Buck Autotransformers, OCPD, and Conductor Sizing

[wwhitney]

Say you have a buck autotransformer on a branch circuit. The wires downstream of the autotransformer will carry more current than the supply to the autotransformer. Is there an NEC section that covers conductor sizing and overcurrent protection of these downstream wires? I'm not finding it.

Thanks,
Wayne

 

[wwhitney]

There's 240.4(F) and 240.21(C)(1), which apply to "conductors supplied by the secondary side of a single-phase transformer having a 2-wire (single-voltage) secondary."

So I guess the question is whether that can be considered to apply to the downstream conductors of an autotransformer, or whether the language implies applicability only to an isolation transformer. I have always assumed the latter, but maybe that's wrong.

Cheers, Wayne