Product review (5 stars): We used this device to hook our Aprilaire humidifier up ...
We used this device to hook our Aprilaire humidifier up to our furnace.  Before using this sensing relay our humidifier would run all the time (dripping excess water 24-hrs per day).  With this sensing relay, the humidifier only kicks on when the furnace blower is running, hence putting moisture into the air rather than just running water down the drain.  We've had this sensing relay for a couple months and it seems to be doing its job