Conductor sizing - 480 VAC 350 Amp Bus to 24 VDC Power Supply

[dsr]

Hello everyone, inside an MCC we have a 480 VAC bus fed from a 350 A MCB. The vendor is showing 14 AWG tapping to this bus which goes into a 4 Amp TM CB and then to a 24 VDC Power Supply. I'm looking, possibly incorrectly, at Article 725.127 which says to size according to chapters 1 through 4 and I'm not seeing in them where we can use 14 AWG. I feel like I'm missing an important principal here. Any insight would be greatly appreciated.

 

[tom baker]

Can you install a bucket withOCPD that plugs into the bus or can be wired to the bus?

 

[infinity]

Is there a code provision. (I don't have my book) for tapping conductors where the tap conductors do not leave the enclosure so #14 is code compliant? I've seen 4000 amp services with 100 amp tap conductors feeding SPD's with OCP.

 

[tom baker]

Yes for tsp’s on control conductors that don’t leave the enclosure

 

[dsr]

Thanks everyone! In summary, the design is acceptable since it is in compliance with Article 240.21(B)(1).