New sub in Detached garage w/ existing circuits

First off - thanks to all who helped with my service upgrade and rewiring questions I asked several months ago. All work went with out a hitch and was approved. Now I am in the process of finishing up the rooms, and want to move my workshop out to the garage from the soon-to-be family room. In order to do that, I need to run a sub into the garage.

First off - the garage is ~30 feet from the SEP in the basement. I will run the cable out the basement wall, and down into a trench / conduit (thinking schedule 40/80 PVC?). I will bury it 18" and run into the side of the garage.

I would like to put in a 60 amp feed. When I went to the BORG, the guy was pretty clueless about the types of wire they sell, and said "8/3 UF was all they had that would work". I figured I needed atleast #6 wire for the sub. Correct? Should I use THWN?

Also, currently the garage has 2 UF feeds to it - 1 12/2 feed for a single outlet and overhead light, and a 14/3 line connected to a 3-way switch that controls a spot light on the house. The other 3-way is inside the house. Do I have to remove the existing circuits? Or can they coexist with the new service.

Here is what I plan on running in the garage - 5-6 outlets, 3 overhead flourescent lights, 120v/15 amp table saw, plus other woodworking tools. I also want to install a garage door opener. I might want/need to run a window AC unit in the summer and some type of heater in the winter. Is 60A way overkill?

TIA,

Tony
PS - yes, I will pull permits.

 

I don't believe it's overkill. By the way, you're only supposed to have 1 circuit run to the garage, not 2.
You'll also need a 4 wire feeder (2 hots, 1 neutral and 1 ground), and the subpanel will have to have separate unbonded neutral and ground bars. You'll probably also need a grounding rod, but I'm not sure on that. If you use conduit I'd go with separate cables instead of NM. A 1 1/4" conduit should be large enough.

 

Does anyone else have comment? Do I have to remove the existing 3-way? Removing the existing recep / overhead light isn't a problem.

Or, can the sub coexist with the other circuits?

Is there a way to leave the other circuits comming into the garage, but not connected anywhere (eg at main SEC)? I don't want to have to dig up the driveway more than I have to.

Thanks!

 

Leave the 3-way.

Remove the other circuit, but you can leave the wire in the ground.

You can buy 6/3 UF and install without conduit, buried 24" deep. Home Depot sells it if you can't find it anywhere else.

Yes you need grounding rod(s).

60 amps might be overkill, but it's not "way" overkill. I'd go with it.

 

Thanks for the quick reply John! I know I need the ground rod - does the Depot sell that too?

Would I be better of with the conduit approach? I wouldn't mind direct burial, but I think I might want to use conduit since it will be pretty much in my wifes flower beds...

Also, if I went with the 6/3 romex, would I run it directly through the wall into the basement and then to the main panel? Or should I put in a j-box on the outside of the house?

Or should I just buy the 3 #6 THWN (2 black, one white?), 1 green #8 THWN for ground? I am not sure that the depot carries the #6. I might have to go to an electrical supply place.

 

Yeah Home depot sells ground rods... Usually right with the conduit (at least with at my local one)... If you run the PVC with THHN, its not that bad, but if you have the space and sounding like your going below ground, go a little bigger on it then the minimum.. I did it for the first time tonight and it was a pain, cuz I got the smallest acceptable size... Do-able, but just a pain..