Underground service for detached garage

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Bobbyxp88

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Massachusetts
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Electrician
Have to feed a detached garage with a 200 amp main breaker panel; completely separate from the house. Now the garage does not fall under the definition of a dwelling unit therefore I can not size it to 83% like a house? Just looking to confirm this. Anywhere in the code where I could calculate this or just use 310.15b thank you


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If the calculated load is under 180A should be able to use the next higher standard circuit breaker which is 200A, with 4/0 AL, since there is no 180A breaker, only 175A.
 
Two assumptions: You have a load that warrants a 200 amp panel OR you are installing a 200 amp panel to cover any future loads.
In either event, you need to size the conductors accordingly just as you did the panel. Locally, most would use 4/0AL
 
As Augie stated just use #4/0 AL and you'll end up with the same conductor size that you would use with the 83% rule.
 
Put a 200 amp service on a detached garage last week, mostly due to tesla car charger plus roughin for potential 2nd charger, a few shop tools , AC , refrigerator, freezer. 125 would have worked but 200 meterpack around same price and more readily available here, plus improved customer perception of value.

4/0 AL
 
I always run 4/0 aluminum when doing a 200 amp service but because this is not for a house I.e. a dwelling unit I wasn’t sure if I could use the 83% rule. I thought I had to size the wire for 200 amp which would be 250’s


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Bobbyxp88 said:
I always run 4/0 aluminum when doing a 200 amp service but because this is not for a house I.e. a dwelling unit I wasn’t sure if I could use the 83% rule. I thought I had to size the wire for 200 amp which would be 250’s
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Read post #4 regarding the next size up rule in 240.4(B).
 
As long as your load is not more than 180 amps then 4/0 is fine on a 200 amp breaker based on what was mentioned above
 
And if your load doesn't warrant a 200a svc run a sub feed from the house. Most of our customers don't want that $40 meter fee every month forever. Unless you are having someone else pay the power bill.
 
Poweranytime said:
And if your load doesn't warrant a 200a svc run a sub feed from the house. Most of our customers don't want that $40 meter fee every month forever. Unless you are having someone else pay the power bill.
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That's why youn run a 400/320 meter main with 2 200amp disconnects. One for the house, one for external buildings. The additional cost is negligible compared to the cost of everything else.
 
Amen if you have room for a 2nd building that's a great way to start. I like the one with the 816 feed thru on the 1st main and then you have an open spot for another 150 or 200.
 
I was brushing through changes for the 2020 and saw something about a new requirement services that would do away with meter mains with more than one main breaker. Don't have the book in front of me but remember it saying the grouping was the same but all separate enclosures required for 2-6 throws and handles readily accessible?
 
Poweranytime said:
And if your load doesn't warrant a 200a svc run a sub feed from the house. Most of our customers don't want that $40 meter fee every month forever. Unless you are having someone else pay the power bill.
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What is that? I've never heard of that. Is it a local thing? I'm in Va.
 
All power companies here have a base meter fee. Regardless if you draw no kwh. You pay a monthly charge. Look at your power bill its in there. Mine is 34 a month
 
qcroanoke said:
What is that? I've never heard of that. Is it a local thing? I'm in Va.
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I am served by two different rural coops. One charges $41 and the other $43 per month “facility charge”. In reality, it’s there to keep published rates look low.

If I use 1000 KwH at the published rate of 0.12, I’m actually paying more than 0.16.
 
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