How Does a Dirty Cooling Coil Affect Your HVAC System?

February 9, 2016

In order for your HVAC system to function properly and efficiently, it needs free airflow. Where there exists any obstructions to airflow, such as a dirty cooling coil or a clogged furnace filter, you are going to experience a corresponding loss in heating and cooling efficiency, comfort and performance. Here's why.

Dirty Cooling Coil

The cooling coil is the indoor portion of your central A/C system. It typically sits on top of or beside of your furnace inside the plenum. The cooling coil (also called the evaporator) cools your home in warmer weather by circulating very cold refrigerant that extracts heat from passing airflow. Whether in heating or cooling mode, airflow must pass through the coil's thin air passages. During the cooling process, condensate forms on the coil. The condensate makes it very easy for dirt and debris to stick to and clog up the coil's air passages. Additionally, coils are great places for mold development that further obstruct airflow. Following are the consequences of a dirty cooling coil:

  • Reduced heated and cooled airflow due to dirt and debris blockages means reduced comfort for you.
  • The blower must work harder and use more electricity to pull airflow through the blocked coil passages.
  • A dirty coil can contaminate supply ducts and reintroduce contaminants to your home -- including mold development and spores.
  • In heating mode, obstructed airflow through the coil may cause your furnace to overheat and shutdown.
  • In cooling mode, a dirty coil usually results in ice accumulation, which halts cooling capability and stresses other A/C components and functions.
Preventive Maintenance
Your furnace and A/C should be professionally maintained in the fall and spring. Coil cleaning is performed during professional maintenance, but if you want to do the task yourself, following are the basic steps:
  • Turn off power to the furnace and A/C.
  • Remove the plenum and coil compartment doors.
  • Thoroughly spray the coil inside and outside with a self-rinsing foaming coil cleaner.
If a dirty furnace coil is impeding your comfort and furnace efficiency, contact the experts at Lozier Heating & Cooling, serving Des Moines customers since 1906. Our goal is to help educate our customers in the greater Des Moines, Iowa area about energy and home comfort issues (specific to HVAC systems). Credit/Copyright Attribution: "ChristianChan/Shutterstock"