Our power voltage is 208v. The new equipment requires 240v +/- 10%. We have 204v at the outlet. The company has instaled a buck-bost trans. out of the panel and then back throug the panel to feed the outlet the now 240v. Is alowed ??? Artical number please. THANKS
A buck - boost is an autotransformer. There are couple sections in art 450 that refer to autotransformers. None of what you have mentioned is part of topic in those sections.
There were several hits in a search of the word autotransformer - the most relevant besides the ones in art 450 that deal directly with what your topic of discussion is exception 1 to 210.9. Same exception appears after 215.11.
Exception No. 1: An autotransformer shall be permitted without the connection to a grounded conductor where transforming from a nominal 208 volts to a nominal 240-volt supply or similarly from 240 volts to 208 volts.