Supply Side Connections in Power Packs

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ohmti787

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What is everyone's take on these type of service panels? We call them Power Packs and they're very common up in the Panhandle (Florida).1648234210821.png

It's my understanding that if we put a backfeed breaker here it would be consider a supply side connection since there is no actual "service disconnecting means" between the meter and the busbar. If my PV system is the only power production source connected here, per 705.12(A) my backfeed breaker can be as big as whatever the service is rated for, since technically I'm on the supply side. However, if the sum of the other breakers goes over the service rating, wouldn't that post a risk of overloading the busbar in a worst case scenario (eg: all these other breakers pull whatever they're rated for at the same time)?
 
ohmti787 said:
However, if the sum of the other breakers goes over the service rating, wouldn't that post a risk of overloading the busbar in a worst case scenario (eg: all these other breakers pull whatever they're rated for at the same time)?
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That risk exists whether the panel is supplied only by a service or by a service and a PV system. Either way, the risk is only mitigated by the load calculation.

Cheers, Wayne
 
ohmti787 said:
What is everyone's take on these type of service panels? We call them Power Packs and they're very common up in the Panhandle (Florida).View attachment 2559980

It's my understanding that if we put a backfeed breaker here it would be consider a supply side connection since there is no actual "service disconnecting means" between the meter and the busbar. If my PV system is the only power production source connected here, per 705.12(A) my backfeed breaker can be as big as whatever the service is rated for, since technically I'm on the supply side. However, if the sum of the other breakers goes over the service rating, wouldn't that post a risk of overloading the busbar in a worst case scenario (eg: all these other breakers pull whatever they're rated for at the same time)?
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There is usually a main breaker in the combo units like this I have seen, but if there isn't, all the breakers are service disconnects, so you are correct; you are only limited by the size of the service. The rating of the busbar is not relevant because it already has a virtually infinite current supply.
 
Not many people seem to know this but the sum of the breakers is allowed to exceed the service ratinf if a load calculation checks out for the size of the service. The code is 230.90 (A) Exception 3.

Note also that the 2020 NEC bans this type of enclosure and that may raise issues with adding any breakers once you're on it.
 
The individual breaker stabs are frequently rated for less than the rating of the service equipment, and this might limit the size system you can backfeed on a single breaker.
 
jaggedben said:
Not many people seem to know this but the sum of the breakers is allowed to exceed the service ratinf if a load calculation checks out for the size of the service. The code is 230.90 (A) Exception 3.

Note also that the 2020 NEC bans this type of enclosure and that may raise issues with adding any breakers once you're on it.
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You are still limited by the ampacity of the service conductors, are you not? For line side interconnected PV, I mean.
 
ggunn said:
You are still limited by the ampacity of the service conductors, are you not? For line side interconnected PV, I mean.
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Yes. But the sum of the load breakers can exceed that ampacity, if the load calc doesn't. And the PV doesn't figure into the load calc. So for example it wouldn't be at all inconceivable to have 300 or 400A worth of breakers on a 200A service, especially if one of them were a large PV system.
 
This type of service panel is pretty common in NC as well, these follow the 6 handle rule and you are only limited by your service conductor sizing. As long as you are just adding a breaker and not replacing the panel you shouldn't have any issue with this not following the 2020 NEC.
 
BradPV said:
This type of service panel is pretty common in NC as well, these follow the 6 handle rule and you are only limited by your service conductor sizing. As long as you are just adding a breaker and not replacing the panel you shouldn't have any issue with this not following the 2020 NEC.
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Hope you're right, but that's really up to the AHJ.
 
ggunn said:
There is usually a main breaker in the combo units like this I have seen, but if there isn't, all the breakers are service disconnects, so you are correct; you are only limited by the size of the service. The rating of the busbar is not relevant because it already has a virtually infinite current supply.
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So pretty much nothing is protecting the busbar from overloading in these types of enclosures. Not sure what the "work around" would be here without doing load calculations. Technically i'm on the supply side no matter where i put my breaker, but still.......i feel like the load side connection requirements should be followed for these power packs.....as much as i would like to consider this a supply side connection 🤷‍♂️
 
ohmti787 said:
So pretty much nothing is protecting the busbar from overloading in these types of enclosures. Not sure what the "work around" would be here without doing load calculations. Technically i'm on the supply side no matter where i put my breaker, but still.......i feel like the load side connection requirements should be followed for these power packs.....as much as i would like to consider this a supply side connection 🤷‍♂️
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To a certain extent, you can if you want. But you shouldn't have to, and in most cases it's impossible to interpret the load side rules to the letter. For example, you might think it prudent to put the PV breaker at the opposite end from the main feed. But since there is no main breaker, the sum of the main and PV can't exceed 120% of the busbar. ;)
 
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