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Old 08-15-2012, 02:46 PM   #1
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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!

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Old 08-15-2012, 02:51 PM   #2
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6% voltage drop for 60 amp sub panel?


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

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Old 08-15-2012, 03:01 PM   #3
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6% voltage drop for 60 amp sub panel?


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?
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Old 08-15-2012, 03:02 PM   #4
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6% voltage drop for 60 amp sub panel?


If this was your garage, what size wire would you run?
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Old 08-15-2012, 03:03 PM   #5
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6% voltage drop for 60 amp sub panel?


2 seems awfull big
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Old 08-15-2012, 03:09 PM   #6
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6% voltage drop for 60 amp sub panel?


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...
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Old 08-15-2012, 03:15 PM   #7
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6% voltage drop for 60 amp sub panel?


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.
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Old 08-15-2012, 03:18 PM   #8
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6% voltage drop for 60 amp sub panel?


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?
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Old 08-15-2012, 03:21 PM   #9
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6% voltage drop for 60 amp sub panel?


Which do you think would be the cheaper route to go, #4 THWN or #2/0 aluminum? Any drawbacks to going with #2/0?
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Old 08-15-2012, 03:41 PM   #10
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6% voltage drop for 60 amp sub panel?


Quote:
Originally Posted by stevekem View Post
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.
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Old 08-15-2012, 04:00 PM   #11
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6% voltage drop for 60 amp sub panel?


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?
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Old 08-15-2012, 04:01 PM   #12
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6% voltage drop for 60 amp sub panel?


2/0 AL XHHW is cheaper than #4 THHN/THWN? Don't believe it.
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Old 08-15-2012, 04:02 PM   #13
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6% voltage drop for 60 amp sub panel?


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?
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Old 08-15-2012, 04:03 PM   #14
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6% voltage drop for 60 amp sub panel?


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:
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2/0 AL XHHW is cheaper than #4 THHN/THWN? Don't believe it.
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Old 08-15-2012, 04:05 PM   #15
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6% voltage drop for 60 amp sub panel?


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

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