Honeywell Humidifier HM512DG115 - TrueSTEAM 12 Gal Humidifier IAQ Manual

The Honeywell HM512DG115 TrueSTEAM is a 12-gallon whole-home steam humidifier designed for Indoor Air Quality (IAQ) management. It integrates with forced-air HVAC systems to provide precise humidity control, featuring automatic operation, a digital humidistat, easy installation, low maintenance with self-cleaning technology, and compatibility with most furnaces. Below are key sections for safety, features, installation, setup, operation, maintenance, and troubleshooting.

1. Features at a Glance 2. Installation 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Connecting to HVAC System 7. Operation Modes 8. Maintenance & Cleaning 9. Regulatory Information 10. Troubleshooting

Features at a Glance

Key components: Steam Generator Canister, Control Panel with Digital Display, Humidistat, Water Supply Valve, Drain Line, Installation Kit.

FeatureDescription
Steam OutputUp to 12 gallons per day (GPD) capacity
Control SystemDigital humidistat with automatic humidity control
InstallationDuct-mounted or bypass installation options
Self-CleaningAutomatic cleaning cycle to reduce mineral buildup
CompatibilityWorks with most forced-air gas, oil, or electric furnaces
Water Connection1/4" copper or plastic tubing for water supply
Power Requirements120V AC, 15A dedicated circuit
Safety FeaturesOverheat protection, low water detection, automatic shutoff
Warranty5-year limited warranty on steam canister
DisplayBacklit LCD showing humidity setpoint and status

Installation

Unpack and inspect all components. Ensure proper location near furnace and water supply.

  1. Mounting: Install unit on supply duct (recommended) or return duct using provided brackets.
  2. Water Connection: Connect 1/4" water supply line to cold water pipe with saddle valve.
  3. Drain Connection: Attach drain hose to unit and route to suitable drain location.
  4. Electrical: Connect to dedicated 120V, 15A circuit with proper grounding.
  5. Steam Hose: Connect steam distribution tube to furnace duct (6-12 inches from furnace).

WARNING! Installation should be performed by qualified HVAC technician. Ensure power is OFF during installation.

First-Time Setup

After installation, power on unit and configure settings.

  1. Initial Power Up: Turn on power; display will show current humidity.
  2. Set Desired Humidity: Use UP/DOWN buttons to set humidity level (recommended 35-45% for winter).
  3. Calibration: Allow 24 hours for system to calibrate to home environment.
  4. Test Operation: System should begin steam generation when humidity drops below setpoint.

CAUTION! Do not set humidity above 50% to prevent condensation on windows.

Specifications

Controls and Settings

Control Panel: Power button, UP/DOWN buttons, Display with backlight, Indicator lights.

Display Indicators: Power (green), Heating (orange), Service (red), Clean (yellow).

Settings Menu: Press and hold UP button for 3 seconds to access: - Humidity Setpoint: 15% to 50% RH - Fan Delay: 0-45 seconds after call for humidity ends - Diagnostic Mode: Shows error codes and system status - Factory Reset: Restores default settings

Connecting to HVAC System

TrueSTEAM connects to furnace control board for automatic operation.

  1. Locate furnace control board and identify HUM terminals.
  2. Connect two-wire humidistat cable to HUM terminals (polarity not important).
  3. Ensure furnace fan control is set to AUTO for proper operation.
  4. Test connection by lowering humidity setpoint; furnace fan should activate.

Tip: Use included wire nuts and follow local electrical codes for all connections.

Operation Modes

Automatic Mode: Default operation; system monitors humidity and activates when needed.

  1. Normal Operation: Humidistat calls for humidity when below setpoint.
  2. Fan Activation: Furnace fan turns on (if in AUTO mode) when steam generation begins.
  3. Steam Generation: Canister heats water to produce steam; cycle lasts 5-15 minutes.
  4. Self-Cleaning: Automatic cleaning cycle runs every 12 hours of operation.
  5. Manual Mode: Press and hold POWER for 5 seconds to force steam generation (for testing).

WARNING! Steam output is hot; avoid contact with steam distribution tube during operation.

Maintenance & Cleaning

Regular maintenance ensures optimal performance and longevity.

  1. Monthly: Check drain line for clogs; clean if necessary.
  2. Seasonal: Inspect steam hose for mineral deposits; replace if hardened.
  3. Annual: Replace steam canister (typically every 1-2 seasons depending on water hardness).
  4. As Needed: Clean exterior with damp cloth; never use harsh chemicals.

CAUTION! Always disconnect power before performing any maintenance. Allow unit to cool completely.

Regulatory Information

UL Listed: Certified to UL Standard 507 for Electric Humidifiers. FCC Compliance: Part 15 Class B digital device. EPA Registration: Not required for residential humidifiers. Copyright © Honeywell International Inc. All rights reserved. For technical support, visit www.honeywellhome.com or contact 1-800-468-1502.

Troubleshooting

SymptomPossible CauseCorrective Action
No steam productionPower, water supply, or canisterCheck power connection; verify water valve is open; replace steam canister if old.
Service light illuminatedMineral buildup or component failurePerform manual cleaning cycle; if persists, replace canister or contact service.
Water leakingLoose connections or clogged drainTighten all fittings; clear drain line of obstructions.
Humidity too high/lowSettings or placementAdjust humidistat setpoint; ensure proper duct installation location.
Unusual noisesMineral scale or air in lineDescale canister; purge air from water line by briefly opening supply valve.

Reset Procedure: Turn power OFF for 30 seconds, then ON to reset control board.

Service: 1-800-468-1502; www.honeywellhome.com

Honeywell Humidifier HM512DG115 - TrueSTEAM 12 Gal Humidifier IAQ Manual © - All Rights Reserved 2025