In regards to Article 300 Section 300.3(B), is it necessary to run the neutral in the same raceway or nipple when installing a emergency panel that is backed up by a generator and the "hots" are being routed from the main panel through a nipple to the transfer switches and back to the main panel? I hope this makes sense. The customer has all the "home runs" in the main panel and the neutral bus is in the main panel and the emergency panel, connected by a nipple. has no neutral bus. So the question becomes, does the emergency panel need a neutral bus? Should I run the neutrals of the branch circuits over to the emergency panel? Can I run a single neutral from the main panel to the emergency panel?
The manufacturer is saying "no neutral is needed in the emergency panel"
George,
I say you need the neutral per 300.3 (B). Should there be a severe imbalance in the load, and no neutral to counteract the magnetic fields, there could be a considerable heating problem without a neutral. The 24” nipple rule is a gift but I’m sure the code panel felt that 300.3 (B) would be abided by when they wrote it. To take up to 30 circuits through a nipple and not use all the conductors of the circuit seems to be pushing it. Just my AHJ 2 cents worth.
Tony
maybe I am confused but...
If you don't need a neutral, don't run one, then the question is moot. If this is just switching the hots and they go in and out in the same pipe there is no heating. It is just a switch loop. I am guessing they are not switching the neutral and the generator is not bonded at the generator end.
300.3(B)(4) indicates, that the code panel doesn't find an issue with terminating the neutral in an adjacent enclosure, with regards to nipple heating, etc.
Steve, if you look at the picture in the handbook of this the adjacent enclosure they show is, again, only a switch loop (with O/C devices instead of switches). For the purposes of this discussion it is appropriate tho.
George
Curious did the switch come with a Neutral Bar??? If so was it listed and labeled as tested that way??
Also check out 300.20 2005 N.E.C.
Ernie- Some Panel have a need for a neutral for the indicator lights and some don't. As for a neutral buss, I can't say for sure. I look at a lot of Generac set up and they come with a harness that only contains one neutral of a small gauge wire. I don't believe it is the neutral for all the circuits in the harness. You can bet the farm I'll be watching for it on the next one.
I'm thinking too of all the switch loops out there that don't contain a neutral so I guess if a piece of equipment does not have a neutral buss, and if it's Listed I'd look at the Manufacturers Specs as an installer or as an Inspector.
And one more thing- Look at 300.20(A) {note- applies to metal raceways} and 404.2(A) for switch loops whether metal or nob-metallic.
I think some of you may be missing the point here. The nipple carrying the branch circuits from the emergency panel back to the house panel does not contain switch loops or neutrals that nullify the magnetic fields. This nipple contains only the branch circuit conductors from the emergency panel back to the normal house panel where they are spliced and leave that panel. The feed for the emergency panel is in a separate nipple fed from the transfer switch. If the feed for the emergency panel were to be in the same nipple as the branch conductors leaving the emergency panel, I would agree that the nipple would act as a conduit containing switch loops. This however is not the case. This conduit carries no switch loops or neutrals, just 30 conductors leaving the emergency panel from separate circuit breakers.
Tony
If the feed for the panel and the branch circuit coming out are not in the same raceway and you didn't pull the neutral through there, then you have made an inductive heater.
Sorry for the confusion. If you loop the neutral therough your emergency panel following the path of of the hots it is OK or you could take the feed to the house panel with the neutral and snake it in with the branch circuit conductors making that switch loop out of it (what I thought was happening) you would be OK.
Now I think you get the picture. George and I were discussing this topic because it happened on one of the jobs I was inspecting and we are seeing this quite often. I made the contractor pull a neutral the same size as the line conductors feeding the emergency through the nipple carrying the branch circuits back to the main house panel. I also made him terminate that neutral on an additional neutral bar where he would connect the neutrals from the circuits being fed from the emergency panel. This would in effect make the house panel be nothing more than a junction box for the circuits being fed from the emergency panel and it would also resolve the inductive problems by having a neutral included with the branch circuit conductors in the same nipple. I hope that helps explain the problem and how I asked the contractor to resolve it. George’s original question is still unanswered though. We are seeing manufacturers of the generator equipment telling the contractors the original installation is fine. Is anyone eles anyone seeing this as well?
Tony
I think Tony has it right.
The hots from the transfer panel are supplied from the generator during emergency. They are all hots with no neutrals to balance the magnetic field.
Not sure how that circuit will even work without a return path. Is there a ground, or is the nipple, being used as the return ?
I bet they are landing the neutral from the generator straight to the neutral bus in the service panel. That is an inductive heater.