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#99425 - 11/02/05 10:05 PM 215.4B  
Steve Miller  Offline
Joined: Aug 2001
Posts: 325
Loudoun Cty, VA
This isn't new to 05 but here's the question:
As we read this it disallows a paralleled feeder to a sub panel (from a main dist panel) if the sets are in 2 or 3 pipes (one set per pipe). We have many panels fed by two EMT pipes that originate at a breaker in a dist panel, where each contains all the phases, a neutral and a grond. We're obviously missing something here. Maybe we aren't defining "common neutral" properly. Or maybe we have a lot of illegal panels.
Your input is appreciated.

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#99426 - 11/03/05 12:45 AM Re: 215.4B  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,069
The reference to common neutral means you are only running one neutral back to the panel for multiple parallel phase sets. If you pull a neutral with each set you can split them up in separate raceways.
It is just an inductive heating problem because all neutral current would be in one pipe with the outgoing current split up among the others.

Greg Fretwell

#99427 - 11/03/05 07:22 AM Re: 215.4B  
Steve Miller  Offline
Joined: Aug 2001
Posts: 325
Loudoun Cty, VA
We follow that but here's what threw us: look at the cut & paste from the code ... what does the NEC mean by "ALL conductors of ALL feeders". Doesn't that seem to indicate every individual conductor of each set? Or do they interpret each set as a separate feeder? Or, again, are we just interpreting it wrong?

"Where installed in a metal raceway or other metal enclosure, all conductors of all feeders using a common neutral shall be enclosed within the same raceway or other enclosure as required in 300.20."

#99428 - 11/03/05 08:27 AM Re: 215.4B  
resqcapt19  Offline
Joined: Nov 2000
Posts: 2,148
If you have a grounded conductor in each raceway, you don't have a common neutral and the section that you cited does not apply. The section for your installation is 310.4.


#99429 - 11/03/05 06:51 PM Re: 215.4B  
Steve Miller  Offline
Joined: Aug 2001
Posts: 325
Loudoun Cty, VA
I see we were just interpereting "common neutral" wrong. Thanks for the input.

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