Help running 220 to garage, underground

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  #1  
Old 09-26-04, 12:07 PM
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Help running 220 to garage, underground

I just finished a new garage and want to run a 220 line into a subpanel in the garage and run circuits from that. Basically, I do a lot of woodworking and often have many large power tools running at once, causing the need for the 220 and numerous circuits.

I just checked my main box in my house and the main breaker is a double 100 amp.

In order to run this electric, I need some help. My understanding is that I'd run a romex wire (6 gauge?) to a junction box just before it leaves the house (to underground conduit), where I would make a junction with single strand wire made for underground conduit. Then, after that enters the garage, there would be another juntion box that would connect back to the romex, which would run to the box and a main breaker, which I could then add other breakers too?

My dad's electrician did his this way (we live in Bflo, NY). What I need to what type of wire/guage I use for the romex and single strand? Also, does set-up sound correct? My father's past his electrical inspection so I assume that it is correct?

Once I get mine run, I'm having a friend who is an electrician tie everything together. But I'd like to have this done correctly before he comes!!!

thanks
 
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  #2  
Old 09-26-04, 12:22 PM
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often have many large power tools running at once
If you want to make sure you have sufficient power, you should quantify this statement with how many is "many" and how large is "large". And to properly design for voltage drop, you should also figure out exactly how many feet the run between panels will be.

Your basic plan sounds fine. Put a double-pole 60-amp breaker in the main panel, and use 6/3 NM-B Romex inside, and #6 THWN wire in PVC conduit buried at least 18 inches deep.

Note that you could use 6/3 UF-B for the entire run (buried 24 inches deep), or #6 THWN in conduit the entire run, and avoid the junction boxes. But it's fine your way too.

Assuming that this garage is detached, install a grounding rod at the garage, and make sure you keep the neutrals and grounding bars electrically isolated at the garage.
 
  #3  
Old 09-26-04, 12:41 PM
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The tools were talking about are 1-4 HP table saws, compressor, mitre box, dust collection (to come soon!). Not arc welders or anything like that! Might have a compressor running along with a mitre box plus lighting and eventually dust collection.

As for the run from the main box in my house, all told it'd be about 65 feet, with about 25 underground from the house to the garage.

Yes, I forgot to mention the ground rod. Would 8-foot copper be sufficient?

Cna you explain this a little. Maybe it's something my electrician knows:

Assuming that this garage is detached, install a grounding rod at the garage, and make sure you keep the neutrals and grounding bars electrically isolated at the garage.
 
  #4  
Old 09-26-04, 01:04 PM
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An 8-foot copper rod would be just fine. You'll probably be hard pressed to find anything else at your home center anyway. Drive it so that 100% of it is underground.

If you've never read about keeping the grounding and neutrals separate in a subpanel, then you have not studied enough to begin this job yet. That's Subpanels 101. The idea is to prevent any of the neutral current from flowing on the grounding wire. It often requires you to purchase a separately-sold grounding bar kit, and always requires you to discard the green bonding screw or remove the bonding strap. Don't mess up this critical detail.
 
  #5  
Old 09-26-04, 01:13 PM
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Thanks again. I can get a 10-foot copper rod at my local hardware store!

That's why I asked for a clarification because I haven't done this. My intention, as I mentioned in my initial post, was to just get everything ready for my friend to actually complete the service. I plan to do nothing more than rough it in and let him finish.
 
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