A frozen A/C unit is a sign that something drastic is wrong. It requires immediate intervention. Start by turning off the system.
Why it Happens
Your air conditioning unit is a well-balanced system that depends on certain thermodynamic laws to function correctly. Specifically, the Joule-Thomson effect dictates that if all other factors stay the same when a gas expands, its pressure (and temperature) decrease. If a gas is compressed, its temperature will increase.
In an A/C unit, the evaporator coil expands the refrigerant within, which is how the warm air in your home is cooled. The heated refrigerant is then compressed and all heat is transferred to the outdoor environment. Then the cycle starts over again. But if something is thrown off in the balance of this equation, it’s because some outside factor has interfered with the process, causing the refrigerant to cool more than it should, freezing up the system.
Four Common Causes
The first cause of a frozen A/C unit is limited airflow. If there isn’t enough hot air blown over the cooled evaporator coil with refrigerant inside, the heat transfer will not take place and the refrigerant will continue to cool, eventually freezing the entire system.
Another cause is low refrigerant. With less refrigerant in the system, the evaporator coil is forced to work harder to expand more, and this can result in a lower temperature. The moisture in the air might freeze when it meets the low temperature of the coil, leading to an icy buildup.
Your air conditioner could freeze if it’s operating in less-than-optimal conditions. If you have your system turned on when outside temperatures are lower than 62 degrees, it could lead to a frozen A/C unit.
Finally, mechanical errors can also affect the unit’s operation and cause it to freeze over. Some examples include a leaking refrigerant line, a broken fan motor or a clogged filter.
How a Technician Can Help
You can help your A/C unit function more efficiently to reduce the chances of it freezing, but some repairs only a licensed technician should handle. On your end, you can change filters and open all supply vents throughout the home. Closed or blocked vents can reduce airflow to the system, one of the top causes of this problem.
A mechanical malfunction, leaking refrigerant line or grimy evaporator coil are all problems you need a technician to repair and you shouldn’t take on yourself.
What Should You Do Now?
If you have already tried to resolve the problem on your own but you’re still left with a frozen A/C unit, call My Buddy the Plumber, Heating & Air. We will put your request at the top of our priority list.