HVAC Filters

by May 10, 2022

What is an HVAC filter?

An HVAC filter, or furnace filter, allows air to flow through while collecting particles or contaminates such as dust, dirt, dander, allergens, and other pollutants. The type and amount of material the filter collects depends on the quality of the filter.

Why are HVAC filters important?

The primary purpose of HVAC filters is to keep the parts of the its air handler system clean and operating efficiently. The parts it protects include the blower, heat exchanger, air conditioner evaporator coil, and ductwork. As an added benefit, the filters also improve indoor air quality by keeping the air you breathe cleaner.

Where is the filter located?

The filter’s location depends on the HVAC system’s setup. In most cases, the filter is in the return ductwork just outside the furnace cabinet. It is sometimes located inside the compartment that houses the blower fan.

How does the system work?

The air handler, or air circulation system, starts with the blower fan. The fan pushes heated or cooled air through the supply ducts to the rooms in a house. Then, it draws air back to the HVAC cabinet through the return ducts. Airborne contaminates in the rooms will also be drawn back through the return ducts and collected by the filter.

When should the filter be changed?

The timing of filter changes depends on several factors. Those factors include filter type, size of house, pets, air quality, and family health. You should change or clean HVAC filters more often during summer and winter when the system is used more often. Low-quality filters should be changed every 4-to-6 weeks. Higher-quality filters may only need changing twice a year.

What types of HVAC filters are there?

Filters have a MERV (minimum efficiency reporting value) rating. This is a measure of how effectively a filter removes particles from the air that passes through it. The higher the MERV rating, the more effective the filter. 

There are three types of standard filters:

  1. One-inch fiberglass. This low-cost, disposable filter will only catch larger particles. You should probably replace these HVAC filters every 4-to-6 weeks, depending on HVAC use.
  2. Polyester/pleated. These HVAC filters are available in a variety of widths. The wider filters, such as the four-inch, have more surface area than the one-inch. Wider filters also tend to last longer. Polyester pleated filters are superior to fiberglass filters as the material has smaller pores and can collect smaller contaminates.
  3. Washable. There are different types of washable materials but, in general, they perform along the same lines as fiberglass filters.

When shopping for filters, you can compare their effectiveness by checking their MERV rating. 

Filter maintenance is a very important practice for the proper and efficient operation of the HVAC system as well as indoor air quality. Waiting too long to replace the filter will allow dirt to build up and reduce air flow. Reduced air flow will make the HVAC system work harder, reduce its life expectancy, and negatively affect comfort levels and utility costs. 

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