LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I don't know which "you" you're addressing, but yes, in my for instance.
New service
- Thread starter brichter
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e57
Senior Member
- Location
- San Francisco, CA
From the '02
Current interpations, via new wordings obviously don't allow multiple feeder reduction in size, but I fear the reduction of the main or only one feeder is in jeapardy in the future. Or, and this is more likely, that the resi load calcs changed to reflect the real world - of the Mc Mansion. I'm sure many of us have removed 30A services from back when they thought that was enough at the time.
Separate food for thought: What if the feeder was pararleled sets?????
Note the parenthesis S's.... In the past the interpatation varied from this allowing the feeders of a multi-family to each unit, and depending on who you talked to, multiple feeders of a single family. The size reduction was/is allowed to accomadate diversity and the fact that it was the rare home that ever even reached 100% of the calculated load for the dwelling. So it mattered little if it was the whole house or two parts of the same IMO, both would rarely reach 100% of the calc'ed load for each respective feeder. That said, I am finding more and more often with the populatity of recessed cans, more & more electronic devices and higher wattage appliances that the "Calculated load" that we are allowed to do with the 3VA, 3K at 100%, remaining at 35% - is far too low.
Current interpations, via new wordings obviously don't allow multiple feeder reduction in size, but I fear the reduction of the main or only one feeder is in jeapardy in the future. Or, and this is more likely, that the resi load calcs changed to reflect the real world - of the Mc Mansion. I'm sure many of us have removed 30A services from back when they thought that was enough at the time.
Separate food for thought: What if the feeder was pararleled sets?????
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e57
Senior Member
- Location
- San Francisco, CA
Note there is still an "S" behind feeders in the portion that you put in bold....
Only the word panelboard is singular now....
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
Does Table 310.15(B)(6) apply to paralleled conductors? If so, two sets of Al 4/0 conductors could be a 400 amp feeder to a gutter located above two 200 amp panelboards, and the feeder could be tapped with 3/0 Cu or 250 kcm Al to each panelboard? Perhaps the gutter size required for this configuration would make this impractical.
Cheers, Wayne
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Unfortunately Table (B)(6) or art.(B)(6) do not mention parallel conductors.
Parallel conductors, or multiple sets? I still see a typical 400A service as a grey area for 310.15(B)(6) if you have a meter where you split to two sets of service conductors each to a main breaker panel. These two sets of wires are Service Entrance conductors, so the definition of main power feeder does not apply.
The reason I says its grey is because I'm not convinced that the whoever wrote 310.15(B)(6) intended to allow two sets of service conductors to apply to that section.
The reason I says its grey is because I'm not convinced that the whoever wrote 310.15(B)(6) intended to allow two sets of service conductors to apply to that section.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
But, as Dennis just pointed out, parallel conductors are not included in the Table - so how would you configure a pair of panelboards with a single unparalleled set of conductors to feed them? Would you call them two 200A services and use two sets of conductors?
They are not parallel conductors because they do not terminate at the same source and destination (nor likely meet other constraints as defined in 310.4). Following the terminology in article 230, I would call these multiple sets of service conductors.
For a truely parallel install of service conducotrs, I'm not sure how to interpret 310.15(B)(6) either. It avoids ampacity and says "service or feeder rating". So if you want a 400A service or 400A feeder, those size wires are allowed. So I would tend to agree that paralleled service conductors can't use 310.15(B)(6).
Because 310.15(B)(6) doesn't mention multiple sets to me doesn't mean it can't apply. The only constraint I now see is "Service rating". Just what is the service rating? I'm thinking it may be the whole service and not portions that are tapped off. So certainly the whole service can use 310.15(B)(6). Whether two sets each to a 200A panel have a "Service Rating" of 200A, I don't know.
For a truely parallel install of service conducotrs, I'm not sure how to interpret 310.15(B)(6) either. It avoids ampacity and says "service or feeder rating". So if you want a 400A service or 400A feeder, those size wires are allowed. So I would tend to agree that paralleled service conductors can't use 310.15(B)(6).
Because 310.15(B)(6) doesn't mention multiple sets to me doesn't mean it can't apply. The only constraint I now see is "Service rating". Just what is the service rating? I'm thinking it may be the whole service and not portions that are tapped off. So certainly the whole service can use 310.15(B)(6). Whether two sets each to a 200A panel have a "Service Rating" of 200A, I don't know.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
I'm not 100% sure in the case of service conductors either.
230.80 would indicate we find the "service rating" by adding the handles together.
230.2 would indicate the two enclosures are considered one service.
Edit to add: I have submitted a proposal to clarify 310.15(B)(6) in the 2011. We'll see if they accept it this time.
I just noticed that there should be a period, not a comma, after "both".
230.80 would indicate we find the "service rating" by adding the handles together.
230.2 would indicate the two enclosures are considered one service.
Edit to add: I have submitted a proposal to clarify 310.15(B)(6) in the 2011. We'll see if they accept it this time.
I just noticed that there should be a period, not a comma, after "both".
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That would do a lot to clean things up. As a software person, I don't find it difficult to write things in a way where the logic is deterministic, but you'll be getting it in FORTRAN or C style. With english, you can't always tell where the and's and or's apply.
If only there was a compiler for the NEC to catch the stupid redundant language and the non-deterministic words... I remember reading a proposal last time that said "with or without ground" was redundant. They panel didn't seem to get that, and I don't know why. "With and without" cover all permutations.
If only there was a compiler for the NEC to catch the stupid redundant language and the non-deterministic words... I remember reading a proposal last time that said "with or without ground" was redundant. They panel didn't seem to get that, and I don't know why. "With and without" cover all permutations.
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