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#193788 - 04/19/10 11:45 PM Neutrals in same panel???  
sparkync  Offline
Joined: Oct 2002
Posts: 828
I added a subpanel directly next to the main panel. I had to move 2 circuits into the new panel to make way for the "main" feeding the new panel. Since the neutrals were already terminated in the existing panel, can I just move the hots to the new panel through the 1 1/2 pvc conduit I run the feeder through or is there something in the code that won't allow this??? Thanks for the help...

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#193791 - 04/20/10 01:12 AM Re: Neutrals in same panel??? [Re: sparkync]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,121
It could be argued that this is basically a switch loop. (certainly from a current flow standpoint).
I can't think of a violation.

Greg Fretwell

#193797 - 04/20/10 10:09 AM Re: Neutrals in same panel??? [Re: sparkync]  
KJay  Offline
Joined: Nov 2007
Posts: 763
IMO, since it's now on the load side of the service disconnecting means, you would need to isolate the neutrals from the equipment grounding conductors for any circuits supplied by that subpanel, so as is, I believe the current install would likely be a violation of 250.24,[5].

I would normally install a 4-wire feeder to a subpanel with a separate neutral bus and equipment grounding terminal bar.

#193799 - 04/20/10 12:23 PM Re: Neutrals in same panel??? [Re: KJay]  
Alan Nadon  Offline
Joined: Mar 2005
Posts: 399
Elkhart, IN. USA
I believe sections 300.3 (B) for all the conductors in a circuit to be in the same raceway, auxillery gutter , etc. would apply.
Also section 250.4 (A)(5) for a low impedence path could be a problem with the hot coming from one panel and the grounded in another.
I don't believe it is worth the possiblity of having problems. Just extend the groundeds to the sub panel and be done with it.

If it was easy, anyone could do it.

#193803 - 04/20/10 12:55 PM Re: Neutrals in same panel??? [Re: Alan Nadon]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,121
The way I see this he is only talking about a circuit that has it's overcurrent device in the second panel. Electrically that is a switch loop. There will not be any inductive heating problems with that arrangement.
I assume the neutral and grounds are separated in that second panel but he is still not imposing any objectionable current on the EGC so that concern is allayed.
250.4 refers to the EGC and you have a lower impedance to ground in the main than you do in a sub.
By wire nutting an extension on the neutral you are simply adding 2 more possible places for this to fail.
The bottom line is, if the AHJ wants it you probably have to do it but I am not sure what the justification would be beyond that.
The only case I could think of would be if this is a multiwire circuit (240.4(D)) but even then the code would make something less safe by adding one more connection than was necessary.

If this is a pure 240v load there wouldn't be a neutral anyway. Maybe the trick would have been to swing over the water heater.

Greg Fretwell

#193807 - 04/20/10 02:45 PM Re: Neutrals in same panel??? [Re: gfretwell]  
HotLine1  Offline

Joined: Apr 2002
Posts: 6,872
Brick, NJ USA
IMHO, accepted trade practices would put all of the circuit conductors within the 'source' panel, in this case the 'new' subpanel.

Common practice is to relocate the cable(s) that have to be moved to the new subpanel.

The OP didn't say how he moved the hots, we can assume either a splice, or they may have been of sufficient length to move.

Alan has a point & an Article that I would used if pressed.


#193810 - 04/20/10 03:38 PM Re: Neutrals in same panel??? [Re: HotLine1]  
EV607797  Offline
Joined: Oct 2006
Posts: 745
Fredericksburg, VA, USA
I'm glad this question came up because I do this all the time, especially when adding circuits for hot tubs. I often make it a point to move the water heater circuit to make room for the breaker feeding the sub panel as a general practice.

I recently installed a manual generator transfer panel (interlocked main breakers), connected to the main panel with a single 2" PVC nipple between them. Into the sub panel, I moved the cooktop, water pump and about eight lighting/SA circuits and left the neutrals in-place in the main panel. After the fact, I've been bouncing this concept around in my head ever since.

It passed inspection, and I don't think that there's anything wrong with this, but I can see where it would raise a few eyebrows.


"But the guy at Home Depot said it would work."

#193811 - 04/20/10 06:24 PM Re: Neutrals in same panel??? [Re: HotLine1]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,121
Alan has a point & an Article that I would used if pressed.

Which one? 250.4 refers to the EGC so that is not relevant.

The idea of all conductors in the same raceway is to address inductive heating and that is not an issue here. Electrically this is a switch loop.
If the AHJ told me to do it, I would wire nut some white wire in there to make him happy but I would still be wondering why.

Greg Fretwell

#193812 - 04/20/10 08:42 PM Re: Neutrals in same panel??? [Re: gfretwell]  
HotLine1  Offline

Joined: Apr 2002
Posts: 6,872
Brick, NJ USA
I was leaning to 300.3 (b), not 250.4.

My comments stem from 'the way I was taught', like I mentioned accepted trade practices.

I'll do a little research reading later on, time permitting.


#193818 - 04/20/10 11:33 PM Re: Neutrals in same panel??? [Re: HotLine1]  
leland  Offline
Joined: Aug 2007
Posts: 853
Lowell area, Ma. USA
So,Now you got me thinking.
I was in a customers house a few years back,with a 'Gen-tran' switch. side by side panels,and a few ckts from each panel on the gen switch.

Didn't give it much thought then. As I saw it as a sw loop.

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