[RE-wrenches] Splices in service panel

[Ray Walters]

Hi August;

I'm glad you brought this up.  When I first saw only the hots being 
brought to the Critical Load Panel, I thought it was wrong too, but then 
I recalled that this is similar to a switch leg.  Does 300.3 forbid 
switch legs too?  the exception in 404.2(A)  allows switch legs, but 
does it apply here?  I don't have a definitive answer in regard to 
300.3, other than to note it has numerous exceptions. 300.3(B)(4) may 
also apply, and further, over current device enclosures and J boxes are 
not specifically mentioned either.

To be clear, I am not the originator of this idea;  I just copied this 
method from Reliance and Generac's wiring of their UL listed circuit 
transfer switches.  I have used it since 2003, and never had an AHJ have 
an objection.  I've discussed it with AHJs and electricians that 
specialize in generators, and this is common when retrofitting a backup 
generator.

Also in response to the person that posted about having trouble with the 
neutrals: we have no neutrals at all in the CLP, if done this way.  All 
neutrals land on the main neutral buss in the main panel. The CLP only 
has hots to the breakers, and the "neutral" bar in the CLP is used only 
as the equipment ground for the enclosure by adding the green bonding 
screw.

To be clear, I would not use this method on new construction where the 
branch circuits could be brought straight to the CLP.  This is for 
*retrofit only*.  I also would not do this if the CLP and main panel 
were connected with a nipple longer than 24".  Further, I over size the 
nipple and use PVC to reduce any possible inductive heating issues. For 
very short nipples, I have to use RMC, but I would never use EMT.

This method helps keep the space requirements down to comply with 
312.8(2), and keeps the wiring cleaner, fewer splices, and less over all 
disturbance to existing wiring in the sometimes aging and crowded main 
load center.
The trade off is possible inductive heating of a short nipple caused 
only by lower current 120 vac circuits (the 240 vac hots cancel each 
other's inductance).

  Again, I'm not the AHJ, and I'm not the originator of this method. I'm 
just doing my best to describe a method used in the backup generator 
world that I've found helpful.
The NEC and our work essentially is a compromise of numerous competing 
safety concerns.  The code describes many wiring methods; its up to us 
to optimize each situation for overall safety.

Here's a screen shot from the Reliance manual:



R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 9/9/2016 12:45 PM, August Goers wrote:
>
> Ray,
>
> I’m intrigued by this. We’ve always gone off NEC 300.3(B):
>
> (B) Conductors of the Same Circuit. All conductors of
>
> the same circuit and, where used, the grounded conductor
>
> and all equipment grounding conductors and bonding conductors
>
> shall be contained within the same raceway, auxiliary
>
> gutter, cable tray, cablebus assembly, trench, cable, or
>
> cord, unless otherwise permitted in accordance with
>
> 300.3(B)(1) through (B)(4).
>
> I interpret this to mean that we need to run neutrals along with any 
> branch circuits we are moving over.
>
> Best,
>
> August
>
> From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org 
> <mailto:re-wrenches-bounces at lists.re-wrenches.org>] On Behalf Of Ray 
> Walters
>
> Sent: Thursday, September 08, 2016 5:44 PM
>
> To: RE-wrenches
>
> Subject: Re: [RE-wrenches] Splices in service panel
>
> Hi Chris;
>
> Its the same as a switch leg for a light.  The neutral stays at the 
> light, only the hot is run down to the switch and back.
>
> Also, with some critical load panel set ups available (ie Generac), 
> there is no provision to even run the neutrals to the new CLP.
>
> This is cleaner and involves much less splicing.  Fewer connections is 
> usually better in my book.
>
> R.Ray Walters
>
> CTO, Solarray, Inc
>
> Nabcep Certified PV Installer,
>
> Licensed Master Electrician
>
> Solar Design Engineer
>
> 303 505-8760
>
> On 9/8/2016 6:22 PM, Chris Mason wrote:
>
> I disagree with the response that you do not need to move the 
> neutrals. You should never have the load's phase wiring in one panel 
> and the neutral in another.
>
> Chris Mason
>
> NABCEP Certified Solar PV Installer™
>
> Solar Design Engineer
>
> Generac Generators Industrial technician
>
>
>
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