Service wire size

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NewbieElec

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Hey there, I'm a fairly new electrician trying my hand at some residential, after working mostly industrial.

I need to run some direct bury cable from a meter 200ft to the panel in a cabin. I'm coming up with 2/0 copper that I'll need to stay in voltage drop tolerance. Just wanted to double check to make sure that's correct.

Thanks!
 
infinity

infinity

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With #2/0 copper you could put in a 200 amp service. VD compensation is this case is optional but if you ran the numbers then you should be good to go.

Welcome to the Forum. :)
 
roger

roger

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You're going to have to give a lot more detail as to the calculated load per article 220, what size service, what is the actual distance you're figuring the VD at, etc....

Your question is something like asking if 14" tires will work on your car.
Without giving the particulars a correct answer is unlikely.

Roger
 
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NewbieElec

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I apologize for the fuzzy details. I just went to the site today to check it out for myself. The current service drop is about 200ft from the house and is 100A. I will be installing new service equipment at the pole to supply both the house and cabin. The total distance from the meter at the service drop to the cabin is 350ft direct buried. I'll be installing a disconnect on the side of the cabin which will then stub into the panel inside. The service for the cabin will be 100A.

So i'm plugging in these numbers:

(2 * 350ft * 100A * 10.7) / (120v *.03) = 208,055cm

So I'm coming up with #4/0 (211,600cm) that I will need from the Meter to the Disconnect. I feel like that is too big, but am unsure what I am doing wrong.

Thanks
 
infinity

infinity

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NewbieElec said:
I apologize for the fuzzy details. I just went to the site today to check it out for myself. The current service drop is about 200ft from the house and is 100A. I will be installing new service equipment at the pole to supply both the house and cabin. The total distance from the meter at the service drop to the cabin is 350ft direct buried. I'll be installing a disconnect on the side of the cabin which will then stub into the panel inside. The service for the cabin will be 100A.

So i'm plugging in these numbers:

(2 * 350ft * 100A * 10.7) / (120v *.03) = 208,055cm

So I'm coming up with #4/0 (211,600cm) that I will need from the Meter to the Disconnect. I feel like that is too big, but am unsure what I am doing wrong.

Thanks
Click to expand...

According to my Southwire App if you used aluminum, 350', 240 volts and 100 amp load the minimum size needed for less than 3% VD is 250 kcmil aluminum. For 80 amps of load you could drop down a size to #4/0 Al. Again the VD compensation is optional.
 
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NewbieElec

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electrofelon said:
Are you using copper or aluminum? I know you said copper in your first post, but around here, copper USE is pretty rare to find in stock. I would use aluminum, probably #2, 2/0, or 4/0 depending on the specifics.
Click to expand...

After seeing the actual distance, I will probably use Aluminum.

infinity said:
According to my Southwire App if you used aluminum, 350', 240 volts and 100 amp load the minimum size needed for less than 3% VD is 250 kcmil aluminum. For 80 amps of load you could drop down a size to #4/0 Al. Again the VD compensation is optional.
Click to expand...

Why is the VD compensation not necessary? Wouldn't that lead to problems down the line if I'm out of 5% total VD from service to branch circuits?
 
infinity

infinity

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NewbieElec said:
After seeing the actual distance, I will probably use Aluminum.



Why is the VD compensation not necessary? Wouldn't that lead to problems down the line if I'm out of 5% total VD from service to branch circuits?
Click to expand...

For your installation vd compensation is not required by the NEC.
 
ActionDave

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NewbieElec said:
After seeing the actual distance, I will probably use Aluminum.



Why is the VD compensation not necessary? Wouldn't that lead to problems down the line if I'm out of 5% total VD from service to branch circuits?
Click to expand...
Along with what Infinity said about not being required voltage drop is load dependant. My whole house lit up like 4th of July and Thanksgiving day combined doesn't pull more than 80A. Unless you have a lot of electric heat I can't see a cabin pulling 100A, probably half that is more realistic.
 
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