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tpagel 07-07-2008 10:38 PM

Outbuilding wiring and underground wiring questions
First off, I am not an electrician, so my apologies in advance for any REALLY stupid statements/question. ;-) I plan on doing research for my project, doing the grunt work, like pulling wires/cables and such, and then letting a licensed electrician review it all, make connections, and power it all up! That said, here's my situation:

I have a 200A main service in the house I bought last year. I also have a 600 SF outbuilding I plan to convert to a small shop/studio. It is about 175 feet from the main panel in the house (in the attic level, actually) The previous owner had the same idea, and already ran a couple PVC conduits from the house to the outbuilding, underground, though I don't know the depth yet. Going by memory here, one conduit is 2" diameter and one is about 3/4" diameter.

My little shop will probably have a table saw, a drill press, a disc sander, scroll saw, and radial arm saw as its main "equipment", along with some shop lighting, maybe a window mounted air conditioner, stereo system/radio, and hopefully, computer capabilities. It will be only me in this shop, so only one "tool" would be running at any one time.

My questions are: How would I determine the wire size for this load and this length of run? Would a 60A sub-panel be adequate? Is PVC conduit OK for this kind of thing, and what depth is required by code?

From my reading, I believe that the panel size is OK, and will require a separate grounding rod bonded to the ground terminal in the sub-panel, and the ground and neutral will need to be separate in the sub-panel as well. Right? Additionally, my GUESS is that romex is the wrong way to go, and that maybe 10/2 wire is OK to pull for this application, on a GFCI from the main panel?? Another post I read said something like "Pull 3, #8 THWN (2 blacks and one white) and a #10 green" for a similar situation?? Was planning on a 12 space/24 circuit panel.

So what have I got right, and what have I got wrong? Any other suggestions/comments are most appreciated.

Thanks again!

jimmy21 07-08-2008 12:17 AM

39 Attachment(s)
if it were me, id pull 2 #6's and a #8 nuetral. Then run bare #6 to 2 ground rods. That would give you 60 amps. To put that in perspective, thats 60 amps per phase, thats a lot of current. Which should be enough for your application, as long as your not going to hook up a big welder or a giant air compressor.

oh and yes pvc is the right thing to use, And i believe its 18 inches for depth, but i always try for 2 feet

BillyD 07-08-2008 06:21 AM

I have read that a 60 amp. breaker gives you 30 amps each leg.

jbfan 07-08-2008 06:26 AM


Originally Posted by BillyD (Post 137024)
I have read that a 60 amp. breaker gives you 30 amps each leg.

What you read is wrong!

HouseHelper 07-08-2008 07:37 AM

60A should be plenty, but given the distance I would run #4Cu, or better yet, buy some mobile home feeder (2-2-4-6) Al and save some money. Run this in the larger pipe, and run your phone/cable in the smaller one. You will need ground rods at the shop and an isolated neutral.

BillyD 07-08-2008 08:28 AM

So it is a 120 amps 60 amps each leg but will be marked as a 60 amp? 200 amp main does that also mean 400 amps?

HouseHelper 07-08-2008 08:32 AM

It is 60A each leg, marked as 60A.

jimmy21 07-08-2008 08:38 AM

39 Attachment(s)
ya, it would just be a 60A 2 pole breaker. 2 pole meaning 2 legs, each one rated at 60A

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