Residential 200A ATS and MSP Neutral wiring

[wwhitney]

Ok. But don't you need at least 1 service neutral in that conduit with all those line conductors to cancel out the magnetic fields so as not to create unbalanced magnetic fields and induced heat as stated above by master nater?

No, it's just like a switch loop. When on utility power, the current on the black wire to the ATS from the MSP is canceled by the equal current on the black wire from the ATS to the distribution panel. Likewise for the red wire. The load current on the white wire when on utility power doesn't have to go through the ATS enclosure at all.

Cheers, Wayne

 

[Seven-Delta-FortyOne]

Then I am correct. As long as the line and load conductors to the ATS are in one nipple, the service neutral need not be routed through the ATS.

The black dotted line in your diagram will never see more than the generator's neutral current. I wired one exactly like this a few years ago.

And the ATS is not the service disconnect and need not be service rated because of the disco ahead of it.

So now that I’m thinking about this, I think I have been oversizing neutrals on a lot of my 200A installs.

I guess it does only need to be sized to the generator MCB.