NEC really gets on my nerve sometimes. I understand safety but sometimes the rules makes no sense or are overkill.
I use a cooling motor in a vacuum furnace.
The motor runs in a pure argon atmosphere enviroment.
Because it is in Argon it must be rated at 230V by NFPA 86. )I believe this is related to the fact that argon gas can be "charged" to carry current, so higher voltages MAY cause the windings to "flash over".)
Now NFPA is fire protection code......in a pure argon environment, how is a motor going to catch fire?
I have several jobs overseas that are running 415V motors for years with no issues..... in an argon enviroment.