Switching Neutral or not?

[Open Neutral]

So given a poco provided HV:480/277 wye, a main disconnect and meter, a generator backup, and a transfer switch....

That is (I believe) the separately derived service case so that we'd need a 4-wire transfer to switch 3+neutral....I think.

But suppose that all use the same ground point for neutral, the Ufer. The poco neutral is grounded there; the generator is also grounded there, etc.

Does that change things?

 

[iwire]

You can choose to set it up as an SDS which will mean you must switch the neutral.

You can choose not to set it up as an SDS which will mean you would mean you would not switch the neutral.

If the service or feeder has GFP it may be wise to set it up as an SDS to reduce the possibility of circulating currents tripping the GFP.




SDS = Separately derived system 250.30

GFP = Ground Fault Protection 215.10 / 230.95