Servicing Air Filters

Overview

Air filters receive a Minimum Efficiency Reporting Value (MERV) rating which is a rating of the filtering efficiency of an air filter that has been evaluated using the ASHRAE Standard 52.2 Test Procedure. The higher the rating the more effective the filter is in capturing particles.

Remember that the filter is your only line of defense to clean the air that you breathe. A throw away filter only catches approximately 10% of the dirt and bacteria that floats by it. Air filters also protect the evaporator coil and blowers on your equipment and the ductwork in your building. As the coils get blocked with the particles flowing through the filter, the unit will not be able to dissipate the heat so the unit will run longer and thus use more energy.

The change frequency required will depend on the following:

  • Condition of the internal space (factory or office space) and indoor air pollutants (cigarette smoke, dirt or soot from machines, etc.)
  • Quality of the outside air that is being brought into the building (pollen, smog, dust from dirt roads, etc.)

In an office environment, filters should typically be changed quarterly. In a manufacturing setting filter changes can range from quarterly to monthly depending on the type of operation and particles created by the manufacturing process.

Servicing the Air Filter section of HVAC unit

The steps required to properly service the air filters on a standard roof top HVAC unit include:

  • turning the power off to the unit
  • checking the cabinet for air leakage
  • looking at the filter rack for leakage around the filters
  • checking the filter to see how plugged the filter is getting
  • checking the evaporator coil to see if dirt is getting around or through filter and plugging the coil

A differential pressure gauge can also be used to check the static pressure drop across the filter bank.

Summary

By using the proper type of filter and changing filters at the right frequency you can:

  • improve the quality of the air you breathe.
  • increase the efficiency of your system by keeping the evaporator coil, blowers and ductwork cleaner
  • lower janitorial costs by reducing the amount of dust in the building.

Proper filter maintenance will keep your system running efficiently and reduce your energy consumption thus saving you money.