The Aprilaire 4010 is the correct replacement for the following humidifiers:
The Aprilaire 4010 Humidifier Transformer Replacement is a low voltage transformer that fits selected Aprilaire and Honeywell humidifiers. Also known as part number 4010, this humidifier transformer allows you to convert 110 volts to 24 volts for safe installation. Simply connect the leads to the 110 volt current. The screw terminals will then provide 24 volts. This transformer mounts in a utility box.
Aprilaire Humidifier Transformer 4010 specifications:
The Aprilaire brand is also identified by the following spelling variations: April Aire, April Air or Aprilair. Make sure that all power is disconnected prior to service. You want to also check to make sure that the power is disconnected from a meter.