MLO Main Panel - Sum of Breakers vs. Rating

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Npstewart

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I seem to recall a code section essentially limiting the sum of the main circuit breakers for an MLO panel acting as a main. I dont run into this often. Anyone know what code section this is, assuming im not incorrectly remembering.

The situation is an existing condition for an Electrical service being re-built and it needs to be designed to work using the existing infrastructure if possible.

I have a 480/277v, 1200A, main MLO panel with:
(1) 500A/2P
(1) 400A/2P
(1) 800A/3P
(1) 300A/2P

So in total, this comes up to 2000A, however most of the breakers are single phase. Depending on the code (if there is one). If this were adjusted to account for the service being 3-phase then this would be about 1500A @ 480/3.

Either way, any issue with 2000A / 1500A sum of mains on a 1200A MLO panel?

Any help appreciated.
 
Prior to the 2020 NEC I know of no section requiring what you reference. 408.36 requires main OCP but there was an exception for 230.71, the 6 disconnect service rule.
Starting with 2020 that (six circuit rule) is no longer allowed.
 
augie47 said:
Prior to the 2020 NEC I know of no section requiring what you reference. 408.36 requires main OCP but there was an exception for 230.71, the 6 disconnect service rule.
Starting with 2020 that (six circuit rule) is no longer allowed.
Click to expand...
Interesting about the 2020 not allowing that. We're still on 2017 and I try not to learn to much about future codes until they're current for my state because then ill start applying that.

I hate when something like 270.71 is changed. It creates so many grey areas for existing installations. I seem to see 270.71 / 6 disconnect rule being used for older installations. Electrical services are one of the things usually kept un-altered even for larger renovations and now when you go to add a 6th breaker to a 5 -main breaker building its going to create issues. The NEC rarely speaks of existing vs. new and everything is going to be up for interpretation. Makes it difficult to work in areas you dont often work in because you dont know their interpretation.
 
Even my home panel would be in trouble if there was any kind of code limiting the sum of the branch to main circuit breakers.
My 200A panel has (42) 20A CB's (some are actually larger than they appear :)).
 
ron said:
Even my home panel would be in trouble if there was any kind of code limiting the sum of the branch to main circuit breakers.
My 200A panel has (42) 20A CB's (some are actually larger than they appear :)).
Click to expand...
That's not an issue; the OP's example has no main breaker.
 
ron said:
Even my home panel would be in trouble if there was any kind of code limiting the sum of the branch to main circuit breakers.
My 200A panel has (42) 20A CB's (some are actually larger than they appear :)).
Click to expand...

I knew someone would say this. :rolleyes: As Larry said, this is an MLO installation.

I didn't think this was an issue, just wanted to be sure there wasn't one of those pesky code sections that isnt cited often. Perhaps I was reading a forum post or something that wasn't done being vetted.

Thanks everyone.
 
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