Ice on copper pipes

Although ice on the copper pipe is often a sign of gas leak, BUT it is important to know 
that too much gas can cause icing problem too!

Therefore, if it is icing caused by too much gas and you top up more gas, that may kill 
your compressor!

The responsibilty of an aircon condenser is to transform a refrigerant (eg, r22) into a liquified gas. In the process when 
gas turns to liquid, enormous heat is produced and that’s why your condenser is blowing hot air.

Why do you want to liquefy gas then? The answer is because when we allow the liquefied gas to evaporate back into gas, 
the reverse happens, it “produces cold air”. So you’ll enjoy the cold air in our room, and your neighbour gets to “enjoy” 
the hot air.

Modern domestic condensers place the expansion devices (be it capillary tube or EEV (electrical expansion valve)) inside 
the condenser. In the past, expansion devices are placed in the aircon blower.

This means that any point after the condenser is now low pressure or rather “suction pressure”: So both pipes are cold. In 
the past, the liquid line is also called the “hot pipe”.

The liquefied gas as mentioned above is ready to “flash” or evaporate to produce cold air. When this liquid gas 
evaporates too fast, it becomes too cold and causes ice to form (the ice is the water moisture from the air). When the gas pressure is 
low, eg 40psi, often you will start to see ice forming on the “liquid line”. Ice will also form at the fan coil. Usually, the 
liquefied gas will be fully evaporated in the fan coil, therefore, there will be no more ice on the returning pipe or commonly 
known as the suction line. The liquid line is the smaller pipe. Please see picture below. The normal operating suction line 
pressure for a r22 gas is ~60psi to 80psi.

BUT!!! if it ice is on the suction line, do not top up gas. It means that the aircon in the room is not fully evaporating the 
liquefied gas. This can be caused by several reasons:

1) The fan motor in the aircon blower is not turning (either jammed or faulty). Under such a condition, the indoor fancoil 
will ice up too. Or had you set the remote controller to “dry”. That will occasionally stop the fan motor, and when the fan isspinning, 
the motor will be spinning slowly. If it is caused by the “dry” mode, the fan coil will not ice up, but the suction pipe 
may ice up.

2) The compressor is still running even when the aircon is turned off (therefore fan is not turning). This will be caused by 
a jammed magnetic contactor.

3) Having mentioned above that icing at return suction line is caused by the blower not fully evaporating the liquefied gas, 
the same symtom can therefore be a result of having an oversized compressor or having an undersized blower.

4) In respect to point 3 above, if your indoor aircon blower is badly choked up, technically speaking, your blower becomes 
“undersized”, isn’t it. If it is so, you will find that the air is not coming out strong. You’ll need to conduct a thorough chemjet servicing to unchoked it.

Following is a picture of an iced suction pipe, which is the bigger pipe. Usually, the suction pipe is the one with the 
charging valve.

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