STEP-UP AND STEP-DOWN TRANSFORMERS

Hello guys,

I wanted to start a discussion on wiring transformers in reverse.
What are some important considerations when you wire a step-up transformer in reverse to make it a step-down transformer? And what are the important considerations when you wire a step-down transformer in reverse to make it a step-up transformer? Is this against Code?
I look forward to hearing all the brilliant minds comment on this!

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