Industrial Control Panel Article 409.20 & 409.21(c)

[cdmaster]

Which standard do I use when sizing the feeder, and the short circuit protection for an industrial control panel? Are we supposed to use the FLA on the industrial control panel from the OEM?

Do I use NFPA 70 409.20 Conductor min. size and 409.21(c) for overcurrent protection or do I use UL 508A section 32.3.1a for sizing feed and OCP?

 

[Jraef]

Which standard do I use when sizing the feeder, and the short circuit protection for an industrial control panel? Are we supposed to use the FLA on the industrial control panel from the OEM?

Do I use NFPA 70 409.20 Conductor min. size and 409.21(c) for overcurrent protection or do I use UL 508A section 32.3.1a for sizing feed and OCP?

UL508A is for whomever is BUILDING the control panel and planning on listing it.

For the field wiring, if you are planning the FEEDER circuit size, you would use 409.20 and 21 if the ICP is NOT UL listed and/or doesn't have it's own main OCPD already. If it is already self contained and UL listed when it arrives, then I just use 125% of the stated FLA of the panel for the minimum conductor size, then size the feeder to protect the conductors you select. A UL 508A listing of the panel has to include a FLA rating for the entire panel on the nameplate for this very purpose.