Multi-family Apartment Building

[ggunn]

Just to be clear, I'm not saying a Y-Y won't work. IIRC, @ggunn has used them, maybe he will chime back in.

I don't any more. Years ago I used a wye - wye transformer a few times on the advice from an inverter company; the systems worked but we saw instances of current imbalance coming out of the utility side of the transformer when we ran a neutral back to the service, plus it's a needless expense. The consensus now is pretty much that it's better for the transformer to be a delta on the utility side.