neutral length

[jim sutton]

We have a situation where we are installing an automatic transfer switch on a generator. We are running two feeders in conduit from the loadcenter. The existing feed to this loadcenter is spliced to the feeder to the ATS and connected to the "normal lugs". The other feeder connects to the "load" lugs in the ATS and then to the main lugs in the loadcenter. We have been installing a neutral conductor in each conduit. We have been told that this is unnecessary, that the neutral is only needed in one feeder! I dont agree and have been looking for a code reference. This is not a parallel feeder because the conductors are not joined at both ends.
I remember being taught that the neutral should be close to the same length as the phase conductors due to overheating problems. At the time we were discussing long switch legs, not parallel feeders.

Any thoughts, comments or code references to support my position? Or am I wrong?

Thanks in advance!

 

[iwire]

The neutral length is irrelevant it does not have to be even remotely close to the same length as the phase conductors.

Other than that there is 300.3(b).

300.3(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 (4).

From your description it sounds like you need to run the neutral.

By the way, the ATS may want to have the neutrals at it's neutral bar for operational reasons beyond NEC requirements.

Many ATS's monitor both normal and emergency/standby voltages phase to phase and phase to neutral.

 

[jim sutton]

Thanks Bob!

I'll go with you on 300.3(b).

In the case of one neutral, there would be a neutral in "one" of the feeders, connecting the n bus of the loadcenter to the n bus in the ATS.

The way I am doing it is to disconnect the existing neutral from the loadcenter, splice it to the neutral going to the ATS, and then bring a neutral back to the loadcenter n lug (in the other feeder).

This way under normal power, the phase and neutrals are the same length and in the same raceway. Under emerg. power, the phase and neutral are still the same length and in the same raceway.

If you don't install a neutral in both raceway's the above will not be true.

Is your pic Josie Wales or the High Plains Drifter?

 

[LarryFine]

I have an idea: run the feeders both to, and back from, the ATS in one conduit. This way, a single neutral conductor will suffice, and it only needs to be big enough for the ATS's needs.