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#209270 - 03/20/13 07:34 PM Sub Panel with no neutrals  
BigB  Offline
Member
Joined: Mar 2004
Posts: 721
Tucson, AZ USA
Probably everyone has seen it. Main panel is full so a sub panel is set next to it, however it is not supplied with a neutral feeder, only hots and a bond. The circuits all enter the main panel first and only the hots are extended into the sub panel, the neutrals and grounding wires are landed in the first panel. Does a violation exist?


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#209271 - 03/20/13 09:49 PM Re: Sub Panel with no neutrals [Re: BigB]  
Tesla  Offline
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Joined: Jun 2004
Posts: 1,273
Sacramento, CA
Neutral-less panels are as common as dust in industrial settings. These are designed to fit within the 'web' of a vertical I beam/ column. Since such panels are also very, very, likely to feed 3-phase loads, the neutral doesn't get a lot of action, anyway.

You'll find them listed in Square D catalogs.

They are frowned upon elsewhere. The operative assumption being that subsequent players are going to be so stupid as to not correctly land neutral conductors. The 'savings' from omission of a neutral path into the adjacent panel are insignificant.

I must be a rare electrician, I've never seen the set-up described. I don't work the heavy industrial side of the street.

Last edited by Tesla; 03/20/13 09:50 PM.

Tesla

#209272 - 03/20/13 09:59 PM Re: Sub Panel with no neutrals [Re: Tesla]  
sparkyinak  Offline
Member
Joined: Jul 2007
Posts: 1,328
Alaska
Perhaps the sub-panel was set up to run only phase to phase loads. That's not a code violation.


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#209274 - 03/20/13 10:22 PM Re: Sub Panel with no neutrals [Re: sparkyinak]  
sparkyinak  Offline
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Joined: Jul 2007
Posts: 1,328
Alaska
I may have to eat my words. More to follow...


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#209275 - 03/20/13 10:26 PM Re: Sub Panel with no neutrals [Re: BigB]  
watersparkfalls  Offline
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Joined: Mar 2005
Posts: 222
Washington...Not DC
"the neutrals and grounding wires are landed in the first panel. Does a violation exist?"

I can't quote the code ref, however I remember from school that grounded and ungrounded must originate from same panel.

And the grounding seems weird to run back to first panel too.

I could be wrong, since I have no ref(too tired to look right now) but expressing my humble opinion.

H20


#209278 - 03/20/13 10:53 PM Re: Sub Panel with no neutrals [Re: sparkyinak]  
sparkyinak  Offline
Member
Joined: Jul 2007
Posts: 1,328
Alaska
I have seen them before but can't swear they were to code. I'm gonna keep digging because it has my cariousity. So far, in article 215 Feeders, there is a minimum grounded conductor size shall not be smaller the required by 250.122. However I'm not sure what they mean by that


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#209279 - 03/20/13 10:53 PM Re: Sub Panel with no neutrals [Re: BigB]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,142
Estero,Fl,usa
The neutral does not need to extend beyond the service disconnect enclosure.
Back when there were real computer rooms, we never brought the neutral to the computer panels. They had a "building" panel supplying the lights and the 120v loads but none of them were computer related, everything was 208 or 240 L/L loads. The 120v monitors were plugged into a service outlet in the CPU that ran off an isolation transformer.

There was still a neutral style bar in the panels but it had a green wire feeding it usually with a yellow tracer and was the isolated grounding conductor that went to the machines.
The can and the raceways were bonded to the "bare wire" ground (the one with green only if it was insulated).

This fell out of vogue about the time they stopped water cooling the machines (and coincidentally the CMOS got a lot less noise sensitive)


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