Pennsylvania Electrical Suppliers - #2 SER for 100A sub??

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emf10

Member
Location
Southeast PA
Flex said:
Im still confused, If I add a 100A subpanel in a basment for, say 3 circuits in an addition, I am wrong to use #1. It needs to be 1/0?
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According to NEC 2005, IF you have 75degree terminals at both ends of the cable #1AL SER is adequate for 100amps. If your under NEC 2008 or have 60degree terminals on any side they're saying #1/0AL SER is adequate for 100amps.
 
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SEO

Senior Member
Location
Michigan
If you are under the 2005 NEC a #1al would be ok for 100 amps using ser cable to a subpanel. The change in the 2008 NEC would require you to use a 1/0 ser cable. Section 338.10 (4) refers you to Part II of art 334 which requires you to use 60c when sizing ser overcurrent protection.
 
infinity

infinity

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Location
New Jersey
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Journeyman Electrician
SEO said:
If you are under the 2005 NEC a #1al would be ok for 100 amps using ser cable to a subpanel. The change in the 2008 NEC would require you to use a 1/0 ser cable. Section 338.10 (4) refers you to Part II of art 334 which requires you to use 60c when sizing ser overcurrent protection.
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Even under the 2005 and earlier code cycles when using SE at 75 degrees I don't recall hearing that this was a problem. I'm kind of surprised that the CMP would just go along with a change that has little to do with safety and more to do with company profits. The fact that they didn't rely on empirical substantiation to foster this change is bothersome.
 
Dennis Alwon

Dennis Alwon

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Chapel Hill, NC
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Retired Electrical Contractor
SEO said:
Dennis what if you had a 100amp disconnect nippled on the meter fed with #2 al and the subpanel was located in the house. The ser feeding the subpanel carries the entire load. Now based on section 338.10(B) (4) type Se cable used for interior wiring shall comply with the requirements of Part II of art 334 the ampacity shall be in accordance with the 60 C conductor rating. In this case you would have to use a 1/0 ser cable for the subpanel .
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IMO 338.10(B)(4) does not enter into the equation in the case you presented. Odd yes but 310.15(b)(6) allows se cable as a feeder if it carries the entire load of the dwelling. So I would say that #2 is allowed.
 
Dennis Alwon

Dennis Alwon

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Location
Chapel Hill, NC
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Retired Electrical Contractor
Flex said:
Im still confused, If I add a 100A subpanel in a basment for, say 3 circuits in an addition, I am wrong to use #1. It needs to be 1/0?
Click to expand...

Flex based on 310.16 #1 SE cable used at 60C (art. 338.10(4)) is only rated 85 amps. You can put it on a 90 amp breaker as long as the calculated load does not exceed 85 amps.

If the subpanel carried the entire load of the house then a #2 would be okay for the subpanel. Figure that out but it all has to do with diversity of loads and the oddity of the article.
 
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Flex

Senior Member
Location
poestenkill ny
Dennis Alwon said:
Flex based on 310.16 #1 SE cable used at 60C (art. 338.10(4)) is only rated 85 amps. You can put it on a 90 amp breaker as long as the calculated load does not exceed 85 amps.

If the subpanel carried the entire load of the house then a #2 would be okay for the subpanel. Figure that out but it all has to do with diversity of loads and the oddity of the article.
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how could it be a subpanel and carry the entire load of the house? I really want to understand the reason for the right size wire and appreciate your explaining.
 
Twoskinsoneman

Twoskinsoneman

Senior Member
Location
West Virginia, USA NEC: 2020
Occupation
Facility Senior Electrician
don_resqcapt19 said:
There is no technical substantiation for the change but it was proposed by a cable manufacturer. There were no comments on this proposal.
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Wow... I have to say it is shameful if this type of things happens where rules are "pushed through" without subsantiation.... Manufacturers submitting rule changes should throw up a red flag immediately!
 
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emf10

Member
Location
Southeast PA
Flex said:
how could it be a subpanel and carry the entire load of the house? I really want to understand the reason for the right size wire and appreciate your explaining.
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If the panel carries the entire load of the house "subpanel" wouldn't really be the correct term imo. This would be the main panel.

I guess you can look at it this way: when a feeder carries the entire load for a house it is subject to additional demand factors, thereby allowing the smaller size wire.

Note: The NEC does not distinguish between subpanels and main panels.
 
Dennis Alwon

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Flex said:
how could it be a subpanel and carry the entire load of the house? I really want to understand the reason for the right size wire and appreciate your explaining.
Click to expand...

Suppose you have a 100 amp meter base with a 100 amp main breaker as the service. The main breaker feeds a panel inside the house--- this panel is a sub panel and it carries the entire load of the house.
 
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Flex

Senior Member
Location
poestenkill ny
What would be the reasoning for the larger wire if it doesnt carry the entire load? Also I know around here almost everyone uses #2 for "sub" subpanels
 
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