Aprilaire 866 Modulating Steam Humidifier with Model 850 Fan Pack

Product Description

The Aprilaire 866 is a whole-house modulating steam humidifier designed for residential and light commercial applications where precise humidity control matters most. Built for HVAC professionals and contractors, this unit delivers up to 34.6 gallons of steam per day and is capable of humidifying spaces up to 6,200 square feet. Unlike fixed-output humidifiers, the modulating design continuously adjusts steam output to maintain a tighter relative humidity level, reducing temperature swings and improving overall indoor air comfort. This makes the 866 a strong choice for installations where occupant comfort and air quality are priorities.

The Aprilaire 866 generates steam by energizing electrodes that are submerged in water held inside a disposable canister. This electrode-based steam generation eliminates the need for water filtration, which simplifies installation and reduces long-term maintenance requirements. Water level inside the canister is managed automatically through coordinated drain and fill valves, keeping the system running efficiently without manual adjustment. When maintenance is needed, the canister is simply removed and replaced. There is no cleaning or scrubbing required, which reduces service time on the job.

This model includes the Model 850 Fan Pack, which provides ductless humidification throughout the home. The fan pack consists of a wall-mounted discharge grille, a fan blower assembly, and a stainless steel dispersion chamber. This ductless configuration makes the 866 a practical solution for installations where ductwork is inaccessible, not present, or not preferred. The unit operates at 120V, 208V, or 240V at 16 amps and features an LED user interface for straightforward monitoring. A modulating control is required to enable the variable output capability. The supply connection measures 1 quarter inches.

• Modulating steam output for precise relative humidity control in spaces up to 6,200 square feet
• Includes Model 850 Fan Pack with stainless steel dispersion chamber for ductless whole-house humidification
• Disposable canister system requires no cleaning, scrubbing, or water filtration for low-maintenance operation

Product Highlights

The Aprilaire 866 delivers high-capacity modulating steam humidification with a built-in fan pack, making it well suited for ductless installations where consistent indoor humidity control is required. Its electrode-based canister system minimizes maintenance while supporting reliable, whole-house performance.

Product Information

Standard Information

• Brand: APRILAIRE
• Manufacturer Part Number: 866

Technical Specifications

• System Type: Steam
• Product Type: Humidifier
• Type: Modulating
• Amperage: 16 Amps
• Capacity: 34.6 Gallons Per Day
• Coverage Area: Up to 6,200 Square Feet
• User Interface: LED Lights
• Application: Air Quality
• Voltage: 120V, 208V, 240V
• Supply Connection: 1/4 inches
• Warranty: 5 Year