Top Causes of Frozen Evaporator Coils

Where is my evaporator coil located?

You can find your evaporator coil in your indoor air handler system. Your air handler's blower, or fan, blows air over your evaporator coils, which absorb the air's heat and humidity.

See this energy.gov graphic for a recap of how your A/C works:

1. Dirty Evaporator Coils

If dust and dirt build up around the evaporator coils, which transfer refrigerant to the heat pump, it will put extra strain on your system to condition the air, putting your evaporator coil at risk of freezing. The coils need to be cleaned periodically for proper heat absorption to occur; otherwise, the coils may just freeze over.

This is another reason why it is important to schedule annual professional maintenance - your system will be cleaned and inspected in order to avoid potential problems like this one. Better yet, join a home maintenance plan so you never forget this important home maintenance task.

Solution: 

Schedule professional HVAC maintenance once a year to avoid these sorts of problems. You can also DIY clean your HVAC system, including your indoor air handler's evaporator coils. Watch this video and learn how:

If you do choose to clean your evaporator coils yourself, make sure you are using the proper equipment!

2. Refrigerant Issues

Since refrigerant, most commonly Freon, runs in a closed system, you shouldn't have to replace your refrigerant unless there is a leak somewhere in the system. Although leaks coming from regular wear and tear are common, they sometimes go unnoticed for long periods of time. Running your HVAC system with low refrigerant levels creates unnecessary strain on your system and can cause ice to build up on your evaporator coils.

Solution: 

There really is not DIY way of doing this, so your best bet is to call in a professional to inspect your system for leaks and restore your refrigerant levels. If you don't address the underlying leak, you will simply run into the same problem again soon.

3. Airflow Problems

You may have a frozen evaporator coil because there is improper airflow from your blower. This can happen for a number of different reasons, but most often involves a dirty air filter.

Other causes of insufficient airflow include:

• Tight or improperly sized filter
• Undersized or damaged ductwork
• Dirty heat pump and air handler
• Blocked return grills and closed vents
• Blower motor (or fan) isn't working properly (call us!)

Solution:

Although you may need to have repairs, cleaning, and/or maintenance to fix this issue, most airflow problems can be eliminated with a DIY cleaning and air filter replacement. For optimum efficiency, we recommend replacing your air filter every 30 days during peak use. A good test to see if you need to replace your air filter is to observe if light can shine through the filter or not. Set phone and calendar reminders as an extra precautionary measure to remember this important home maintenance task.

The other thing you should check for is proper airflow through your supply and return vents and registers. Although you may have heard it is a good idea to close off vents in unused rooms to save money, this is never a good idea! In fact, you should go around your home and make sure that all vents and registers are unblocked. Look behind furniture, underneath rugs, and behind heavy drapes to make sure that airflow isn't being blocked this way.

4. Inside and Outside Temperatures

Your heat pump and air handler will not function very well when outside temperatures are below 60 degrees.  Sometimes, the evaporator coil will freeze if the A/C is running  when it's cool outside.

Solution:

Diagnose your thermostat for any obvious problems. Try to avoid using your air conditioner at night when the temperatures drop. We recommend setting your programmable thermostat to 78 degrees or higher while at home and 84 degrees or higher while away from home. Setting your thermostat too low, especially when it isn't that hot out, can cause your system to malfunction and freeze up.

5. Drainage Problems

Especially in humid climates, your evaporator coil will have to work extra hard to get rid of all that humidity in the air. When the humidity is removed, condensation forms and is drained away from your home. This is fine, except when you have a clogged drainpipe, which can cause the water top back up and freeze on your evaporator coils. The frozen condensation further exacerbates the problem.

Solution:

In order to fix this problem, you will need to unclog your drainpipe. This can be done easily by calling in your HVAC technician, however, there is a DIY method you can try. It involves a wet/dry vac:

https://www.youtube.com/watch?v=HyvPR7yMqbk

While you were inspecting and fixing any airflow, refrigerant, thermostat, and drainage problems, your frozen evaporator coils should have defrosted by now. If it hasn't finished thawing, you can help it out with a hair dryer, but be careful!

Once it is completely thawed, turn your system back on and see if any of your DIY troubleshooting solved the problem. If not, don't worry, it probably isn't your fault. Most likely, you have a refrigerant leak that needs to be checked out by a professional.

If your evaporator coil still freezes up when you turn your A/C back on,  call Interstate Heating & Cooling for fast and efficient solutions!

You can count on Interstate Heating & Air Conditioning as the solution to all your cooling needs this summer.

Give us a call at 405-794-8900 (available 24/7).

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Stay Cool, OKC!