Feeder Sizing

[Alwayslearningelec]

If you have a bus duct switch feeding a panel do you base your feeder size of the switch or the panel? Thanks.

 

[Buck Parrish]

Kind of both. Your panel can be rated more then the switch but not less. And depending on your load's

 

[shockin]

I would base it on the size of fuses inside the switch.

You could have 40 amps fuses / wire feeding a 600 amp panel. Perfectly legal, just seems odd.

 

[skeshesh]

The question if kind of backwards. You size the OCPD to protect your feeder. So you would choose a panel that exceeds your load and accounts for future growth; then the size of the feeder is based on your load calculation x 1.25 and account for voltage drop, derate, etc. ; finally you choose your OCPD to protect your feeder.
What's the actual situation you're dealing with?