Can there be too much of a good thing? When it comes to cooling, there's no doubt that the answer is "yes!" Your home's air conditioning works by transporting heat outside your house and then distributing the cooler air to each conditioned room. A system that's correctly functioning should produce air with a consistent temperature at each vent.
Your evaporator coils make this process work by transferring heat from the air into the refrigerant. Since moisture tends to condense onto the evaporator, a too low temperature can cause ice to form. The ice then acts as an insulator, preventing the system from operating efficiently and potentially causing damage to other components.
Why Do Evaporator Coils Freeze?
Ice on your coils usually occurs for one of two reasons: inadequate airflow or improper refrigerant pressure. Just as a furnace heat exchanger may overheat without cool air blowing across its surface, your evaporator coils can freeze without a steady supply of warm air. Without warm air, the ambient temperature around the evaporators becomes too cold, and the condensed water will freeze.
Refrigerant pressure is another common reason that evaporators can freeze. Reduced refrigerant pressure can cause the temperature at the evaporator to drop too far, potentially freezing surface condensate even if the system has sufficient airflow. In these cases, the frozen evaporator coils may lead to increased home humidity, as well.
How Do You Know If Your Coils Are Frozen?
Any disruption to the regular operation of your air conditioning system can mean trouble down the line. A frozen evaporator coil interferes with the refrigerant cycle by preventing the refrigerant from taking up ambient heat. Ultimately, this interruption will force your compressor to work harder, potentially causing it to overheat or simply wear out more quickly.
To avoid this situation, you'll want to be able to recognize the signs of a frozen evaporator so you can act quickly. To begin with, check for ice on your outdoor refrigerant lines near the condenser unit. Ice on these lines usually indicates a refrigerant leak, but it may also be a sign that your refrigerant can no longer absorb interior heat at the evaporator coil.
Short-cycling (the system rapidly turning on and off) along with cold, clammy air at your vents are also sure signs of a frozen evaporator. If the airflow at your vents seems normal, it's a good bet that you have a refrigerant leak or another problem with your refrigerant cycle. You should stop using the system rather than allowing it to continue to short-cycle.
As with most air conditioning issues, it's an excellent idea to check your filter before performing any more diagnostic work. If your filter seems to be in good condition, an AC repair technician can help you find the underlying causes before they cause additional damage.