What happens when your filter clogs up with dust and debris? The effects of a clogged HVAC air filter in your air conditioner or heat pump can cause failure of the system operation that will result in a call for an air conditioner repair service. Furthermore, dirty AC air filters can have a detrimental impact on your AC and heating systems.
An AC, heat pump, gas furnace, electric furnace, or even an oil furnace needs the proper amount air flow across the coil or heat exchanger to operate properly. Therefore, when the filter clogs the air flow is minimized the blower works harder and harder to pull the proper amount of air across the coil or heat exchanger. What are the effects of a clogged filter in your HVAC system?
Serious Harmful HVAC Issues | Effects of a Clogged HVAC Air Filter
- Dirty AC Air Filters cause your air conditioner to stop cooling
- Clogged AC filters will cause your air conditioner to freeze up and when it thaws the water from the melting ice can overwhelm your condensate drain and cause water damage
- Cause a serious mechanical issue with your compressor in your air conditioner or heat pump technically referred to as liquid slugging
- Lastly, dirty filters will cause your furnace and/or heat to stop heating
Dirty HVAC Air Filters
- As the system airflow is reduced from a restricted and clogged filter your air conditioner or heat pump (in cooling mode) evaporator coil will begin freezing up resulting in less and less air flow from the supply vents. The refrigerant is still flowing through the coils but with no air-flow, there is no heat absorbed into the coils and refrigerant. The refrigerant falls below the freezing point. Any moisture in the air around the coil begins freezing. It effectively turns the air conditioner or heat pump evaporator coil into a freezer. If the air filter is changed then you will still have problems until the evaporator coil is defrosted. With an air-conditioner, you turn it off for several hours to allow it to thaw. With a heat pump, you can simply turn it to heat mode. It will automatically defrost the evaporator coil. However, this problem can cause serious water damage to your home or business.
- Furnaces with clogged air filters will stop heating. As the air flow is restricted the heat in the heat exchanger gets higher and higher. Designed into every furnace are limit switches that will open when the temperature exceeds a designed temperature. When the high limits open the burners turn off and the heat stops. Many times these are automatic reset switches and will automatically reset when the temperature of the heat exchanger cools but if the clogged air filter is not corrected then the problem will recur and the furnace will not provide the proper amount of heat. Sometimes the limit switch will get stuck in the open position. Furthermore, this results in a service call from a contractor to replace the part.
Pressure in the HVAC System and Dirty AC Filters | Effects of a Clogged HVAC Air Filter
Furthermore, the pressure in the HVAC duct system and air handler are very important. If your system was designed correctly the designer designed the system for a specific amount of pressure. The pressure as recommended by the manufacturer of the equipment. When your filter gets dirty you change the pressure inside the system and by doing so you change the amount of airflow flowing through the air handler and ductwork.
There are other ways to change this pressure inside the ductwork such as closing off too many supply vents, a bad blower motor, or collapsed/restricted ductwork. However, here we are focusing on dirty air filters. We have covered those other things in other articles. Lastly, please browse our other articles for that information to help you learn. Finally, here is an example to illustrate the pressure in the system:
Air Filter Categories
- Mechanical Air Filters – This is your typical off-the-shelf throw-away HVAC filter. This filter collects particles in its filtering medium. After it collects so many particles you simply remove it, throw it away, and replace it with another. Note that some mechanical filter media are washable. HEPA (High-efficiency particulate air filters) are also in this category. There are three sub-categories of mechanical air filters. These are:
Mechanical Air Filter Categories
- A1 and A2 – these are the standard 1 inch thick filters. These are typically rated MERV 1 to MERV 4. These are the least effective filters and designed for basic protection of your HVAC system and not health.
- B filter media’s are 2 to 4 inches thick. These filters typically range from MERV 1 to MERV 12.
- C filter media represent the HEPA filters. MERV ratings for these filters exceed MERV 13 and are the most expensive. High-efficiency particulate air filters are excellent for filtering the air but, again, they are the most expensive. An HVAC system with this type of filtering system needs to be specifically designed for this type of filter. Additionally, it is important to make sure these filters do not load up and stop airflow. As noted above, that can have a detrimental effect on your HVAC system.
Other Types of Air Filters
- Electronic Air Cleaners – The electronic air cleaner does not qualify for a MERV rating. Because its efficiency can change depending on how clean it is. It is important that electronic air cleaners are cleaned on a biannual basis (more frequently in dusty environments) for the best performance. Additionally, these work best when used in conjunction with a mechanical filtering media.
- Gas Phase Absorption – uses carbon to absorb odors and gases from the air stream. This media is not very effective at removing particulates and is used mainly in laboratory and industrial settings.
Furnace Filter Problems | Effects of a Clogged HVAC Air Filter
The effects of a clogged air filter in your HVAC system can end up causing damage to the air conditioner, heat pump, or furnace so make sure you keep the air filter clean and free of debris. One other big mistake that will have the same effect of closed-off supply vents. Anything that reduces the airflow in your HVAC system is not good for it. Keep the supply vents open and filters clean and avoid costly repairs.
Effects of a Clogged HVAC Air Filter - HVAC
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I recently had my oil furnace replaced and subsequently had the ducts cleaned. About a month later i was noticing dirty dust throughout the house. I checked the filter in the new furnace and it was completely covered with about an inch of dirt and soot. It seems the duct cleaners did not replace or clean the filter after cleaning the ducts. I’ve replaced the filter but am wondering if there is possible damage to my new furnace as a result of this. Is that possible after a short period?
I should have said, I was noticing dirty dust throughout the house, so about a month later I checked the filter in the new furnace…
Doubt it will damage the furnace but you need to have the ductwork inspected for integrity. Take a visual look to make sure it is good with no holes where it can suck in dirt or debris from crawl spaces or otherwise. I would also take photos of the filter and call the duct cleaning company and let them know about their shoddy work.
I had my 22-year-old Trane XE80 furnace serviced and the repairman said to change out my filters to an electrostatic one. Since then, the pipe on the outside of the furnace has been freezing up during the cool mode. The repairman came back and said that the new filter is too dense and that is why it’s freezing up. While he was here I pointed out a cord coming from the furnace which was not plugged in and asked him if that could be the problem. He told me it was needed for the old filters but it doesn’t need to be plugged in for the new electrostatic filter. Does this sound right and can I plug in the cord and use it with the new filter?
Not enough information. I do not know what the cord is hooked to. Maybe an Electronic Air Cleaner? Maybe an Ultra Violet Air Cleaner? You can take a photo and easily upload it so I can see what you are talking about here. Either way, with a UAV or an EAC you still need a filter and to maintain proper air flow. Both the EAC and the UAV need maintenance from to time also.
Thank you for getting back to me. The cord is hooked up to nothing. It’s coming from the side of the furnace and just hangs. The repairman said it’s used to force air through the filters but since I got an electrostatic filter it is not needed any more. You asked for pictures but there is no place on this form to submit them so I guess I will need your email address.
I still do not know what you are talking about. The menu to the right – you will find “HVAC Document & Photo Uploads”. Click on that and it will take you to the page where you can upload photos.
Okay Debbie, I do not know what it goes to…………….off the top of my head there are three possible things it could be: 1) a plugged for an electronic air cleaner 2) a plug for an ultraviolet air cleaner 3) a plug for a condensation pump (least likely of the three). Either way this plug being unplugged is likely not your problem. You have a problem with air flow if its that critical that using an electrostatic air filter will cause the system to freeze up. The best way to solve the problem is to have a technician test the pressure differential from one side of the evaporator coil to the other. The pressure drop from the return to the supply side of the coil should be anywhere from .3 to .6 inches of water column. This is simply a ballpark but the pressure drop across the coil should be in the manufacturers literature somewhere…………hopefully you still have it.
If the pressure falls out of this range as recommended by the manufacturer then you have a problem with airflow that could the result of: 1) a dirty filter 2) a bad blower motor 3) improperly sized duct 4) damaged duct 5) a dirty evaporator coil. I have found, working as technician, all of these problems causing issues with air flow in HVAC systems. When you put in the electrostatic air filter you decreased the air flow across the coil. Electrostatic air filters are good filters but they load up faster than normal filters and cause the blower to work harder. I would start with the static pressure test first and then look at the other things I have explained to you here. If I was a betting man I would say your evaporator coil is dirty. In some cases the coil can be cleaned without disassembly of the duct work or the refrigeration system. There are some systems where I had to cut the coil out from where it was located and take it to a car wash and wash it with the high pressure nozzle (no kidding…the coil was that dirty).
In any case, then you can discover where that mysterious cord goes…..and once again, if I was a betting man I would bet it goes to an ultraviolet air cleaner. As far as the tech saying it is something to force more air…………….I have no clue what he is talking about…………..never heard of such a thing. What forces the air flow is the blower.
I crawled under my double wide mobile home to instal a ice maker water line for my new fridge. I noticed my vapor barrier was dropping really bad in one spot. I punched a small hole in the barrier material and water started pouring out. Had the mobile home dealer in to locate the leak. They told me it’s the A/C. They called in the A/C man and he said the filters across the condenser were so clogged that water was dripping straight down into the heat exchange and this was causing the water to collect in the barrier. Does this sound like a correct diagnosis?
Yes, it is entirely possible that is what occurred. I would also check the drain for the evaporator coil pan to make sure it is not plugged and that it has a proper trap. It also needs a grade to drain. All these things I would check to make sure this does not occur again. I would also replace any ductwork that got wet if it is flex duct. If it is hard duct I would make sure it was dry inside and out and then re-insulate.
In our A/C system the filter was very clogged. We called technician and he told us that compressor has gone bad it needs to be changed. Did the compressor go bad because of clogged filter?
It is a possibility yes, however with any major repair I always advise a second opinion even though it will cost you to get the second opinion it will be cheaper if the second opinion reveals the compressor to not be bad. Condemning a compressor is difficult in some situations simply because most compressors are hermetically sealed and cannot be disassembled to see the broken parts.
You mentioned that a clogged air filter can make it so that your AC stops cooling and your furnace stops heating. I think that is what is going on with our HVAC system. We have been thinking about calling in someone to take and look and see what is going on. We will have to see if changing the air filter makes a difference.
Have a forced air furnace with a filter. Was wondering if additional filters in the duck system outlets would hurt the furnace.
Have been told any additional filters would harm the furnace. The extra filters are kept clean.
furnaces need a certain volume of airflow and filters will block the airflow or reduce it. Get an electronic air filter.