The Aprilaire 4406 is the correct replacement for the following humidifier:
The Aprilaire 4406 Humidifier Float Valve Assembly floats in the scale control insert/float chamber to control the water supply. There are two float assemblies required: one assembly on the right hand for function and one assembly on the left hand for safety backup. When the water evaporates and the float reaches the bottom, the electronic switch is activated and the water supply turns on. When the water level is high, the right hand float turns the water supply off. The Aprilaire brand is also identified by the following spelling variations: April Air, April Aire or Aprilair.