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HVAC Filters, Furnace Filter Maintenance, and Indoor Air Quality

We all know know that fresh clean air is important to our health. We should also know that our home air filters need to be kept clean not only for our health but also to protect the air conditioning and heating equipment. A dirty (or worse, no filter at all) filter can cause our heating and air conditioning equipment to fail. By maintaining a good filter maintenace schedule we protect our health and the heating and cooling equipment.

Before we discuss the different types of air conditioing and heating furnace filters and which one is the best for you, I want to stress the importance of keeping your air conditioning and heating furnace filters clean. Air flow is very important to the efficiency of your HVAC system and furnace filters play a key role in maintaining the proper air flow. Whether it be your A.C. system or your Heating system, both HVAC systems need the proper amount of designed air flow throughout the HVAC system. Dirty HVAC furnace filters restrict the airflow which results in higher energy and HVAC repair costs to you.

With the advent of SARS, anthrax, avian flu (bird flu), biological, and chemical terrorism, filtering media's and refining the air we breathe has become a necessity for healthy living. Granted, it takes the best of HVAC filtering media's and technology to stop the aforementioned hazards, but the better we can filter the air in our living spaces the better we protect ourselves and our health from harmful particulates and compounds. It is a fact that certain dwellings cause people to become or remain ill. When an indoor air quality program is instituted in these environments, people begin to recover from illnesses that seemed insurmountable. The air we breathe inside of buildings can be toxic to our health and needs to be addressed before our health is affected in a negative way. You will find indoor air quality solutions on these pages that will help you with the sick building syndrome. Take it seriously now and breathe easier and healthier later.

Furnace Filter Categories

There are different definition, categories, and ratings for HVAC filtering media. High Performance HVAC will do its best to take the confusion out of this and help you better understand these different categories and ratings so you may choose for yourself. First of all, HVAC furnace filters are rated by a MERV value. MERV stands for Minimum Efficiency Reporting Value and is a method developed by ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers) to test the effectiveness of HVAC air filters. The higher MERV number the higher the effectiveness of the HVAC furnace filters to block certain particles and compounds. There are three distinct categories for HVAC air filters. These are:

• 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's are washable. HEPA (High-efficiency particulate air filters) are also in this category. There are three sub-categories for mechanical air filters. These are:

1. A1 and A2 - these are the standard 1 inch thick filters. These are typically rated MERV 1 to MERV 4.
2. B filter media's are 2 to 4 inches thick. These filters typically range from MERV 1 to MERV 12.
3. C filter media's represent the HEPA filters. MERV ratings for these filters exceed MERV 13 and are the most expensive.

• 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 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 in mainly laboratory and industrial settings.

It is important to understand that the better the mechanical filter is at filtering the air the faster it will load up (or become clogged with particles). This can affect the performance of your equipment and the frequency of filter changes. Unless your dwelling is particle and dust-free do not believe that the filter will last for three months despite the air conditioner filter manufacturers claims. Additionally it is imperative that the filter has the proper fit with no air leaks around the frame which holds the filter.

Now that you understand HVAC air filters, how they work to eliminate particles from the air, and the different types and ratings for HVAC filters, you need to take action to set up a planned filter changing routine. It is recommended that HVAC air filters at least be checked every 30 days for excessive load up of particles. If the filter is excessively loaded on a thirty day check then you need to narrow the time 3 weeks or relax that schedule if they are not loaded up. Some modern digital thermostats come with a air filter reminder feature that will flash based on number of days or runtime of the fan. These thermostats help you remember to change or check your HVAC air filter on regular intervals.

In closing, remember that HVAC air filters are very necessary not only to keep particles out of the air inside the dwelling but also to protect the equipment. If you don't have a filter in the system somewhere or there is a filter that is excessively clogged the HVAC equipment will fail and you will lose your HVAC comfort system until corrective action is taken. Set an air filter schedule and stick to it so that you keep your air clean and the equipment protected.

The Supply Vent Myth

A myth many people believe is that they can close off some of their supply registers and save money. This may be true if you only close off less than ten percent. The system installed in your home is designed for a certain amount of airflow. If this airflow is restricted in any way it causes the system to function improperly and could cause system failure. This myth most likely goes back to the early days when people would close off most of their large home in the winter to save on coal and wood usage. Today's modern systems are designed specifically for a certain amount of airflow and if you restrict that airflow, whether it be by a dirty air conditioner filter or closing off supply vents, problems will occur. Open those supply vents, closing too many off is the same as a dirty or restricted filter. The following is a true story of a service call where an extremely dirty furnace filter was found:

Technician arrived at customer's residence on a no heat call. Greeted customer and went straight to the thermostat. Turned T-stat to heat and turned up to highest set point. Checked filter and found it almost completely blocked with dust. Changed filter and went to furnace. Checked unit and found limit switch open. Replaced limit and furnace started. Rollout flames became the next issue. Because the filter was dirty and airflow was restricted it caused an unusual amount of soot build up in the heat exchanger. Technically speaking, it was a pressure problem where the blower created, because of leaks around the blower compartment, a negative pressure too close to the burners. This caused roll out flames and exacerbated the soot build up. Roll out is when the flames come out the front of the unit and into the control area of the unit. The reason these flames "roll out" is because the path they are designed to follow (the inside of the heat exchanger) is blocked off or plugged. This is a very dangerous problem and could very well have been prevented by regular air conditioner filter maintenance. The unit was in a tight closet and made the job of tearing the unit down and cleaning the heat exchanger much more difficult. Three hours after arriving, technician departed customer (who now has an efficiently working furnace and a lesson in changing the filters) with a check for $172.00. $172.00 that the customer could have spent on other things. Change your furnace filters and your air conditioning filters on a regular basis!

Home of Furnace Filters, Electronic Air Cleaners, Ultraviolet Air Cleaners, and Indoor Air Quality Consumer Information.

Good video which shows why it is important to keep clean HVAC filters.

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