Aprilaire 300 Humidifier Instruction Manual
Aprilaire 300 Humidifier
Aprilaire 300 Humidifier
Aprilaire 300 Humidifier Instructions
Here we offer the Aprilaire 300 Humidifier manual completely free and in English. We have cataloged this manual in the Humidifiers section on Manualverse, and it has been rated by 1 users with an average rating of 5. If you have any specific questions about Aprilaire 300 Humidifier, we suggest checking the Frequently Asked Questions (FAQs) section of this manual.
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Aprilaire 300 Humidifier Specifications
| Feature | Specification |
|---|---|
| Model | AprilAire Model 300 |
| Humidifier Type | Evaporative, flow-through (drain-equipped), with built-in fan |
| Heat Source for Evaporation | Hot supply water (works independently of the HVAC system) |
| Supply Water Temperature | Minimum 120°F (49°C), maximum 140°F (60°C) at unit |
| Minimum Hot Water Supply | 6 gallons per hour (GPH) |
| Maximum Water Pressure | 125 psi |
| Compatible Water Types | Hot, hard or mechanically softened water (hot water required) |
| Power Supply | 120 VAC, 60 Hz, prewired with cord and plug |
| Humidity Control | AprilAire Model 65 Manual Digital Humidifier Control, 24 VAC, wall-mounted |
| Airflow | 250 CFM at 0.1 in. w.c. external resistance (equivalent to 80 effective feet of duct) |
| Evaporative Capacity | Approx. 12.5 to 14.5 gallons per day, depending on effective duct length (lab test at approx. 70°F and 30% RH) |
| Rated Intake Air Temperature | 70°F |
| Minimum Intake Air Temperature | 65°F |
| Duct Connection | 8 in. round duct |
| Discharge Grille | Standard grille with at least 50 sq. in. free area, on an inside wall |
| Water Supply Line | 1/4 in. O.D. copper tubing (not furnished) with saddle valve provided |
| Drain Line | 1/2 in. I.D. plastic hose |
| Mounting | Suspended from floor joists, parallel or perpendicular, joist brackets approx. 15 in. apart |
| Joist Spacing Note | Top mounting holes required if joist spacing is less than 14.5 in. |
| Mounting Hardware | #8 x 1/2 in. screws (angle supports), #8 x 1 in. screws (joist brackets) |
| Door Undercut for Return Air | 1/2 in. minimum, or a grille |
| Replacement Water Panel | AprilAire Water Panel 35 |
| Water Panel Replacement Interval | At least once a year |
| In-line Strainer Part No. | 4004 |
| Orifice Part No. | 4231 (yellow) or 4232 (blue), by model |
| Optional Condensate Pump | AprilAire Part #4856 |
| Housing Material (water contact parts) | Non-metal, rust- and corrosion-proof |
| Limited Warranty | 5 years from date of purchase |
| Technical Support | 800.334.6011 |
Aprilaire 300 Humidifier Details
The AprilAire Model 300 is different from the rest of the AprilAire range because it does not use the furnace's heat. Its built-in fan pulls air through a Water Panel that is kept wet with hot supply water, and that hot water provides the heat for evaporation. So the unit works independently of the HVAC system, and humidified air leaves through its own duct and discharge grille. A small, steady stream of water runs to the drain and flushes away most of the minerals, and it also stops water from standing in the unit.
The core of the unit is the Wet Pack assembly. It holds the Water Panel inside a scale control insert that traps mineral deposits. A distribution tray on top has a synthetic fabric liner that spreads water evenly across the panel, but only if the unit is mounted level. A factory orifice keeps the water flow correct. The saddle valve should be either fully open or fully closed and should never be used to adjust flow.
The Manual Digital Humidifier Control mounts on an interior wall and always shows indoor RH%. When you press ON, the display shows ON, but the humidifier runs only if the control and unit have power and indoor RH is below the set point. You lower the set point yourself before cold weather arrives. For example, the guide recommends 35% RH at 20°F outdoors and 25% at 0°F. Fog or frost on windows means humidity is too high.
When a humidity call ends, the fan keeps running for several minutes. This dries the Water Panel and clears humid air from the ductwork. To find out how long hot water takes to reach the unit, divide the distance to the water heater in feet by 10, then add a couple of minutes. For example, 50 feet gives about 5 minutes. Install the saddle valve on the smallest hot water line, as close to the heater as you can.
The installation guide gives several practical tips. A short section of braided tubing near the unit reduces water hammer. Never sweat a metal drain line to the drain fitting or use solvent adhesives on it. The drain needs a steady downward slope with no low spots. Tankless heaters can be too hot (above 140°F) and may not switch on at 6 GPH. Hard duct gives the best evaporation, while flex duct runs quieter.
Yearly maintenance starts with turning off the control, disconnecting power and shutting off the water. Then unscrew the access panel knobs, lift the Wet Pack, swing it out and slide it forward. Push down on the distribution tray to separate it, then clean its "V" openings. Vinegar or a lime remover loosens stubborn scale. Fit a new Water Panel 35, check the feed tube for cracks, and flush the drain line with water under pressure before you reinstall the Wet Pack against its guide flanges and drain spud.
Every year, the water line should also be checked. Clean or replace the in-line strainer, make sure the orifice opening is clear, and double-wrench all compression nuts so they don't leak. For summer shutdown, lower the set point to OFF. Do not install the unit where it could freeze, or near gas- or oil-fired equipment. Keep fireplace dampers closed, and air out the home if condensation lasts for several hours.
The five-year limited warranty covers replacement parts only. It does not cover labor, Water Panels, shipping, or damage caused by improper installation. You can register at aprilaire.com/warranty.
Frequently Asked Questions (FAQs)
Can't find the answer you need? Here are some frequently asked questions about the Aprilaire 300 Humidifier, and we answer them below.
