[jlsanborn]

Those are going to be cool pieces Vic!

Surprised the compressors don't have built in reliefs? Maybe look at OEM radiator fan relays, or even *ord style starter relays if the Accuair controller can drive a coil that big. I'd bet it's just the high motor current that's smoking the contacts as opposed to a collapsing field or "kick-back". On the control side, it wouldn't hurt to use diodes across the relay coils to help protect the outputs of the Accuair controller.

Edit... Assume the Accuair is calling the compressors to run based on a pressure switch input OR is the pressure switch hard wired to the pump relays?