sub panel questions- thhn and gray pipe

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Old 11-16-09, 07:34 AM
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sub panel questions- thhn and gray pipe

Hi to all,

I plan on running #6 THHN thru gray pipe to my garage 90 feet away for a 50A subpanel. I plan on connecting the gray pipe from the main to the sub panel. Can I run the gray pipe along the out side of my foundation wall( which is underneath my deck) until I get to the end of my house and then down 24" in the ground to the garage?

Thanks, JB
 
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Old 11-16-09, 08:33 AM
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Yes, as long as the conduit is properly strapped within 3' of each termination and no more than 3' between straps. You may need to consider an expansion fitting where subject to ground movement from frost heave.

You need to use THWN in an exterior and underground application. THHN is only for interior usage. Most THHN will be dual rated THHN/THWN but check before purchase.

Where subject to physical damage Schedule 80 PVC would need to be used.

You will also need a grounding system at your outbuilding.
 

Last edited by ibpooks; 11-16-09 at 09:26 AM.
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Old 11-16-09, 10:57 AM
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Thanks PCB,

I have another question about the ground. An electrian told me that I could use #10 ground wire instead of #6 but I need an 8ft ground rod at the garage sub panel. Is that true?

thanks, JB
 
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Old 11-16-09, 12:04 PM
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A #10 copper ground green or bare only is fine with #6 copper. Yes you need an 8 foot ground wire to comply with 2008 NEC.

See: http://forum.doityourself.com/electr...-drawings.html
 
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Old 11-17-09, 03:15 PM
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Thank you Ray for your help on this. JB
 
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Old 11-17-09, 05:35 PM
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Originally Posted by Jethro buckeye View Post
Hi to all,

I plan on running #6 THHN thru gray pipe to my garage 90 feet away for a 50A subpanel. I plan on connecting the gray pipe from the main to the sub panel. Can I run the gray pipe along the out side of my foundation wall( which is underneath my deck) until I get to the end of my house and then down 24" in the ground to the garage?

Thanks, JB
I don't what to throw you a curve in this but you can use #8 wire on this 50 amp sub panel if your are using THHN/THWN wire the complete way. As long as your termials on the breakers or lugs are rated for 75c you're good. It could save you some money.

Thanks!
Jim

 
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Old 11-17-09, 06:01 PM
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Along that same vein, if you stick with the #6 you can increase the breaker to 60A.
 
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Old 11-17-09, 08:32 PM
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Originally Posted by ray2047 View Post
A #10 copper ground green or bare only is fine with #6 copper.
If you run the pipe outside then the ground can only be insulated. Not bare.
 
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