Why does AC coil freeze up?

- Apr 04, 2018-


Why does AC coil freeze up?


The small-scale split air conditioner often has an evaporator ice icing in the indoor unit in the summer. Why is it frozen and how can it be eliminated? The details are as follows:


1. Insufficient refrigerant

If a split air conditioner is installed or used for a long time, leakage or leakage of refrigerant may occur. After the refrigerant in the refrigeration system is reduced, the evaporating pressure is too low, causing the evaporator to freeze, and the freezing position is generally in the front part of the evaporator. Remedy is to first deal with the leak, add enough refrigerant, the fault will be ruled out.


2. Compressor failure for a long time, the compressor compression efficiency is reduced, or the compressor distribution system is damaged, causing the pressure to be too low and freezing. The icing position is also in front of the evaporator. The former adds some refrigerant and the fault can be eliminated. If the fault persists, replace the compressor. 


3. More refrigerant. Some air conditioners are re-injected into the refrigerant due to displacement, leakage, and the like. Inadequate operation by maintenance personnel adds more refrigerant, causing excess refrigerant to evaporate and freeze when it flows to the evaporator. This type of ice is more concentrated in the back of the evaporator and around the compressor return pipe. Discard excess refrigerant and trouble will be eliminated.


4. When the evaporator air conditioner is used for a period of time, the dust in the air or the microorganisms produced by the evaporator will accumulate on the evaporator, hindering the air circulation, causing the heat exchange to decrease, and the evaporator temperature to be too low to freeze. The icing position is in the rear part of the evaporator. After the ice is melted, flush the evaporator with water and use a soft brush to brush the fins. Be careful not to wet the electrical parts. After cleaning, the fault will be eliminated.


5. Temperature control failure Mechanical thermostat temperature sensing package gas pressure changes with temperature, driving the thermostat contact action. The contactor is normally closed due to contact adhesion, lack of spring force, etc. The air conditioner is continuously turned on, causing freezing. Replace the thermostat and troubleshoot.

There are also special cases where the thermostat is not damaged and the air conditioner has a short downtime or non-stop. Since the bulb is suspended in the middle of the evaporator with a u-shaped plastic rack, it is approximately 2mm away from the fins. It is estimated that the manufacturer's design is intended to allow the temperature controller to sense the temperature to delay the temperature and prevent the air conditioner from starting frequently within a short time (within 3 minutes). In the summer season, with high indoor temperatures and the limitations of the air-conditioning itself, it is difficult for the thermostat to achieve a temperature control breakpoint, the air conditioner has a short downtime, and even a continuous power-on, resulting in icing. This kind of ice is mostly in the lower part of the evaporator. In this case, the temperature-sensing package must be moved to the lower end of the evaporator and the evaporator fins should be tightly fixed. The fault is eliminated. 


6. Small air volume. After air conditioner has been used for a period of time, some fan blades have a lot of dirt that affects the air supply and causes the evaporator to freeze. Remove dirt, troubleshooting.

Some fans also have slower speed due to mechanical and electrical failures, and the air volume is small, causing the evaporator to freeze. The mechanical causes are mostly bearings, bearing bushes wear, resistance increases, and the speed becomes slower. Electrical faults are mostly due to capacitive charging and discharging failures or fan-to-turn short circuits, causing slow speeds, and even blown fan windings that do not turn the motor. This icing phenomenon must be repaired or replaced as the case may be.


7. Temperature setting is too low. Some users set the air conditioner's temperature too low, the air conditioner's cooling capacity couldn't keep up, the room temperature dropped below the set temperature for a long time, or the downtime was very short, which could cause the evaporator to freeze. In some rooms, the temperature drops so low that it also causes the evaporator temperature to become too cold. This kind of ice begins to bind from the lower part of the evaporator. As long as the temperature is set higher, the fault can be eliminated.