Most central heating and air conditioning systems have a filter located as close to the blower unit as possible, in the cold air return duct. Remove the filter grill that holds the filter in place. Make sure to put your used filter in a bag to contain any dirt.

Install the new / clean filter with the air flow arrow towards the blower. If you have a higher dust level in your home due to changes in the season, dry weather, or construction, you may need to check your filter more often than the recommended period of 30 days for a fiberglass filter or 90 days for a pleated filter.

  • Fiberglass Glass – Last up to 30 days
  • Pleated- Last up to 90 days
  • Washable Filters- Wash every 30 days / Last up to 5 years

Life expectancies are different for all types of filters. It also depends on the environment and airborne contaminants in the area due to weather, construction, animals, and increased activity in the home or building.

Pleated filters have more surface area to capture and hold dust particles.

A pleated filter has more media per square inch inside the filter frame compared to a fiberglass filter.

MERV is an acronym for Minimum Efficiency Reporting Value. This is now an international industry standard set up by the committee that oversees the filter industry. This standard is used for determining the filters ability to capture and hold dirt and dust in specific size ranges. Some filter manufacturers use their own rating system.  Which is not approved as an industry standard.  Always ask for the standard MERV number.

The terms pressure drop and resistance are the same with respect to HVAC units and the elements, including filters, that comprise them.  Airflow is a very important factor in an HVAC system.  It helps in determining the efficiency of the unit and an excess amount can even spell problems that could result in expensive repairs or replacement of a system. The more pressure drop or resistance experienced by an HVAC system the less airflow that system has. The way a system is designed and installed as well as the filter used determines how much resistance to the airflow there is.  This includes the type of duct work used, the amount and size of the room outlets and return air openings, the length and amount of turns in the system duct work, the filter size and other factors.  It is important to try and keep the filter changed or washed as often as needed.  As the filter gets dirty the resistance increases, thus increasing the total resistance of the HVAC system and lowering the amount of airflow.  There is no easy way for a homeowner to tell how much resistance there is in the HVAC system. Check you filter often and if it is dirty, then it is time to change your filter or wash it.

The nominal filter size is the approximate size up of the filter rounded up to the nearest “whole” inch.  This makes the filter easier to identify for the consumer and allows for filters to comfortably fit into specified space in a residential furnace without air by-pass. The tolerances allowed for with this nominal size are +/- 1/8″ for both the width and length. The actual size is just as it sounds; it is literally the exact dimensions of the filter. For example, the nominal size of a Dust Shield filter could be 20x20x1 however its actual size is 19 5/8″x19 5/8″x13/16″.  This may not be true for all manufacturers.  Be sure to note the actual size required for you unit before purchasing and changing your filter.

Heating, Ventilation and Air Conditioning.