Product review (4 stars): Good product, documentation only for newer model humidifiers
This worked well out of the box and as I used it, I noticed the point where it clicks to trigger the circuit increased as the humidifier ran. I purchased this to run my Aprilaire 700. Warning: If you have the pre-2008 Aprilaire model, non of the wiring diagrams will work correctly as the humidifier itself only requires a circuit to complete, not 24 volts in. I spent 5 hours trying to figure that out. You need an additional relay to make this work if you have a 24 volt transformer inside of your humidifier unit.