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With proper maintenance, you can avoid common air handler problems
Common Air Handler Problems - Everyone loves to be comfortable, so when there is a problem with the HVAC system, we can become very uncomfortable. The air handler in the HVAC system has electrical and mechanical components inside it that can experience problems from time to time. Some of the most common problems with air handlers can help you identify the problem and possibly fix the issue — many common air handler problems you can avoid with regular air handler maintenance.
Although some of the issues listed will need the attention of a professional HVAC technician to repair the air handler, after all, an HVAC technician will have all the tools and likely the parts available to make a fast and efficient repair. Furthermore, since every air handler is different it is possible the problems described here do not apply to your situation.
Common Air Handler Problems
Some of the most common problems with air handlers are:
- Clear, clean pathway for good airflow
- Blower motor failure
- Regular filter maintenance
See below for the descriptions and maintenance best practices to avoid these issues:
Clear Duct System and Good Airflow | Common Air Handler Problems
Since the AHU is the central unit that moves the air throughout the ductwork, it is important to make sure nothing obstructs the airflow through the air handler, such as dirty or clogged air filters. A regular air filter maintenance schedule will help you maintain good airflow through the duct system. It also helps keep the air handler components inside clean and free of debris and dust. If you maintain good filter maintenance, you will not have to worry about a dirty evaporator coil or any other components clogging with dust or debris. Furthermore, this includes closing off supply vents.
Dusty and dirty components lead to big problems which can cause your air conditioner to freeze up along with other major issues. Maintaining a good air filter maintenance schedule is easy especially if you have a good digital thermostat. Many of the newer digital thermostats have air filter change reminders. Maintain good filter maintenance and prevent several future problems. Dirty filters can lead to many problems including causing water damage to the home. Finally, the problem can become catastrophic under the worst situations.
Blower Motor Failure
The next most common problem that can occur with an air handler is a failure of a blower motor, whether it be the blower motor or something else that causes the blower motor to fail. It could be a bad relay, control board, run capacitor, or the blower motor itself. It could also be the blower wheel. These are AHU (Air Handling Unit) problems that need the attention of a professional HVAC technician.
An HVAC technician can identify the problem quickly and make the blower motor repair. It may require ordering parts, or the part may be available on the service truck, but the problem will get resolved quickly and efficiently.
Proper Filter Maintenance | Air Handler Maintenance Procedures | Common Air Handler Problems
Most of the issues described can be avoided with proper filter maintenance. Even the blower motor failure can be enhanced by bad airflow resulting from no regular filter maintenance. It makes the motor work harder, creating more heat and pulling more amperage, which costs you more electricity costs. The dirt from dust that builds up also hurts the motor and creates more heat which can have detrimental effects on the motor. Consequently, the lesson is to keep a good clean filter in the system, and you will reduce any problems that may occur with your air handler.
Air Handling Units  | HVAC Airflow Problems and Troubleshooting | Common Air Handler Problems
Again, it is recommended that an HVAC professional do this work. Make sure you read the High Performance HVAC disclaimer before proceeding. A professional will have all the proper HVAC tools to complete the HVAC repair or maintenance job quickly and efficiently. It does not matter what type of equipment you have.
You can have a Trane, Goodman, York, Rheem, or Carrier HVAC system, and it all needs to be maintained. If you decide to do it yourself, make sure you follow the safety procedures as noted on the Air Handler Page about cutting power to the air handling unit before attempting to clean the evaporator coils.
Once you have turned the power supply off to the air handler, open the air handler panel where the suction and liquid lines run into the air handling unit. Be very careful not to bend or crimp these lines or any lines in the air handlers. Another thing to avoid is the fins on the coils. Do not bend them.
That would defeat the purpose of cleaning the coils because it will reduce the amount of air flowing through the coils. Plus, the evaporator fins can cut you. Be careful. Furthermore, check the condensation drain line before you begin this procedure.
Basic Check | Air Handler Maintenance Checklist | Common Air Handler Problems
See the condensate drain section below for more information on this subject. Soak the air handling unit evaporator coil with a soap and water solution. Professionals use an industrial-strength coil cleaner, which may be available at some hardware stores. Let this solution soak for a few minutes. Then take a rag and wipe as much dust off the surface of the evaporator coils as possible. Repeat these steps until the evaporator coils look clean.
Take a flashlight and look between the fins on the evaporator coils. The evaporator fin on the coil should appear to be clean. If not, soak the evaporator coils again and use a brush with light bristles to brush the evaporator coils.
Remove as much dust, dirt, and debris as possible from the evaporator coil. Remember there are two sides to the coil and make sure both sides are clean. The side that will most likely be dirty will be the side where the return airflow comes from. If your evaporator coils are clean and the rest of your air handler components are operating normally you should have a nice cool summer inside your home no matter what the weather is outside.
Checking the Air Handler Blower Motor | Air Handler Maintenance Check
The air handler blower comprises different components in most units. It has an electric motor, a squirrel cage blower wheel, and a cage typically referred to as a squirrel cage. Some air handling units have belt-driven motors, and most have capacitors for the air handler electric motor, and typically, they only required HVAC maintenance on the blower is oiling the air handler blower motor if it has oil ports or checking the belt if you have a belt-driven motor.
Not all blower motors have oil ports. These blower motors use sealed bearings, and never require oil. The air handler blower motors that do have oil ports have little plastic dust caps that are removable so that oil can be applied.
Checking the Air Handler Condensate Lines | Air Handler Leaking in Attic Prevention
Checking the air handler condensate lines is especially important if your air handler is located in the attic. Since the air conditioner evaporator coil (inside the air handling unit) operates at a temperature less than the dew point, it will condense the moisture from the air. This air handling unit coil is designed to allow the moisture to drip into an evaporator condensation pan. Most condensation pans have a 3/4 inch PVC line attached to them that allows the moisture to drain to the outside of the house.
The PVC condensation drain line often becomes clogged with algae and muck. Consequently, it needs to be blown or flushed out from time to time. If your air handler is in an attic, it should have a secondary pan to catch the water in case the primary condensation pan or condensation drain line gets clogged. Typical items that clog condensation lines are algae, muck, and trash, like insulation from the attic. You can treat the evaporator pan and condensation drain lines with algaecide which should work throughout the season.
Prevention of Air Handler Leaks | Troubleshooting | Common Air Handler Problems
For double protection, I recommend that all secondary condensation pans have float switches installed. The float switch will cut the air handling unit off if the secondary condensation pan starts to overfill. That will save you from buying a ceiling from a condensation leak. Your local HVAC service company can install float switches. Check to make sure that the air conditioner condensate line is not plugged. You can do this by pouring water into the air conditioner condensation pan. If it drains fast then the line should be okay.
If it drains slowly or not at all, then the condensation drain line is plugged or beginning to plug. I often find the end of the line outside and take a hose and flush the line. You must be careful if you do this procedure. You can flood the condensation pan and cause water damage. That will clean the line in most cases.
Additionally, you can make sure that the condensation drain line has a downward slant to it. Sometimes people place things in the attic on the condensation drain lines, and it won’t drain. If you’ve checked all that and the condensation water still doesn’t drain properly, you need to call an HVAC professional.
Professional HVAC Technician Maintenance | Air Handler Maintenance
The HVAC professional should have all the necessary HVAC tools to blow the condensation line properly. All of these checks are made by your local Heating and Air Conditioning HVAC company. Just call and ask for a spring tune-up or an HVAC maintenance agreement. A little HVAC preventive maintenance on your HVAC system can save you a lot of money in the future. Take the time to have this HVAC maintenance done and save yourself from the expense and hardship that comes with HVAC breakdowns and HVAC component failure.
In-depth HVAC information:********
HVAC Duct Work should be sealed and insulated. Then the insulation should be sealed to provide a vapor barrier. Commercial HVAC ductwork commissioning requires a pressure test to make sure the ductwork was correctly installed and meets specifications.
Refrigeration
*By the time it (HVAC refrigerant) reaches the end of the coils, it should have absorbed enough heat to change it from a liquid to a vapor*. What are the reasons why the coil wouldn’t absorb enough heat to change the state of the refrigerant?
- Dirty Filters
- Dirty Coils
- Collapsed Duct
- Too many supply vents closed off
- A bad blower
The bottom line is airflow. There must be the proper amount of airflow across the coils for your system to operate efficiently. Take this one step further. If you have one of the problems mentioned above and the refrigerant remains a liquid, what happens? Refrigerant leaving the evaporator is on a non-stop trip to the compressor. The refrigerant must be changed from a liquid to a vapor before it reaches the compressor. The liquid doesn’t compress and can cause major problems if it reaches the compressor. It’s called liquid slugging and can cause irreparable damage to the compressor.
HVAC Variable Speed Motors | Common Air Handler Problems
Today’s technology, while being more expensive to purchase upfront, can pay for itself over time in energy savings by increasing efficiency. Variable-speed blower motors not only increase efficiency but also increase your comfort. Conventional HVAC systems are designed to maintain comfort based on basic parameters. The parameters include a peak load of 95 degrees Fahrenheit outside temperature with 75 degrees Fahrenheit and 50 percent relative humidity inside.
That means even when the temperature outside is 80 degrees Fahrenheit the system will still operate full blast. It will run as if it were 95 degrees Fahrenheit outside. Imagine you had a car that only did one speed. Sure it would get you there, but how efficient would it be? Both Trane, York, and Carrier HVAC systems have specifically designed systems with variable speed blowers for greater efficiency and humidity removal. Other manufacturers have followed their lead.
Variable Speed ECM Motors Bonuses |Â Common Air Handler Problems
Variable speed motors (technically called ECM or Electronically Commutated Motor) along with two-stage compressors and multi-stage furnaces offer better control and efficiency. These components and controls help your system runs at the speed it needs to run. The appropriate speed to meet the current load demand. Temperatures are even, and the equipment cycles per hour have an observable reduction. In both the summer and winter, the motor runs at a slower speed until the demand increases. Then it ramps up to meet that higher demand. It only runs or consumes enough energy to meet the current demand. Furthermore, other benefits of having variable-speed motors are:
- Soft-start capabilities
- Quieter operation (research indicates up to 50 percent less noise than conventional blowers)
- Better humidity control adds increased comfort in the summer
- On higher SEER condensing units, variable-speed motors are used for the condenser fan motor
- When used in conjunction with multi-stage furnaces the AFUE rating increases
Different manufacturers offer different options with available speeds and control of the variable speed motor. It is important to compare when shopping for new equipment. Use the High Performance HVAC links page to see the different options available from different manufacturers. Variable speed motors used with other high-efficiency options are definitely worth the extra cost of installation. Consequently, it will pay for itself by saving you money in energy costs over the long term.
Conclusion | Air Handler Maintenance
Again, remember that you can have the best, most efficient HVAC machine any manufacturer can design. However, if your ductwork is sub-standard and leaking, you’re losing efficiency. The efficiency you gained by having the best system installed. Ductwork deficiencies are probably the most overlooked problems with an air conditioning and heating HVAC system. Before you spend a ton of money having the best HVAC system installed, check the ductwork. Finally, make sure the ductwork has airtight integrity and is properly insulated.
  Common Air Handler Problems & Maintenance Schedules
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Hi:
We live in Florida. On Dec 29, 2021 my air-handler in the garage caught fire. We all got out ok. It blew fire into the attic and we had substantial damage which we are now rebuilding. The HVAC people I have talked to, in that our new system is going to be installed, don’t know about a auto shut off device that can shut down the air handler to prevent the fire. Can you point me in the right direction on such a device. I heard they are used in commercial applications.
Thank You, Terry Gannon
We didn’t remove your story. We have an auto-moderation feature to prevent the copious spam from bots. Sometimes comments get caught in the moderation queue.
To answer your question see this page
V speed air handler freezing up- it s 10 yrs old. I cleaned vy well the 14″ flex line intake to plenum- was vy dusty all around. I vacuumed the fins- they look clean. I did not use any Chemical cleaner on fins and coils going through them. It still freezes – sometime partially on bottom 1/4 . I even used a blower to try to blow any dust off fins / coils..the fins look clean but hard to see beneath into coils. Electron filter and mesh cleaned.. any thoughts? Many thx.
If it’s not an airflow problem then it’s a refrigeration problem. Likely a refrigerant leak.
Greetings, I have a residential Rheem central gas heater air handler. Which I believe calls for a slower blower speed on heat than a/c. So the issue presenting is either due to the thermostat or electronic control board. Which is intermittently dropping out the blower relay/relays. Which only happens intermittently for approximately 1 second. I notice after closely listening that it could be jogging to the lower speed winding and back to the higher speed. Which I’m assuming requires disengaging and engaging two different board relays. So far I can’t hear any evidence that the same brownout is occurring at the outside condensing unit. The blower in question has a single 10uf 370vac run cap. Which has been replaced once a few years ago. I’m going to change the blower run cap again to see if it clears. But I suspect this time the main control board may be the issue. Any thoughts would be appreciated. Thx, DD
It’s likely the control board however that is impossible to 100% verify unless the board is properly checked out.
nice notes
Hi: maybe you can help me, my air handler stop working, l hear clicks but the
fan not turning and not warm , the compressor unit running and refrigerant line is cold by the evaporator coil.
Thanks
Not sure with info provided. Call for service.
We had a Trane heat pump and a Trane air handler. The heat pump quit due to electrical surges. The contractor installed a Rheem heat pump and we are now have trouble with getting proper heat out of the new unit. Are these two different brands compatible?
Yes, they are as long as the capacity of the coil to the condenser match it will work. See this a lot. It is not uncommon to replace Brand A air handler with Brand B condenser or vice versa. I would definitely make sure to take care of the power surge issue so you don’t have a similar problem. As far as the heat, I would call the company that installed the new condenser and have them take a second look. If they balk or refuse I would call another contractor to come out and check everything out. It could be something simple or something major. Either way, the installing contractor, as most contractors, should have given you a one year warranty on their work. Especially a job like this.
Thank you so very much for your speedy advice. Your advice is very helpful. The contractor is due here Monday morning. So we will see how do you handle the problem. Again thank you
No problem. Glad we can help!
The previous owner of my house did his own duct work which leads from the AHU (located in a lower attic) all the way up to the higher attic. The duct work is all folded together in the higher attic which provides air conditioning to all the upper floor bedrooms and bathrooms.
Recently, I found out there is mold in the AHU as well as the ducts. I have regular maintenance done on my unit so I’m wondering why the mold wasn’t discovered earlier and/or cleaned up. Now I’m told I have to replace everything! The new air handler unit will be installed in the upper attic instead of the lower attic.
I’m not sure if this is the best way because I’m concerned about the unit being right above the bedrooms. The upper attic is a crawlspace with lots of insulation. I’m also worried about leaking ceilings. What would you recommend? Thanks.
I think I would trust the HVAC designer in this case as long as they are a reputable firm they likely know whats best. Now as far as the air handler being above the bedrooms. They only thing I can think of is any noise it makes which should be very minimal provided proper installation. If it is installed on the floor a secondary condensation pan should be installed under it. Any reputable HVAC company will put this drain pan under the air handler especially when installed in any attic. Next they will will put rubber pads under the air handler to avoid vibration issues which would cause noise if these rubber pads were not installed under the unit.
Next is the issue of water leaks from the air handler. Again, if it is installed properly and by code the air handler will have a primary drain and a secondary drain. The secondary drain should drain somewhere where you will notice it if water is draining from the secondary drain. If you see water dripping from the secondary drain then you know there is a problem with the primary drain. This should not occur as the primary drain should have a sensor installed in it that detects clogs. This will shut the unit down. Next, installed in the pan under the air handler should be a float switch. This switch is designed to shut the unit down if water starts filling the secondary pan. So several precautions are taken to avoid overflow and damage to your ceiling. In any case where I have found damaged ceilings it was because these precautions were not used ie improper installation.
Next, regular maintenance should be done. This is for various reasons but if regular maintenance is performed then a professional will see the unit on a regular basis and if any problems do exist then he can take of the problems before they cause severe damage.
Lastly, mold in your ductwork. First make sure the new ductwork is properly insulated and has a good vapor barrier. Next I would purchase additional features for the system to prevent any mold in the future. A UV air cleaner and an electronic air cleaner along with the normal filtering media you use would be a good thing to have for the duct work to prevent the growth of mold in the system. Air handlers are dark and moist and you will get some mold growth inside the system especially in the primary drain. That is where regular maintenance comes in. When I do maintenance on any system I place some tables in the system. You can find the tablets here – http://amzn.to/2x477iC
Those tablets are designed to kill algae and mold that can get in the system. They will also prevent condensation drains from being plugged up by algae. All this information can be found on this website. Thanks and good luck to you!!!
Today I had the piping to the air handler re insulated. I was surprised to see that the electrical valves had been included inside the insulation. Since there may be condensation on the pipes would that dampness not get to the two electrical valves? I also have a question re replacing the water drain pan within the unit. Is this a simple thing to do? Thank you.
Not sure what you are talking about concerning the electrical valves except maybe a solenoid to prevent refrigerant migration that is installed in some systems based on specific circumstances. However, the electrical part is likely rated for it and water proof. Besides, if it is insulated correctly then no moisture should be forming on the pipe. The insulation should provide a vapor barrier to keep moisture out. The vapor comes from moisture in the air and the insulation keeps that out.
The drain pan can be replaced. Sometimes, depending on your system, the pan may have to be custom made at a sheet metal shop. As far as it being simple I cannot say without seeing it. Sometimes it can be done in an hour and sometimes it may take longer depending on the situation and how the air handler is installed. You can take a photo and send it to me. Upload your photo here……….https://highperformancehvac.com/hvac-guest-post/ ignore the guest post part and use the uploader to send me the photo. Thanks!!
I will take a photo to send to you. The air handler is located in my high rise condo. Cold water is piped in for cooling and hot water for heating. Heating and cooling is done centrally in the building and risers ? are used in the delivery to each unit on the various floors. Hopefully this info will provide you with a basic idea of the set up. The electrical valves have EMC on them.
Okay, I got it. We are not talking talking about a heat pump or conventional air conditioner……….its chilled water and hot water.Okay, now things make sense. Yes, photos will work better. Thanks!
Yes, thanks, the photos will definitely help me identify things betters………now I understand its chilled water and a DX refrigeration system.
have 4 ton and 5 ton rheem air handlers in attic. also 2 drain lines. 4 ton never has a problem and does not get water in overflow pan. 5 ton is always giving problems water in overflow pan and comes out second drain. stops running because water high in pan. have serviced every 3 months and it still happens. air cond company keeps saying happens because in attic. this I do not understand because 4 and 5 ton sit side by side in attic and only one acts up. also main drain is not closed as 4 ton drains well. units are 5 yrs old and I have been fighting this problem for last 3 yrs. now they talk about putting a pump in attic to drain 5 ton. doesn’t the unit have a condensate pump built in it. help
I think a pump is your best option, however I would investigate the problem further with the drain/humidity/air handler issue.
Just had an inspection, was told i had an air leakage at the plenum. what is it where is it is it something a person can repair. I can’t even find a good picture of it . Is it in the attic or on the roof with the air conditioner?
The plenum in residential is typically where the duct work attaches to the air conditioner and is most often built with sheet metal but it can also be wood. It is simply to channel air. It can be repaired. Probably best call an HVAC contractor to handle it especially if you do not know what it is or even where it is. They will have all the tools and materials to fix it. No part of a duct system should leak air.
My air condition unit froze up and the service man put Freon in it and he checked the air handling unit in the attic and told me it was leaking and needed to be replaced. Is that a true statement??
It is possible but without looking at it myself I cannot answer your question. The air handler has the evaporator coil inside it with refrigerant lines running from the evaporator to the condenser. A leak can develop in any part of the system and should be repaired or if the equipment is very old then it should be replaced.
In first AHU chilled water line inlet water is 15 degree c and out let is 20deg c and same chilled water line is given to other AHU inlet 10deg c outlet 15deg c cooling is good but no coolling in first AHU why pls tell its an request