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"
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.
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.
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.
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.
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.