Aprilaire 400M Humidifier Instruction Manual
Aprilaire 400M Humidifier
Aprilaire 400M Humidifier
Aprilaire 400M Humidifier Instructions
Here we offer the Aprilaire 400M 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 400M Humidifier, we suggest checking the Frequently Asked Questions (FAQs) section of this manual.
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Aprilaire 400M Humidifier Specifications
| Feature | Specification |
|---|---|
| Product Type | Evaporative bypass whole-home humidifier (400 Series) |
| Humidifier Control | Manual Humidifier Control (mounted on the cold air return duct or an interior wall) |
| Width (including solenoid valve) | 15-3/8 in |
| Height (including drain spud) | 15-3/4 in |
| Depth | 10-1/4 in |
| Plenum Opening | 10 in W x 12-3/4 in H |
| Bypass Duct Opening | 6 in diameter |
| Electrical Data | 24 VAC, 60 Hz, 0.5 A |
| Replacement Water Panel | AprilAire Water Panel 45 |
| Water Panel Replacement Interval | At least twice per heating season |
| Water Supply Line | 1/4 in copper tubing (not furnished) |
| Overflow Drain Line | 1/2 in I.D. hose (not furnished) |
| Compatible Water Types | Hot, cold, hard or mechanically softened |
| Maximum Hot Supply Water Temperature | 140°F (60°C) |
| Maximum Water Pressure | 125 psi |
| Maximum Supply/Return Pressure Differential | 0.4 in. wg |
| Bypass Damper | Built-in, WINTER (open) / SUMMER (closed) positions |
| In-Line Strainer Part Number | 4004 |
| Orifice Part Numbers | 4231 (yellow) or 4232 (blue), by model |
| Installation Location | Supply or return plenum, reversible for left or right bypass |
| Limited Warranty | 5 years from date of purchase |
| Technical Support | 800.334.6011 |
Aprilaire 400M Humidifier Details
The Aprilaire 400M is an evaporative bypass humidifier. It does not heat water itself. It uses heat from the HVAC system, which moves air from the supply duct, through the humidifier and into the return duct. When the control calls for humidity and the system fan is running, water flows into a distribution tray. From there it runs down over the Water Panel, where warm, dry air evaporates it. The humidified air then circulates through the whole home. A factory orifice keeps the water flow correct, so the saddle valve must stay fully open or fully closed and never be used to regulate flow.
Unlike the drain-equipped models in the AprilAire range, the 400 Series uses a scale control insert/float chamber with floats and a water level sensor assembly. Because of this, there is no constant stream of water to the drain. Under normal operation the overflow drain line should never contain water. Instead, the Water Panel and scale control insert trap the minerals, which is why the Water Panel 45 has to be replaced at least twice per heating season. Hard water leaves hard, scaly deposits and softened water leaves soft, fluffy ones, but the panel's service life is the same either way.
The Manual Humidifier Control has no automatic outdoor temperature compensation, so you have to lower the setting yourself before cold weather arrives. AprilAire's recommended indoor RH ranges from 45% at +40°F outdoors down to 15% at -20°F. For example, at 20°F the correct setting is 35% RH. If the forecast drops to 0°F, lower the setting to 25% several hours before the temperature falls. To find the current indoor RH, turn the knob slowly back and forth and listen for two clicks. The actual RH lies between them.
Checking that the unit works is simple. Make a heat or fan call at the thermostat so the HVAC fan runs. Then set the knob to the highest RH set point and confirm the saddle valve is open and the humidifier has power. Afterwards, return the knob to the desired set point. If you see condensation or frost on windows, humidity is too high. If condensation lasts several hours, ventilate the home. Keeping fireplace dampers closed when not in use helps prevent heat and humidity from escaping.
All housing parts that touch water are non-metal, so they will not rust or corrode. The distribution tray has a synthetic fabric liner that spreads water evenly over the top of the panel, provided the unit is mounted level. During routine service, unsnap the tray and lightly brush off any mineral deposits without stretching the liner. Soaking the tray in vinegar or a lime-removing agent helps with stubborn scale. Also remove the float cover, clean the floats and chamber with a disinfecting cleaner, and make sure both floats move freely.
When removing the Water Panel evaporative assembly, tip it only as far as needed so you don't over-bend the water level sensor assembly. Periodic water line service includes flushing the in-line strainer, checking the feed tube for cracks, and confirming the orifice is not plugged. Use two wrenches when reconnecting fittings to prevent leaks. For summer, turn the bypass damper handle to SUMMER and set the control knob to OFF. Do not install the humidifier in areas where freezing temperatures can occur, and do not mount it on the furnace jacket.
Frequently Asked Questions (FAQs)
Can't find the answer you need? Here are some frequently asked questions about the Aprilaire 400M Humidifier, and we answer them below.
