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Old 12-01-2009, 10:53 AM   #1
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Default 320 amp service cable size

I'm a commercial electrician, never did a 320 amp service. My neighbor wants to upgrade his resi service to a 320 with two 200 amp panels. My questions are: (2008 code cycle)

does a 320 meter socket come with parallel lugs?

Do I use t310.15(b)(6) or t310.16 for cable size to each panel?

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Old 12-01-2009, 11:05 AM   #2
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Originally Posted by I Conduit View Post
I'm a commercial electrician, never did a 320 amp service. My neighbor wants to upgrade his resi service to a 320 with two 200 amp panels. My questions are: (2008 code cycle)

does a 320 meter socket come with parallel lugs?

Do I use t310.15(b)(6) or t310.16 for cable size to each panel?
Firstly, lets get the terminology straight because it is confusing. A 200 amp service has a 200 amp meter base that is rated 160 amps for continuous load but rated 200 amps for non-continuous loads. A 400 amp meter base is rated 400 amps non- continuous loads and 320 amps (80%) for continuous loads.

So the service you are installing is a 400 amp service and I don't know why they call the meter 320 amps instead of 400 amps. Why do they use continuous load rating on the 400 and the non continuous load rating for the 200 amp meter. It is confusing.

Okay now the meters do come with double lugs or you can buy a combo meter panel that has the meter and the the 2- 200amp breakers already installed as one unit.

Now the question about T. 310.15(b)(6) is one that is debated much on the forums. My opinion is that T. 310.16 must be used in this case since T. 310.15(B)(6) does not state anything about a 400 amp service being used with 2-200 amp panels. I would check with your AHJ-- some are still allowing T.310.15(B)(6) to be used.

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Old 12-01-2009, 12:36 PM   #3
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Firstly, lets get the terminology straight because it is confusing. A 200 amp service has a 200 amp meter base that is rated 160 amps for continuous load but rated 200 amps for non-continuous loads. A 400 amp meter base is rated 400 amps non- continuous loads and 320 amps (80%) for continuous loads.

So the service you are installing is a 400 amp service and I don't know why they call the meter 320 amps instead of 400 amps. Why do they use continuous load rating on the 400 and the non continuous load rating for the 200 amp meter. It is confusing.

Okay now the meters do come with double lugs or you can buy a combo meter panel that has the meter and the the 2- 200amp breakers already installed as one unit.

Now the question about T. 310.15(b)(6) is one that is debated much on the forums. My opinion is that T. 310.16 must be used in this case since T. 310.15(B)(6) does not state anything about a 400 amp service being used with 2-200 amp panels. I would check with your AHJ-- some are still allowing T.310.15(B)(6) to be used.
Thanks for your very informative and timely response. I think I will go with your advice and use table 310.16, that avoids any issues with the AHJ. I will be giving my neighbor a nice discount on labor (it's a side job) so to spend a little more for cable is not going to be a big deal.
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Old 12-01-2009, 02:19 PM   #4
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It is tidbits like Denni's post that make this site more than worth the yearly membership fee's.

Seriously very nice Dennis, I always wondered about the 320 amp Meter can.
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Old 12-01-2009, 05:20 PM   #5
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Yeah, but he probably just copied and pasted it from some other site. Just kidding Dennis!

Is this underground or overhead?
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Old 12-01-2009, 05:27 PM   #6
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There is such a MP here that is rated for 320 amp.

It can only be used for (2) 150 amp panels.. some other places will allow (2) 200 amp. panels for a 320 service
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Old 12-01-2009, 05:30 PM   #7
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There is such a MP here that is rated for 320 amp.

It can only be used for (2) 150 amp panels.. some other places will allow (2) 200 amp. panels for a 320 service
I doubt it. Are you sure that is not just the ignorance of the inspectors talking?
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Old 12-01-2009, 05:37 PM   #8
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I doubt it. Are you sure that is not just the ignorance of the inspectors talking?
I just did a service a year ago using the 320 MP. with (2) 150 panels and both POCO and inspector signed off on it.

They are a common item here.. half the size of a 400a MP and half the cost
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Old 12-01-2009, 05:47 PM   #9
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I just did a service a year ago using the 320 MP. with (2) 150 panels and both POCO and inspector signed off on it.

They are a common item here.. half the size of a 400a MP and half the cost
Don't think he' saying its wrong, he's saying you could put 2 200's on that pan is what I'm saying
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Old 12-01-2009, 05:48 PM   #10
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There is such a MP here that is rated for 320 amp.

It can only be used for (2) 150 amp panels.. some other places will allow (2) 200 amp. panels for a 320 service
I am going with 'doubt it' also. I think you have been lied too.

Seriously, read the tag carefully.

Maybe your power company may restrict it to that, or your inspectors are misinformed but a 320 class meter is rated 320 continuous and 400 amp non-continuous.

The combined capacity of two 200 amp 'standard' load centers are also rated 320 amp continuous and 400 amp non-continuous.

On the other hand the combined capacity of two 150 amp panels is only 240 amp continuous and 300 amp non-continuous.
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Old 12-01-2009, 05:50 PM   #11
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I just did a service a year ago using the 320 MP. with (2) 150 panels and both POCO and inspector signed off on it.

They are a common item here.. half the size of a 400a MP and half the cost
I am sorry -- I am surprised it would be called a 320amp meter pan. It doesn't make sense since 320 amp is not a standard service size. Now if you said there is a 300 amp MP that would make sense.


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It is tidbits like Denni's post that make this site more than worth the yearly membership fee's.

Seriously very nice Dennis, I always wondered about the 320 amp Meter can.
Thanks Brian
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Old 12-01-2009, 05:54 PM   #12
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I call it a 300A MP when I order it from supply house.. only on these forums is it called 320A
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Old 12-01-2009, 05:56 PM   #13
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I call it a 300A MP when I order it from supply house.. only on these forums is it called 320A
Cool, I call it a 400 amp meter pan. I'm better than you
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Old 12-01-2009, 05:58 PM   #14
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I call it a 300A MP when I order it from supply house.. only on these forums is it called 320A
We are probably talking about 2 different animals. When I order a service for 400 amps I ask for a 400 amp meter base and I get a base that is marked 320 amps. It is rated 400 amps noncontinuous so it works well for a 400 amp service. The question is why they use 320 amps instead of the 400 amp nomenclature.
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Old 12-01-2009, 05:58 PM   #15
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Cool, I call it a 400 amp meter pan. I'm better than you

Not a 400.. does not use CT's.. why so much cheaper in price
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Old 12-01-2009, 05:58 PM   #16
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Not a 400.. does not use CT's.. why so much cheaper in price
Says you
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Old 12-01-2009, 05:58 PM   #17
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Not a 400.. does not use CT's.. why so much cheaper in price
The 400 amp meter bases we use do not have CT's either.
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Old 12-01-2009, 05:59 PM   #18
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We are probably talking about 2 different animals. When I order a service for 400 amps I ask for a 400 amp meter base and I get a base that is marked 320 amps. It is rated 400 amps noncontinuous so it works well for a 400 amp service. The question is why they use 320 amps instead of the 400 amp nomenclature.
Right, on the milbanks site it calls it a 320 amp base.
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Old 12-01-2009, 06:09 PM   #19
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I just did a service a year ago using the 320 MP. with (2) 150 panels and both POCO and inspector signed off on it.

They are a common item here.. half the size of a 400a MP and half the cost

The cost..... my most common power company to deal with is PSEG, and if I have an approved permit for a service upgrade for a single family or 2-family, the meter is free. All I have to do is go pick it up.
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Old 12-01-2009, 06:12 PM   #20
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Page 8 is a pic of a 300A MP

http://www.milbankmfg.com/products/C...tionalGrid.pdf

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