I picked up some '70s era GE NEMA 1 magnetic contactors, NOS, military spares. They have overload relays that accept heater inserts and are adjustable within ±15% of nominal via a thumbwheel. Clearly the heater inserts are literally just that - they heat the inside of the overload relay. Beyond that, though, I'm stumped. I'm trying to figure out how these overload relays work. Anyone know? The overload relay number is CR124 if that helps.
Grant