310.15(B)6 loophole?

[electricmanscott]

Not sure loophole is the correct term but anyway....

Suppose one was to install a new 40 ckt panel with a 200amp main breaker in a dwelling. This is now your service and this main is your disconnect. At the time of install this panel contained no other breakers feeding anything else.

A feed thru kit would be installed to feed thru to the existing panel in the dwelling the supplies power to all of the loads in the dwelling at this time. This feed is sized based on table 310.15 B 6. 4/0 al ser.



I say no. But I can see how technically you might be able to say yes.

Yay or nay?

 

[tom baker]

this section has changed in nearly every code since 1999.
The 2011 NEC has fixed if for once and all.
What code cycle are you on?

 

[electricmanscott]

this section has changed in nearly every code since 1999.
The 2011 NEC has fixed if for once and all.
What code cycle are you on?

Not 2011, unless that helps me.

I'm on '08

I know the section pretty well. I don't think it makes much sense. Of course what does that have to do with anything.

In a nutshell the way I see it as of now.

Feeder for entire load of dwelling can be reduced per 310.15 B 6

Feeder carrying partial load must be full size.

See, that makes sense.

 

[cpal]

Scott I think you have a technical point.
iF there are no other ocpd in the main loadcenter the feeder to the existing panel supplies the entire load. In MA rule 3 could cover your installation. Inspectors should not anticipate a future code violation.

I've read the ROP and I'm not conveinced that the new language is as clear as one would hope. The Chair made a statement that the there was editorial work to be done at the comment meeting.

 

[steve66]

What about 210.15? "Feeder conductors for an individual dwelling units or mobile homes need not be larger than service conductors." ?

I can't figure out if "for an individual dwelling unit" means it only applies to feeders that carry the entire load, or not.

 

[shortcircuit2]

I say yes.

I also would also look under code section 240.4(B) which allows next size breaker above the rating of the 4/0 AL cable which has an allowable ampere rating under 310.16 of 180 amps 75 degree column. This would only be allowed if the load calculation was 180amps or less.