Frozen Air Conditioner | HVAC Troubleshooting

When Your AC Freezes Up – Frozen AirConditioner

Frozen Air Conditioner – This is a common problem for people and it can be caused from one of two things.

Most people figure out they have this problem of a frozen airconditioner when they are outside and see ice building up on the outside condenser unit or ice on the refrigeration pipes. Others know they have this problem when they see the air handler and the pipes running into the air handler have ice. This in addition to a noticeable decline in cooling capacity is a sure sign you have frozen airconditioner problems that need to be resolved immediately. The best thing to do once you notice your air conditioner is frozen is to turn it off. If it is summer and you have a frozen heat pump (a heat pump provides heating and cooling using the process of refrigeration) you can turn it to heating mode and everything will defrost. However, be aware that if an excessive amount of ice is on the evaporator coil (located at the air handler usually inside the home) defrosting the frozen heat pump may overwhelm the condensation drain and you will have some water damage as a result. This may happen either way you defrost the system especially if the air handler is located in a hot attic. Turn the frozen air conditioner to the off position and turn the fan switch to on (manual on) on the thermostat selector switch. This will help aid the defrost of the frozen evaporator coil and the frozen air conditioning unit.

Frozen Air Conditioner – Why is the Air Conditioner Frozen? Possible Cause Number One

Frozen Air Conditioner - Ice on Air Conditioner

Dirty Evaporator Coil can Cause an Air Conditioner to Freeze

This is enough to cause concern because the air conditioner pipes have ice on them. Ice on the pipes is not normal. An airconditioner or heat pump is not designed to make ice. An air conditioning unit is designed to cool the home or business and it is abnormal for ice to form on an air conditioner. A heat pump will form frost or ice on the outside condenser coils in the winter time but frozen condenser coils is common and the heat pump is equipped with a method to defrost the condenser coils.

To solve problem number one with the frozen air conditioner you need to look at airflow first. Every airconditioner or heat pump system is designed to have a specific amount of air flow go through the evaporator coil when the unit is in the cooling or air conditioning mode. Unless you have a high velocity air conditioning system the evaporator coil needs at least 400 cubic feet per minute (CFM) of airflow across the evaporator coil per ton of air conditioning. If you have a 3 ton air conditioning unit or heat pump you need 1200 CFM’s of airflow across the evaporator or the air conditioner will freeze up. This means that if you have a:

  • Extremely dirty filter
  • Collapsed duct work
  • Bad blower motor
  • Something obstructing the ductwork
  • Dirt built up on the evaporator coil

Or anything else which would restrict airflow you will get ice build-up on the airconditioning system. This will cause a diminished capacity for the system to cool if it will cool at all. Defrost the system and then check the airflow. Make sure the entire system is defrosted before checking the airflow of the system. It may take several hours to defrost the air conditioning system completely. The important part is to make sure all the ice has melted from the evaporator coils before checking airflow. After checking the airflow and you find a problem then repaired the problem. If you don’t find a problem then proceed to the next air conditioning problem below.

Frozen Air Conditioner – Why is the Air Conditioner Frozen? Possible Cause Number Two

A frozen air conditioning system can also be caused by a refrigeration problem. The most common problem is a refrigerant leak (refrigerant is commonly referred to as Freon. Freon is a trademark name of DuPont Corporation). This means that the air conditioning is low on refrigerant. This leak needs to be repaired and then the system recharged by a professional. When the refrigerant leaks out the air A frozen air conditioning system can also be caused by a refrigeration problem conditioner pressures drop in the evaporator. A pressure drop in the evaporator coil means that the refrigerant will likely be colder than the dew point. When the evaporator coil in your air conditioner or heat operates below the dew point the moisture or humidity in the air will freeze to the coil. A little frost will appear and then more frost on the air conditioner evaporator coil. This will eventually form into ice and restrict the air flow of the air conditioning system. An air flow restriction in the air conditioner will only exacerbate the problem. You need to call a professional to have this problem repaired. They have all the tools necessary to repair a refrigerant leak and restore the frozen air conditioner to normal operation sans the ice. There is another refrigeration problem which will cause the air conditioner to freeze up. This will require the attention of a trained HVAC professional to troubleshoot and repair the frozen air conditioner. Remember, when you see ice on your air conditioner pipes shut the system down and allow it to defrost. Check for proper airflow. If proper airflow is not present find the problem (or call in an HVAC professional to find and repair the problem).

Frozen Air Conditioner

The following video is of a window unit making ice. No matter what type of HVAC unit you have it is not normal for the air conditioning unit to make ice. In the video they state the system has a leak. This may or may not be true for your frozen air conditioner based upon what is written above.

More about refrigeration and air conditioners can be found here.

Frozen Air Conditioner

High Performance HVAC

Frozen Air Conditioner – Ice on Air Conditioner