Dirty Evaporator Coil - Tri County Mechanical

Tri County Mechanical 1724 Pelican Oval Azle, TX 76020 - Phone: (817) 444-8880

Excerpts form an article by

Wayne W. Mulholland Operations Manager, Tri County Mechanical.

Published in the Azle News March 2005.
(Other publications also)

Dirty Evaporator Coil?

Your technician just told you that the evaporator coil in your unit is "dirty" and needs to be cleaned. Please rest assured, he is not implying that you or your family are dirty people. There are many unseen and unknown causes that will effect the evaporator coil in an air conditioner and heating system.

Below is a crude depiction of how an evaporator coil works to cool your home.

A "dirty evaporator coil" is a common phrase used in our industry. The technician actually means that it is clogged and it's now restricting air flow through the system. The primary cause (76%) of a "dirty" / clogged coil is lack of maintenance not only by a professional, but also by the homeowner. Most homeowners don't know or don't even think about this common problem.

Do you change your filter when it gets dirty, or do you wait a specific amount of time because the box says this is a 3 month filter?

Do you notice it's completely clogged when you do change it?

Does your filter fit snugly in the filter compartment?

Is the filter contained while it's in this compartment, or can it lift up when the fan comes on?

If the filter can lift up, then dust and dirt will get past it every time the unit runs.

Or is the system just OLD and finally needs the preventative maintenance you should have had once a year.

HELPFUL HINT: change the 1" pleated fliter when you pay your electric bill each month.

Is your heater and filter in a closet? If it is, next time you change it, use a flash light and look down under the heater into the closet platform to see if that area is clean, also notice if it is sealed with a 'paste like' material so that only the air from inside your home is what will be pulled in by the fan and then recirculated throughout . If your heater is in the attic, take a look to see if the return air ducts are sealed with that 'paste like' material. Is the area behind the return filter grill sealed with this material?

So why should I get the evaporator coil cleaned? There are 3 basic and serious reasons - -

A clogged coil will make your air conditioner run longer and very inefficent trying to cool your home with reduced air flow, HIGHER UTILITY BILLS , as much as 30% each month.
The freon will not get evaporated properly, which can send liquid refrigerant back to the compressor, this causes what we call 'liquid slugging' and can ruin a compressor causing it to fail very quickly, VERY COSTLY, not to mention the hot nights spent waiting for a replacement. AND most warranty companies do not cover failures caused by lack of Maintenance.
In the winter with the heater on, a clogged evaporator coil may cause a dangerous situation. If the air flow is restricted, and can not flow past the colgged coils, the heat generated by the heat strips or the gas furnace can exceed the manufacturer's recommendations. There are safety switches that will shut the system off if the heater box gets too hot, but you won't know it, that is until you get your utility bill. You see, the heat will shut off on "high limit" when it is too hot then start up again when it cools down. You may notice wide swings in the temperature inside, then compensate for it by raising the setting on the thermostat, - - (more cost).
All the dirt and debris on the coil obviously has contaminants in it and it is now being blown throughout your home everytime the system runs creating very poor Indoor Air Quality.

This coil must be removed to be cleaned properly. We can't get to the dirty part which is up inside without removing it, and we need to clean inside those 2' thick fins.