Conductor Sizing

Master Nater said:
why woudn't it apply?

310.12(A) Services - for a service rated 100a through 400a, the service conductors supplying the entire load associated with a one-family dwelling, or the service conductors supplying the entire load associated with an individual dwelling unit in a two-family OR MULTIFAMILY DWELLING, shall be permitted to have an ampacity not less than 83 perceent of the service rating. If not adjustment or correction factors are reuquired, Table 310.12(A) shall be permitted to be applied.

who said it wouldn't apply?
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It only applies to service or feeder load for an individual dwelling NOT the conductors feeding multiple dwellings.
 
Seven-Delta-FortyOne said:
Eaton 1MP4124

It requires a barrier kit from Eaton to comply with 230.71

Originally PG&E wanted a disco ahead of the meter stack, but when I showed them that one they approved it.
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Do you have a model number of these barriers? I did see them in the Eaton catalog. A barrier just protecting the lugs is not complaint. The breakers need to be in separate compartments/enclosures. Maybe if they completely separated each breaker area horizontally it could work but you would need to bring the feeder conductors out of the side of each barrier area.
 
Master Nater said:
why woudn't it apply?

310.12(A) Services - for a service rated 100a through 400a, the service conductors supplying the entire load associated with a one-family dwelling, or the service conductors supplying the entire load associated with an individual dwelling unit in a two-family OR MULTIFAMILY DWELLING, shall be permitted to have an ampacity not less than 83 perceent of the service rating. If not adjustment or correction factors are reuquired, Table 310.12(A) shall be permitted to be applied.

who said it wouldn't apply?
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Seem like it does,
 
curt swartz said:
It only applies to service or feeder load for an individual dwelling NOT the conductors feeding multiple dwellings.
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i don't read it that way.

i guess either way, he'd be better off doing an actual load calculation on the entire building, and then sizing from there. up to him.
 
AC\DC said:
Not how I read it
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For one-family dwellings and the individual dwelling units of two-family and multifamily dwellings,..
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This does not permit the conductor sizes in Table 310.12 to be used for any conductor that supplies more than one dwelling unit. The main service supply conductors are based on the total calculated load with no reduction. The service or feeder conductors that supply individual dwelling units are sized per Table 310.12.
 
Never mind after reading it you’re right

This seems stupid if he can give a reduction on the units you should also be able to give a reduction on the service.
Like how they have for RVs the more RVs you have the more reduction you have should be the same for multiple units
 
don_resqcapt19 said:
This does not permit the conductor sizes in Table 310.12 to be used for any conductor that supplies more than one dwelling unit. The main service supply conductors are based on the total calculated load with no reduction. The service or feeder conductors that supply individual dwelling units are sized per Table 310.12.
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That was my understanding of it.
 
AC\DC said:
Never mind after reading it you’re right

This seems stupid if he can give a reduction on the units you should also be able to give a reduction on the service.
Like how they have for RVs the more RVs you have the more reduction you have should be the same for multiple units
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If you have 4 dwelling units that calculate to 100A each, the calculation for the 4 dwelling unit building is going to have demand factors and will not be 400A. So maybe the NEC CMPs think a multifamily calculation with diversity factors is more accurate than the single dwelling calculation so you get no discount on the service conductor ampacity. Insteading of fixing the dwelling unit calculation, they use this 83% factor on the dwelling conductor instead. There are also historical reasons for the 83% factor on dwelling units as well.
 
curt swartz said:
Do you have a model number of these barriers? I did see them in the Eaton catalog. A barrier just protecting the lugs is not complaint. The breakers need to be in separate compartments/enclosures. Maybe if they completely separated each breaker area horizontally it could work but you would need to bring the feeder conductors out of the side of each barrier area.
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So I called Eaton and asked them about this, they gave me the model number of 1MMBK, and stated that was a compliant barrier to comply with 230.71.

If I end up having to do a disconnect I will. Eaton has stated they currently have no equipment that meets 230.71 on its own.

And I can’t get GE, SqD, or other brands here, and after 30 years of dealing with Eaton I have no knowledge of the others anyway, which kind of pisses me off. But that’s another story.
 

I'm not really sure what that is but it looks like it covers the bussing from the meter sockets. Definitely not a solution for 230.71.

As I mentioned earlier I think Siemens is the only manufacture finally making equipment that complies. The manufacture have had over 6 years to redesign equipment but have chosen not to. Square D has finally redesigned their Class 320 service entrance devices.
 
curt swartz said:

I'm not really sure what that is but it looks like it covers the bussing from the meter sockets. Definitely not a solution for 230.71.

As I mentioned earlier I think Siemens is the only manufacture finally making equipment that complies. The manufacture have had over 6 years to redesign equipment but have chosen not to. Square D has finally redesigned their Class 320 service entrance devices.
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It was definitely a little confusing. Eaton told me that is what they have to meet compliance, but I’m skeptical.

Installing a line side disco is still an option.
 
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