Why Is My AC Freezing Up?
Learn about HVAC & Home Performance in Houston.
Houston is a city that gets very hot in the summer and air conditioning is a necessity, not a luxury. If your air conditioning is not working properly, you want to get it fixed as soon as possible.
The main job of an air conditioner is to remove heat from the air. Airflow is extremely important for this to take place. When there is not proper airflow, a component inside your air conditioner called an evaporator coil may freeze.
When the evaporator coil freezes, you need to turn the air conditioner off. You should do a bit of troubleshooting to see if you can fix the problem. Chances are, you will have to call an HVAC technician if you have a frozen air conditioning system.
How an Air Conditioner Works
An air conditioner relies on both refrigerant and machinery. Although you may think an air conditioner chills the air, it works by removing heat from the air.
When you set your thermostat to the temperature you want, it will activate the condenser fan.
The compressor begins moving refrigerant through your system. Refrigerant is constantly changing from a gas to a liquid and back to a gas throughout the air conditioning process. This helps it to move heat from the inside to the outside of the home.
Refrigerant goes into the compressor as a low-pressure vapor. Once it is compressed, it turns into a high-pressure vapor. The refrigerant makes its way through the condenser coil. The vapor condenses into a liquid. The heat is released into the air outside. This is done with the aid of the AC unit fan.
When the refrigerant exits the condenser, it will be a high-pressure liquid with a medium temperature. At this point, the refrigerant will be transported to a thermal expansion valve. The valve will adjust the flow of the refrigerant.
The pressure of the refrigerant will drop quite a bit as it makes its way through this valve. The refrigerant will then turn into a mixture of liquid in vapor. The refrigerant will flow through the evaporator coil as the blower circulates air in the home. The return duct pulls in room-temperature air.
The air flows through a filter which removes particles in the air. The refrigerant that is inside the evaporator coil will absorb the heat from the air. It will then dispense cold air via the ducts in the home. The air will flow over the evaporator coil, and the refrigerant starts boiling and is transformed back into a liquid.
This causes moisture to accumulate on the coil. That moisture is carried away through a condensate line. The heat that the system collected is blown outside.
When the thermostat senses that the interior temperature is at the level you set on the thermostat, it shuts the air conditioner off. When the room starts to get hotter, the air conditioner will turn back on and the process will begin again.
Cause of a Frozen AC Unit
There are a few things that can cause an air conditioner to freeze. Some of them are easy to fix and some of them will require a visit from House Pro.
Dirty Air Filter
A dirty filter can cause an evaporator coil to freeze. Your air conditioner’s air filter catches particles in the air before they get into your house. Air filters do not last long and when they are filled with particles, they will need to be changed.
If a filter is restricting airflow, air cannot enter your home or your HVAC system. When this happens, moisture from humidity in the air will freeze on the AC coils. The layer of ice will simply become thicker until you change the filter. It is important to change your filter often. You should change your filter as often as the filter manufacturer recommends.
The quality of a filter is determined by the Minimum Efficiency Reporting Values rating. The MERV scale goes from 1 to 20, with 1 being the lowest quality filter and 20 being the highest. You should use a filter with the MERV rating that the air conditioner manufacturer recommends. For home systems, this is normally a rating between 12 and 16.
If you notice that the condenser unit’s side panels are freezing up, refrigerant is likely to be leaking from your air conditioner. When refrigerant gets to a very low level, The evaporator coils will become very cold and the air that touches it will freeze. You may also hear a hissing sound when this happens. Your house may be uncomfortably humid. Leaking refrigerant can cause poisoning, so it is very important to get an ac repair person to your home right away.
Although you may only be comfortable when it is rather chilly, You should not run your air conditioner unless it is hot outside. When you run an air conditioner in weather that is under 63 degrees, the pressure might go down. You should never set the air conditioner to the same temperature as outside. A ceiling fan may help to keep the air circulating and generate a breeze if you are too hot when you are inside.
If the fan in your air conditioner is not working properly, it can interfere with airflow and cause the evaporator coil to freeze.
The fan enables the cold air to come through the house and to blow the warm air outside. When a fan is loose or worn down it will not work very well or at all. Condensation will continue to accumulate in the coils. Water will build up and the coils will freeze.
Dirt in the Air Ducts
Your air ducts need to be clean for air to flow in and out of your home. Dirty air ducts will block the flow of air through your home just as dirty air filters will. When airflow is blocked, the evaporator coil will freeze.
Blocked Condensate Line
A condensate drain line runs through the central air conditioning system from the inside to the outside of a building. Made from PVC pipe or metal, a condensate line acts as a funnel for the moisture generated by air conditioner evaporator coils.
Like any damp pipe, a condensate line will collect debris. Mold will start growing in the line. Eventually, the line will become clogged. When the system cannot drain water, that water will start freezing on the evaporator coil.
How to Fix the Problem
A frozen air conditioner is a serious problem and you are likely to need a professional AC repair person to fix it. However, you can do a bit of troubleshooting to see if you can fix the problem.
Make Sure the Filters Are Clean
The first thing you should do is make sure the filter is not dirty. If it is clogged or discolored, you need to replace it.
Inspect the Coils
Look at the coils that are located near the evaporator. If they look dirty, you can try removing any dirt with a brush. You can also inspect the coils and cooling fins around the evaporator to see if they need cleaning. If so, use a soft brush and gently remove any dust or debris. Make sure all of the vents in your home are opened and that nothing is blocking them.
You May be Low on Coolant
If you do not have the proper amount of coolant in your AC system it can affect the ability of the HVAC system to work well and the unit may freeze.
If your system is blowing warm air, there is a good chance you are low on coolant. The refrigerant should not dissipate. If your coolant levels are low, you probably leak. You should call us for service if this is the case. A leak should always be fixed by a trained HVAC technician.
Reset the Power
Once you have finished troubleshooting, you should reset the power on the unit. Shut the breaker off and turn it back on and set the thermostat to a cool temperature. You should feel cold air coming out of the vents. If the system still is not working, you need to give House Pro a call. We can provide you with a free consultation.
Why You Need an HVAC Professional
Although the basic concept of air conditioning may be simple, troubleshooting a problem with an HVAC system can be complicated. If you follow a DIY video, you may end up pulling your unit apart without ever finding the problem. It can be very difficult to find out where a leak is coming from.
An experienced technician will have a much better idea of where a leak might be and they will have special equipment to find leaks. They will have advanced knowledge of individual makes and models of systems and they will be familiar with any problems those makes and models are known to have.
An air conditioner freezing can eventually cause it to break. If you don’t get it fixed right away, you may have an expensive problem.