One of the biggest issues we encounter in the cooling repair business is the formation of ice on an air conditioning system. When a homeowner sees ice on their unit, they often turn it off until the ice they see is melted and then they turn the unit back on instead of calling for help. This is the worst mistake they could make and it could end up destroying their outdoor unit in the process. The outdoor compressor needs to have the correct amount of air moving across the indoor coil and if is not, you need to turn it off and not continue to run without having the system repaired. The unit often times cools again if it is turned back on, but it will freeze again and this is very hard on the compressor.
There are a couple of reasons why ice forms on a residential air conditioner. One is poor airflow across the indoor evaporator coil and the other is low refrigerant charge. The lack of airflow can simply be a dirty air filter blocking the proper amount of air from moving across the coil. This can also be caused by a dirty blower wheel packed with dust and debris which will restrict airflow and cause a freezing. Another very common problem we encounter is an improper amount of intake or return ducts which doesn’t allow enough air to reach the indoor coil, thus causing a freezing up issue. When the indoor blower motor or fan fails, this breakdown will cause instant icing and the unit needs to be shut off. People may still feel some cool air through the vents from the block of ice melting in the unit, but continued operation of a unit in this condition will cause the compressor damage.
The ice one sees is only the “tip of the iceberg” so to speak. The larger piece of ice is located in the duct work of a unit and it is formed on the indoor cooling coil. The ice forms a sheet over this coil and blocks airflow which causes the unit to ice even quicker and before long a block of ice a foot high and wide can be on the cooling coil.
One symptom of this problem is reduced airflow to your rooms. There are few other problems that can so severely reduce airflow, so if this condition happens to you, turn your system off and look for possible ice. Be very careful with the ice melting as the melting water will run down on the furnace and can harm the electronic controls. Try to soak it up with towels and keep from running down in the furnace and drain pan as it can flood your ceiling if your unit is in the attic.
Most of the icing problems we encounter are not due to blower or filter problems, but rather caused by low refrigerant charge. When a unit is low on refrigerant, before it stops cooling altogether, it will reach a state where ice forms on the coils and it is not something a homeowner can repair. Be sure and turn off your unit 5 or 6 hours to thaw before your service tech arrives, because they will not be able to properly repair a frozen air conditioner and they will have to come back another time, which will only add to the frustration of being hot with no cooling.