Can a UV light be installed by my Aprilaire Humidifier?

Friday, May 25, 2012 by Aprilaire Team

Consumer question:

I plan to install the UV-C light in the supply air plennum above the AC evaporator coil. How far away from the humidifier should the light be? I understand the UV light may damage plastic parts? or is there no problem?

Aprilaires' response:

Thank you for your email regarding your Aprilaire UV-C Light. You are correct, the light will damage the plastic parts on your model 700. Mounting your UV light at least 8 inches above the AC coil the model 700 cannot have any direct light. Therefore you can shield the light from the model 700, or a better alternative would be to move the model 700 to the return side of your HVAC system and supply it with hot water.


My model 400 Aprilaire humidifier is not running in normal conditions, suggestions?

Wednesday, May 23, 2012 by Aprilaire Team
Consumer question:
Water flows and humidifier on light comes on only in reset mode but humidifier does not come on and activate water flow in normal mode. I have turned dial to max humidity but still does not activate water flow when furnace comes on. I am running in automatic mode with wiring installed per installation manual. I have the outdoor sensor installed but not run outside yet. Please advise. Thank you
Aprilaires' response:

Thank you for your email regarding your model 400 Aprilaire humidifier. If the outdoor sensor is in an area where the temperature is above 60F the humidifier will only run in the test mode. You may confirm this by moving the manual/auto switch to the manual position. This will allow the control to work off the manual sensor on the control rather than the outdoor sensor.


I have manual control for my whole house humidifier. I've been noticing water on the windows in the morning.

Saturday, May 12, 2012 by Aprilaire Team
Consumer question:
I have manual control for my whole house humidifier. I've been noticing water on the windows in the morning. When I look at the humidistat it is set for 32% (doesn't say RH but thats what I assume). I got another Aprilaire humistat that just measures RH and put it on top of my existing control. Where the existing control indicates about 32%(5% hysterisis) the standalone unit indicates 44%RH. How do I know which is correct and what do I do if my existing manual control is wrong? IS there a way to clean or calibrate it?

Aprilaires' response:

Thank you for your email regarding your Aprilaire humidistat. If you turn the dial from left to right you should hear two clicks. The actual humidity in your home will be the area between the two clicks. For example, if the humidistat clicks at 30% and 36% your actual humidity would be 33%. There is not a way to calibrate the humidistat. It is unclear from your email if the original humidistat is an Aprilaire humidistat, so it is difficult to say if it is out of spec. The accuracy of our Aprilaire manual humidistats are +/- 5%

The moisture on your windows is due to the surface temperature of your windows reaching dew point. This occurs when there is more humidity in the home than what the home can hold based on the current outdoor temperature. As the temperature outside drops you want less humidity in your home. For example when the outdoor temperature is 20F or above we recommend 35% humidity at a room temperature of 70F. If the outdoor temperature drops to 0F you'll want 25%.

Thank you for giving us the opportunity to be of service.

Our Aprilaire 760 runs all the time but our 550 humidifier only run with the furnace blower is on, which is correct?

Friday, May 11, 2012 by Aprilaire Team

Consumer question:

I didn't notice this until recently, but our Aprilaire 760 runs regardless of the furnace blower running, whereas our 550 model does not. Is that typical for the 760?


Aprilaires' response:

Thank you for contacting us with regards to your model 760 Humidifier. Both the 550 and 760 should run only when the furnace is on, or at least the blower is running. When there is no air moving through your ducts, Aprilaire humidifiers should be off, as well. If your 760 runs without the furnace, we would recommend that you contact either your original installer or current Aprilaire service technician. If you don't have a current technician, please visit us online at and enter your ZIP code into our dealer locator. You should get contact information for several nearby companies.
We appreciate the opportunity to be of assistance.


Ultrasonic Wall humidifier?

Thursday, May 10, 2012 by Aprilaire Team

Consumer question:

Does anyone make in-the-wall humidifiers that are silent ( like ultrasonic ) but won't put out minerals or chlorine? We want something for our bird room, that won't make noise when it comes on, like our Aprilaire 360 does, because we don't want to scare the birds at night while they sleep.

Aprilaire response:

Thank you for contacting us.
We don't have an Ultrasonic Wall unit. Our 360 is our only wall through offering. This unit has a decibel rating of 73.
One option might be our 800 steam humidifier with our 850 fan pack. The fan pack would be mounted in the wall and has a decibel rating of 50. There would be some fill and drain noises associated with the 800 itself but those could potentially be mitigated by an installer.


My Aprilaire model 760 humidifier that has worked great for the last 11 years has a short

Thursday, May 10, 2012 by Aprilaire Team

Consumer question:

My Aprilaire model 760 humidifier that has worked great for the last 11 years has a short that apparently cannot be repaired. So what would it cost to get a new one that will fit my furnace exactly like my 760 did. Also the cost of a new one, or can mine be sent in for repair.


Aprilaires' response:

Thank you for using Aprilaire products in your home comfort system.

I am sorry to hear that your model 760 has failed after 11 years of service. I am please to let you know that you local heating and air conditioning company can assist you in obtaining a replacement for your model 760. Our current model 700 humidifier would replace the model 760 for area coverage, the dimensional size may vary slightly.


No water comes in to the model 500 aprilaire humidifier when running. What could be happening?

Wednesday, May 9, 2012 by Aprilaire Team
Consumer question:
No water comes in to the model 500 aprilaire humidifier when running. Could it be a problem with the solenoid valve??

Aprilaires' response:

Thank you for contacting us.
No water could be an indication of an issue with the solenoid valve.
If you have an Automatic Control try putting it into test mode:

A. No click at the solenoid valve indicates an electrical problem. Contact the heating and air conditioning dealer to further check the electrical components of the Aprilaire Humidifier.

B. If the solenoid valve makes a click sound and there is no water draining from the unit, this would indicate the flow of water is being obstructed.

1. To determine if water flow is being obstructed, turn the dial of the humidifier control to the off position. 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.

2. 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 attached). 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.


What is the minimum water temperature to supply an Aprilaire 350 humidifier?

Tuesday, May 8, 2012 by Aprilaire Team
Consumer question:
What's the minimum water temperature needed to supply this Aprilaire model 350 humidifier unit? We want to reduce the water temp for the summer so it doesn't heat the house while it runs. Here in Denver we still need the moisture all year around.

By the way, do you make a in-the wall ultrasonic unit with a humidistat, that can run from filtered water that removes minerals and chlorine?
Aprilaires' response:

Thank you for your email regarding your model 350 Aprilaire humidifier. The minimum water temperature for our self contained humidifiers is 140F. This is required in order for the evaporation process to take place. When the hot water flows over the water panel, the water evaporates off the water panel and into the room temperature air moving through the water panel. Lowering the water temperature will reduce the amount of humidification produced. The water to the humidifier can be hard or softened but should not be from a reverse osmosis system. We do not manufacture ultrasonic humidifiers.


What is the replacement for the 2120/2140?

Monday, May 7, 2012 by Aprilaire Team
Consumer question:

We had our A/C system replaced last year. We had an Aprilaire filter system installed at the recommendation of the contractor. He said that the filters were Aprilaire 2120/2140 and a Humidifier Panel 400. What is your current replacement for these. I do not see them on any site selling your product.

Aprilaires' response:

Thank you for contacting us regarding replacement media for your Aprilaire products. The models 2120 and 2140 are two different air cleaners and would take different filter media. Please follow the links below for more information on the filter media for the two air cleaners:

Furthermore, please follow the link or navigate through the estore for information on the replacement water panels for the model 400 humidifier:

If you have any further questions regarding this or any of our products, please feel free to contact our customer service department at your earliest convenience.


How can I tell the difference between the old aprilaire 400 series humidifiers?

Monday, May 7, 2012 by Aprilaire Team
Consumer question:
How can I tell what model I have? (please add this question/answer to your FAS's).

My unit is probably at least 25 years old. I am having a problem with it (leaking water coming from unit's housing), and would like to understand which model I am dealing with.

I have a unit that is installed on ductwork associated with the furnace. The unit is drained by a flexible tube that goes into a pump (on the floor) that evacuates the excess water to a nearby sink. The unit uses warm water.

The rheostat/control is installed on ductwork as well, about 3-4 feet away from the unit. The Rheostat is a dark brown/black control knob, in the middle of a rectangular panel that is also dark brown/black. All the printing on the rheostat's panel (that was once a faint gold perhaps) is worn away, except the '25' at the top/middle of the dial, and - in the upper right- the lettering 'aire.'

Some pages from the original manual were pasted on the inside of a cabinet door in the basement by a previous owner (until today I had not known what they were for.). The instructions say that the Summer Shut-off instructions are to turn the dial to 25. I was unable to find a manual on your website that contains those instructions.

However, from the pictures in, it appears like the models shown on pages 13 and 14 (Models 440, 445-448).

How can I tell which model it is? thank you.
Aprilaires' response:

Thank you for your email regarding your Aprilaire humidifier.
The following is the best way to tell the difference between the model 440 and the model 445-448. The 445-448 will have a thumb screw on the bottom of the Humidifier to hold on the reservoir. The 440 does not have a thumb screw because it does not have a reservoir.
Turn your Humidistat knob clockwise until it stops (to the off position) to turn your Humidifier off. You will have to set it to the desired percent when your humidity levels begin to decrease.


I need humidity in the Summer, what should I do?

Wednesday, April 25, 2012 by Aprilaire Team
Consumer question:
My heating/air cool unit is now controlled by a new thermostat that allows fan circulation about 35% of the time whether the heat or cooling is running or not. Will the humidifier work when the fan is on whether it is on heating or cooling? I live in an area which humidity averages about 12% during the summer. I need to add humidity during those times.
Aprilaires' response:

Thank you for that very good question regarding the Aprilaire humidifier operation.

The answer to your question depends on the type of humidity control that was installed with the humidifier. In the event that the humidity control was the type that used an outdoor temperature sensor to regulate the humidity, then the humidifier would not add humidity in the summer months. this type of control would disable the humidifier when the outdoor temperature would go above 60 degrees. If the humidity control does not use the outdoor temperature sensor, then you may be able to humidify during the summer months. Just be aware that the air conditioning system will remove some humidity during its normal operation; which would take longer to bring the humidity level up.


Summer time use of my Aprilaire Humidifier Model 700?

Tuesday, April 24, 2012 by Aprilaire Team
Consumer question:
I recently moved into home that has Aprilaire Automatic Humidifier Model number 700. My question is during the Summer time when I switch the heat off and turn on the A/C at the thermostat. Will the Humidifier stay off or do I need to somehow turn the unit off?
Aprilaire response:
Thank you for contacting Aprilaire.

To live in Indiana, the humidifier would typically not bother to come on during summer, as nature gives us more humidity than we need. Any time the level of humidity is higher than the selected level, (or max of 45%) the humidifier will not come on.

Some people, just to make sure, will go ahead and turn down the humidistat to 'off' or at least the lowest setting. Then, for the same reasons as listed above, the humidifier will not come on.

Please let us know if you have any further questions.



Summer's High Humidity Affects Indoor Air Quality

Monday, April 2, 2012 by Aprilaire Team

Summer is almost here and with it we welcome the long-awaited warm weather but not the sticky, high levels of humidity that often come with it.  High humidity affects the quality of indoor air and can affect the health of you and your family in a variety of ways.

High humidity levels can cause mold, encourage dust mites which are a major cause of allergies, and cause a hot of problems in the home that can affect your physical health.  Visible signs of high humidity levels include condensation on windows, peeling wallpaper, damp patches on walls and ceilings, a musty smell and dampness.  But there are also numerous problems that go undetected because you can not see or smell them. 

A few of the most common health effects of too much moisture in the home include the following:

Dust mites:  At least 10 percent of the population suffers from a dust mite allergy.  Half of American homes have enough bedding with enough dust mite allergen to cause allergies.. Of these homes, 24 percent had levels that were five times greater than the threshold to cause allergic reactions.

To control dust mites, experts recommend regular cleaning to reduce dust, as well as encasing mattresses, box springs and pillows in allergy-free cases.  The more dust-free the home, the less likely it will be able to support significant populations of allergen0causing dust mites.  Some of the symptoms associated with it include sneezing, itchy, watery eyes, nasal stuffiness, runny nose, stuffy ears, respiratory problems, atopic dermatitis and asthma.

Bacteria: you can't see or feel bacteria but they live on countertops, table surfaces, carpet, pillows, mattresses and just about anywhere people are.  Bacteria also grow profusely when there is plenty of moisture present.

Formaldehyde: When humidity levels are high, products such as furniture, cabinets, building materials and even some latex paints then to release formaldehyde into the air at a faster rate.  Studies have suggested that people exposed to formaldehyde levels ranging from 50 to 100 parts per billion for long periods of time are more likely to experience asthma-related respiratory symptoms, such as coughing and wheezing.

If you suspect that the air in your home is too moist, be sure to vent the areas that create moisture, like the show or bathroom.  You may also consider a whole home dehumidifier like the Aprilaire Model 1710A, 1730A,1750A or the 1770A.  The Aprilaire dehumidifiers can work independently or in tandem with the heating and cooling systems to remove extra moisture from your home.  A system like this will allow homeowners to achieve the EPA recommended humidity levels in the house of 30-50 percent.

Aprilaire Periodic Preventative Humidifier Maintenance

Monday, April 2, 2012 by Aprilaire Team

Periodic Preventative Maintenance

  • NOTE: Periodic inspection and preventive maintenance of your total heating system is important for efficient and safe operation. Your heating contractor should include humidifier service at the same time. All models are equipped with an in-line water strainer and orifice as shown below. These parts should be inspected and cleaned periodically to assure continued proper unit performance.

Aprilaire Humidifier Recommended Annual Maintenance

Monday, April 2, 2012 by Aprilaire Team

Recommended Annual Maintenance

  • The water panel should be changed once a year, with a few exceptions.
    • The model 400 has a panel that should be changed twice a season
    • If extremely hard water is used in any Aprilaire humidifier, the panel should be changed more frequently than once a season. 
    • The water panel cannot be cleaned because it has a special coating that helps the water adhere to the panel while the air is passing through it.  Without the coating, more water will go down the drain and less will be converted into a vapor.
  • Drain line
    • Detach the drain line from the drain spud at the bottom of the unit. 
    • Bend it at the various points to loosen calcium deposits which may have formed on the inside of the line, and flush it with pressurized water. 
    • You can also pour bleach through it prior to the water.  This will kill any micro-organisms that happen to be living in the drain line. 
    • The drain line can be replaced should it prove difficult to clean. 
  • Feed tube
    • Detach the tube from the nozzle at the top of the unit, and unscrew the end of the solenoid valve at the other end of the feed tube. 
    • Run high pressure water through the tube and replace. 
    • When reconnecting the feed tube, remember to double wrench the connections to prevent leaking.
  • Inside of unit
    • Look for any mineral deposits on the Scale Control Insert after removing the water panel, and get rid of them by wiping the insert with a damp towel or rag.  They should come right off. 
    • If there are deposits on the inside of the cover, or in the case of a 700, on the fan blade, it may be indicative of a larger problem known as entrainment.  ()
    • Do not remove granulated coating on the distribution tray – not an issue with the new ones. 
      • The granular coating is there to break up the surface tension of the water.  This allows water to flow evenly through all of the openings in the water distribution tray. 
      • The newer trays have a fabric along the bottom of the tray which does the same thing as the granular coating.  The difference is the customer doesn’t have to worry about scraping off the fabric.
  • Hard or Soft Water
    • Aprilaire offers total flexibility in the installation of our humidifiers in that they will operate properly with either hard or soft water. Connecting to hard water may leave mineral deposits on the water panel that are scaly and hard in nature. Connecting to soft water may leave mineral deposits that are fluffier in nature. The bottom line is the water panel will typically last a full heating season using either type of water.  When extremely hard water is used in the humidifier, maintenance should be performed approximately every six months. 

Summer Aprilaire Humidifier Shutdown

Monday, April 2, 2012 by Aprilaire Team

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.

Humidifier Contol:

Digital Humidifier Control in Automatic Mode (See Figure A):

No adjustment is necessary.


Digital Humidifier Control in Manual Mode (See Figure B):

Set the knob to the "OFF" position.

Manual Humidifier Control (See Figure C):

Set the knob to the "OFF" position.

I Love Craigslist

Monday, April 2, 2012 by Tom Ruse

I have to admit I'm kind of a Craigslist junkie. Buying, selling, always looking for deals.

I came across this ad over the weekend and thought it was pretty cool. In case it's too hard to read in the picture, it says:

Room humidifier - $10

I'm selling a room humifier that comes with several fragrances. You can run it with just water or with water and a fragrance. It has been used a total of about five hours, but now that we have an AprilAire system, we don't need it. It's still in great shape.

Thanks for looking."




Hard or soft water, any concerns?

Monday, March 26, 2012 by Aprilaire Team

Consumer question:
 I have a model 600 Aprilaire humidifier and I didn't see it listed in the FAQ's. Will operation of the humidifier while the water softener is going through it's cycle (backflushing,rinsing, brining) cause problems with either?
Aprilaires' response:

Thank you for your email regarding your model 600M Aprilaire humidifier. All of our Aprilaire humidifiers will function with hot, cold, soft or hard water. The water softener going through it's cycle (backflushing,rinsing, brining) will no affect on the operation of the model 600. The two can operate together or independent of each other.

What humidifier is right for my 1500 sq ft house in Alaska?

Tuesday, March 13, 2012 by Aprilaire Team
Consumer questioni:
I have a 1500 sq. ft. house in Alaska. Very dry in the winter. We have a forced air furnace and a HRV system. Also have hard wood floors that currently are shrinking due to RH in the home of 32%. What humidifier do you recommend to meet our needs?
Aprilaires' response:
Thank you for contacting us with regards to our Aprilaire Humidifiers. Based on the information provided, we could recommend any of our units. Other factors to consider are the age of the home and its relative tightness. The presence of an HRV system must also be taken into consideration. These systems typically provide a constant stream of fresh (and dry) air to your home. HRVs can actually work against your humidification needs by removing humidity already inside the home. You may want to weigh the benefits of the HRV operating during your humidifying season versus meeting your humidifying needs. We would recommend that you contact your local HVAC installer to have them visit your site and provide you with an assessment of your humidity needs and what Aprilaire humidifier would best meet them.


There's a knock whenever the humidifier comes on or shuts off. What is the cause?

Wednesday, March 7, 2012 by Aprilaire Team

Consumer question:

There's a knock whenever the humidifier comes on or shuts off. What is the cause?

Aprilaires' response:

Thank you for contacting us with regards to your model 700 Humidifier. The noise you hear is the humidifier's solenoid valve (water valve) opening or closing. Normally, this valve makes a slight 'click' noise when doing this, but water pressure and the build up of water scale inside the unit can increase this noise. As a test, try turning off the water to the humidifier and then use the humidistat to turn the humidifier on and off. Listen for changes in the noise. Typically, the noise is quieter without any water pressure, but pressure is required to feed the correct amount of water through the unit.
Speak to your contractor about possible remedies if the noise becomes excessive. Anything from cleaning the valve to adding sound-insulating foam rubber to the valve can help dampen the nosie. In some cases, replacing the copper tubing with steel-braided rubber tubing or installing a shock-arrestor can help dampen the noise by absorbing the impact the water makes when the valve closes.