Low-pressure failure of an air conditioner usually means that the pressure on the low-pressure side of the refrigeration cycle in the air conditioning system is lower than the normal working range. In the air conditioning system, the refrigerant needs to circulate under a certain pressure to achieve the process of absorbing and releasing heat.
Low-pressure failure may be caused by the following reasons:
1. The copper pipe of the air conditioning refrigeration system is too long
During the debugging process, the low-pressure alarm time set by the air conditioner at the factory is relatively low (generally 120 seconds); when the copper pipe of the air conditioner being debugged is longer, the time for the refrigerant to return to the evaporator is extended, resulting in a low-pressure alarm failure. The longer copper pipe will cause the refrigerant to encounter greater resistance when flowing in the system, which will increase the pressure loss of the system. For the low-pressure side, this additional resistance may further reduce the low pressure beyond the normal working range.
2. Dirty and blocked filter of the air conditioner's indoor unit
A dirty and blocked filter of the air conditioner's indoor unit will cause air circulation to be blocked, which will reduce the heat exchange efficiency on the evaporator coil, which may cause low-pressure failure of the air conditioning system, because less air circulation will make the evaporator temperature too low. Day after day, the evaporator will freeze, thereby reducing the pressure on the low-pressure side. Regular cleaning of the filter can prevent this from happening and ensure the normal operation of the air conditioner.
3. Dirty and clogged filter dryer in the air conditioner
A dirty and clogged filter dryer or oil-clogged copper pipe in the air conditioner system will lead to poor refrigerant circulation, thus causing low pressure fault. This is because the blockage will increase the resistance inside the system, so that the refrigerant cannot circulate smoothly, especially on the low-pressure side, which will cause the pressure to drop and affect the cooling effect of the air conditioner. Solving such problems usually requires cleaning or replacing the filter dryer and clearing the oil blockage in the copper pipe.
4. Failure of low pressure protector of the air conditioner
The low-pressure protector in the air conditioner system is a safety device used to monitor the pressure on the low-pressure side of the system. When the pressure is lower than the set safety threshold, the low-pressure protector will trigger, cut off the power supply to the compressor, and prevent the equipment from running in an unsafe state, thereby protecting the compressor and other key components from damage.
If the low-pressure protector itself fails, such as false triggering or failure, it may cause the system to stop running when the pressure is actually normal, which will show as a low-pressure fault. In this case, even if there is no actual low-pressure problem in the system, the air conditioner will not work properly due to the erroneous signal of the low-pressure protector.
5. Solenoid valve failure
The solenoid valve is a key component used to control the flow of refrigerant. If the solenoid valve cannot open (stuck or faulty), it will prevent or significantly reduce the flow of refrigerant into the evaporator, causing the pressure on the low-pressure side to drop. This will not only reduce the cooling effect of the air conditioner but may also cause the compressor to stop working due to the activation of the low-pressure protection switch.
When the solenoid valve cannot open, the low-pressure side does not get enough refrigerant supply, and the pressure on the evaporator coil will decrease, resulting in a low-pressure fault. This situation usually needs to be confirmed by checking the working status of the solenoid valve. If it is determined that the solenoid valve is faulty, it may be necessary to clean the solenoid valve or directly replace it with a new one to solve the problem.
6. Expansion valve failure
Blockage: If the expansion valve is blocked, the refrigerant cannot pass normally, which will cause an insufficient refrigerant supply on the low-pressure side, causing a low-pressure fault. At the same time, the pressure on the high-pressure side may rise because the refrigerant cannot flow normally.
Stuck or malfunctioned: If the expansion valve is stuck or malfunctioning due to wear, impurities, or other reasons, it may not be able to properly regulate the flow of refrigerant, resulting in unstable or insufficient refrigerant supply, which will also cause a low-pressure fault.
Improper adjustment: Inaccurate adjustment of the expansion valve can also lead to inappropriate refrigerant flow, which will affect the working efficiency of the evaporator and cause abnormal pressure on the low-pressure side.
7. Refrigerant leakage
Refrigerant leakage is a common cause of low-pressure failure of air conditioners. The refrigerant circulates in the air conditioning system, changing from liquid to gas and then from gas back to liquid. This process continuously absorbs and releases heat to achieve the effect of cooling or heating. If the refrigerant leaks, the amount of refrigerant in the system will decrease, causing the pressure on the low-pressure side to drop. Refrigerant leakage may occur in any part of the system, including but not limited to copper pipe joints, welding points, valves, compressor seals, etc.
8. The condenser heat dissipation effect is too good
Under normal circumstances, good condenser heat dissipation is conducive to the normal operation of the air conditioner, because it helps to quickly dissipate the heat in the refrigerant to the external environment, thereby improving the efficiency of the air conditioner. However, in extreme cases, if the external ambient temperature is very low, it mainly occurs when the ambient temperature is low, such as in winter. We can often see that in winter, some cooling tower equipment will turn off the fan because the condensing pressure is too low. In this case, the pressure of the system is affected.
9. Flattened air conditioning pipes
Flattened pipes will hinder the flow of refrigerant on the low-pressure side, causing the pressure on the low-pressure side to drop.