Transformers in Reverse

[W@ttson]

Sorry one more question does the generator have an OCPD built in.

Yes it does.

 

[W@ttson]

For the reasons that GoldDigger, Jim and others have mentioned, the feeder neutral should be disconnected from Xo. But it could make matters worse if you don't also disconnect the Xo bonding strap. If the strap is left connected, then the possible high current through the neutral that we are concerned about might instead flow only through the bonding strap and feeder EGC.

The connection diagram on the transformer shows taps on the delta side to accommodate different source voltages. The taps allow a consistent and proper volts-per-turn on the windings to be attained over a range of input voltages. Clearly this shows that the transformer was designed to be energized from the delta side, even though the low voltage side is labeled as the primary.

Yeah, that strap is small. Don't want that.

Interesting read on the taps.

 

[wwhitney]

So what's the OCPD in picture #18, and if it is being supplied from the bottom, is it definitely not marked LINE/LOAD with LINE at the top?

Cheers, Wayne

 

[W@ttson]

So what's the OCPD in picture #18, and if it is being supplied from the bottom, is it definitely not marked LINE/LOAD with LINE at the top?

Cheers, Wayne

It is the OCPD on the “primary” wye side. The feeder from the service location ~400ft away terminate into it. Yes it feeds it from the bottom. Not having proper line / load labeling would be not surprising.

I know for sure that the primary is 208/120 and that the secondary is 480.

 

[wwhitney]

Not having proper line / load labeling would be not surprising.

Not having line/load labeling is not a problem. What is a problem is if the breaker is labeled LINE at the top, because that breaker is being supplied from the bottom.

Cheers, Wayne