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Replacement Air Filter Considerations
- Pick Your Filters
- Coose the Quality
- Tell Us How Often
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What to think about in choosing replacement air filters
All HVAC air filters are constructed of a filter media supported by a frame. The filter media is working part of the filter that captures and holds dust and other particles in the air before it is drawn into the HVAC’s air handler. Since the 1950s, the predominant filter media has been the ubiquitous blue unwoven fiberglass flat panel media. This is often just referred to as a “throwaway” filter. Manufactures are now producing filters with pleated synthetic and other media as substantially more efficient alternatives to the throwaway filter.
When choosing a replacement air filter, you should keep three characteristics in mind that are common to all air filters. These are:
- The resistance to air flow that the filter introduces into your HVAC system;
- The amount of dust and dirt that the air filter will hold; and,
- The efficiency level of the air filter which is a measure of its ability to remove various particles of specific sizes from the air.
The challenge in choosing a replacement air filter is optimizing these three characteristics for your HVAC system. Optimizing these factors requires that you consider the following:
1. An air filter introduces resistance to air flow in an HVAC system. The amount of resistance that an HVAC system can handle varies depending upon the type and strength of the fan motor housed in the air handler. Too much resistance will strain the motor and, over time, damage the motor or cause complete failure. The objective is to maximize efficiency without choking the system of air. The more efficient the air filter, the greater its resistance to air flow.
2. Most air filters are least efficient, and introduce the least amount of resistance to air flow, when they are new. This is because as dirt and other particles build up on the filter, the filter is able to capture more and small particles. Unfortunately, as this build-up occurs, the resistance to air flow increases. If not replaced, the air filter could completely choke the system of air causing fan motor failure. This introduces the need to select a filter that has sufficiently high efficiency when new but that does not require replacement so frequently that the cost of replacement filters outweighs the cost of repairing or replacing the HVAC system.
3. Every filter will filter particles from the air at some level. The question is, what is the most appropriate level for your home? This varies depending upon each home’s geographic location and the environment that each person needs to maintain. Homes in high dust areas, near industrial areas and similar environments need to consider the size and nature of the particles in the air. People with allergies need to consider the size of the pollen and other allergens that affect them. As air filter efficiency increases, two things happen. First, the particle size that the air filter will capture decreases. Second, the average number of these decreasing sized particles that the filter will capture increases. So, if you know the size of the particles you need to filter out of the air in your home, you can identify the range of filter efficiency that you need. Then your decision is narrowed down to selecting the percentage of these unwanted particles that the filter captures on average.
To help guide you through this decision process, there is a standardized air filter rating system used by just about all manufacturers. The rating system, know as the Minimum Efficiency Rating Value or MERV, assigns a number to a filter based on a standardized testing procedure. The number assigned is known as the MERV rating and tells the consumer the efficiency level of the air filter with respect to the size and average quantity of particles it will capture. The higher the MERV rating the more efficient the filter.
At On Time Air Filters, we offer 3 quality levels. Our "Better" filter is a MERV 8 pleated filter; our "Best" filter is a MERV 11 pleated filter; and our "Best for Pets" filter is a MERV 8 Activated Carbon Filter. Learn more about the MERV air filter rating system or Ask Merv if you would like expert information to help you select your replacement air filters.
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