310.15(B)(6) and panelboard feeders

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madpenguin

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This wasn't covered in the FAQ, but I've been told several times by various electricians that you can no longer use table 310.15(B)(6) to size a feeder to a sub. The only explanation that I've gotten is, "The wording has changed".... So... I looked it up and it does seem fairly cut and dry but I want to make sure before I file it away upstairs.

You can see the highlighted text directly above the table and my summary would go like this:

"For the purpose of this article, A Main Power Feeder is one that shall supply All loads that are part of the dwelling."

That pretty much rules out your standard sub panel.... No? So, #2 AL for a 100 panelboard is no longer allowed and you must use 1/0 according to Table 310.16, right?

Thanks all.

Jon
 
Many have argued that for years and to those, '08 is simply a clarification.

and yes, 1/0 al would be required for a 100 amp subpanel being fed with NM or SE.
 
Ratings permitted

Ratings permitted

Hi Jon,

Individual Dwelling Main feeder rated amp and conductor size per 2008 NEC is Table 310.15, while Meter Center service size per NEC specifies Table 310.16 for main power and Table 310.15(B)(6) is allowed for use to each tenants panel. rbj
 
gndrod said:
Hi Jon,

Individual Dwelling Main feeder rated amp and conductor size per 2008 NEC is Table 310.15, while Meter Center service size per NEC specifies Table 310.16 for main power and Table 310.15(B)(6) is allowed for use to each tenants panel. rbj
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Thanks. That's what I thought but wanted to make sure before I got into an argument about it tomorrow... :D Now that the highlighted text is in there, you really can't interpret it any other way.

Jon
 
Why not use 2x2x2x4 alum and install a 90 amp breaker at panel. Its not 100A but I never had to cut it that close very often.
 
four said:
I think you can use the 75 degree table just as long as all equipment is rated for that. 110-14(C)(1)(c). 1999 book.
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..for circuits over 100 amps, yes.

but I don't have a 99 here, so I could be wrong, but I always thought this to be the case.
 
Thanks for clarification iwire. Were still 2005 for know. I dont know when will go to 2008, but i just ordered it this week.
 
iwire said:
No problem, where I am we have been on the 2008 NEC since 1/1/08 so I tend to forget some are still on 2005. :smile:
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There is a rumor floating around that Massachusetts is going to change the tag line on license plates from "The Spirit of America" to the "The Spirit of the NFPA." ;)
 
forgive me , I don't have the holy writ in front of me, but if I remember right,.. it says something about the feeder conductors not being required to have an amp. rating more than that of the entrance conductors , when run to a dwelling .. would this include those run in a dwelling??
 
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