The Aprilaire 4410 is the correct replacement for the following humidifiers:
The Aprilaire 4410 Humidifier Water Level Sensor fits the bottom of the scale control insert. Also known as part number 4410, the Aprilaire humidifier water sensor has two magnetic reed switches that searches for the location of the two floats in order to ensure the proper level of water is in the reservoir. The two floats are sold separately.
Aprilaire 4410 Water Level Sensor Assembly specifications:
The Aprilaire brand is also identified by the following spelling variations: April Air, April Aire or Aprilair. This water level sensor turns the water solenoid valve on and off, based upon the water lever in the scale control insert.