If the Poco transformer wired Wye they will demand the neutral be brought in as a matter of course.
I've never seen it omitted.
But, I haven't seen everything.
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Reno: the transformer that you're in need of is a ZigZag.
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You're also telling the tale of woe that caused EUSERC to entirely abandon delta Services -- unless there's a compelling reason.
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375 Watt lamps are now available that produce the same lumens as 400 Watt classics.
The economics are astoundingly favorable for swapping over ASAP.
