[marklgreen]

I have a pair of Carrier 100 BTU furnaces controlled by a Honeywell programmable thermostat. There is a Aprilaire humidifier with a completely separate control attached to the furnace. I purchased a fan relay Steveco 90-293Q to wire the humidifer inline with the furnace thermostat control. I would think that wiring the coil in series with the 24v furnace thermostat and wiring the humidifier control in series with the 120v leads of the relay would only turn on the humidifier when the furnace thermostat was triggered. It seems like there is not enough power feeding the relay coil to engage the relay and close the circuit when the furnace thermostat triggers. I have check that the humidifier wirring is correct by connecting it to the other 120v relay lead and indeed the ciruit is closed and the humidifier will turn on appropriately. Is there another way to wire this in series with the furnace fan motor? So when the furnace fan motor turns on the humidifier control circuit is closed and it will run if needed (if the room humidity is below the control setting).

Thanks

[rickdb1]

Purchase a current sensing relay. It hooks to the fans low speed(Red) wire...