When the air conditioner is running properly, it should be nearly silent and should not have any frost or ice build-up. However, when paying attention to the system, home owners will have very likely seen part of it icing up at times.
How air conditioners work
Before digging into what causes air conditioners to freeze, home owners should understand how they work in the first place.
The air conditioner circulates refrigerant between the outdoor condensing unit and the indoor evaporator coil. It cools the home by absorbing the heat from the air moving through the HVAC system and venting it outside.
Regulating the pressure of the refrigerant
To accomplish this, the system must regulate the pressure of the refrigerant
To accomplish this, the system must regulate the pressure of the refrigerant. When the pressure goes down, the refrigerant gets cold. When the pressure increases, the refrigerant gets hot.
The refrigerant at the evaporator coil should be low, making it cold and allowing it to absorb the most heat. Then, the compressor increases the pressure, allowing it to effectively transfer the heat to the air moving through the condensing coil. If the pressure cannot be regulated or if the air is not moving through effectively, the system may experience a freeze.
Listed below are the four most common causes of an air conditioner freeze-up:
- Dirty coils
As air moves through the system, it deposits airborne contaminants on the evaporator coil. Eventually, these particles restrict the flow of air moving through the coil. The dust particles create an insulating effect on the coils.
In both cases, the refrigerant cannot absorb the proper amount of heat, which keeps the evaporator coil too cold. This lack of heat leads to freezing in the coil and areas farther down the refrigerant line. To deal with these contaminants, the AC system should be carefully cleaned annually, during routine maintenance period.
- Clogged air filters
The air filters are critical to keeping these particles out of the system and protecting them from excessive build-up. However, it is also the gateway to the system for the air needed to circulate. If the filters are clogged, then air cannot flow through the system properly, leading to the same issue as dirty coils.
Home owners should check the air filter regularly, in order to keep air flowing freely. Most experts recommend changing the filter about every three months, depending on the filter type and air quality. However, the life of the air filter can be extended by checking it monthly and gently vacuuming the intake side.
- Ineffective circulating fan
The circulating fan is responsible for drawing air into the system, through the coil and pushing it back out. Like the evaporator coil and air filter, contaminants settle on the fan wheel, reducing how much air it moves.
In addition to collecting these contaminants, the fan motor itself can also cause an issue. As the motor ages and nears the end of its service life, it may not spin as rapidly. This again reduces the amount of air it draws into the system.
- Refrigerant leaks
The system must have a certain amount of refrigerant circulating to operate correctly. If it is too little, the compressor cannot create the pressure needed. This causes the pressure in the lines leading to the compressor to drop, which in turn leads to a freeze.
A leak is what causes the refrigerant level to be too low. These leaks may be minor and will build over time, or they may be major and very noticeable. Either way, they both result in the same frozen system.
Importance of regular system maintenance
If home owners suspect that there is a freeze in their AC system, they should turn it off and allow it time to thaw
If home owners suspect that there is a freeze in their AC system, they should turn it off and allow it time to thaw. While it is thawing, they can double-check their air filters, so as to be sure that they are clean. If the issue still persists, home owners can consider calling a qualified technician to troubleshoot the problem.
Preventing these issues is the best way to protect the system, and that can be done with annual routine maintenance. During a maintenance visit, a technician will clean the coils and fan, check the refrigerant level, and test each component. Once the maintenance is completed, home owners will know that the system is ready to handle all the heat and humidity that the summer throws at it.
AC maintenance and repair expert
Island Heating & Air Conditioning has been the trusted name for air conditioning maintenance and repair, around the Oak Harbor region, in Washington, USA, for over 35 years.
The company’s technicians are also experts in indoor air quality (IAQ) and heating installation, repair, and maintenance. Interested individuals can call to schedule their home’s air conditioning maintenance or repair appointment with one of the expert technicians.