Why Do Evaporator Coils Fail?

  May 31, 2016      Jeff Rosenblum


We have all seen or diagnosed a bad or poorly performing evaporator coil. Over my years in the eld, I have diagnosed bad coils and the reasons why they fail can be surprising. So why do they fail? Here are a few things we have seen.

Coil plugging. When filters are neglected, the dirt can bypass the filter and plug up the evaporator coil. This will restrict the airflow and cause poor heat transfer. How do you combat this problem? Maintenance and proper filter design will usually solve this. Change the filter often, make sure it is sized correctly and the static pressure drop is not excessive, and verify there is not air bypassing the filter.

Vibration. If the coil is sitting on top of an air handler and the blower is out of balance, the vibration can cause the coils to crack and fail. Make sure there is not excessive vibration being transmitted through the system.

Corrosion. This has been a big one lately. We all hear about corrosion of coils. This  is a big reason why they fail. Sometimes, if the coil is in a corrosive environment, a coated coil may be needed to resolve this. Look at where this system will be installed and take the necessary precautions.

Freeze ups. Allowing the coil to freeze and thaw and freeze and thaw several times can cause failures with the coil. I always tell people that if ice can move a mountain it can crack a coil. Make sure the refrigerant charge is correct and most importantly, the airflow is right.

System Design. If the system was never properly designed right in the first place, or the wrong coil was chosen for the application, you can expect the coil to fail well before its time comes.

So these are 5 reasons why a coil can fail. As always, if you have any questions please feel free to contact the Famous Supply HVAC Tech department.

Jeff Rosenblum 
Technical Support
17 Years Industry Experience
Cell (330) 962-2491