Doug,
I have used Square D 8536 starters for small RPCs, that is , 3 hp and 5 hp but they are hard to make connections between the contactor section and the overload section. You will need to make connections between the contactor and overload relay for all the capacitors. Yesterday, jminer99er sent me a photo of a size 3 Square D starter (I do not know the model) which has large copper tabs sticking up where the contactor connects to the overload relay. This one will be easy to use for a RPC as these tabs have threaded holes for bolted connections.
Some simple math. the size 2 starter is rated for 45 amps which is just marginal for a 7-1/2 hp RPC. I think it will work fine if you do not have more than 7 hp total load running at any one time. You should probably use wire good for 50 amps just in case you have to use a 50 amp breaker.
I am just finishing a new 7-1/2 hp and took photos last night. I do not have them with me at the moment but can send some next week if you will send me a private message and your email address. Mine is built with a seperate contactor and overload relay so it will look a little different. It has run capactirors per Fitch Williams' design, uses a capacitor start with potential relay and has two output fused circuits. This one is a 60 amp design intended for a 50 or 60 amp single phase circuit. The design will work for either a 7-1/2 hp idler or a 10 hp idler with changes only to the overload heaters and the capacitors.
See the posting I made a few days back about ideas for a capacitor rack. some of the responses may give you some ideas for mounting the capacitors.
Bruce Norton
