire and treat it like you would with non-metallic cable.

Depending on how far you have to go, it will not be easy to fit 6 conductors in 1/2" PVC. I would suggest at least 3/4". Tape all six conductors together to make the job of pushing them through the conduit easier. Be sure to use electrical grade PVC and glue as well as wide angled ells if you need to make any 90ties.

Bill - Thanks for the input. I'm not sure why the contractor didn't suggest the subpanels, but I'll ask him. They seem like a good idea, especially since we're going to have to run multiple conduits from each junction box to the panel due to the space constraints and derating.