MCP with OL protection in a VFD located in a separate downstream enclosure.

[corvalan]

Is it a violation of the NEC or UL (for the MCP), the following installation:

1. An MCC bucket has only an MCP.
2. Downstream from the MCC, there is another enclosure with a VFD that includes an OL protection function.

I understand that the NEC motor protection requirements are satisfied by this arrangement. However, I am concerned about installing an MCP in an MCC bucket without OL protection in the same bucket. Is this a violation of the NEC, UL 508 (if it applies) or UL 845 (if it applies)?

 

[infinity]

So there is a circuit breaker at the MCC and it is feeding a VFD which is feeding the motor? That is a standard installation practice. The OCPD at the bucket is sized according to the recommended OCPD value for the VFD and the conductors to the VFD are sized at 125% of the VFD input current value.

 

[don_resqcapt19]

You can only use an MCP (assuming you mean instantaneous only breaker) as part of a listed combination starter. The proposed installation would not be permitted.