There is nothing worse than getting home from work and realizing it is unusually warm in your house. You check your thermostat to find it is 8 degrees warmer than it is set for. You go to check if the system is running and you see it. Ice. Lots of ice.

So what has caused this ice buildup on the copper lines connected to your air conditioner? Great question! To understand why an air conditioner is freezing up, you must first understand the principals of how an air conditioner works.

Air conditioners don’t cool the air; they remove the heat from it. Refrigerant moves into the indoor coil (evaporator coil) at a below freezing temperature. As the refrigerant moves through the coil, indoor ambient temperature air is pulled into the air handler and across the evaporator coil. As the air passes across the coil, heat is transferred from the air onto the refrigerant. Air, now with less heat (around 20 degrees cooler), moves through the duct system and back into the house.

Now lets say for instance, what would happen to the air conditioner if there was no ambient temperature air moving across the indoor coil? I’m glad you asked!

The answer: The #1 reason why an air conditioner freezes up.

Insufficient Air Flow

Airflow is the most important component in air conditioning. Airflow is king! If airflow is reduced or in some cases not present at all, there is no heat to transfer onto the refrigerant. This causes the refrigerant in the evaporator coil to stay at a temperature that is below freezing (32 degrees). Humidity then begins to turn to frost on the surface of the copper lines. The frost then compounds until it turns into solid ice.

If insufficient airflow is suspected, the first item we check is the filter. A filter is designed to catch dust, debris, and airborne particles before they have an opportunity to reach the evaporator coil. The filter catches a certain amount of debris before airflow begins to become restricted. Every home is different, but in most cases we recommend that homes in Central Florida replace their filter on a monthly basis. If your air conditioner is freezing up and you find your filter in a restricting condition, your filter may be the primary cause. Replace the filter with a new one and give your system an opportunity to thaw out before using it.

As you can see in this photo, if filters are not changed on a regular basis, or forsaken completely, the evaporator coil becomes the filter. The repair for this damage is not simple, and should never be attempted by a home owner. The airflow across a dirty coil will always be restricted until the coil is professionally removed from the air handler, and cleaned with special coil cleaners. Do not attempt to clean a coil unless you have the right equipment and training. You can permanently damage the coil requiring it to be replaced.

A faulty blower motor or blower component is the third most likely reason for insufficient airflow. ECM (Electronically Commutated Motor) have become more common as requirements on energy efficiency continue to increase. ECM motors have a higher rate of failure than it’s PSC (Permanent Split Capacitor) counterparts. Whether it is a failed and under-performing capacitor, a failed or failing ECM module, or a failed motor bearing or winding, without the properly designed amount of airflow, the air conditioning system is going to freeze up.

The last component to inspect when considering insufficient airflow is the condition of the duct system. If a duct is collapsed, damaged, or breached, you will not have the heating or cooling results you are looking for. If a return duct is collapsed like the photo above, the reading could be very close to what a dirty filter reading look like. If a duct restriction is suspected, or if there is sudden insufficient airflow after someone has gone into the attic or crawlspace, you should call an air conditioning professional right away.

Refrigerant Restriction

The second reason that should be considered when your air conditioner has ice on it is a refrigerant restriction. A component such as a filter dryer or metering device (piston or TXV) can experience a clog from oil migrating or another non-condensable. This clog will cause the system to experience a high head pressure, and a low suction pressure. Pressure and temperature go hand in hand, so if the restriction is great enough, and the suction pressure is low enough, then the suction line temperature can freeze.

Low On Refrigerant

Last and definitely least, an air conditioner can begin to freeze and exhibit ice if it is low on it’s refrigerant charge. It is similar at first glance to a refrigerant restriction, with exception that the head pressure will be low along with the suction pressure. If a air conditioner requires having refrigerant added, it is because there has been loss. Refrigerant is not consumed like a combustible gas, but rather continues moving through the refrigeration cycle, changing from state to state. Loss, or a leak, can be located anywhere, in any copper line, coil, or component. If refrigerant has to be added to your air conditioning system on a regular basis, a leak detection service should be performed and repairs made to prevent future loss.

A low on charge diagnosis can only be confirmed once airflow is properly ruled out. If your HVAC technician comes to a low on refrigerant charge diagnosis without checking for proper airflow, they are doing you and your air conditioner a disservice. Refrigerant can be added to overcome insufficient air flow symptoms, but it is not a repair and will cause your air conditioner to become very inefficient.

If your air conditioning system has ice on it, has insufficient airflow, or is running inefficiently, Beacon is here to help. We love to fix things!

Our friendly, knowledgeable technicians will inspect the issues you are experiencing, and provide you with options available to get your air conditioner operating correctly again.

Beacon Services & Appliances | Beacon Air & Heat Inc.

Striving for Excellence, with Exceptional Products, and Exemplary Service

352-726-7530 License # CAC1814312