Understanding HVAC Issues

« Back to Home

How Can You Know If You Have A Frozen Evaporator Coil?

Posted on

Frozen evaporator coils are a common problem on many air conditioning systems, and this issue can strike even relatively new equipment. Your evaporator coil sits on the interior side of your air conditioning system, meaning it must transfer heat from your home to the refrigerant. In transferring heat, water will condense from the now cooler air, reducing humidity.

Air conditioning manufacturers carefully design their systems to maintain temperatures above freezing at the coil. Colder temperatures can cause condensation to turn to ice, forming a layer of insulation that will stop the system from functioning. Unfortunately, numerous issues can cause the temperature at the evaporator coil to drop, ultimately leading to ice formation.

Why Do Evaporator Coil Temperatures Fall?

There is a direct relationship between refrigerant pressure and evaporator coil temperature. In other words, lower refrigerant pressure will result in lower temperatures at your evaporator coil. This relationship can often be confusing since many expect a refrigerant pressure drop to cause their air conditioner to cool less effectively.

Refrigerant leaks are the most common cause of cold evaporator temperatures. As the system loses refrigerant, the refrigerant pressure in the evaporator coil will fall. Restrictions in the system are another potential culprit, with the filter/dryer and thermostatic expansion valve (TXV) being the two most common locations for obstructions.

What Makes Frozen Evaporators Dangerous?

A frozen evaporator coil will affect your system in several ways. Small amounts of ice build-up will reduce evaporator efficiency and potentially lead to increased humidity. You may notice especially cold, damp air from your vents since the return air will pass over the ice on the coil. As the air moves across the ice, it will pick up moisture and redistribute it through your home.

However, a frozen coil can do more than make you uncomfortable. Once there's enough ice on the coil, the refrigerant will no longer be able to absorb heat and boil off. Since liquids are non-compressible, liquid refrigerant returning to the compressor can cause severe damage. In most cases, the compressor's internal overload protection will cause it to shut down.

How Can You Tell If Your Coil is Frozen?

Unlike your exposed outdoor condenser coil, your evaporator coil will be inside your air handler cabinet. If you aren't comfortable removing the door and peeking inside, there are a few other warning signs you can look for. In addition to cold, damp air, pay attention to short cycling. If your air conditioner frequently shuts off before hitting your thermostat setpoint, you may have a frozen coil.

Remember that a frozen evaporator coil is a serious issue. While you may not be able to make a slam-dunk diagnosis yourself, these warning signs can alert you to the problem's existence. If you suspect your coil may be freezing, stop using your system and contact an air conditioning professional as soon as possible for further diagnosis.