HVAC Depot stocks overload relays including Furnas, Reznor, Carrier, Danfoss, Lennox, Honeywell and more. Overload relays protect a motor by sensing the current going to the motor. Many of these use small heaters, often bi-metallic elements that bend when warmed by current to the motor. When current is too high for too long, heaters open the relay contacts carrying current to the coil of the contactor.