How does the overload relay on an 8536SCO3S starter work if the overload contact is normally open?
NEMA style Overload Relays
The normal position is with thermal units installed in all 3 poles and the pawl arms down. The thermal unit wheels hold the pawl arms down which, in turn, hold the overload contact closed. In an overload condition, 1 or more of the thermal unit alloy pots heats up and melts the alloy, allowing the wheel to move and release the pawl arm. This mechanically opens the contact and cuts control power to the coil. After cooling down, the alloy resolidifies and allows the overload to be reset.