Formation of Ice on cooling coils

During operation of an Air conditioner the moisture present in the room air gets condensed in the form of water droplets on the coil surface. Condensation is a continuous process and the condensed water is moved out by the installed drain piping continuously.

Ice on AC coil

This is basically caused due to extremely low coil surface temperature I.e. when the coil surface temperature nears waters freezing point of 00C.

At this point the moisture present in the room air gets condensed and starts converting in the form of ice on the coil surface. If this continues the Ice will cover the coil completely and clogging it thereby reducing and stopping the airflow altogether.

AC working with very low or no airflow on the cooling may cause serious damage to the system and the compressor will eventually breakdown due to liquid (un-evaporated) refrigerant returning to compressor suction side.

The problem arises when the coil temperature nears waters freezing point. So our actual problem is very low coil surface temperatures.

Now let us understand the causes behind freezing coil temperatures

  1. Dirty filters – a filter is installed on the AC Cooling coils to keep the room air clean. A dirty clogged filter will reduce the amount of airflow over the coils and may cause the coil surface temperature to drop towards freezing limits. It’s simple to remove and clean the filter with normal water and mild soap.
  2. Low refrigerant level – As the refrigerant in the AC unit is continuously circulating under high pressures there is a chance of some very minor leakages resulting in loss of refrigerant over a period of time. This needs an expert to attend with special tools (if the leak is major then complete refrigerant will escape and the AC will not work at all)
  3. Defective Expansion valve – A choked or defective expansion valve will restrict the flow of refrigerant and thus have the same effect as low refrigerant level. This also needs an expert attention.
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