You may notice ice on the coil of your central air unit and wonder how this can happen in the middle of summer.
Your central air controls the temperature, flow, and pressure of the air passing through it. If one of these is not balanced, the cold air created by the refrigerant in the system can freeze the coils. When a central air unit is frozen, it could blow warm, cool, or no air at all.
Your central air unit cools the air by using coils filled with cold refrigerant. Warm air blows across the unit’s coils, cooling the air, while also keeping the coils warm so they don’t freeze.
It works like this…the indoor coil removes heat from the inside and transfers it to the outdoor coil’s refrigerant. This pushes the heat out on a straight cool system. This is the reason why it feels like the outdoor unit is blowing air that’s hotter than the outside temperature.
The central air unit manipulates the pressure using the refrigerant circuit. When the wrong pressure is applied to the inside coils it can cause the coils to become too cold. This will lead them to freeze. The same thing happens when warm air is inhibited from blowing over the coils. This article reviews some of the signs it’s time for an AC replacement.
Air Pressure and Air Flow
An air conditioner’s blower fan helps remove warm air and transport cold air where it needs to be. Air that’s cooled inside an air conditioner becomes dense. This makes it difficult to travel out on its own. The blower fan will “suck” the hot air out and move the cold air in. An air conditioner’s ability to do this effectively is dependent on whether there is the right balance between air pressure and airflow.
When a blower fan is broken or damaged the airflow inside of the air handler will be affected. Condensation will begin to build up and droplets of water won’t drain correctly or evaporate. The refrigerant line can also freeze when a broken fan fails to move the hot air over the right parts. Once a refrigerant line is frozen, this leads to other problems because it can freeze everything in the outside condenser unit.
Poor airflow is another common cause of frozen central air units. Without enough air, there isn’t enough heat that can be generated to keep condensation off the coil.
Air Filters could be the cause of this poor airflow. These should be replaced often to keep your unit working effectively. The size and type of your filter will determine how often it should be changed. Your environment will also play a contributing factor in the replacement or cleaning of your filters.
This article can provide guidance on What Size Air Filter Do You Need For Your HVAC System.
You can improve your central air efficiency by 5 to 15 percent by keeping up with your filters according to the U.S. Department of Energy. They have put together this comprehensive infographic on the various air conditioners.
Another area to check is the air vents. You can check them by holding a hand over them and feeling for air leaks that are coming from the sides. Closed dampers, blocked or closed grates, and blocked ducts can also cause airflow problems.
Low Refrigerant Levels
Chlorodifluoromethane, also known as R22, is the name for the refrigerant that central air units use. This could be a cause for a frozen central air unit. The physical properties of this refrigerant can change based on different levels of pressure. When it is functioning normally, the R22 refrigerant passes at a temperature at which condensation might form on the outside as it passes through the lines.
A change in pressure will cause the R22 to react differently. Moisture will condense, freezing the coils. Ice forms when warm air originating from the home circulates over the evaporator.
Minor frost issues may not cause noticeable changes in performance. However, when too much ice forms, it will insulate the central air system, preventing it from working correctly. The refrigerant will evaporate quickly.
Once refrigerant levels are too low, the air conditioner can no longer freeze the line. Cooling from the system will no longer occur, even if the ice melts and airflow problems stop. There is potential for water damage when the central air system doesn’t cool anymore.
The temperature that’s set on a thermostat could be the culprit behind a frozen unit. When a thermostat is set too low or is faulty, an air conditioner might run constantly. This will cause the temperature of the condenser to eventually drop to below freezing. Temperatures set below 60 degrees Fahrenheit will not function properly for most outdoor units. Temperatures that are set too low during the night can also cause operational problems and freeze a central air system.
If a central air unit is constantly turning on, try some of these remedies to see if the thermostat is faulty:
- Check for dirt and residue
- Ensure that the box is level
- Set the temperature lower or higher to determine if it affects how long the unit stays on
A dirty coil is another common cause of a frozen central air unit. This happens when ice is obstructing the airflow of the system. A little bit of frost can turn into a solid block of ice. Air conditioners dehumidify a home in addition to cooling it by pulling water out of the air. This can cause the condensation to build up on the evaporator coils.
There is a drip pan that collects these condensation droplets that fall off the coil. An overflowing drip pan will not operate normally and will result in the coils becoming full with water, eventually freezing. It’s also possible for dirty coils to cause freezing. When a layer of dirt forms on top of the coils, it prevents water absorption to occur quickly.
Call an HVAC Professional to Examine Your System
A frozen central air unit most likely needs to be examined by a professional to identify the cause of the problem. Regular AC maintenance t will also help prevent these issues from turning into bigger more costly issues.
The professionals at Presidential Heating and Air Conditioning, Inc. in Gaithersburg, MD have been providing expert advice since 1982. Schedule your analysis today using their online system or by calling them at 301.615.2760.