Steve Merrick
Member
- Location
- Anchorage, AK
Can bare copper bus bar be used as an “open wiring on insulators” wiring method in accordance with NEC 398?
Our consultants have designed a battery room where the POS and NEG terminals of a 250 VDC stationary battery land on individual sections of wall-mounted copper bus bar located about 6 feet apart on insulated standoffs, before continuing on to the DC breaker panel. The bus bars and terminal lugs are protected by acrylic covers and otherwise meets the requirements of Article 398. Additionally, our application looks identical to the last two sentences of 300.37, however that wiring method appears to only be allowed above 1000 volts.
I think we're OK under Article 398, but one of our contracted electrical inspectors has given us an unsatisfactory finding because the bus bar is not UL listed for the application (the bar is listed for grounding applications only). To my knowledge, there is no UL listing for bare copper bus bars used as a power circuit conductor; just as in nob-and-tube wiring methods, the bare circuit conductors are not UL listed but are still approved wiring methods.
Your guidance and opinions are requested.
Thanks!
Our consultants have designed a battery room where the POS and NEG terminals of a 250 VDC stationary battery land on individual sections of wall-mounted copper bus bar located about 6 feet apart on insulated standoffs, before continuing on to the DC breaker panel. The bus bars and terminal lugs are protected by acrylic covers and otherwise meets the requirements of Article 398. Additionally, our application looks identical to the last two sentences of 300.37, however that wiring method appears to only be allowed above 1000 volts.
I think we're OK under Article 398, but one of our contracted electrical inspectors has given us an unsatisfactory finding because the bus bar is not UL listed for the application (the bar is listed for grounding applications only). To my knowledge, there is no UL listing for bare copper bus bars used as a power circuit conductor; just as in nob-and-tube wiring methods, the bare circuit conductors are not UL listed but are still approved wiring methods.
Your guidance and opinions are requested.
Thanks!