Do you mean...
Hi George-
When you say 'start contactor'... do you mean... the contactor actually carrying start current through the starting capacitors... or the contactor which engages the RPC idler to the LINE?
LINE contactor should be capable of carrying the full current of everything... INCLUDING the start current of the idler motor... starting caps and all.
The START contactor (which engages the start caps) needs to carry the capacitor currents.
Neither of these contactors should be sissies... there's a good whomp goin' through there. I took one additional step with my RPC's control box- I added a LOAD-side contactor, that wouldn't close until after the idler was started and up-to-speed AND the START contactor had been dropped out. This makes sure that I don't try to start a machine before the idler startup and capacitor currents have long-since passed.
If you're running a 208-250v system, I'd say you should be able to switch at least 50A through the contacts, and contacts should be rated for 250v or more.
The start capacitor circuit can use a three-phase contactor, where all three contacts are in parallel... and you'll get away with having a physically smaller contactor doing that job.
