Aprilaire 866 Humidifier, Whole House Steam w/Modulating Output & Fan Pack - 1.4 Gallon/Hr.

by Aprilaire
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The Aprilaire 866 is a whole house humidifier with modulating output and a fan pack. This modulating capability allows the unit to meet a tighter relative humidity control for a much more comfortable environment. This model is capable of humidification of up to 6,200 feet and has a maximum steam capacity of 34.6 gallons per day.

This Aprilaire humidifier provides humidity in the form of steam to conditioned space through the included fan pack. This fan pack includes a wall mounted discharge grill with a fan blower assembly and stainless steel dispersion chamber. This provides ductless humidification throughout the home.

This model generates steam by energizing electrodes that connect to water in a disposable canister. To modulate this steam output, a modulating control must be used. Proper water level in the canister is maintained through cooperating drain and fill valves. Adding humidity through steam is an efficient and effective way to solve dry air issues in the home. Air with improper humidity can damage respiratory health as well as the home's paint, furniture and electronics.

A ductless installation allows for whole house humidification in scenarios where intensive ductwork is not possible or preferable or when the ducts are not accessible. In addition, maintenance is also easy with no cleaning or scrubbing! All that is required is for the canister to be removed and replaced. Plus, water filtration is never required for the operation of this digital humidifier.

The Aprilaire 5558 is a wall mounted humidistat kit for this model. It allows for automatic control over this unit and comes with an outdoor temperature sensor.


  • One high capacity unit can provide between 11.5 and 34.6 gallons per day
  • In this set, the Model 801 marries with the Fan Pack to provide comfortable humidity levels in homes without duct work
  • Electrode-type humidifier generates steam by energizing two electrodes that extends into the steam canister
  • Current flowing in between the electrode causes the water to boil creating steam
  • The Model 866 accepts an input signal of 0-10 Vdc, 0-20mA, 2-10 Vdc, or 4-20mA
  • Aesthetically pleasing model is designed to blend into a home's environment
  • Easy to install fan pack is recessed into a wall and connects directly to the Model 801 Steam Humidifier
  • The Model 866 consists of the Model 801 Steam Humidifier, Fan Pack, Model 4028 Drain trap assembly, steam hose, and drain tubing
  • Display panel provides power switch for on/off operation, illuminates LEDs to show fill, drain, steam operations, and diagnostics
  • Internal control board manages the complete operation of the humidifier
  • The board fills and drains to maintain proper amperage draw, water level and notifies when service is required
  • Back flow protection from air gap in the fill cap to prevent pressure build up
  • Water level sensor manages the water level in the steam canister to prevent overfilling
  • Unit automatically flushes and fills periodically to maintain the proper conductivity
  • Unit uses cold inlet water to temper the canister water reducing the drain water temperature below 140°F to protect PVC piping and condensation pumps
  • End-of-season drain:
    • After a 72-hour period with no call for humidity the humidifier will drain the water from the canister
    • Unit will remain in stand-by until next call for humidification
    • Steam capacity adjustment is accomplished by using a dip switch


    • Aprilaire Model: 866 Fan Pack
    • Ducted or Ductless: Ductless
    • Steam Capacity (adjustable via dip switch):
      • 120 volts:
        • Max amperage (16 amps): 5.6 lbs./hr. (16.0 gpd)
        • Reduced amperage operation (11.5 amps): 4.0 lbs./hr. (11.5 gpd)

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