Healthy Humidity |

Whole-House Humidifier FAQs Tackle Balancing Humidity and Humidifier Filters

5 minute read

Listed below are the top-10 Humidifier FAQs. If your humidifier question is not answered, you also search our larger humidifier FAQ database.

If your question is not answered here or if you require more assistance, please contact our knowledgeable live Technical Support team.

How do I know which humidifier I have on my furnace? (Old owner’s manual has pictures to help identify which model)

A picture of the humidifier can be found in either our non-current or current humidifier owner’s manual. Please open either the non-current or current humidifier owner’s manuals and find the picture of the humidifiers towards the back of the owner’s manual.


What is a water panel?

A water panel is the replaceable evaporative element in a humidifier that facilitates the conversion of water to vapor. AprilAire produces two types of water panels, metal mesh, and wicking. The metal mesh is made of layered slit-and-expanded aluminum with a porous, ceramic-type slip coating that absorbs water and maintains the proper level of hydration for the evaporation process. The wicking type uses a heavy-duty paper panel and coated with an anti-microbial agent to prevent the growth of mold. It is reinforced with two layers of aluminum mesh. As warm air passes through the water panel, moisture is absorbed and carried into the home.

Related: Why Water Panels Need to be Changed Annually

My contractor plumbs my humidifier with hot water. Is that how it should be installed with my 600 Humidifier?

We recommend plumbing the 350, 360, 500, 600, and 700 Humidifiers to hot water in order to get the most out of the humidifiers. We advise using a standard hot water heater when plumbing to hot water in the home. The AprilAire Humidifiers do not draw enough water to trigger tankless hot water heaters.

Will a 500 humidifier adequately humidify my 3000 sq ft home? Will the 600 or 700 Humidifier adequately humidify my 4000 sq ft home?

The 500 Humidifier can add up to about 11 gallons of humidity to the home per day, which is usually good for homes up to 1500 sq ft. The 600 and 700 Humidifiers each add up to 16-17 gallons of humidity a day, which is good for homes up to 3000 sq ft.

How does the blower activation operate with the humidistat?

The Blower Activation Switch is set to the “ON” position to allow the humidifier control to activate the HVAC fan for maximum humidification. For this setting, the Models 500, 600, and 700 Humidifier must be connected to hot water.

If the HVAC system has been idle for 1 hour, the humidifier control will activate the HVAC system fan to sample the air for 3 minutes. If the RH is lower than the setpoint, the humidifier control will activate the humidifier and keep the fan running. The humidifier will continue to operate for 2 hours or until the humidification setpoint is reached.

If the RH set point has not been reached by the end of a call for heat, the control will continue to operate the humidifier and the HVAC fan until the humidification setpoint is reached or 2 hours have elapsed.

When the Blower Activation switch is in the “OFF” position, the humidifier control will only operate the humidifier if humidity is required and the HVAC system fan is operating or the HVAC system is producing heat.

How accurate is the 60/62 humidistat?

The 60/62 Humidistats are tested to be within +/- 3% accurate from the factory before they are shipped out.

Do you have any other controls to control the humidifier or than the 60 or 62 humidistat?

The 65 Digital Manual Humidistat and 4655 Manual Humidistat are two humidistats that can be mounted on the wall to control the humidifiers. The 8620, 8620W, 8910, 8910W, and 8920W AprilAire Thermostats all can control the humidifier in place of the 60 or 62 Humidistat.

Why is the service light flashing on the steam humidifier a week after changing the canister?

The Flashing Service light indicates sensed amperage is 75% of the maximum amperage recorded.

The reason why the flashing service light may be occurring is that the humidistat may not be giving the humidifier enough run time to condition the canister. If the hose is getting hot and the light is flashing, let the unit run and the flashing light will go away eventually once the amp draw in the canister grows. If the hose is not getting hot, then contact the service tech to troubleshoot the humidifier.

Related: Cleaning & Maintaining your AprilAire Humidifier

How much water does the humidifier use per day when humidifying?

The 400, 500, 600, and 700 Humidifiers have a 3 gallon per hour feed rate. The 800 Steam Humidifier has an 11.5 gallons per hour feed rate. The 350 and 360 Humidifier have a 6 gallon per hour feed rate. The output of the humidifier and water usage is affected by the run time of the furnace, the set point of the humidistat, and the home’s ability to hold the humidity within the home.

During normal operation customers typically see 1-2 gallons of water usage per hour trying to maintain the humidity level with the 500, 600, and 700 humidifiers. We encourage the use of hot water with the 500, 600, and 700 Humidifiers in order to get a boost in the output of the humidifier. Water runs through the water panel and out through the drain when the furnace is running and whatever evaporates off of the water panel is what gets sent into the home. The 500 has a .5 gallon per hour evaporation rate, and the 600 has a .7 gallons of evaporation rate. The 700 has a .75 gallon per hour evaporation rate when mounted on the supply side of the furnace, and when mounted on the return air duct the humidifier has a .5 gallon evaporation rate. Hot water is required as a heat source with the 700 humidifier when mounted on the return air duct.

The 400 Humidifier evaporates 100% of the water supplied to the humidifier and uses .7 gallons of water per hour.

Customers with the 800 Steam Humidifier installed see water usage between 1-3 gallons of water per hour when trying to maintain the humidity in the home. The voltage level supplied to the humidifier will determine how quickly the canister heats up the water to boiling. The higher the voltage the faster the water heats up in the canister. Cold water is required with the 800 steam humidifier in order to temper the hot water that comes out of the drain of the humidifier when it completes its weekly drain of the canister.

Water usage for the 350 and 360 Evaporative Humidifiers usually see water usage between 2-3 gallons of hot water per hour when humidifying the home. Hot water is required as a heat source with the 350 and 360 humidifiers in order for evaporation to occur with the humidifier. The 350 and 360 Humidifier have a feed rate of 0.5 gallons of evaporation per hour.

Does a UV light affect my humidifier in any way?

We encourage UV light installers to direct the light away from the plastics or to protect them with something like aluminum tape, which is UV immune. The scale control insert (plastic frame around the water panel) is made of a UV-resistant material but is not immune to the effects of the UV light. The water panel is clay-coated aluminum, so it will not be affected by UV light exposure.