Moving Circuits to Subpanel - 300.3B Debate

[hitehm]

We had to make room in our main panel that was full, so we installed a small 6 space Eaton sub next to the main connected through a short 8" section of EMT. The feeders plus the 5 returning branch circuits all went through the same 8" of EMT. Then of course the NEC 300.3.B rule came up and we had to make a decision on also splicing over the neutrals and EGCs or keeping them landed in the main panel. In the end we decided to follow the letter of the law and spliced every Hot, N and G from all 5 circuits to the sub. After we we're done I concluded it would've been better to keep the N and Gs landed in the main since it really stressed the wiring to fully relocate these circuits. I won't bore you with the details but it was very tight and very difficult on the wiring to do this.

I have seen several opposing viewpoints on this topic including on this forum. It seems split between those who move everything because of concern for EMI heating effect and staying strictly compliant to 300.3B and those who feel it's best to keep the neutrals and grounds in the main. So my questions are:

1 - Why are the EGCs also required to be brought over as well? This really seemed unnecessary from an electrical stand point since they aren't normally current carrying and also in our case no matter how gentle we were trying to be, put stress on the cables trying to trace them down and untangle them from each other.
2 - For practical purposes, is there a minimum distance that's considered a "raceway" when deciding to be strict to 300.3B? We didn't use a nipple because of the angle but there was only 8" between main and sub.
3 - What if we used PVC between main and sub? No EMI can induce in the conduit causing heat so why isn't there an exception for all nonmetallic conduit?
4 - What is anyone's opinion about how literal you need to be with 300.3B, especially when just relocating to a very close sub panel and what do you normally do in this situation?

 

[roger]

Ask yourself "can I run just a hot and a switchleg in a conduit without problems"

 

[infinity]

Induction wouldn't be an issue if you only brought over the ungrounded conductors but the NEC has no provision to do so for a sub-panel.

 

[hitehm]

Ask yourself "can I run just a hot and a switchleg in a conduit without problems"

It feels like this is too easy and there's a catch but yes, I can. So would you have left the Ns and Gs in the main?

 

[macmikeman]

In any case the NEC requires derating conductors, so I am curious as to 5 circuits and the feeder in one conduit.
Did you upsize any wires to account for that ? I normally count it out and plan how many conduit required before
adding the sub panel.

 

[wwhitney]

In any case the NEC requires derating conductors, so I am curious as to 5 circuits and the feeder in one conduit.
Did you upsize any wires to account for that ?

The EMT mentioned in the OP is only 8" long, so it is exempt from derating.

Cheers, Wayne

 

[infinity]

The EMT mentioned in the OP is only 8" long, so it is exempt from derating.

Cheers, Wayne

I agree. Conductors in up to 24" nipples are exempt from the derating requirement.

 

[LarryFine]

As long as all conductors are in one conduit, there won't be induction issues, regardless of whether neutrals are relocated.

The neutrals should be relocated, but the EGCs need not be.

 

[roger]

It feels like this is too easy and there's a catch but yes, I can. So would you have left the Ns and Gs in the main?

Yes, I would have.

 

[hitehm]

In any case the NEC requires derating conductors, so I am curious as to 5 circuits and the feeder in one conduit.
Did you upsize any wires to account for that ? I normally count it out and plan how many conduit required before
adding the sub panel.

310.15.B.3.2 - Less than 2ft

 

[hitehm]

As long as all conductors are in one conduit, there won't be induction issues, regardless of whether neutrals are relocated.

The neutrals should be relocated, but the EGCs need not be.

So I assume this is more your practical answer not code answer because 300.3B includes the EGCs? And what is your feeling about it being in non-metallic conduit? No induction issue so why the need to relocate the Ns and Gs at all?

 

[Dennis Alwon]

Yes, I would have.

How is this compliant? I realize the emt would act as the ground so no equipment grounding conductor is needed to be run or at most one is all that is needed.

I don't see how you get around 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).

 

[roger]

How is this compliant? I realize the emt would act as the ground so no equipment grounding conductor is needed to be run or at most one is all that is needed.

I don't see how you get around 300.3(B)

So, do you ever run just a hot and a switchleg in a conduit? If so how do you get around 300.3(B)?

The way I see it is, if the neutral is not needed and is not being used as part of that portion of a circuit it does not need to be included in a raceway,

 

[Dennis Alwon]

So, do you ever run just a hot and a switchleg in a conduit? If so how do you get around 300.3(B)?

The way I see it is, if the neutral is not needed and is not being used as part of that portion of a circuit it does not need to be included in a raceway,

It is not the same as a switch loop. That is basically one conductor. Whether it is a waste of time or not I don't think it is code compliant but you know that. Also with metal piping wouldn't there be inductive heating on the conduit?

 

[roger]

It is not the same as a switch loop. That is basically one conductor. Whether it is a waste of time or not I don't think it is code compliant but you know that. Also with metal piping wouldn't there be inductive heating on the conduit?

Dennis, you are not seeing it correctly. The OP has 5 conductors going into the new panel and 5 conductors returning IOW's 5 feeds and 5 switchlegs back.

Of course if this is not what the OP has then I misunderstood.

 

[roger]

Dennis, I think I am the one not getting it. I'm thinking more on the lines of a multi-pole contactor however the current in the feeders would still negate the current in the branch circuits.

 

[wwhitney]

Dennis, I think I am the one not getting it. I'm thinking more on the lines of a multi-pole contactor

So why is a multi-pole contactor different from a feeder/branch circuit?

Seems to me if the neutral is not used in the subpanel (no AFCIs or GFCIs), 300.3(B) doesn't require it to be present in the conduit.

Cheers, Wayne

 

[hitehm]

Dennis, you are not seeing it correctly. The OP has 5 conductors going into the new panel and 5 conductors returning IOW's 5 feeds and 5 switchlegs back.

Of course if this is not what the OP has then I misunderstood.

We have an 80A feeder going TO the sub. We then came off of the breakers that we moved into the sub with short conductors BACK INTO THE MAIN and spliced onto the original hots leaving the main going to the branch outlets. Because of 300.3B we also spliced jumpers from the Ns and Gs of the same original branch circuits into the N bus bar of the sub and the G bus bar of the sub and YES, they are isolated from each other in the sub.

 

[roger]

So why is a multi-pole contactor different from a feeder/branch circuit?

Seems to me if the neutral is not used in the subpanel (no AFCIs or GFCIs), 300.3(B) doesn't require it to be present in the conduit.

Cheers, Wayne

A multi-pole contactor would have each branch circuit going and coming whereas the panel would most likely have feeders and swithlegs from each branch. I agree, the neutrals are not needed in either case.

 

[roger]

We have an 80A feeder going TO the sub. We then came off of the breakers we moved into the sub with short conductors BACK INTO THE MAIN

And I still would have done as I said.