Matt, what are the signs of a dirty or clogged evaporator coil, and how does it affect system operation?

In this edition of “HVAC Skill Builder,” Matt discusses the negative effects of a dirty or clogged evaporator coil on the overall operation of an HVAC system.

Matt, what are the signs of a dirty or clogged evaporator coil and how does it affect system operation? Well one sign is determining if it is in fact dirty by actually examining the unit. Now if you can’t get easy access to the coil you can take a pressure drop reading across that coil and then compare it to the manufacturer’s chart on the allowable pressure drop for that system. If you determine that you have a dirty evaporator coil it will exhibit signs of system performance issues such as freezing, could cause a system to run longer than what it needs to be, but the bottom line is though you want to keep the evaporator coil clean so you have the proper heat transfer going throughout that system and if you identify that the evaporator coil is dirty you need to figure out why is it dirty. Do you have leaking ducts? Do you have air gaps going into the system? Is your filtration poor? It’s all about the source control so again if you have a dirty evaporator coil it can affect the system efficiency not allowing for proper heat transfer and also you need to get down to the source of the problem and not provide just a band-aid fix.