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#182079 - 11/17/08 01:36 PM SER sizing
highground Offline

Registered: 11/14/04
Posts: 50
Loc: Chama, NM
What is the correct size of AL SER cable to use a feeder for a 100A subpanel in a residential setting? I seem to be getting different opinions from my two inspectors. I'm using the 2008 code.

Thanks in advance

2014 / 2011 NEC & Related Books and Study Guides
#182083 - 11/17/08 02:13 PM Re: SER sizing [Re: highground]
George Little Offline

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
I just read in the '08 NEC Article 3 Section 310.15(B)(6) and as I read it the feeder must be #1 Alm. Unless it carries the entire load of the dwelling and then it can be a #2 Alm.
The Code panel has waffled back and forth and reworded this one many times and now with the '08 I think the aforementioned sizes would be proper. That would be my call — Until someone convinces me otherwise.
George Little

#182089 - 11/17/08 05:16 PM Re: SER sizing [Re: George Little]
gfretwell Online   content


Registered: 07/20/04
Posts: 9026
Loc: Estero,Fl,usa
I am with George, The confusion comes when people confuse a "main feeder" with a load side feeder in a residence.
Greg Fretwell

#182105 - 11/18/08 05:04 PM Re: SER sizing [Re: gfretwell]
Tom Offline

Registered: 01/01/01
Posts: 1069
Loc: Shinnston, WV USA
I agree with the above posts. The confusion was even worse until they removed that pesky "s" at the end of feeder(s).

AFAIK, the CMP responsible for this always felt that the feeder was meant to carry the entire load and table 310.15(B)(6) has probably led to a lot of bad language & a few fistfights.
Few things are harder to put up with than the annoyance of a good example.

#182111 - 11/18/08 06:08 PM Re: SER sizing [Re: Tom]
Electricmanscott Offline

Registered: 01/12/02
Posts: 1478
Loc: Holden, MA USA
I see undersized feeders all the time. Seems many mis-apply 310.15 B 6

#182404 - 11/25/08 11:02 AM Re: SER sizing [Re: Electricmanscott]
macmikeman Offline

Registered: 07/16/02
Posts: 718
Loc: Honolulu, Hawaii
Shortly my town will be adopting the 2008, and this will bring about new awareness of the requirements of feeder sizing, due to the fact that the NEC has made it clear that 310.15 B. 6 applies to a single feeder carrying all the load of a dwelling. Couple that with the new temperature rating for ser cable to the 60 deg column in 310.16 and the feeder sizes will increase by an avarage of two sizes on most new dwellings. Stictly my own opinion, but with the proper sized overcurrent protective device ahead of the "sub' feeder, the old sizing standard used for ser cables was already more than adaquate for the real life loads encountered. These new rules are huge overkill, but still it is in the code, so therefore it is just how it is, like it or not.


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