all conductors terminating in the same box?

[rszimm]

Is there code that states that all conductors (including the grounded conductor) have to terminate in the same breaker box? I've seen it a couple times now where someone has added a small subpanel directly next to the main panel and for the few circuits in there terminate the hots in the sub-panel breakers, but run the neutrals back to the main panel. I honestly don't understand why they would do that, but I've seen it a few times now and figured I'd ask. Seems unnecessary and confusing for the next guy (me)...

 

[Dennis Alwon]

Section 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).

 

[texie]

Section 300.3(B)

Dennis, I'm not sure that 300.3 prevents this. Of course there is 210.4 for MWBC. But if the branch circuit is not part of a MWBC, I'm not sure what in the code would prevent the OP's situation. I've often wondered about this as, like the OP, I have seen this many times and think it is an incredibly bad practice and potentially very dangerous.
Just imagine you open the main to a panel and think all a safe and you remove a grounded branch circuit conductor from it's termination and discover it is live from another panel.
Seems like we need simple language that says all conductors of of a circuit must terminate in the same panel regardless of whether it is part of a MWBC.

 

[charlie b]

Dennis, I'm not sure that 300.3 prevents this.

I think it does prohibit this. There is a conduit between the main panel and the subpanel. That conduit contains the neutral of a circuit, but does not also contain the phase conductor of the same circuit. So it violates 300.3(B).

 

[Dennis Alwon]

Seems clear to me. I believe you could have heating issues if you use metallic raceways. Think of 10 wires running thru a short nipple from one panel to the other. EC leaves the neutral in the existing panel and runs all the circuits thru that nipple. Do you see an issue?

 

[rszimm]

I think it does prohibit this. There is a conduit between the main panel and the subpanel. That conduit contains the neutral of a circuit, but does not also contain the phase conductor of the same circuit. So it violates 300.3(B).

I tend to agree, but one could argue that it does have the phase conductor inside that conduit, it's just before the breaker. In other words, the electrons going through the phase conductor in the conduit go through the breaker and into the circuit, eventually routing back through that neutral.

 

[GerryB]

Seems clear to me. I believe you could have heating issues if you use metallic raceways. Think of 10 wires running thru a short nipple from one panel to the other. EC leaves the neutral in the existing panel and runs all the circuits thru that nipple. Do you see an issue?

How about those generator sub panels where they give you a whip with a ground and a neutral and a lot of circuits. I always wondered about them.

 

[Dennis Alwon]

How about those generator sub panels where they give you a whip with a ground and a neutral and a lot of circuits. I always wondered about them.

The equipment grounding conductor is not an issue but IMO, there is an issue with the whip.

 

[infinity]

Seems clear to me. I believe you could have heating issues if you use metallic raceways. Think of 10 wires running thru a short nipple from one panel to the other. EC leaves the neutral in the existing panel and runs all the circuits thru that nipple. Do you see an issue?

The circuits run in and out in the same raceway so there is no heating issue. No different than a switch loop. Having said that it still violates 300.3(B).

 

[texie]

Seems clear to me. I believe you could have heating issues if you use metallic raceways. Think of 10 wires running thru a short nipple from one panel to the other. EC leaves the neutral in the existing panel and runs all the circuits thru that nipple. Do you see an issue?

My issue is that if one were to meet all the requirements of 300.3 there is nothing to expressly prohibit what the OP described. I just find it odd that the code does not have the same requirement for a non-MWBC as it does for a MWBC as in 210.4.

 

[Dennis Alwon]

The circuits run in and out in the same raceway so there is no heating issue. No different than a switch loop. Having said that it still violates 300.3(B).

For the life of me, I can't remember but are both conductors hot at the same time in those whips? I seem to think not but it has been 20 years since I have messed with them

 

[charlie b]

Now I am confused. I think one of two things must be happening. Which one is it?

1. Attach a black wire to a breaker in the sub panel. Attach a white wire to the neutral bar in the main panel. Run the white wire through the nipple between the two panels. Then run both the black and the white wires out a conduit that goes from the sub panel to the load.
2. Attach a black wire to a breaker in the sub panel. Attach a white wire to the neutral bar in the main panel. Run the black wire through the nipple between the two panels. Then run both the black and the white wires out a conduit that goes from the main panel to the load.

In example 1, you have neutral wires inside the nipple, and you don't also have the ungrounded wires in the same nipple.
In example 2, you have ungrounded wires inside the nipple, and you don't also have the neutral wires in the same nipple.
In both examples, you have a violation of 300.3(B). In both examples, if the nipple is metallic, it could overheat.

 

[GoldDigger]

For the life of me, I can't remember but are both conductors hot at the same time in those whips? I seem to think not but it has been 20 years since I have messed with them

When one of the branch circuit transfer switches is in the normal position the hot lead current goes from the existing breaker to the switch and back again to the branch wiring through the whip.

When that switch is in the generator position the current flows in the whip only on the load side of the switch, *but* the neutral current from the generator will now be flowing through the whip (possibly over a larger common conductor rather than an individual conductor.)
In both cases the current in the whip is balanced.

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