aprilaire 800 installation manual

Overview of the Aprilaire Model 800 Steam Humidifier

The Model 800 is a canister steam humidifier that injects steam into the HVAC ductworkor an optional Aprilaire 850 fan pack.It creates steam by energizing two electrodes immersed in water, boiling the water to raise indoor humidity efficiently

Features and Typical Applications

The Aprilaire 800 Steam Humidifier delivers precise humidity control by generating steam through two high‑current electrodes that boil water inside a sealed canister. Its compact design fits standard HVAC return ducts, and the optional Aprilaire 850 Fan Pack expands coverage to larger spaces or multi‑zone systems. Key features include:

• Dual‑electrode steam generation for rapid, consistent moisture output.
• Built‑in safety shut‑off that stops operation if the water level falls below the electrodes.
• Low‑power consumption—only 1.2 kW during operation, reducing electrical load.
• Integrated thermostat wiring compatible with most HVAC control panels.
• Easy maintenance: removable canister for quick water refills and cleaning.

Typical applications range from residential homes with high‑efficiency HVAC units to commercial buildings requiring uniform humidity. The humidifier is ideal for:

• Preventing dry‑air damage to wood flooring, furniture, and musical instruments.
• Improving indoor air quality for occupants with allergies or respiratory issues.
• Maintaining optimal humidity levels in museums, libraries, and archival facilities.
• Supporting HVAC systems in schools, offices, and healthcare environments.

Installation is straightforward: the unit connects to the supply and return ducts, requires a 120 V 60 Hz source, and a 1/2″ water line. The control module interfaces with the thermostat via a 4‑wire connection, allowing set‑point adjustments and automatic shut‑off during low‑humidity periods. Regular cleaning of the canister and checking the water supply filter ensures longevity and prevents mineral buildup.

Advanced features include an optional humidity sensor that can be wired to the thermostat for closed‑loop control, and a built‑in drain line that directs condensate to the building’s waste system.

Overall, the Aprilaire 800 provides a reliable, energy‑efficient solution for maintaining comfortable indoor environments while protecting building materials and enhancing occupant health.

Safety and Compliance Guidelines

Follow all local codes: use a 120 V 60 Hz supply, install a 1 in. copper water line, and a 1/2‑in. drain. Ensure the humidifier is mounted level, with the canister sealed. Wire the thermostat with a 4‑wire connection, and install a GFCI outlet to protect against moisture‑related shocks. GFCI tested.

Electrical and Water Safety Precautions

Before starting, turn off the 120 V 60 Hz supply and close the main water valve. Verify the circuit is dead with a tester and that the water line is depressurized. Install a dedicated GFCI‑protected outlet or breaker and confirm grounding to the building’s electrical ground per NEC 250.

All water‑related connections must use approved copper tubing. Fit a 1‑inch supply line with a dielectric union to avoid galvanic corrosion and a ½‑inch drain line sloping at least ¼ in. per foot toward a floor drain or condensate pump. Tighten fittings to the manufacturer’s torque specs and check for leaks.

Mount the canister level on a non‑combustible surface and verify the seal. A broken seal can let steam reach electrical parts, creating shock risk. Keep wiring at least 6 in. from the steam outlet and run it in heat‑resistant conduit. Use UL‑listed terminals and secure all connections with wire nuts.

Finally, inspect the installation for compliance with local building and plumbing codes. Record the GFCI test result, water‑line pressure, and drainage slope. Keep this checklist for future service and verify all adjustments before regular operation.

Implement a leak‑detection routine by inspecting the canister and water connections for moisture or drips. Install a shut‑off valve on the water line and label all electrical terminals. Schedule annual maintenance to clean the electrodes, verify thermostat calibration, and confirm the drain line remains regularly clear.

Tools and Materials Required for Installation

Required items: 120 V GFCI outlet, 1‑inch copper supply line, ½‑inch drain line, dielectric union, 3‑in. mounting brackets, wrench, torque wrench, pipe cutter, sealant, water‑line shut‑off valve, thermostat wiring kit, multimeter. Also add a 1‑inch copper supply, ½‑inch drain, dielectric union, ¼‑in. drain pipe, inch valve.!

Comprehensive Tool Checklist

Installation of the Aprilaire Model 800 requires a specific set of hand and power tools, fasteners, and consumables to ensure a safe, code‑compliant, and efficient fit‑up. The following checklist covers every item typically called for in the official installation manual and is organized by function.

• Electrical preparation: 120 V GFCI receptacle, voltage tester or multimeter, insulated screwdriver set, wire stripper, 12‑AWG thermostat wiring kit, wire nuts, electrical tape, torque wrench (10‑15 in‑lb) for terminal connections.
• Plumbing and water‑line work: 1‑inch copper water‑supply tubing, ½‑inch PVC or ABS drain pipe, dielectric union, ¾‑inch water‑line shut‑off valve, pipe cutter, tubing deburr tool, pipe‑thread sealant, T‑fitting, compression fittings, leak‑detecting spray.
• Mechanical mounting: Three 3‑inch mounting brackets, #10‑12 wood or metal screws, drill with 3/16‑in. and 1/4‑in. bits, impact driver, level, stud finder, safety glasses, gloves.
• HVAC duct integration: Sheet‑metal snips, duct‑seal foil tape, flexible duct connector, clamp, screwdriver, insulated duct‑wrap, optional Aprilaire 850 fan‑pack mounting kit.

Verify that each tool meets the manufacturer’s specifications before beginning work. Missing items should be acquired prior to opening the humidifier housing to avoid interruptions during the installation process.

Tools listed are essential.!!

Parts Identification and Exploded View

The exploded diagram labels the canister housing, two heating electrodes, water fill valve, drain outlet, humidistat control board, high‑limit safety switch, power connector, optional 850 fan‑pack bracket, and mounting screws. Tagged for fast assembly now.

Detailed Component List

Below is a comprehensive enumeration of every part that constitutes the Aprilaire 800 Steam Humidifier. Each item is identified by its part number, function, and typical installation location. This list assists technicians in verifying inventory, ordering replacements, and troubleshooting component failures during installation or maintenance.

• Part 800-01 – Canister Housing: The primary enclosure that holds the water reservoir and electrodes.
• Part 800-02 – Heating Electrodes (2 units): Stainless‑steel plates that generate steam when energized.
• Part 800-03 – Fill Valve: Allows water to be introduced into the canister via the supply line.
• Part 800-04 – Drain Outlet: Facilitates removal of condensate and prevents water buildup.
• Part 800-05 – Humidistat Control Board: Receives signals from the thermostat and regulates steam output.
• Part 800-06 – High‑Limit Safety Switch: Automatically shuts off power if temperature exceeds safe thresholds.
• Part 800-07 – Power Connector: Provides 120 V AC input to the heating elements.
• Part 800-08 – Mounting Bracket: Secures the unit to the HVAC frame or wall.
• Part 800-09 – Optional 850 Fan Pack Bracket: Attaches the fan pack for duct‑free operation.
• Part 800-10 – Wiring Harness: Connects the control board to the thermostat and power source.

All components comply with UL and CSA safety standards, ensuring reliable operation and ease of maintenance for HVAC professionals!

Physical Installation Procedure

Mount the unit on the HVAC frame using the bracket, connect the water supply to the fill valve, attach the drain line to the floor drain, wire the power and thermostat leads, then test for leaks before finalizing. Secure connections and verify operation commissioning.

Mounting, Duct Connection, and Optional Fan Pack Installation

Begin by securing the Aprilaire Model 800 canister unit to the HVAC plenum with the supplied mounting brackets. Position the brackets over the steel studs, insert the #10-12 wood screws, and tighten to the recommended torque to prevent vibration. Route a 4‑inch insulated flexible duct from the unit’s steam outlet to the main supply plenum, using stainless‑steel hose clamps at each connection and sealing with HVAC‑rated duct tape to eliminate air leakage. Ensure the duct does not cross sharp edges or moving parts that could damage the hose. If the optional Aprilaire Model 850 fan pack is being installed, attach the fan pack housing to the side of the humidifier with the provided mounting plate, then connect the fan’s inlet and outlet ducts to the same plenum, maintaining proper airflow direction as indicated in the schematic. Connect the fan pack’s electrical connector to the humidifier control board, observing polarity markings, and secure the fan mounting bolts. After all mechanical connections are complete, perform a pressure test by briefly pressurizing the ductwork with a calibrated blower, checking for pressure drops and confirming that no steam escapes when the unit is energized. Once the test passes, re‑tighten all clamps, verify alignment, and document the installation for future maintenance. Verify that the water fill valve is fully open, the drain line slopes downward at least one‑quarter inch per foot, and all connections are free of corrosion.

Electrical Wiring and Control Integration

Connect the 120‑V supply to the unit’s power terminal, observe proper polarity, and secure the cable. Wire the thermostat to the control board, ensuring setpoint calibration. Attach the optional fan pack’s power lead, test the circuit with a a multimeter.

Power Supply, Thermostat Wiring, and Fan Pack Connection

The Aprilaire Model 800 requires a dedicated 120‑V, 15‑amp branch circuit protected by a correctly sized fuse or circuit breaker. Strip the cable back ¾ inch, attach the black (hot) and white (neutral) conductors to the L‑1 and N‑1 terminals, and secure the green ground to the chassis grounding screw. Verify polarity with a multimeter before energizing the unit.

Thermostat wiring follows the standard humidifier control scheme. Connect the humidifier’s “H” terminal to the thermostat’s “Humidifier” output, the “C” terminal to the common (24 V) line, and the “R” terminal to the 24 V hot. If the thermostat provides a separate “Fan” signal, link it to the Model 800 “FAN” terminal to allow coordinated fan operation during humidification cycles. Program the thermostat setpoint according to the manufacturer’s recommended indoor relative humidity range (30‑50 %).

When an Aprilaire Model 850 fan pack is installed, route the fan‑pack power lead from the fan‑pack’s connector to the Model 800 “FAN‑PWR” terminal. Ensure the fan‑pack’s internal fuse is intact, then tighten the connector lock tab. After wiring, perform a continuity check across the fan‑pack circuit and confirm that the fan engages when the humidifier calls for steam. Finally, power up the system, observe the initial start‑up sequence on the control board, and verify that the thermostat, power supply, and fan pack all respond correctly. Inspect all wiring yearly to maintain optimal safety now.

Water Supply and Drainage Configuration

Install the 1‑in. water line to the inlet valve, using a 3‑way solenoid for automatic shut‑off. Connect the drain line to the nearest floor drain, ensuring a 1‑in. slope away from the unit. Use a check valve to prevent backflow, and secure all fittings to avoid leaks. Check for leaks cycle; replace washers in

Fill Valve, Drain Line Setup, and Leak Prevention

The Model 800 is a canister steam humidifier that injects steam into the HVAC ductwork or an optional Aprilaire 850 fan pack. It creates steam by energizing two electrodes immersed in water, boiling the water to raise indoor humidity efficiently.

Leak prevention requires regular inspection of fittings. Replace worn O‑rings or washers after the first season. Apply silicone sealant around the fill valve’s base and drain collar to create a watertight seal. Test the system by filling the unit to full capacity, then monitor for 30 minutes for dripping or moisture accumulation. If leaks are detected, tighten fittings or replace faulty components before operating the unit again.

Regularly check the fill valve seal replace the O‑ring if cracked.!

During installation, verify the water supply line is free of debris and that the fill valve is correctly oriented. Mount the unit on a stable surface and slope the drain line away to prevent standing water. Use a 1‑inch compression fitting for the drain and install a P‑trap to capture condensation. After connecting, perform a pressure test to confirm no leaks. Keep the area clear of obstructions and schedule maintenance to replace worn seals and clean the drain line for performance.

Startup, Calibration, and Operation

Power the unit, verify 120 V supply, then run the test cycle. Observe steam output, ensuring no leaks. Set the desired humidity setpoint on the thermostat, typically 30-45%. Allow the humidifier to stabilize; confirm humidity readings match the setpoint ±5%.

Initial Testing, Humidity Setpoint Adjustment, and Performance Verification

After confirming the unit is securely mounted and all water and electrical connections are verified, restore power and initiate the built‑in test cycle from the control panel. The test cycle runs the electrodes for a short period, producing a brief burst of steam. Observe the canister for any signs of leakage, ensure the drain line is clear, and listen for abnormal noises. If steam is generated and no leaks are detected, proceed to the next step.

Set the desired humidity setpoint on the thermostat or dedicated humidifier controller, typically between 30 % and 45 % relative humidity for most residential applications. Allow the system to run for at least 30 minutes so the humidifier can reach steady‑state operation. Use a calibrated hygrometer placed in the supply plenum or a representative room location to compare the measured humidity with the programmed setpoint.

Performance verification is complete when the measured humidity stays within ±5 % of the setpoint for three consecutive readings taken at five‑minute intervals. Record the initial reading, the final reading, and any adjustments made to the water fill valve or fan pack speed. If the humidity deviates beyond the acceptable range, re‑check the water level, verify the fan pack is operating at the correct speed, and confirm that the thermostat wiring matches the wiring diagram in the installation manual.

Record final humidity values and note adjustments for future reference.!