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-   -   6% voltage drop for 60 amp sub panel? (http://www.diychatroom.com/f18/6-voltage-drop-60-amp-sub-panel-153794/)

stevekem 08-15-2012 03:46 PM

6% voltage drop for 60 amp sub panel?
 
Hello,

I am planning on installing a 60 amp sub panel in my detached garage. Originally I was going to run (3) #6 THWN feeders with a #8 ground, buried in conduit. The total distance from main panel to sub panel is about 160 feet.

After using a voltage drop calculator at southwire, it is saying my voltage drop is going to be 6%+ using this wire.

1) At what percent of voltage drop should I try to stay under?

2) Southwire calc is recommending #2 THWN or #2/0 Aluminum for my feeder, does this sound about right?

Thanks for the help!

Speedy Petey 08-15-2012 03:51 PM

Depends on your calculated load.
If you figure a calculated load of 48A I come up with #4cu.

stevekem 08-15-2012 04:01 PM

Thanks Speedy... Right now, I'm only planning on using overhead lights and a space heater. This will be used for storage of products for my home based business. When I finally decide to use it as regular garage, I will have more load from the typical tools such as a table saw, compressor, etc... I'm not real sure what calculated load I should be going for. Any thoughts?

stevekem 08-15-2012 04:02 PM

If this was your garage, what size wire would you run?

andrew79 08-15-2012 04:03 PM

2 seems awfull big

stevekem 08-15-2012 04:09 PM

Andrew79, that's what I thought too... I'm trying to avoid going up to #4 THWN if possible because of price, but if that's what is needed then I guess I have to...

andrew79 08-15-2012 04:15 PM

Speedy's most likely right with the number 4 I would think. Still smaller than 2 so should save you some coin.

It depends on your heater. You can really only have one or two tools running at the same time so the wattage of your heater will determine your service size for the most part.

stevekem 08-15-2012 04:18 PM

Garage is only 300 sq ft, not sure if that affects anything... I guess I could drop my breaker size down to 40 amp, but not sure if that would be enough in the future or not?

stevekem 08-15-2012 04:21 PM

Which do you think would be the cheaper route to go, #4 THWN or #2/0 aluminum? Any drawbacks to going with #2/0?

k_buz 08-15-2012 04:41 PM

Quote:

Originally Posted by stevekem (Post 989515)
Which do you think would be the cheaper route to go, #4 THWN or #2/0 aluminum? Any drawbacks to going with #2/0?

Drawbacks:
1) 2" PVC
2) 60A breaker not rated for 2/0 connections.

stevekem 08-15-2012 05:00 PM

I just priced the 2/0 (w/ground) and it's much cheaper than the copper... I think I will go this route. At 160 ft, what size breaker should I go with that is rated for 2/0 connections?

k_buz 08-15-2012 05:01 PM

2/0 AL XHHW is cheaper than #4 THHN/THWN? Don't believe it.

stevekem 08-15-2012 05:02 PM

Just to clarify my question, at what breaker size should I go with (that is rated for 2/0 connections) that will keep my voltage drop at an acceptable level?

stevekem 08-15-2012 05:03 PM

At HD, price was only $1.42/ft for 2/0 with ground. #4 THWN was more than double that. Am I pricing the wrong wire?


Quote:

Originally Posted by k_buz (Post 989540)
2/0 AL XHHW is cheaper than #4 THHN/THWN? Don't believe it.


stevekem 08-15-2012 05:05 PM

I am pricing 2-2-2-4 SE cable at $1.42/ft


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