HVAC Technology / October 30, 2018

Air Conditioner Refrigerant Filters

3 Things to Know About Air Conditioner Refrigerant Filters

Most air conditioning systems contain a vital component known as the filter drier, which plays two key roles. The first involves removing unwanted moisture from the refrigerant, thus preventing problems such as corrosion, freeze-ups, and the formation of destructive acids. The second function of the filter drier involves removing physical contaminants from the refrigerant.

Unfortunately, even within the HVAC industry, many people fail to recognize the importance of a filter drier’s second role. If you would like to improve your knowledge of how an air conditioner protects against destructive contaminants, keep reading. This article outlines three key things to know about the filter portion of a filter drier.

  1. Two Filter Types Exist
    A filter drier contains one of two different filter types: a screen filter or a depth filter. Each of these types removes physical particles from the refrigerant stream in a slightly different way. Screen filters consist of a single layer of tightly woven mesh screen, much like the screen found on a faucet aerator.

    Depth filters, on the other hand, utilize a three-dimensional filtration medium. In other words, a depth filter can retain particulate matter at a range of different depths. As a result, depth filters tend to have much greater capacities than screen filters, meaning they last longer before needing replacement.

    Depth filters also tend to provide more effective filtration. Smaller particles often slip through the mesh of a surface filter. As particles build up on the screen, that number gradually increases. Of course, by that point the filter’s capacity has already begun to decrease.

    A depth filter routes particles through many different layers of filtration. Larger particles become stuck on the initial layers. Smaller particles may succeed at penetrating farther into the filter, however, they will be snared by the smaller openings formed by the overlapping layers of filter. Meanwhile, refrigerant can still easily flow through other pathways.

  2. Depth Filters Come in Three Different Materials
    More and more HVAC technicians recommend depth filters, in view of the advantages discussed above. Yet within the world of depth filters, three different filter materials exist: bonded desiccant core, fiberglass, and bonded fiberglass. These three styles differ primarily in terms of the size of the openings and the rigidity of the filter material.

    Bonded desiccant core filters tend to have the smallest openings highest rigidity. While bonded desiccant core filters have lower capacities than fiberglass, they tend to withstand damage better as time goes on. Such damage often ensues from the high velocity of the refrigerant. Debris particles in the refrigerant stream can cause damage to fiberglass filters as they strike the fibers.

  3. All Filters Have a Finite Capacity
    As alluded to above, the greater capacity of depth filters increases filter lifespan and cuts down on maintenance needs compared to surface filters. Yet that doesn’t mean that a depth filter won’t eventually reach its peak capacity as well. When that happens, your refrigerant will suffer from a restricted flow.

    Flow restrictions create unwanted pressure differentials between the two sides of the filter. As pressure mounts on the upstream side of the filter, the other side will experience a corresponding drop in pressure, since less refrigerant can pass through the filter at any given point in time.

    This pressure drop causes the refrigerant to expand as it reaches the downstream side of the filter. If the pressure change is great enough, the refrigerant shifts from a liquid to a gaseous state. Such a premature phase change can greatly reduce the cooling capacity of your system. It will also cause the system to run longer and harder in order to achieve a given cooling task.


To prevent restrictions, you must have your filter inspected and replaced on a regular basis. For more information about this vital part of air conditioner maintenance,  contact the cooling pros at Mauzy Heating, Air & Solar.

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