Troubleshooting evaporator coils often means diagnosing the cause of coil icing. Ice formation is never a good sign. It frequently indicates problems elsewhere in the system, remote from the coil itself. In addition to shutting down your A/C on the hottest day of the year, an iced-up coil that’s strangling system airflow can cause irreparable damage to expensive components like the blower motor or compressor.
The evaporator located inside the indoor air handler extracts heat from indoor air as it’s drawn through the coil by the blower fan. Refrigerant circulating through the coil at about 40 degrees absorbs heat energy, then conveys it to the outdoor condenser coil where it’s released. Here are some theories and practices for troubleshooting evaporator coils as a result of one of the following problems.
Low Airflow
When the air volume passing through the coil is below specified minimums, insufficient heat energy is transferred into the refrigerant. This causes refrigerant temperature to drop below 32 degrees and triggers ice formation as condensation freezes on coil surfaces. Low airflow is most often caused by a dirty or clogged air filter. Replacing the filter may resolve freezing coil issues. You can check for other causes of low airflow, including obstructed return air vents in rooms.
Insufficient Refrigerant
When refrigerant pressure meets specifications, refrigerant temperature stays above freezing. When the refrigerant charge is low, however, the refrigerant temperature may drop and condensation on the coil may turn to ice. Low refrigerant charge is almost always indicative of a leak that requires professional service from a qualified HVAC technician.
Dirty, Dusty Coil
When dirt or dust coats coil surfaces, heat transfer into refrigerant is inhibited. Refrigerant temperature declines and icing occurs as condensate freezes. Coil inspection and cleaning are part of annual A/C maintenance offered by your HVAC contractor. An annual tuneup also ensures optimum energy efficiency, cooling performance and extends component life.
For more about troubleshooting evaporator coils to resolve coil icing, contact the professionals at Paitson Bros. We’ve been the Terre Haute source for qualified A/C service since 1922.
Our goal is to help educate our customers in Terre Haute, Indiana about energy and home comfort issues (specific to HVAC systems). For more information about evaporator coils and other HVAC topics, download our free Home Comfort Resource guide.
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Jeff Paitson is a third generation business owner who continues to run the business with the same values that have been passed down from previous generations since 1922.
Jeff’s belief is that the business belongs to Jesus Christ; therefore 10 percent of the company’s profits go toward the Maryland Community Church.
Jeff is a Terre Haute Chamber of Commerce member and in his spare time, he enjoys 
Ethan Rayburn is a lifelong resident of Terre Haute and a 2005 graduate of Purdue University.
An Eagle Scout, Ethan spent four years as a non-profit executive with the Boy Scouts of America before joining Paitson Bros. as a comfort advisor and later General Manager. In that role, Ethan has brought a renewed enthusiasm for customer care, integrity, value, and service to Paitson Bros. Heating & Air Conditioning.
Ethan enjoys singing and was a member of the Purdue Varsity Glee Club. He also enjoys playing and coaching soccer, spending time with his family and two young boys, and volunteering his time and resources with his church, Terre Haute First Baptist Church, which he has attended from a very young age.
Paitson Bros
1 (812) 232-2347
Serving the Wabash Valley, IN Area Since 1922