Getting Your Aprilaire Humidifier Ready to Use

An Aprilaire humidifier connects to your home's heating system and adds moisture to the air as it circulates through your ducts. Before you turn it on, you need to install a water panel, set the humidistat, and check that your furnace can support it. Most models take 15 to 30 minutes to prepare for the first time.

Start by locating your humidifier on the return air duct near your furnace. You'll see a removable cover or access panel. Open it and look inside—you should see a slot where the water panel sits. The water panel is a cardboard or foam insert that absorbs water and lets it evaporate into the air stream. If your humidifier is new or the panel looks dry and crumbly, you need to replace it before running the unit.

Slide the old water panel out and dispose of it. Insert a new panel (the correct model number is printed on your humidifier's frame) so it sits flat in the slot. The panel should fit snugly but not require force. Close the access panel and move on to the humidistat.

Key Takeaways

  • Install a new water panel in the humidifier slot before first use, and replace it every heating season or when it looks dry and brittle.
  • Set your humidistat to 30 to 50 percent relative humidity, depending on outdoor temperature—lower settings prevent window condensation in winter.
  • Check that your furnace blower is set to run continuously or at least during heating cycles so the humidifier has air to work with.
  • The humidifier draws water from your home's water line, so you may need to shut off the water supply valve if you're leaving for more than a week.
  • Clean or replace the water panel every heating season, and have a technician inspect the water line and drain annually.

Installing the Water Supply Line

Your Aprilaire humidifier needs a water line connected to your home's cold water supply. If this is your first time setting it up, a technician should have already run the line during installation. If you're replacing an old humidifier or moving one, you'll need to connect it yourself or call a technician.

Locate the water inlet valve on the side or back of the humidifier. You'll see a small plastic or brass fitting. Turn off the water supply to your home at the main shutoff valve. Attach the water line (usually 1/4-inch tubing) to the inlet fitting by hand-tightening the connector—do not use a wrench, as you can crack the fitting. Turn the water back on and check for leaks around the connection for a few minutes. A small drip at the fitting is normal for the first few seconds; if water continues to drip, tighten the connector slightly or call a technician.

Setting the Humidistat to the Right Level

The humidistat is a dial or digital control mounted on your furnace or wall that tells the humidifier when to add moisture. It measures the relative humidity in your home and turns the humidifier on and off to keep the air at your target level. Setting it correctly prevents both dry air and condensation on windows.

In winter, outdoor air is very dry, so your home's air becomes dry even with a humidifier running. A setting of 30 to 40 percent relative humidity is comfortable for most people and prevents condensation on windows and doors. If you live in a very cold climate (below 0°F regularly), lower the setting to 25 to 30 percent to avoid frost buildup on glass. In milder winters, you can raise it to 45 to 50 percent.

Turn the humidistat dial slowly until you reach your target number, or use the up and down buttons on a digital model. The humidifier will not turn on when ready—it waits until the air drops below your setting. You may not hear it running for several hours if the air is already moist. This is normal.

Checking Your Furnace Blower Settings

The humidifier only works when air is moving through your furnace and into your ducts. If your furnace blower is set to run only during heating cycles, the humidifier will sit idle on mild days when the heat is not running. To get the most out of your humidifier, check your furnace's fan setting.

Look at your thermostat. You should see a switch labeled "Fan" with options like "Auto" and "On." If it is set to "Auto," the blower runs only when the furnace is heating. Switch it to "On" to run the blower continuously, which lets the humidifier work all day. This uses slightly more electricity but distributes moisture evenly throughout your home. If you prefer to save energy, leave it on "Auto," but understand that the humidifier will only run during heating cycles.

Some furnaces have a separate fan switch on the furnace itself rather than the thermostat. If you cannot find the setting, take a photo of your thermostat and furnace controls and ask a technician to show you where it is.

Running the Humidifier for the First Time

Once the water panel is installed, the water line is connected, and the humidistat is set, you are ready to start. Turn on your furnace or heating system as you normally would. The humidifier will not turn on until the air drops below your humidistat setting, which may take a few hours or even a day depending on how dry your home is.

Listen near the humidifier for a soft humming sound and a faint rushing noise as water flows into the panel. You may smell a musty or earthy odor the first time it runs—this is the water panel absorbing moisture and is normal. Open a window briefly if the smell bothers you. After a few hours of running, the smell should fade.

Check your windows and doors after the first day. If you see condensation forming, lower your humidistat setting by 5 to 10 percent. If the air still feels dry and your skin or lips are uncomfortable, raise the setting by 5 percent. It usually takes two to three days to find the right balance for your home.

Maintaining Your Humidifier Throughout the Season

The water panel is the main part that needs regular attention. As the heating season goes on, minerals from your water build up on the panel and reduce how much moisture it can release. By mid-season (January or February in most climates), the panel may look white or tan and feel stiff. This is mineral buildup, and it means the panel is no longer working well.

Replace the water panel every 4 to 6 weeks during the heating season, or sooner if it looks dry and brittle. To replace it, turn off the water supply valve on the humidifier (a small shutoff on the water line), open the access panel, slide out the old panel, and insert a new one. Turn the water supply back on. The whole process takes less than five minutes.

Once a year, usually at the end of the heating season, have a technician inspect the water line for leaks, check the drain line to make sure it is not clogged, and clean the humidifier housing if needed. This maintenance costs $75 to $150 and prevents mold growth and water damage.

Shutting Down for Warm Months

When spring arrives and you stop using your furnace, turn off the humidifier. Set your humidistat to 0 percent or the lowest setting, or turn off the water supply valve on the water line. This prevents water from sitting in the panel and growing mold during months when you do not need humidity.

Before you shut it down, remove the water panel and let it dry completely, then store it in a dry place or discard it. In the fall, install a fresh water panel before you turn the heat back on. If you leave the old panel in place over the summer, it will become brittle and may fall apart when you try to remove it.

Frequently Asked Questions

Why is my humidifier not adding moisture even though it is running?

The water panel may be clogged with mineral buildup, or the panel may not be installed correctly. Check that the panel is sitting flat in the slot and that water is flowing into it (you should see moisture on the panel). If the panel looks white or crusty, replace it. Also check that your furnace blower is running—if it is set to "Auto" and the heat is not on, the humidifier will not distribute moisture.

My windows have condensation. What should I do?

Lower your humidistat setting by 5 to 10 percent. Condensation means the air is too moist for the outdoor temperature. In very cold weather, a setting of 25 to 30 percent is usually the highest you can go without condensation forming. If condensation persists after lowering the setting, check that your water panel is not oversaturated or that the humidifier is not leaking.

How much water does the humidifier use?

An Aprilaire humidifier typically uses 2 to 4 gallons per day during the heating season, depending on how dry your home is and your humidistat setting. This is a small amount compared to your overall household water use and should not noticeably increase your water bill.

Can I use filtered or distilled water instead of tap water?

You can, but it is not necessary. Tap water is fine and is what most people use. Distilled water may slightly reduce mineral buildup on the panel, but the cost is usually not worth the benefit. If your tap water is very hard (high mineral content), you may want to replace the water panel more often—every 3 to 4 weeks instead of 4 to 6 weeks.

What if I am away for several weeks during winter?

Turn off the water supply valve on the humidifier water line so water does not sit in the panel and grow mold. You can leave the humidistat setting as is; when you return and turn the water back on, the humidifier will resume working. If you will be away for more than a month, remove the water panel and store it in a dry place.