Aprilaire 400 Humidifier Instruction Manual
Aprilaire 400 Humidifier
Aprilaire 400 Humidifier
Aprilaire 400 Humidifier Instructions
Here we offer the Aprilaire 400 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 400 Humidifier, we suggest checking the Frequently Asked Questions (FAQs) section of this manual.
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Aprilaire 400 Humidifier Specifications
| Feature | Specification |
|---|---|
| Model | Aprilaire 400 Automatic Humidifier |
| Humidifier Type | Evaporative, bypass, with float chamber (no continuous drain flow) |
| Unit Dimensions | 15" x 14 3/8" x 10" |
| Mounting Location | Supply or return plenum of a forced air system |
| Bypass Configuration | Reversible for left-hand or right-hand bypass (factory set to left side discharge) |
| Bypass Duct | 6" round duct with 6" collar and 90° elbow |
| Bypass Duct Support | Required for runs over 4' |
| Compatible Furnace Configurations | Upflow, downflow and horizontal |
| Replacement Water Panel | AprilAire Water Panel 45 |
| Water Panel Replacement Interval | At least twice per heating season |
| Humidifier Control | Automatic Digital Humidifier Control (ADHC), Automatic or Manual mode |
| Control Location | Cold air return duct |
| Control Dial Range | OFF, 1 to 7, Test/Reset |
| Maximum Controlled RH | 45% RH |
| Automatic Adjustment Rate | 1% RH for every 2°F change in outdoor temperature |
| Line Voltage | 120 VAC |
| Transformer | 24 VAC, 10 VA minimum |
| Current Sensing Relay | Research Products Model 50 (not furnished, when needed) |
| Water Supply Types | Hot, cold, hard, softened or unsoftened |
| Maximum Hot Water Temperature | 140°F (60°C) |
| Maximum Water Pressure | 125 psi |
| Water Supply Tubing | 1/4" O.D. copper tubing (not furnished) |
| Safety Overflow Hose | 1/2" I.D. plastic hose (not furnished) |
| Water Connection | Saddle valve (furnished), fully open or fully closed |
| In-Line Strainer Part Number | 4004 |
| Orifice Part Numbers | 4231 (yellow) or 4232 (blue), by model |
| Mounting Hardware | Six #8 x 3/4" plated hex head SMS screws (not furnished) |
| Minimum Clearance | Template at least 3" above furnace housing or cooling coil |
| Test Mode Duration | 1 minute |
| Blower Activation Sampling | 3-minute fan run after 1 hour of HVAC idle time |
| Blower Activation Maximum Run | 2 hours or until set point is reached |
| Error Codes | E1, E2, E3, E4 |
| Limited Warranty | 5 years from date of purchase |
| Technical Support | 800.334.6011 |
Aprilaire 400 Humidifier Details
The Aprilaire 400 is an evaporative bypass humidifier that uses the heat of the HVAC system to add moisture to warm, dry air. When the control calls for humidity and the system fan is running, water flows into a distribution tray. A synthetic fabric liner spreads it evenly over the top of the Water Panel. Dry, warm air from the supply duct passes through the wet panel, picks up moisture as vapor, and moves on to the return duct. From there it circulates through the home.
Unlike the drain-equipped models in the Aprilaire range, the Model 400 has a scale control insert/float chamber with two floats and a water level sensor assembly. Because of this, there is no steady stream of water to a drain during operation. The overflow drain line is only a safety feature and should never hold water under normal conditions. Both floats must rest at the bottom of the chamber for the humidifier to run, even in test mode.
The Automatic Digital Humidifier Control reads indoor RH in the return duct and outdoor temperature from a sensor. It then adjusts the humidifier's run time on its own. It has three lights: green Humidifier On, yellow Change Water Panel and red Service Required. The Water Panel timer is set by the installer based on the model and water hardness. Turning the knob to Test/Reset resets the timer, and the green light flashes to confirm it.
For the first heating season, Aprilaire recommends starting at dial setting 5 and adjusting over the next 24 to 48 hours. If windows show condensation, turn the dial down one step. If the air is too dry, turn it up one step. If the dial is already at 7, you can turn on Blower Activation, but this needs a hot water supply. In Manual mode (internal switch set to MAN, with "M" on the display), you have to lower the setting yourself before cold weather arrives.
The housing parts that touch water are non-metallic, so they won't rust or corrode. To service the unit, press the latch tabs to remove the front cover. Then pull the feed tube out of the distribution tray and tip the evaporative assembly forward. Tip it only as far as needed so you don't bend the water level sensor assembly. Clean the floats, float chamber and insert with a disinfecting cleaner. Check that both float stems pass through the float cover and that the floats move freely.
Clean mineral deposits from the distribution tray gently so you don't stretch the fabric liner. Soaking the tray in vinegar or a lime remover helps with hard scale. Once a year, check the water line: flush the in-line strainer, check the feed tube for cracks, and make sure the orifice is clear. Use two wrenches on the compression nuts so they don't leak. Before summer, move the integral bypass damper handle from WINTER to SUMMER to close the bypass for the cooling season.
During installation, do not mount the unit or its bypass on the furnace jacket, in places that can freeze, or where blanked-off ends of the cooling coil block airflow. Do not wire the transformer to multi-speed blower motors. Do not sweat or attach a metal line directly to the overflow fitting, and do not use solvent adhesives on it. On downflow furnaces, the blower must keep running after a heat call so high temperatures don't damage the control.
Frequently Asked Questions (FAQs)
Can't find the answer you need? Here are some frequently asked questions about the Aprilaire 400 Humidifier, and we answer them below.
