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Aprilaire Model 800 Humidifier

The Aprilaire Model 800 Humidifier is a steam humidifier designed for home applications where evaporative units are less practical. The Model 800:

  • Accommodates crawl spaces, attics and areas of the country with milder winters and non-forced air heating. 
  • Provides humidity to the largest of homes (up to 6,200 square feet). 
  • Features truly automatic control but can be installed in manual mode as well. ​
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Right Choice

The Aprilaire Model 800 Humidifier is a whole-home solution that helps you achieve total comfort through humidity control. As a steam model, the 800 complements non-forced air heating sources and other specialty heating systems. It is installed by a local HVAC professional.



Features

  • Runs independently of your HVAC system to accommodate larger homes (up to 6,200 square feet)
  • Delivers optimum levels of humidity control with the Automatic Digital Humidifier Control.
  • Performs quietly and with simple maintenance. You only need to replace the canister.
  • Has a capacity of 11.5, 16.0, 20.5, 23.3, and 34.6 gallons per day, depending on electrical draw.
  • Uses cold water, which may be hard, soft or softened.

Protect Your Family From Overly Dry Air

When you use the Aprilaire Model 800 Humidifier, you eliminate the unhealthy and damaging effects of overly dry air on your family and home. Find a dealer near you to decide if the Model 800 is right for you based on your home's size, age and construction. Or get replacement parts for your existing Model 800 here.

FAQs

  • Will mold grow inside my Aprilaire Humidifier?

    In order for microbial growth to occur three conditions must exist: There must be an organic food source for the microbes, the temperature must be in a certain range (different molds grow at different temperatures), and water must be present for an extended period of time. These conditions can exist in some types of humidifiers, but Aprilaire evaporative humidifiers are designed to prevent microbial growth.  None of the materials in Aprilaire humidifiers provide a food source. Even the paper Water Panel in Model 400 is treated with an anti-microbial agent. Most significantly however, the drain-through technology in Aprilaire evaporative humidifiers leaves no standing water once the humidifier turns off.  All the water delivered to an Aprilaire evaporative humidifier is either evaporated or goes down the drain, leaving all surfaces dry between humidification cycles.

  • What is the warranty for my Aprilaire humidifier?

    Aprilaire humidifiers carry a 5-year limited warranty on parts from the date of installation, when installed by a licensed HVAC installer. If not, the warranty is void.

  • How do I know when my Aprilaire bypass humidifier is operating?

    If the humidity in your home is 45% or higher your Aprilaire humidifier will not run. This is because the highest humidity level our humidifiers will attempt to attain. If you turn your humidistat from 15% to 45% and the humidifier does not run this is verification the humidity in your home is above 45%. Once the humidity level drops below 45% your Aprilaire humidifier should operate anytime the furnace is producing heat and the indoor relative humidity is less than the humidification set point on your humidistat. If not, we recommend contacting your installing contractor to troubleshoot the humidifier at your home.

  • What kind of humidifier is the Aprilaire humidifier?

    Aprilaire humidifiers take water from a liquid and turn it into a water vapor. The water vapor is added whenever the humidity level in the home is lower than the desired level and the HVAC system fan is moving air. Aprilaire humidifier’s are designed to maintain a relative humidity level of 35% anytime the outside temperature is 20F or above at an indoor temperature of 70F. If your HVAC heating system has a short run time for a heat call, this will result in a short run time for the humidifier and may result in not reaching the desired humidity set point. Whenever there is a need to add humidity to your home, the humidifier control will send a signal to the humidifier to operate. Water is introduced into the humidifier and flows over the Water Panel® evaporator. The air moving through the HVAC system moves through the Water Panel® evaporator absorbing the moisture into the air. The vapor is then distributed to your home, through the duct work by the blower of the HVAC system. The humidifying process continues until the humidification set point is reached or the HVAC system stops operating. Water not used in the evaporation process is used to flush away mineral deposits left behind from the evaporation process down the drain. The only models where deposits are not flushed down the drain are the models 400 and 400M as they are drain less humidifiers. Most Aprilaire evaporative humidifiers are wired by the HVAC installer to only operate when the heat is operating. If the humidifier is supplied with hot water, the humidifier can be wired to operate on an HVAC fan call. The fan call is initiated by the thermostat which includes a switch to run the HVAC system fan continuously. This fan call can be turned off once the desired humidification level has been reached.

  • What is the proper relative humidity to have in my home during the winter?

    Aprilaire like any other humidifier manufacturer designs our humidifiers to maintain an indoor relative humidity of 35% at an indoor temperature of 70F, anytime the outdoor temperature is 20F or above. Some homes may be able to attain a higher indoor humidity , however, factors such as the age, cubic footage (square footage times ceiling height) and tightness of the home, as well as the operating time of the HVAC heating system will affect the actual level achieved. Humidifiers require heat, water and air movement in order to add moisture to the air. Moisture in the form of vapor is added whenever the humidity level in the home is lower than the desired level and the HVAC system fan is moving air. If your HVAC system has a short run time for a heat call, this will result in a short run time for the humidifier and may result in not reaching the desired humidity set point.

  • Will an Aprilaire Humidifier cause mold in my home?

    Aprilaire Humidifiers are designed to accurately control the level of humidity in the home. This is accomplished by the use of an outdoor temperature sensor that continuously communicates with a computer equipped control. In conjunction with a precision humidity sensor which samples the air coming back to your furnace, the Aprilaire Automatic Digital Humidifier Control responds immediately to changing outdoor conditions. Remember, it’s just as important to shut the humidifier down when the humidity control reaches its set point as it is to deliver even more comforting humidity to the home when it’s warmer outside. The Models 400, 500, 600, and 700 come with this automatic digital humidifier control which allows the humidifier to deliver the optimum amount of humidity based on the current outdoor conditions. This will typically range from 20% on a really cold day to as much as 45% when it’s warmer outside. This is of importance because industry data shows that mold does not grow in humidity levels below 60%. The bottom line is no Aprilaire humidifier will contribute to the growth of mold, when installed, operated, and maintained as recommended.

  • What causes condensation on my windows and how can I eliminate it?

    Cold air outside your window cools the air just inside your window more than the air in the rest of the room. If the well-humidified air just inside the window cools too much or too quickly, it can’t hold as much moisture as before and water appears on the window. To eliminate this, follow the suggested settings on your manual humidistat and adjust the setting in the morning for the anticipated night time low temperature. Another option is to upgrade your manual humidistat to an automatic digital humidifier control (model 60), which always maintains proper level of humidity with minimal or no adjustment required by the homeowner. To obtain a model 60 please contact your heating and cooling contractor. If you need the name of a local dealer, please use the Dealer Locator on our website.

  • Will an Aprilaire humidifier harm my heating and cooling system or air cleaner?

    Aprilaire humidifiers are an evaporative-style humidifier. Unlike misting or atomizing humidifiers which put water droplets into the air stream, Aprilaire humidifiers use a natural evaporation process to generate humidity. The humidity created is a gas which simply passes through any component in the heating and cooling system or any air cleaner including an Aprilaire air cleaner with no adverse effects. The humidity created by your Aprilaire humidifier is no different than the humidity present in your home during the summer months.

  • Can I purchase an Aprilaire Humidifier at a retail outlet?

    No. Aprilaire products are sold through licensed heating and cooling contractors as they are best suited to help you choose the right unit, install it correctly and handle any warranty situations in the unlikely event one would occur. If you need the name of a local dealer, please use the Dealer Locator on our website.

  • What will it cost to install an Aprilaire Humidifier in my home?

    The cost of every Aprilaire Humidifier installation varies based on your specific application. It is recommended you secure competitive bids and choose the contractor you believe best meets your needs.

  • Why does Aprilaire offer an automatic and a manual humidifier control for the Aprilaire humidifiers?

    As the #1 manufacturer of humidifiers in the country, Aprilaire feels it is important to offer a humidifier control option for all applications. The automatic digital humidifier control is the top of the line when it comes to technology. An outdoor temperature sensor continuously reports changes in the outdoor temperature to the automatic digital humidifier control located on the cold air return duct. The automatic digital humidifier control uses this information to determine if the home requires additional humidity, to ensure the optimum humidification level is maintained. However, we realize there are some applications where it is impractical or impossible to run an outdoor temperature sensor to the outside. This is why we provide a high quality manual humidifier control for such applications. The automatic digital humidifier control also includes the option of operating in manual mode. Manual operation requires the homeowner to manually adjust the humidity level on the humidifier control as the outdoor temperature changes. Having these options allows flexibility to meet every customer’s humidification needs.

  • Can an Aprilaire humidifier operate in automatic mode without the outdoor temperature sensor?

    No. The outdoor temperature sensor is what allows your Aprilaire humidifier to be an automatic humidifier. If the automatic digital humidifier control is installed and is operating in the automatic mode (as referenced by the faceplate on the automatic digital humidifier control) the outdoor sensor is required for proper operation. The outdoor temperature sensor continuously reports changes in the outdoor temperature to the automatic digital humidifier control located on the cold air return duct. The automatic digital humidifier control uses this information to determine if the home requires additional humidity, to ensure the optimum humidification level is maintained.

  • Can my Aprilaire Humidifier be upgraded to operate automatically?

    Any Aprilaire furnace mount humidifier can be upgraded to an automatic humidifier by installing an Aprilaire automatic digital humidifier control with the outdoor temperature sensor. It is the control which upgrades the humidifier to an automatic humidifier. The model number for the control to use with our Aprilaire evaporative humidifiers is the model 60. The model number for the control to use with our Aprilaire steam humidifier is the model 62. The outdoor temperature sensor continuously reports changes in the outdoor temperature to the automatic digital humidifier control located on the cold air return duct. The automatic digital humidifier control uses this information to determine if the home requires additional humidity, to ensure the optimum humidification level is maintained. You will receive up to 50% more humidity compared to a manual humidistat which will increase your home’s comfort. Your Aprilaire Dealer can install this component so you can enjoy fully automatic operation—just set it and forget it!

  • Which Aprilaire humidifier should we purchase for our home?

    There frequently are several different Aprilaire models which will adequately humidify your home. The most qualified person to help you decide which Aprilaire humidifier model will best fit your needs is your local heating and cooling contractor. They can recommend and install the best Aprilaire humidifier for your home based on its size, age and construction.

  • How do I determine the Aprilaire humidifier model to interface with my HVAC system while properly humidifying my home?

    There are several Aprilaire Humidifiers which will effectively humidify a home. Factors to consider are the age, cubic footage (square footage times ceiling height) and tightness of the home, as well as the operating time and size of the duct work of the HVAC heating system. Humidifiers require heat, water and air movement in order to add moisture to the air. Moisture in the form of vapor is added whenever the humidity level in the home is lower than the desired level and the HVAC system fan is moving air. If your HVAC system has a short run time for a heat call, this will result in a short run time for the humidifier and may result in not reaching the desired humidity set point. While your heating and cooling contractor is the best one to determine which of our models would be best for your home, the chart below is a guideline for how many gallons per day a home requires.

  • What Aprilaire humidifier should I chose for my horizontal HVAC system?

    The Aprilaire humidifier’s which we recommend for a horizontal HVAC system are the bypass model humidifiers; 400, 400M, 500, 500M, 600, 600M or the model 800 steam humidifier. The Aprilaire power humidifier, model 700 or 700M will not work properly on a horizontal heating system. Because of how the air moves through the power humidifier, the evaporative capacity of the model 700 or 700M is reduced from 18 gallons per day, to 9 gallons per day. The exact humidifier required will be based on the age, cubic footage (square footage times ceiling height) and tightness of the home, as well as the operating time and size of the duct work of the HVAC heating system. Humidifiers require heat, water and air movement in order to add moisture to the air. Moisture in the form of vapor is added whenever the humidity level in the home is lower than the desired level and the HVAC system fan is moving air. If your HVAC system has a short run time for a heat call, this will result in a short run time for the humidifier and may result in not reaching the desired humidity set point. While your heating and cooling contractor is the best one to determine which of our models would be best for your home, the chart below is a guideline for how many gallons per day a home requires.

  • Why would one dealer recommend one Aprilaire humidifier while another dealer recommends a different Aprilaire model?

    There frequently are several different models which will adequately humidify a home. Typically dealers will install an Aprilaire humidifier they are comfortable with, have recommended to their customers for some time, and meet the technical requirements for humidification in your home. Bottom line, choose the dealer you are comfortable with; they know your heating and cooling system and can recommend an appropriate Aprilaire Humidifier.

  • My dealer is recommending an Aprilaire humidifier model not listed on your site. Is the model out-of-date?

    Periodically, we add features or refine some aspects of our Aprilaire humidifiers. When this happens, we modify the model number or introduce a new model number. Models not listed in the main product sections on this site, but still offered by dealers, have very likely been recently discontinued. These are still modern, high-performing Aprilaire humidifiers which will effectively humidify a home. Your heating and cooling dealer is the expert in recommending the best model Aprilaire humidifier for your home and its unique needs. The bottom line is when you purchase an Aprilaire Humidifier; you are buying the finest whole-house humidifier available today.

    Listed below is a description of current Aprilaire Humidifier models and the models they replaced.

    Model Number: 350/360
    This self-contained humidifier is specifically designed for homes with in-floor radiant or baseboard heat.
    Previous Model: Model 330

    Model Number: 400/400M
    This bypass humidifier features drain-free operation. The water panel evaporator is wetted by the standard flow-through system but then wicks excess water up from a small reservoir. Operation can be either manual or automatic.
    Previous Model: Recirculating Models 445 (manual control) & 445A, 448 (automatic control)

    Model Number: 500/500M
    This small bypass model incorporates a built-in bypass damper and easy right or left discharge change-over. Control can be automatic or manual.
    Previous Model: Bypass Models 550 (manual control) & 550A, 558 and 500A (automatic control)

    Model Number: 600/600M
    This large bypass model incorporates a built-in bypass damper and easy right or left discharge change-over. Control can be automatic or manual.
    Previous Model: Bypass Models 220, 224, 440, 560 (manual control) & 560A, 568 and 600A(automatic control)

    Model Number: 700/700M
    This large capacity powered model can be operated in manual or automatic mode.
    Previous Model: Powered Models 110, 112, 760 (manual control) & 760A, 768 and 700A (automatic control)

    Model Number: 800
    This steam humidifier is designed for applications such as crawlspaces, attics, areas of the country with milder winters with non forced air heating.
    Previous Model: N/A

  • What are the dimensions and specifications for the current line of Aprilaire Humidifiers?

  • Should my Aprilaire bypass humidifier be installed on the supply plenum or the return air duct?

    Aprilaire bypass humidifier’s get there air movement through the Water Panel® by the differential pressure between the supply (hot air) plenum and the return (cold air) duct. The supply plenum is under positive pressure and the return duct is under negative pressure. One of the advantages of a bypass humidifier is that it can be installed either on the supply plenum or on the return duct with equal effectiveness. No matter which duct the humidifier is mounted on, the airflow always goes from the supply to the return through the humidifier.   A bypass humidifier will also have no adverse effect on any component in the furnace, air cleaner or filter. Aprilaire® Humidifiers put “water vapor” into the air, not raw water. This is nature’s way of getting relative humidity into the air.

  • Should my Aprilaire power humidifier be installed on the supply plenum or the return air duct?

    Aprilaire power humidifiers are design to be installed on the hot air supply plenum. If however, there is no space available due to the HVAC air conditioning coil or the layout of the mechanical room, the Aprilaire power humidifier can be installed on the cold air return duct. When installed on the cold air return duct the humidifier must be supplied with hot water as the temperature of the air in the cold air return duct is not sufficient for proper evaporation.

  • What are the vents for on my Aprilaire power humidifier?

    The vents in the cover of the Aprilaire power humidifiers are to keep the fan motor from overheating. The air used in the humidification process is drawn into the humidifier from the HVAC system through the Water Panel® and the humidified air is discharged back into the HVAC system. During this process some of the air may discharge through the vents, however it will not affect the operation of the HVAC system. Similarly during the cooling season some air may discharge through the vents. This also will not have an adverse effect on the operation of the HVAC system.

  • How do I know when my Aprilaire power humidifier is operating?

    The almond color power humidifiers have a 24 volt transformer built into the humidifier; therefore, they have their own power. To determine if the fan is working simply touch the two brown leads which extend out of the bottom of the humidifier together, while the humidifier cover is on and the humidifier is plugged into a powered outlet. This would complete the internal 24 volt connection to the relay, which will turn the fan on and open the water solenoid valve. Perform this test while the furnace is off, so the sound of the furnace running will not interfere with the sound of the humidifier fan. If the fan and water solenoid valve operate the unit is ok. If not, we recommend contacting your installing contractor to troubleshoot the humidifier at your home. The grey color power humidifiers require 24 volt power to engage the internal relay which sends the 24 volts to the water solenoid valve and allows the internal fan to operate. Provided the humidity level in the home is not 45% or higher you can determine if the fan and water solenoid valve are working by simply make a call for humidity from the humidifier control while the HVAC system is making a heat call. If the humidity level is 45% or higher in the home the humidifier will not operate. If the humidity level is less than 45% the humidifier internal fan will operate and the water solenoid valve will open during a call for humidity provided the HVAC system is making a call for heat. If the fan and water solenoid valve operate the unit is working properly. If not, we recommend contacting your installing contractor to troubleshoot the humidifier at your home.

  • Can I connect a Model 400 Aprilaire Humidifier to a Heat Pump system?

    All Aprilaire humidifiers require heat, water and air movement in order to add moisture to the air. Moisture in the form of vapor is added whenever the humidity level in the home is lower than the desired level and the HVAC system fan is moving air. If your HVAC system has a short run time for a heat call, this will result in a short run time for the humidifier and may result in not reaching the desired humidity set point. Provided your Aprilaire humidifier is supplied with hot water (approximately 140F), and the HVAC system fan is operating, humidity will be added to your home. Your HVAC installer can wire your Aprilaire humidifier to operate on a HVAC system fan call as well as a heat call. The Model 400 and 400M Aprilaire humidifiers can be installed on heat pump systems. However, since heat pumps deliver lower temperature air to the home than gas furnaces, evaporation will be approximately 60% of our rated capacity. Due to the nature of the wicking water panel used in the Model 400, hot water provides limited benefit. As such, your HVAC installer will need to take the size, construction and age of your home into consideration to ensure the Model 400 will provide satisfactory comfort and protection through adequate humidification during a heat call from your heat pump system.

  • Are there problems with standing water with the Model 400 Aprilaire humidifier?

    No. Problems associated with standing water are addressed in the design of this humidifier since it contains at most, eight ounces of water at any given time. In addition, all the water evaporates, leaving the unit dry for long periods between humidification cycles. Nevertheless, it is recommended that simple recommended maintenance be performed twice a season.

  • Why do I have to change my Water Panel® on my Model 400 Aprilaire Humidifier twice a year?

    To ensure peak performance the Water Panel® should be replaced twice a season. Over time, the wicking capabilities (ability to draw water up the Water Panel) are reduced as minerals build up on the panel. The mid-season change means you will receive proper humidity throughout the humidification season.

  • How often should I clean the floats in the Water Panel® sensor assembly in my Model 400 Aprilaire humidifier?

    The simple maintenance of replacing the Water Panel® and cleaning the scale control insert, floats and float chambers can be completed in less than 10 minutes. For proper operation, this is required twice during the humidifying season, typically every 3 months.

  • Does a drain hose have to be attached to the Model 400 Aprilaire humidifier?

    The Aprilaire Model 400 is a drainless humidifier which uses a technology designed to use 100% of the water entering the unit. This means there is not a continuous flow of water through the humidifier as there is with our other Aprilaire Humidifiers such as the Models 500, 600 and 700. Instead there is a safety overflow connection at the base of the humidifier for an overflow drain line to connect to. In the unlikely event of the water level sensor assembly circuit failing, water will be safely directed to a drain provided there is an overflow drain line attached.

  • What’s the difference between the Model 350 and the Model 360 Aprilaire Humidifiers?

    The Model 350 and 360 Aprilaire humidifiers are completely self-contained and designed for installation in homes with electric baseboard heat, hydronic heat and even with homes with forced air heating systems with special humidification needs. These humidifiers require hot water, electricity and access to a drain. The Model 350 is designed to be hung from the floor joists in a basement. Ductwork is connected from the humidifier to a floor vent in a central location of the home. The humidified air is then distributed to the home through this ductwork. The Model 360 is our through-the-wall humidifier and can be placed in a central location of the home in a closet or laundry room where electricity, water and a drain are available. Humidified air is distributed through a grille on the humidifier into a hallway where the vapor will migrate throughout the home.

  • Why is my Aprilaire model 350 so noisy?

    The Aprilaire model 350 has a decibel range between 63 and 73 depending on the installation. Insulated flex duct may be used to reduce the sound level. The amount of sound created by the model 350 is typically compared to the sound of a box fan. Your HVAC installer can verify the duct work used with your Aprilaire model 350 is moving the proper airflow as increased airflow will increase the noise level.

  • Do I replace or clean the Water Panel® in my Aprilaire humidifier?

    The Aprilaire Water Panels® are designed to be used for the humidifier season and replaced. The model 400 and 400M models require replacing the water panel every 3 months during the humidifier season. The 500, 500M, 600, 600M, 700 and 700M require replacement every humidifier season. In some applications the water panels may require additional replacement. Reduced humidification levels can occur if the water panel is not replaced as described above. This is because some of the minerals left behind from the evaporation process are permanently trapped in the water panel. The water panel will eventually become clogged with these minerals so less evaporation takes place. The result is less humidification.

  • How do I properly install my replacement Aprilaire Humidifier Water Panel®?

    The orientation of your Aprilaire Water Panel® is important for maximum evaporation. Most Genuine Aprilaire Replacement Water Panels® (stock numbers 10, 12 and 35) you purchase will have a paint dot or stripe on one of the short ends. This paint should be placed up, towards the water distribution tray, for proper operation. The exception is if the stock number 35 is being replaced in the models 350 or 360. In these models there is no specific orientation of the water panel. If your humidifier requires the #45 Water Panel Aprilaire humidifier model’s 400 & 400M), there will be no paint dot and the panel can be installed in either orientation.

  • Should we use soft water or hard water with our Aprilaire humidifier?

    Aprilaire evaporative humidifiers can operate with hot, cold, hard or soft water. Hot water is preferred as it supplements the heat from the HVAC system heat call to increase the evaporation rate. When the humidifier is wired to operate on a heat or HVAC fan call, hot water is required as it is the only heat source for the evaporation process. The model 800 Aprilaire steam humidifier requires cold water, which may be hard or soft. Hot water cannot be used because the supply water is used to cool the water going to drain.

  • Should our Aprilaire humidifier be connected with hot or cold water?

    Aprilaire evaporative humidifiers can operate with hot, cold, hard or soft water. Hot water is preferred as it supplements the heat from the HVAC system heat call to increase the evaporation rate. All Aprilaire humidifiers need some source of heat for evaporation to take place whether it is hot water or hot air. When the humidifier is wired to operate on a heat or HVAC fan call, hot water is required as it is the only heat source for the evaporation process during an HVAC fan call. In addition hot water is required when the humidifier is connected to a heat pump. This is due to the lower plenum temperature in a heat pump. Hot water ensures there is an adequate heat source for the evaporation process. When any drain-though Aprilaire Humidifier is connected to hot water, the heat in the water is used in the evaporation process and the water coming out of the drain will be cool to the touch. The model 800 Aprilaire steam humidifier requires cold water, which may be hard or soft. Hot water cannot be used because the supply water is used to cool the water going to drain.

  • Is the water flow to my Aprilaire humidifier regulated with the saddle valve or is it regulated another way?

    All Aprilaire humidifiers include a water-metering orifice designed to regulate the water flow through the humidifier. The water flow rate for the models 500, 500M, 600 and 600M is 3 gallons per hour (GPH). The water flow to the models 350, 360, 700 and 700M is 6 GPH. The water flow for the models 400, 400M is .7 GPH. The saddle valve is not designed to regulate the water flow and should simply be turned to fully open (all the way to the left) so the orifice can regulate the flow. If the saddle valve is not fully open the humidity output from the humidifier will be reduced.

  • Is water supposed to be draining from my Aprilaire humidifier and if so how much?

    All of our Aprilaire drain-through humidifiers (excluding the drainless model’s 400 & 400M) incorporate a self-flushing action. The water going down the drain line serves the important function of flushing away mineral deposits left behind on the Water Panel® from the evaporation process. This flushing minimizes the amount of maintenance required by typically only requiring annual replacement of the Water Panel®. The amount of water draining is determined by the model humidifier you have in your home. If you have the model 500, 500M, 600, 600M Aprilaire humidifiers it will take approximately five minutes to fill a quart jar at the drain. If you have the model’s 700,700M, 760, 350 or 360 Aprilaire humidifiers it will take approximately two and a half minutes to fill a quart jar at the drain.

  • Why is water going through my Aprilaire humidifier when the furnace isn’t operating?

    All Aprilaire Humidifiers require heat, water and air movement in order to add moisture to the air. Moisture in the form of vapor is added whenever the humidity level in the home is lower than the desired level and the HVAC system fan is moving air. Since the HVAC system is not operating, the Aprilaire humidifier may not be wired to only operate when the HVAC system fan is moving air. The water solenoid valve may also be in need of replacement. Your HVAC installer can verify the wiring and operation of the water solenoid valve.

  • Why is water leaking out of my Aprilaire evaporative drain-through humidifier?

    Aprilaire evaporative humidifiers include a water panel® from which water evaporates into the air to produce moisture in the form of vapor. When water evaporates minerals left behind from the evaporation process are flushed down the drain. Minerals not flushed are permanently trapped in the water panel. If not changed, the water panel will eventually become clogged with these minerals. If this occurs, water being fed into the humidifier may leak due to the water panel being clogged. Other factors which will cause water to leak are; The humidifier not being level and plumb(front to back), the drain line being clogged( drain line should be inspected for clogs yearly ), The scale control insert( component water panel slides into) having a crack in it or not inserted into the base of the humidifier correctly, the orifice which regulates water to the humidifier from the water solenoid valve may have become enlarged or is missing(resulting in a larger flow of water to the humidifier) or the feed tube (component which carries water to the water panel) may have a crack in it or not be properly positioned in the distribution tray(component connected across the top of the water panel). A replacement component for any component found to not be performing properly can be obtained through the HVAC installer.

  • How can I test the water solenoid valve on my Aprilaire humidifier?

    If the water solenoid valve does not making a click sound when the humidity level is increased while the HVAC system fan is operating, the solenoid valve may require replacement by the HVAC installer. The water solenoid valve may be tested by the HVAC installer by applying 24 volts to the water solenoid valve leeds.

  • Why is there no water coming out of my Aprilaire evaporative humidifier?

    Aprilaire Humidifiers require heat, water and air movement in order to add moisture to the air. Moisture in the form of vapor is added whenever the humidity level in the home is lower than the desired level and the HVAC system fan is moving air. Provided there is a need for humidification and the HVAC fan is moving air, water should be draining from the humidifier (models 400 & 400M are drainless so no water will be draining during operation). If the water solenoid valve does not making a click sound when the humidity level is increased this would indicate the solenoid valve may require replacement by the HVAC installer. If the water solenoid valve does make a click sound when the humidity level is increased but no water flows this indicates the water flow is obstructed.

    To determine if water flow is being obstructed, turn the control knob of the humidifier control to the off position or the lowest setting. The first location to check for an obstruction would be at the saddle valve located on the water line supplying water to the humidifier. When checking the saddle valve, make sure it is completely open. This can be done by turning the valve all the way to the left. If anything is clogged, it can be dislodged by turning the saddle valve all the way to the right and back to the left. Once this is done, turn the humidifier control dial above the click point and water should be coming out the drain line.

    If water is still not coming out of the drain, check the orifice and in-line strainer to make sure they are not clogged. The orifice is located in the tube on the outlet side of the solenoid valve and the in-line strainer is located on the inlet side of the solenoid valve (see figure below). The orifice may be cleared by inserting a needle through the small opening. The strainer may be cleaned by running it under warm water to dislodge deposits or replace it. After clearing and re-installing the orifice and strainer (be sure to double wrench all water connections), turn the humidifier control dial above the click point and water should be coming out the drain line.

  • Can an Aprilaire humidifier operate with a tankless water heater?

    Aprilaire humidifiers are designed to efficiently use water for the evaporation process. The feed rate of our bypass model humidifiers 400 and 400M, is .7 gallons per hour, for the 500, 500M, 600 and 600M the feed rate is 3 gallons per hour. The feed rate for our power model humidifiers (700 and 700M) is 6 gallons per hour. These feed rates will not activate a tankless water heater as tankless water heaters typically require a certain gallons per minute to activate. A conventional water heater with the ability to handle the household requirement for hot water with the feed rate for the Aprilaire model factored in is what Aprilaire recommends.

  • Where should my humidifier control be installed?

    Aprilaire humidifiers are packaged with one of two types of humidifier controls, a manual non digital humidifier control and an automatic digital humidifier control. The models with an M in the model number (400M, 500M, 600M, 700M) and the models 350 and 360 include the manual humidistat (see below). For the models 400M, 500M, 600M and 700M, the manual humidistat can be installed in the cold air return duct or the living area. For the model 350 or 360 the manual humidistat must be installed in the living area.

    The models 400, 500, 600, 700 and 800 include the automatic digital humidifier control (see below) which is designed to only be installed on the cold air return duct of the HVAC system. It cannot be installed on a wall in the living area as airflow will not adequately get to the humidity sensor on the control. This results in inaccurate humidity levels. 

  • How does my Aprilaire digital humidifier control operate?

    The Aprilaire digital humidifier control can operate in automatic or manual mode, but regardless of the mode, the digital control requires the HVAC system fan to be operating, a water supply and a heat source in order to create humidity. Whenever the HVAC system is moving air (a heat call or a fan call) the digital humidifier control will add humidity if the humidification level is below the desired level. If the digital humidifier control is wired to operate the humidifier during an HVAC fan call, the humidifier will need to be supplied with hot water as that is the only heat source available. A fan call simply circulates room temperature air in the home, typically 70F, which is not adequate to cause evaporation. In the automatic mode an outdoor sensor is installed. This sensor continuously reports changes in the outdoor temperature to the digital humidifier control located in the cold air return duct or outside the home. The digital humidifier control uses this information to determine if the home requires additional humidity, to ensure the optimum humidification level is maintained. In manual mode there is no outdoor sensor. As a result the digital humidifier control will require regular manual adjusting as the outdoor temperature changes, so the home is not over or under humidified.

  • What does a flashing red light mean on my Aprilaire digital humidifier control?

    The Aprilaire digital humidifier control includes three indicator lights. A flashing red light (the call dealer for service indicator) means the control is not operating properly and the installer needs to check the operation of the control. Anytime the red light is flashing a code will be displayed on the LCD screen. There are four error codes; E1 Relative humidity sensor failure, E2 control knob failure, E3 outdoor temperature sensor/manual mode sensor not recognized and E4 communications with model 8570 Aprilaire thermostat not detected. The code may be cleared by rotating the control knob on the humidifier control to the test reset position. The green Humidifier on” light will begin to flash after approximately 5 seconds. Return the control knob to its previous position. If the error code has cleared the humidifier control has returned to normal operation. If not, the HVAC installer will need to review the wiring to determine if the control requires replacement.

  • What does a flashing yellow light mean on my Aprilaire digital humidifier control?

    The Aprilaire digital humidifier control includes three indicator lights. A flashing yellow light (the change water panel indicator) means it is time to change the water panel® in your Aprilaire humidifier. Once the water panel has been changed, you will need to reset the change water panel indicator as it is not intuitive and has no way of knowing when the water panel was changed. To reset the change water panel indicator, simply rotate the control knob on the humidifier control to the test reset position. The green Humidifier on” light will begin to flash after approximately 5 seconds. The water panel change indicator has been reset. Return the control knob to its previous position.

  • I changed by water panel in my Aprilaire humidifier, so why won’t the change water panel light reset?

    The Aprilaire digital humidifier control includes three indicator lights. A flashing yellow light (the change water panel indicator) means it is time to change the water panel® in your Aprilaire humidifier. Once the water panel has been changed, you will need to reset the change water panel indicator as it is not intuitive and has no way of knowing when the water panel was changed. To reset the change water panel indicator, simply rotate the control knob on the humidifier control to the test reset position. The green Humidifier on” light will begin to flash after approximately 5 seconds. The water panel change indicator has been reset. Return the control knob to its previous position.

  • I changed by water panel in my Aprilaire humidifier, so why won’t the change water panel light reset?

    The Aprilaire digital humidifier control includes three indicator lights. A flashing yellow light (the change water panel indicator) means it is time to change the water panel® in your Aprilaire humidifier. Once the water panel has been changed, you will need to reset the change water panel indicator as it is not intuitive and has no way of knowing when the water panel was changed. To reset the change water panel indicator, simply rotate the control knob on the humidifier control to the test reset position. The green Humidifier on” light will begin to flash after approximately 5 seconds. The water panel change indicator has been reset. Return the control knob to its previous position.

  • What does a flashing green light mean on my Aprilaire digital humidifier control?

    The Aprilaire digital humidifier control includes three indicator lights. A flashing green light (the humidifier on indicator) means the humidifier is operating in the test mode. Test mode is used to verify the humidifier is wired properly and lasts for one minute. The blue LCD light and the green humidifier on light will continue to flash at the end of test mode. This is an alert because if left in the test mode the humidifier will not operate. Return the control knob to its previous position so the digital humidifier control will operate your Aprilaire humidifier normally. During normal operation the green light will be on solid during any humidifier call.

  • Can I get a digital humidifier control for my Aprilaire humidifier that installs in my living area instead of on the HVAC system?

    Aprilaire has manufactured 3 digital humidifier controls which install on the cold air return duct. The model numbers are 58, 60 and 62. We also offer a digital manual humidifier control, model 65 which can install in the living area. The model 65 humidifier control measures the humidification level in the space where the control is installed. Anytime the humidity drops below the current set point on the humidifier control, the control will activate the humidifier provided the HVAC system fan is operating. The model 65 will require manual adjustment as the outdoor temperature changes, so the home is not over or under humidified. Any HVAC installer will be able to offer you the model 65 manual digital humidifier control.

  • How do I operate the manual humidistat for my Aprilaire humidifier?

    The Aprilaire manual humidistat is designed to be installed on the cold air return duct or on an interior wall in the living area of the home. To determine the relative humidity in the home, slowly turn the knob on the control clockwise and counterclockwise and listen for 2 clicks. The actual relative humidity in the home is between the 2 clicks. It is important to anticipate a drop in outdoor temperature and reduce the humidity setting in order to avoid excess condensation. The excess condensation occurs because the indoor relative humidity is higher than what the home can support for the current outdoor temperature. To adjust the humidity setting, simply rotate the control knob to the desired setting. Provided the HVAC system fan is operating and the humidification level is lower than the new set point, the manual humidistat will activate the humidifier.

  • How do I turn my Aprilaire humidifier off at the end of the humidifier season?

    All Aprilaire humidifiers include a control which is either located on the cold air return duct or in the living area of the home. Below are a few of the controls we have offered since our humidifiers were introduced in 1954. The humidifier controls which have an off position should be placed in the off position. If the humidifier control does not have an off position simply turn the dial to the lowest setting and follow the applicable steps below. The summer/winter knob on the HVAC duct work is the bypass damper.

    Annual summer shutdown for bypass models 400 series, 500 series and 600 series close the bypass damper, which is a part of the humidifier, with the small damper handle. The model 700 series and model 800 steam humidifier simply require the adjustment of the humidifier control where applicable.

    Humidifier Control:
    Digital Humidifier Control in Automatic Mode (See Figure A below):
    No adjustment is necessary.

    Digital Humidifier Control in Manual Mode (See Figure B below):
    Set the knob to the "OFF" position.

    Figure C Non Digital Automatic Humidifier Control 2003- current
    No adjustment is necessary.

    Figure D old style Non Digital Automatic Humidifier Control 1997-2003
    No adjustment is necessary.

    Manual Humidifier Control (See Figure E, F and G):
    Set the knob to the "OFF" position.
    Figure E

    Figure F

    Figure G

  • What capacity (11.5, 20.5 or 23.3 gallons per day) should my Aprilaire model 800 steam humidifier be set up for?

    The Aprilaire model 800 steam humidifier will operate with 110 volt power (11.5 gallon per day capacity), 208 volt power (20.5 gallon per day capacity) or 240 volt power (23.3 gallon per day capacity). While 240 volt power is preferred to allow for the most capacity, the humidification requirement for your home determined by your HVAC installer will dictate which power supply to utilize.

  • What is the typical operating cost for an Aprilaire model 800 steam humidifier?

    The Aprilaire model 800 steam humidifier is designed to operate with 120, 208 volts or 240 volts, however all current models are defaulted to operate with 240 volts for the maximum humidification output. At 240 volts the 800 would cost about 25 cents an hour to operate. The run time of the humidifier will vary based on the age, cubic footage (square footage times ceiling height) and tightness of the home, as well as the operating time of the HVAC heating system. If the Aprilaire model 800 steam humidifier were to run for 12 hours out of a 24 hour period it would cost about $3.00 per day or $90.00 per month. However, it is unlikely it will run 12 hours out of every 24 hour period and may be much less per month than the amount above. At 120 volts, the 800 could cost about 10 cents per hour to operate. If the Aprilaire model 800 steam humidifier were to run for 12 hours out of a 24 hour period it would cost about $1.20 per day or $36 per month, but again actual run time will vary just as described in the 240 volt application.

  • Will a UV light affect my Aprilaire humidifier?

    An Ultra Violet light may dry out the material used in the components of our Aprilaire humidifiers. The base of the humidifier along with the scale control insert (the 3 sided component which the evaporative water panel sides into) can become powdery resulting in their requiring replacement. Aprilaire recommends locating the humidifier on the opposite side of the HVAC system from where the UV lights are located or out of the direct line of the UV lights to prevent this from occurring. Components requiring replacement due to UV affects are not covered under the Aprilaire warranty.

  • Can I purchase humidifier electrical components direct from Aprilaire?

    While we do offer the water solenoid valve on our Estore, it is the only electrical component we have available for direct purchase. From a safety standpoint, and to insure proper humidifier operation, electrical components such as the water solenoid valve should be installed by a local heating and cooling expert, your Aprilaire Dealer. The warranty of any electrical component will be void if it is not installed by a licensed HVAC installer. If you need the name of a local dealer, please use our Dealer locator: http://aprilaire.com/index.php?znfAction=FindDealer

  • Where can I purchase the replacement parts for my Aprilaire Humidifier?

    Your local heating and cooling contractor who installed your Aprilaire humidifier can help you obtain these parts, or you can search for an Aprilaire Dealer in your area using our Dealer Locator located on this site: http://aprilaire.com/index.php?znfAction=FindDealer . We also offer an E-Store where you may purchase select humidifier parts, http://estore.aprilaire.com/catalog/humidifiers/all-humidifier-parts. If you prefer not to order online, you can contact our parts department, toll-free at 800–931–0014 and someone will gladly assist you.

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