Moving Circuits to Subpanel - 300.3B Debate

[hitehm]

And I still would have done as I said.

I totally agree.

 

[Dennis Alwon]

The OP doesn't have a switch loop. He is running a wire from the new panel to the wire that used to be on a breaker in the old panel. One hot conductor.

 

[hitehm]

My follow up question for everyone is - Is 300.3B solely written to minimize inductive heat in metallic conduit? If so, then again, why no exception for ALL nonmetallic conduit? What else is it protecting against? I'm trying not to be cynical but it seems poorly thought out at best, unless I'm missing another reason for it.

 

[roger]

The OP doesn't have a switch loop. He is running a wire from the new panel to the wire that used to be on a breaker in the old panel. One hot conductor.

Yes, but he also has feeders in the conduit so he has hot conductors going and coming.

 

[winnie]

The OP doesn't have a switch loop. He is running a wire from the new panel to the wire that used to be on a breaker in the old panel. One hot conductor.

He has a multi-pole switch loop. 80A hot(s) (I presume 240V) going to the panel, a bunch of 15-20A hots returning.

But any current flowing on one of the 80A hots must be matched by current flowing in the opposite direction on one of the smaller hots. No net current, just like any properly wired switch loop.

Jon

 

[Little Bill]

Yes, but he also has feeders in the conduit so he has hot conductors going and coming.

I agree!

 

[Dennis Alwon]

Okay I concede... I bow to the more knowledgeable. I always thought what you are saying with the feeder but I thought it was on this site that I was corrected. Probably not since I have CRS...

 

[petersonra]

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

Since the code section cited specifically says something about the grounded conductor "where used", and the grounded conductor isn't used in this case, I don't see how code requires you to run a grounded conductor for the branch circuits. Since the feeder grounded conductor is not used, I don't think you have to run it either.

You certainly don't need to run an equipment grounding conductor since the EMT serves as one.

So I think that it can be fairly interpreted that the code only requires you to run one wire over to the new panel and five wires back.

How an inspector might see this is something different, and making the EMT big enough to accommodate two feeder wires going to the new panel and 10 branch circuit wires coming back might be easier than arguing over it.

Adding 10 wire nuts inside the existing panel board might make it look pretty messy. I might be inclined to use crimp on butt slices to make it neater looking.

 

[kwired]

The OP doesn't have a switch loop. He is running a wire from the new panel to the wire that used to be on a breaker in the old panel. One hot conductor.

and the magnetic effects on that one hot conductor is offset by equal current being on the feeder that is also in the nipple.

If one ran two nipples, one with the feeder and one with the branch circuits, then you would need to also run the individual neutrals in the nipple containg the branch circuits.

Now looking at wording of 300.3(B) it maybe could use a little tweaking, but I think the intent was mostly for the magnetic effects on ferrous raceways/enclosures.

 

[infinity]

I don't have my book, what code section applies to a 2-wire switch loop without a neutral?

 

[petersonra]

I don't have my book, what code section applies to a 2-wire switch loop without a neutral?

Seems to me that the code was changed not real long ago to require switch loops to have a neutral conductor run as well. I think this was to accommodate dimmer switches. I don't recall off the top of my head where this is, assuming my recollection is correct.

 

[infinity]

Seems to me that the code was changed not real long ago to require switch loops to have a neutral conductor run as well. I think this was to accommodate dimmer switches. I don't recall off the top of my head where this is, assuming my recollection is correct.

You're correct that a neutral is required in some installations at a switch but not all. If there is a raceway where the neutral can be added later then a 2-wire switch loop is still permitted.

 

[petersonra]

You're correct that a neutral is required in some installations at a switch but not all. If there is a raceway where the neutral can be added later then a 2-wire switch loop is still permitted.

It doesn't really affect me so I'm not all that up on it but I seem to recall seeing it as a change to the code at some point in the not too distant past.

 

[Greentagger]

I don't have my book, what code section applies to a 2-wire switch loop without a neutral?

404.2 Exception, 300,20(A).

 

[Eddie702]

You can't have hots and neutrals originating from different panels no matter the distance between panels. Never would be code compliant

 

[petersonra]

You can't have hots and neutrals originating from different panels no matter the distance between panels. Never would be code compliant

Where does it say that?

 

[winnie]

You can't have hots and neutrals originating from different panels no matter the distance between panels. Never would be code compliant

If you are referring to 210.4(A) than I believe that only applies to 'multi-wire branch circuits'.

In this particular case, I'd argue that even that doesn't apply. The hot and neutral _are_ originating from the same panel. Everything originates from the 'main' panel, the hot get split up in the 'sub' panel into multiple separate wires, which then _return_ to the main panel to continue on with their respective neutrals.

-Jon

 

[wwhitney]

In this particular case, I'd argue that even that doesn't apply. The hot and neutral _are_ originating from the same panel. Everything originates from the 'main' panel, the hot get split up in the 'sub' panel into multiple separate wires, which then _return_ to the main panel to continue on with their respective neutrals.

Since 210.4(A) refers to where the the branch circuit originates, I don't think that argument flies. The ungrounded conductors of the branch circuit originate at the panel with their circuit breaker. If the neutral of the branch circuit isn't present in that panel, it can't originate there.

However, the presence of the language in 210.4(A) suggests that for other than MWBC, there's no requirement that every conductor of a branch circuit needs to originate in the same panel.

Cheers, Wayne

 

[LarryFine]

Multi-switch generator transfer panels get away with doing it.

 

[Dennis Alwon]

I can say in response to the feeder neutral being used for the purpose of the branch circuits is not compliant in this case.

200.6

(A) Installation.

Neutral conductors shall not be used for more than one branch circuit, for more than one multiwire branch circuit, or for more than one set of ungrounded feeder conductors unless specifically permitted elsewhere in this Code.