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View Full Version : Adding new sub panel box to exixting service


Wthompson
Sep 27, 2007, 04:51 AM
I need to run a new circuit to a new shop/garage that I just built. My plan was to add another sub-panel box beside my main service and then trench out to my shop with an underground service.

I have a 200 amp main, in an all electric home, about 2500 sf total, the new shop is 720 sf. But will be just light duty tools, will be an 220 service for possibly a stand up compressor, I figured that I need a 50-80 amp service to the shop.

My existing home supports, range, hvac, hot water, hot tub, the existing garage which was already running the above items needed in the new shop, and all the other normal items in a home.

My question is can I tie onto the bottom lugs of the main service panel to tie in this new sub panel box, we live in the country, so I do not have to go through any city inspectors, but is this process safe and sound.

Thanks

Wthompson
Sep 27, 2007, 02:46 PM
I need to run a new circuit to a new shop/garage that I just built. My plan was to add another sub-panel box beside my main service and then trench out to my shop with an underground service.

I have a 200 amp main, in an all electric home, about 2500 sf total, the new shop is 720 sf. but will be just light duty tools, will be an 220 service for possibly a stand up compressor, I figured that I need a 50-80 amp service to the shop.

My existing home supports, range, hvac, hot water, hot tub, the existing garage which was already running the above items needed in the new shop, and all the other normal items in a home.

My question is can I tie onto the bottom lugs of the main service panel to tie in this new sub panel box, we live in the country, so I do not have to go through any city inspectors, but is this process safe and sound.

thanks
Anybody??

tkrussell
Sep 27, 2007, 03:07 PM
Sorry , I saw your post this AM, but been on the run all day, as I manage a service dept of 8 guys working in critical customer locations, and of course, because I need to travel out of state tonight, we had a power issue in a datacenter that needed to be dealt with, so, wheww.

Not sure I understand completely. If you install a subpanel next to the main, what will you run through the trench? All the branch circuits? Or is the sub for the feeder main to a subpanel in the garage?

If you have spare live lugs at the bottom of the main panel, on the load side of the main breaker, you may feed a subpanel from there.

Would be better, and more appropriate, to install a 2 pole 50-80 amp breaker in the main panel, as long as there is two spare breaker slots, and then run the feeder out to the garage panel. This feeder needs to be 4 wire, two hots, 1 neutral, and 1 equipment ground.

Next need to decide on a feeder size , to chose the feeder breaker and feeder wire size, and equipment ground size. Then decide what wiring method will be for the buried feeder, PVC conduit with pulled THHN/THWN copper wires, or direct burial URD aluminum cable.

So I should have more time the next couple of days to a answer any other questions you may have. I can manage my guys via phone, as I need to go do some moonlight electric work in another state for a relative. No rest for the weary.