Honeywell Humidifier HE225H8908 - Bypass Manual

The Honeywell HE225H8908 is a bypass humidifier designed for whole-home humidity control, typically installed on the warm-air supply (or return) plenum of a forced-air furnace. It works by diverting warm air from the furnace through the humidifier, where water evaporates into the air stream, and then returns the moistened air to the duct system. This manual covers safety, installation, operation, maintenance, and troubleshooting for proper use.

Features at a Glance

Key components: Bypass humidifier unit, Water panel (evaporative pad), Humidistat control, Bypass duct, Drain hose, Mounting hardware.

Installation

Unpack and inspect all components. Ensure furnace is off before beginning.

1. Select location: Install on warm-air supply plenum (recommended) or return plenum. Ensure space for bypass duct.
2. Cut opening: Mark and cut opening in plenum per template provided.
3. Mount unit: Secure humidifier to plenum using mounting bracket and screws.
4. Install bypass duct: Connect flexible duct between humidifier and return plenum (or supply if on return).
5. Connect water: Install saddle valve on cold water line; connect tubing to inlet valve.
6. Connect drain: Attach drain hose to outlet and route to floor drain.
7. Wire control: Connect humidistat and solenoid valve to furnace transformer (24V) as per wiring diagram.

WARNING! Turn off furnace power and water supply before installation. Follow local plumbing and electrical codes.

First-Time Setup

After installation, restore power and water.

1. Set humidistat: Turn to OFF position. Restore furnace power.
2. Open water valve: Turn saddle valve handle to open water supply.
3. Test operation: Set humidistat to highest setting; furnace blower should run, water should flow to panel, and drain should have steady stream.
4. Adjust humidistat: Set to desired humidity level (typically 35-45% for winter).
5. Check bypass damper: Adjust for proper air flow (fully open initially).

CAUTION! Ensure all connections are tight to prevent leaks. Check for proper drainage within first 24 hours.

Specifications

• Model: HE225H8908 (Bypass Flow-Through).
• Coverage: Up to 2,800 sq ft (depending on home tightness and furnace capacity).
• Water Usage: Up to 0.75 gallons per hour (at maximum output).
• Electrical: 24V AC, 0.5A (connects to furnace transformer).
• Drain Flow: Continuous flow-through design.
• Dimensions (Unit): Approximately 15.5" L x 10.5" H x 7.5" D.
• Duct Connection: 6" diameter bypass duct.
• Water Connection: 1/4" OD copper tubing (included).
• Operating Temp: For use with forced-air furnaces.
• Warranty: Limited warranty (refer to documentation).

Controls and Settings

Humidistat Control: Mount on wall in living area (not in duct). Settings: OFF, LOW, MEDIUM, HIGH, or numeric scale (0-60% RH).

Operation: Humidistat calls for humidity when indoor RH is below set point, activating furnace blower (or using fan circuit) and opening water valve. Bypass Damper: Manual slide damper to adjust air flow through unit (more open = more humidity). Service Indicator: Light or signal when water panel needs replacement (typically once per season).

Connecting to HVAC System

Bypass duct connects humidifier to return plenum. Wiring connects to furnace control board or transformer.

1. Ensure furnace is OFF at breaker.
2. Connect bypass duct: Secure with clamps; ensure smooth bends for air flow.
3. Wire humidistat: Typically connects to HUM terminals on furnace board, or to transformer and fan circuit.
4. Wire solenoid valve: In series with humidistat; valve opens when humidity is called for.

Tip: Install humidistat on interior wall away from moisture sources (kitchen, bathroom) for accurate reading.

Operation & Humidity Control

Set humidistat based on outdoor temperature to prevent window condensation.

1. Refer to outdoor temperature/humidity chart (in manual).
2. Typical setting: 35% RH when outdoor temp is 20-40°F.
3. Lower setting when colder: e.g., 25% RH when below 20°F.
4. Unit runs only when furnace blower is on (in heat mode).
5. Adjust bypass damper if humidity is too high/low.
6. Turn to OFF in summer or when not needed.

WARNING! Excessive humidity can cause condensation and damage. Adjust settings with outdoor temperature changes.

Maintenance

Regular maintenance ensures efficiency and prevents scale buildup.

• Water Panel: Replace annually (or when indicated). Turn off water/power, remove old panel, insert new one.
• Clean unit: At panel replacement, wipe interior with damp cloth to remove dust/mineral deposits.
• Check drain line: Ensure clear, free-flowing drain monthly.
• Inspect tubing: Check for kinks or leaks at water line.
• Seasonal shutdown: Turn off water supply and humidistat in spring; drain any residual water.

Care & Cleaning

Turn off power and water before cleaning. Use mild detergent and soft cloth; do not use harsh chemicals.

CAUTION! Do not allow water to contact electrical components. Ensure unit is dry before restoring power.

Regulatory Information

UL Listed. Complies with applicable standards. Manufactured for residential use. For technical support or warranty service, contact Honeywell Home Customer Care at 1-800-328-5111 or visit www.honeywellhome.com. This product may be covered by one or more U.S. patents.

Troubleshooting

Reset: Turn humidistat to OFF, then back to desired setting.

Service: 1-800-328-5111; www.honeywellhome.com