50. Aprilaire® Current Sensing Relay (24 V Application)
This humidifier current sensing relay will detect a current when the furnace blower fan is running. If you have a multi-stage furnace, this current will simplify your installation without needing accessory terminals. When you run the fan wire through the top loop of the relay when the fan turns on, the relay will close and allow the 24 volt power on the relay side to flow through in order to turn the humidifer on.