XxaudioholicxX
Member
- Location
- Texas
I have a panel I am looking at that controls a motor. The panel is 480V 3 phase and so is the motor. They have 3 independent circuit breakers, on each phase, before the motor contactor and motor. In my experience, this is not typical or recommended since the possibility exists that one phase could trip and possibly damage the motor by single phasing it.
So I decided to try and look it up in UL 508A, NEC 70, and NFPA 79, the only thing I can find are these references:
7.2.10 Power Circuits in NFPA79 where it says "all ungrounded and grounded conductors open with no pole operating independently"
240.15 Ungrounded Conductors in NEC 70 says: "(B) Circuit breaker or overcurrent device shall open all ungrounded conductors of the circuit both manually and automatically...."
My dilemma is the customer wants the panel to meet UL508A requirements, but I can not find any reference in UL about this issue. Am I overlooking it? My understanding is that since NEC is law binding, all other codes should follow. So I want to tell them that this is not UL, but it would be nice to have proof.
If any one has any ideas please let me know, or if you know any white papers, case studies, etc... that talk about this in more detail, please let me know. The only other code is UL498 for circuit breakers, but I do not have this code...
Thanks,
Jay
So I decided to try and look it up in UL 508A, NEC 70, and NFPA 79, the only thing I can find are these references:
7.2.10 Power Circuits in NFPA79 where it says "all ungrounded and grounded conductors open with no pole operating independently"
240.15 Ungrounded Conductors in NEC 70 says: "(B) Circuit breaker or overcurrent device shall open all ungrounded conductors of the circuit both manually and automatically...."
My dilemma is the customer wants the panel to meet UL508A requirements, but I can not find any reference in UL about this issue. Am I overlooking it? My understanding is that since NEC is law binding, all other codes should follow. So I want to tell them that this is not UL, but it would be nice to have proof.
If any one has any ideas please let me know, or if you know any white papers, case studies, etc... that talk about this in more detail, please let me know. The only other code is UL498 for circuit breakers, but I do not have this code...
Thanks,
Jay