I had quite a few old motor starters that I would have preferred to use, but the space constraints dictated the use of definite purpose contactors. I used 24v contactors to allow the use of low voltage remote control wiring, and designed the system to use readily available replacement parts.
The schematic is a bit more involved than most of the others that I have found, but I designed it for possible enhancements, such as another (additional) idler motor, remote temperature sensing of the idler(s), and remote limit/overload controls. The original design used a third 24v transformer on the manufactured leg to control a start relay, but it proved to be unreliable, since the voltage on that leg exceeded the transformer ratings. The potential relay seems to work fine, although it needed to be adjusted to match the requirements of the idler motor used.
The housings for the components consist of a contactor box and a capacitor box, recessed into the wall. The 10 HP idler motor is mounted in the attic, on two pieces of 2" plywood flooring sandwiching a foam buffer, and on rubber vibration mounts. The assembly is bolted to the ceiling joists, and is completely quiet.
