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What Type of Filter Should I Use?

With so many options available, we often get the question of: what type of filter should I use?  That is why we put together this article to help explain the different types of AC filters and how each one works.  AC filters are not just used to clean the air in your house.  The main purpose they serve is to clean the air so your system can operate properly.  If you allow dirt and dust to circulate throughout your air conditioner, it will clog up the coils and build up on fan blades.  These buildups cause your system to work harder and harder until it can no longer keep up and it breaks.  Hopefully this post answers any questions you may have.  If you are still unsure, hop on over to our contact page and shoot us a message.

First, Understand how HVAC Filters are Rated

What Type of Filter Should I Use

Air conditioner filters are rated by their minimum efficiency reporting value (MERV).  This rating scale was designed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) in 1987.  The ASHRAE recommends a MERV rating of 6 to 12 for residential applications.  There must also be an understanding that there is a difference between efficiency and effectiveness.  Efficiency is calculated as a percentage and is a measurement of how well a filter removes particles from the air.  Whereas effectiveness is the ability to remove particulates from a designated space.

Washable AC Filters

Washable AC Filter

Washable HVAC filters are typically flat and constructed from coarse fibers.  The fibers can be made from various materials including animal hair, glass strands, organic fibers, or some other type of synthetic material.  While these types of filters do save money by eliminating reoccurring filter costs, they are the least effective filter type discussed here.  This is because it does not have the proper surface area to adequately remove small particles from the air.  Washable filters are only designed to catch particles that are larger than 10 microns and have a MERV rating of 1 to 4.  These filters operate at a low efficiency for small particles and a mediocre efficiency for larger airborne particles.  This makes them a poor choice as a filter by themselves, but make a great pre-filter for higher efficiency filters.

Pleated and Disposable Filters

Pleated AC Filter

Pleated filters provide an extended surface area that reduces air velocity in order to trap smaller particle sizes.  This makes them more efficient than the flat washable types.  The design of pleated HVAC filters allows manufacturers to integrate multiple layers if they want to.  In fact, since there are so many different designs and producers, the quality can vary widely within this category.  Most disposable filters are constructed out of synthetic materials, but some brands may use animal hairs or plant fibers in some layers.  They can have a MERV rating anywhere between 5 and 13 and are able to remove particles from 1 to 10 microns.  These are considered medium efficiency filters and are effective at removing small to large particles from the air.

HEPA Filters

HEPA Filter

Allergy sufferers are probably familiar with the HEPA acronym, but it may be unfamiliar to others.  It actually stands for high efficiency particulate air (HEPA).  These filters also have an extended surface area similar to the pleated designs, but to a much finer tolerance.  HEPA filters are typically constructed from submicron glass fibers.  Using such a fine material allows the collection of breathable particles down to 0.3 microns and has a MERV rating between 17 and 20.  To qualify as HEPA, they are required to have an efficiency of 99.97% to 99.99%.  Due to the increased air resistance, true HEPA filters are not typically used in residential systems.  Doing so would probably require professional modifications by an HVAC technician.  The EPA states that filters with a MERV rating between 7 and 13 are almost as effective at removing particles related to health effects as true HEPA filters.

Electronic Air Cleaning

When it comes to electronic AC filters, there are two processes that could be involved.  Electrostatic precipitators are the method usually used in filters and ion generators are often found in stand-alone air cleaners.  With electrostatic precipitation, there are two sections involved to complete the process.  Both portions require an external power source.  First off, the filter has an ionizing area that the air flows through.  This gives any particles an electrical charge.  Then the charged particles flow through a collecting plate that holds an opposite electrical charge from the particles.  When these types of filters are clean, they can have an efficiency of up to 98%.  As the collection plates become full, the efficiency decreases.

Breaking it Down

So now that you know more about the different air conditioner filter types, here is a summary in case you are still wondering: What type of filter should I use?  First of all, any of these options are going to be better than not using a filter at all.  If you were thinking about using HEPA filters, you should probably reconsider as it could damage your unit.  The washable flat type of filters are cheap, but offer very little filtration.  The next step up are the disposable or pleated filters.  Most people will choose a filter within this category and they range from barely better than washable filters all the way up to almost as good as HEPA filters.  Finally, electronic cleaning filters are very efficient as long as they are cleaned regularly, but are more expensive than the other options.  If you are in Bay County, FL and are still unsure what AC filter you should use, contact us and we can point you in the right direction.

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