ATS on transformer secondary

[Electromatic]

This might be simple, but I don't recall encountering it before:

Commercial/Industrial site. 480V service. Transformer down to 120/240V for the office area. They want a generator to back up the office only. Do I need to switch the neutral in the ATS?

 

[ammklq143]

I could be wrong but I don't see why you would need to. I have inspectors that interpret things differently and while one will allow something another won't so it might not hurt to ask your local AHJ. I would think you could leave the neutral unswitched and as long as you don't bond the neutral and ground at the generator.

 

[texie]

This might be simple, but I don't recall encountering it before:

Commercial/Industrial site. 480V service. Transformer down to 120/240V for the office area. They want a generator to back up the office only. Do I need to switch the neutral in the ATS?

Not as long as you set it up as a non-SDS, IE no neutral bond at the genset. The ATS will have to be after the Xformer OCPD, so if you already have a MB panel serving as the secondary protection you will have to rework it with a separate OCPD ahead of the ATS.

 

[Electromatic]

Thanks!
I was trying to think if the derived neutral and the neutral-ground bond at the transformer would create some kind of objectionable path for current getting back to the generator. I guess I was over-thinking it.