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Cleveland HVAC Blog

Are your HVAC Filters Really Doing their Job?

Posted by Paul Wadsworth on Thu, Jul 22, 2010 @ 10:11 AM

The purpose of the filters in your heating and cooling system is to protect you, your family and your HVAC system from dust, dirt and contaminants.  You might say that your filters are on the front line in the battle against indoor air pollution.  So, it’s important that you have the correct filters installed so that they can perform this vital function.

Filters that are appropriate for your system and properly installed will help clean the air you breathe and keep your system operating at peak efficiency.   They prevent dirt and debris from clogging system components such as coils, heat exchangers, fan blades and duct work, thus extending their life.  And, by catching mold and toxic materials, they stop unhealthy particulates from circulating throughout your home.

There are four main types of filters.  The best way to determine which ones are best for your system is to have us come out and measure the air flow in your system.  We can then recommend the correct filter type and size for your application.

Here’s a diagram that shows the different filters and what kinds and sizes of particulate they’re designed to handle:laura


Figure 1. Size of common pollutants and the filters that can capture them.

  1. 1. Low efficiency- Low efficiency filters generally capture up to 80 percent of particles that are 50 microns or larger — the range of dust and larger-size pollens.  They include disposable residential filters and pre-filters that keep large particles of dust from reaching more expensive, higher efficiency filters.  Low efficiency filters do little to remove contaminants from the air.  Their main purpose is to protect the fan, coils, and duct from dirt buildup.
  2. 2. Medium efficiency- Medium efficiency filters capture 80-95% of particles that are 5 microns or larger — the range of small pollens and large bacteria.  Most commercial building filters are in this group.  These filters are usually pleated and pocket filters, which are designed to provide a larger filtering surface than one that is flat facing the air stream.
  3. 3. High efficiency- High efficiency filters capture up to 99 percent of particulates that are 0.3 microns or larger. This range includes all bacteria, about 50 percent of the viruses, and most fumes.  Common types are bag filters and rigid cell filters.
  4. 4. Very high efficiency- Very high efficiency filters are used for special applications such as clean rooms, hospital operating rooms, and laboratories.  HEPA filters are included in this group.  These filters can eliminate almost 100% or particulates from the air, and they are not often used for residential applications.

Mechanical filters are rated based on their minimum efficiency.  This is known as the MERV (Minimum Efficiency Reporting Value) rating, established by ASHRAE.  The higher the rating number, the more efficient the filter is.  Homeowners should know what this term means so they can make sure that their filters are correct.  Ask us about MERV ratings and what they mean to you.  NOTE: Electronic air filters are rated in a different fashion owing to their differing technology.

Another major issue is the resistance that the filter offers to the system fan.  Many times we see well meaning homeowners purchase a high efficiency filter and actually end up creating a serious problem by creating too much added resistance in the HVAC system.  This reduces airflow and can compromise system efficiency, capacity, reliability and life expectancy!  So you can see that the choice of the proper filter and size is not only important to your home’s health, but also the performance of you HVAC system, too.

The filters in your HVAC system are working hard for you every day, keeping unhealthy material out of your air and protecting your system components.  Dirty or improperly installed filters can reduce your system’s efficiency by 15%, so make sure yours are doing their job!  Have us check your filters regularly and replace them as necessary.

P.K. Wadsworth services the Greater Cleveland, OH area including cities Chagrin Falls, Shaker Heights, Eastlake or anywhere in between.  To get started, check out our website.

Topics: common pollutants, indoor air pollution, residential filters

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Welcome! Read our latest posts or explore the archives. You’ll find tips for how to maintain your HVAC equipment to discussions about indoor air quality, conserving energy and saving money, and information about emerging technologies in heating and air conditioning. Bookmark our blog.

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