The Aprilaire Automatic Humidifier is an evaporative humidification system designed to integrate with your home's heating and cooling system to provide optimal indoor relative humidity. It operates on nature's own principle of adding moisture to the air, ensuring comfortable humidity levels throughout the heating season. This system is designed for high capacity, trouble-free performance, and minimal maintenance.
Function Description:
The Aprilaire Humidifier works in conjunction with your furnace blower motor. When the Aprilaire Humidifier Control calls for humidity and the blower motor is active, water flows to a distribution tray at the top of the unit. From there, it is uniformly distributed across the width of the tray and through a scientifically designed system of outlets, flowing by gravity over the Water Panel® evaporator. This Water Panel is the core of the unit, where dry, hot air from your furnace passes through, absorbing moisture in vapor form. The now humidified air is then circulated throughout your home.
For models 550, 600, and 700, the system includes an orifice that determines the correct water flow. When the unit is operating, a small, steady stream of water goes to the drain, flushing away most trouble-causing minerals and preventing stagnant water. This is an effective and inexpensive method for mineral disposal. The Model 400, however, is designed for homes without accessible drain facilities or where high water hardness is not an issue.
The Aprilaire Automatic Humidifier is a high-precision system capable of accurately maintaining relative humidity (RH) in your home, typically between 10% and 45% RH. For every 1° change in outdoor temperature, the control automatically adjusts the indoor RH by 0.5%.
Usage Features:
The Aprilaire Humidifier Control offers both Automatic and Manual modes of operation.
Automatic Mode (Models 400, 600 & 700):
The Humidifier Control is installed in the cold air return duct. During the initial heating season, the control needs to be set to match your home's conditions. You start by setting the dial to "5," which is within the normal range. Over the next 24-48 hours, you may need to adjust the dial for more or less humidity based on your comfort and home's requirements. Minor adjustments might also be necessary during the coldest parts of the heating season, depending on your home's construction. Once set, the system should accurately control humidity in future heating seasons without further adjustment.
To determine the current RH in your home:
- Determine the outdoor temperature.
- Activate the furnace blower by setting your thermostat to a higher temperature.
- Turn the control dial to "Off," then slowly clockwise until you hear the solenoid valve "click on."
- Slowly turn the dial counter-clockwise until you hear the solenoid valve "click off." Note the dial setting at this point.
- Refer to the "Relative Humidity Guide" table in the manual to find your indoor RH based on the dial setting and outdoor temperature.
- Return the thermostat and Humidifier Control to their original settings.
The Automatic Humidifier is designed to prevent excessive condensation by automatically adjusting to outdoor temperature changes.
Manual Mode (All Models):
In Manual Mode, the Aprilaire Humidifier Control is typically installed in the living area or cold air return. It is crucial to anticipate drops in outdoor temperature and reduce the setting accordingly to prevent excessive condensation. For example, if the outdoor temperature is 20°F, the recommended RH is 35%. If the temperature is expected to fall to 0°F, you should reduce the setting to 25% several hours in advance.
Recommended settings on the Humidifier Control are based on extensive research to balance comfort with protection for your home and to avoid window condensation. Condensation or frost on cold surfaces like windows usually indicates excessive relative humidity, which can potentially damage your home.
To check humidifier operation in Manual Mode:
- Activate the furnace blower by setting your thermostat to a higher temperature.
- Turn the control dial to "Off," then slowly clockwise until you hear the solenoid valve "click on."
- Slowly turn the dial counter-clockwise until you hear the solenoid valve "click off." Read the RH on the dial, which will be close to your home's actual RH.
- To check the humidifier's operation, set the knob to "Test/Reset." Ensure the water saddle valve is open and the unit has electricity. The furnace blower motor must be operating, and the furnace must be calling for heat for the Aprilaire Humidifier to function. The humidifier will operate for one minute. After water enters the unit and drains, reduce the humidistat setting to the recommended indoor RH based on the outside temperature. Do not leave the unit in "Test" mode as it will not operate.
General Usage Notes:
- Keep fireplace dampers closed when not in use to prevent heat and humidity escape.
- Indoor activities like clothes drying, cooking, and showers can increase relative humidity. If condensation or frost persists on cold surfaces for several hours, ventilate your home to dissipate excess moisture.
- The humidifier can use hot, cold, hard, or mechanically softened water. Hard water residue is typically scaly and dense, while softened water residue is soft and fluffy. The Water Panel evaporator effectively traps mineral deposits, preventing "white dust" from being distributed.
Maintenance Features:
Periodic maintenance is essential for continued proper unit performance.
Annual Maintenance:
- Water Panel Evaporator Replacement: For best performance, replace the Water Panel evaporator annually. For Model 400, it should be changed twice per heating season. If your Humidifier Control has a water panel timer, the "Change Water Panel" light will illuminate (during operation only) when it's time for replacement.
- Resetting the Water Panel Change Indicator: After replacing the Water Panel, turn the control knob to the "Test/Reset" position until the "Change Water Panel" light blinks to reset the timer. Ensure the blower is operating and the furnace is calling for heat. Then, return the control knob to its normal setting.
Annual Summer Shutdown:
- Bypass Damper: For Models 400 and 600, close the integral bypass damper using the small handle. For Model 550, close the bypass damper installed in the bypass pipe.
- Water Supply: Shut off the water supply to the humidifier by closing the saddle valve.
- Humidifier Control: No adjustment is required for the Humidifier Control during summer shutdown in either Automatic or Manual Mode.
Periodic Preventative Maintenance (All Models):
Regular inspection and preventive maintenance of your entire heating system, including the humidifier, are crucial for efficient and safe operation. Your heating contractor should include humidifier service during their visits. All models are equipped with an in-line water strainer and orifice, which should be inspected and cleaned periodically.
Inspection and Service Instructions:
- Disconnect Power and Water: Disconnect electrical power to the furnace and shut off the water supply.
- Disconnect Water Line (Inlet): Disconnect the water line at the inlet compression nut.
- Remove In-Line Strainer: Remove the in-line strainer from inside the inlet side of the valve using a small nail or wire.
- Clean/Replace Strainer: Flush the in-line strainer clean or replace it with a new one (Service Department, Part No. 4004).
- Reinstall Strainer and Water Line: Replace the in-line strainer and reconnect the inlet water line. Use two wrenches to prevent leaking.
- Disconnect Water Line (Outlet): Disconnect the water line at the outlet compression nut.
- Remove/Clean Orifice: Remove the orifice from the copper or plastic tube and ensure the small opening is unplugged.
- Replace Orifice and Water Line: Replace the orifice and reconnect the outlet water line. Use two wrenches to prevent leaking.
- Restore Power and Water: Turn on the water supply and reconnect electrical power to the furnace.
Model-Specific Maintenance (General Steps):
- Front Cover Removal: Press tabs on the latches to remove the front cover.
- Feed Tube Removal: Carefully pull the plastic feed tube from the distribution tray.
- Water Panel Evaporator Assembly Removal: Tip and lift out the assembly.
- Distribution Tray Cleaning: Unsnap the distribution tray from the scale control insert. Lightly scrape out calcium deposits and clean "V" notches. Do not scrape off the granular coating at the bottom, as this textured surface ensures even water flow. If the coating is removed, apply a small amount of liquid dishwashing detergent to the entire inside surface of the tray to ensure even water flow.
- Water Panel Replacement: Slide the used water panel out and dispose of it. Slide a new Aprilaire Water Panel into the scale control insert/float chamber (with the colored spot up for some models).
- Scale Control Insert/Float Chamber Cleaning: Inspect and clean floats and float chamber for mineral build-up. Wash parts with a disinfecting cleaner. Ensure floats move freely.
- Drain Hose Cleaning: Remove the drain hose from the bottom of the unit, bend and flex it to loosen internal calcium deposits, then flush with water under pressure.
- Reassembly: Reinstall components in reverse order, ensuring they snap into place firmly.
- Check System Operation: After reassembly, check system operation using the "Test/Reset" setting on the Humidifier Control and return it to its original position.
The motor is permanently lubricated and does not require oiling. All unit housing parts in contact with water are non-metal to prevent rust and corrosion. The Water Panel evaporator, along with the Scale Control Insert, efficiently traps mineral deposits, which are then flushed away in drain-equipped models.
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