saianguluri wrote:
I have a low voltage(480V) OCPD feeding a 4/0 cable which feeds a junction box. From the junction box, three sets of 8AWG cables feed three motor starters. The OCPD protects 4/0 cable against short circuits but doesn't protect the 8AWG. When I referred NEC they recommend matching the ampacity of the feeder(4/0) but using a 1/0 is enough for the OCPD to protect the cable. Can anyone suggest what to choose?
Read 240.21(1), the 10ft tap rule, that that section allows your installation where there is OCP at the termination of the tap conductor.
If you do install OCP for each tap, the OCP does not have to be in the enclosure where the tap is made, a fusible disconnect switch attached (conduit stub) to the enclosure is sufficient and is an accepted practice.
Perhaps more important than conductor protection is the lack of protection for the motor starter. In most cases a motor starter will have a max circuit protection rating associated with the UL listing, in this case OCP at the termination of the tap would make your circuit NEC compliant.