In refrigeration systems, if the compressor starts and stops frequently due to a fault, it will seriously affect its service life. Therefore, some air conditioning brands will introduce a "short shock" alarm function in their control systems, which will automatically lock the compressor after the low pressure alarm three times to prevent it from starting repeatedly, thereby reducing the risk of compressor damage. However, low pressure alarms are not always caused by faults, and sometimes they may be caused by other reasons. For example, if the copper pipes in the air conditioning refrigeration system are too long, it may cause a low pressure alarm during the commissioning process. In addition, the low pressure alarm time set at the factory for the air conditioner is low, such as 120 seconds. When faced with a long copper pipe and extended time for the refrigerant to return to the evaporator, a low pressure alarm fault may be triggered.
For this problem, we can take a series of solutions. First, the system can adjust the low pressure alarm time, which can usually be extended to 180 seconds. At the same time, in an environment with changing weather, the low pressure alarm time needs to be appropriately increased according to the actual situation. In this way, we can better deal with the low pressure alarm problem and ensure the stable operation of the air conditioning system.
1. The air inlet or outlet duct of the air conditioner indoor unit is blocked
When the user reports a problem, he can first ask whether the machine room has been renovated recently. If the area of the air inlet or outlet duct is reduced, the air conditioner evaporator will not be able to release the cold, which will cause the evaporator to frost and freeze, and the refrigerant pressure will gradually decrease, eventually triggering a low-pressure alarm.
Solution: This problem can be solved by simply restoring the area of the air inlet or outlet duct before debugging.
2. The filter of the air conditioner indoor unit is dirty and blocked
During the operation of the air conditioner, the air circulation will inevitably absorb dust in the environment to the surface of the filter. If the user ignores this problem for a long time, the filter will be dirty and blocked due to excessive dust accumulation, which will cause the evaporator to freeze and trigger the air conditioner low-pressure alarm fault.
Solution: It is recommended that users regularly replace the air conditioner indoor unit filter (the filter is a consumable item) and prepare a few more in case of emergency. When the filter is found to be too dirty, it can be easily replaced by yourself.
3. The dry filter in the air conditioner refrigeration system is dirty and blocked or the copper pipe is blocked by oil.
During the copper pipe connection process, the copper slag produced by welding may not be completely removed by blowing, and these impurities will gradually accumulate in the dry filter. In addition, when the air conditioning refrigeration system is running, there will be a temperature difference at both ends of the filter.
Solution: If the filter is seriously dirty and blocked, the refrigeration system needs to be blown or cleaned again. The conventional treatment method is to replace it with a dry filter of the same model and specification.
4. Oil accumulation problem in air conditioning pipes.
Due to improper installation of some air conditioners, refrigerant oil accumulates in the pipes, which in turn affects the circulation of the refrigeration system. When the refrigerant cannot return to the evaporator smoothly, a low pressure alarm will be triggered. It is worth noting that oil accumulation in the air conditioning pipes sometimes also triggers a high pressure alarm, which depends on the location of the refrigerant oil accumulation in the refrigeration system and the order in which the alarm is triggered.
Solution: To ensure the normal operation of the air conditioner, the pipes of the refrigeration system need to be rectified and the construction requirements of the specifications need to be followed. As an emergency measure, you can try to release the accumulated oil in the copper pipes to restore the refrigeration function of the air conditioner.
5. Failure of the low-pressure protector in the air conditioning refrigeration system.
In order to detect and solve this problem, it is necessary to perform a meter test on the air conditioning refrigeration system. When the pressure is normal, use a multimeter to measure the circuit of the low-pressure protector, or try to short-circuit the low-pressure protector and start the compressor. During this process, pay close attention to the changes in the pressure of the refrigeration system and be ready to disconnect the compressor at any time. If the refrigeration cycle can return to normal, it can be determined that the low-pressure protector is faulty.
Solution: Replace the faulty low-pressure protector with a new one of the same specification and model.
6. The solenoid valve in the air conditioning refrigeration system cannot be opened.
In order to diagnose this problem, we need to perform a meter test on the air conditioning refrigeration system. After lowering the temperature setting value, when the refrigeration system is ready to run, pay attention to whether the solenoid valve makes an opening sound. If the solenoid valve is not opened, the low pressure will gradually decrease until the low pressure alarm is triggered. At this time, try to reset the alarm on the air conditioning control panel. If the low pressure cannot rise, the solenoid valve coil needs to be measured. If the measurement result shows resistance, the coil is in good condition; if it shows infinity, the coil may be burned.
Solution: Replace the faulty solenoid valve coil with a new one of the same specifications and model.
7. The expansion valve in the air conditioning refrigeration system is faulty.
In order to diagnose this problem, it is also necessary to perform a meter test on the air conditioning refrigeration system. After lowering the temperature setting, we observed that neither the low pressure nor the high pressure could rise, and even with the addition of refrigerant, the low pressure did not increase.
Solution: First try to adjust the opening of the expansion valve to see if it can effectively solve the problem. If the adjustment is still ineffective, then you need to replace a new expansion valve of the same specifications and model.
8. Refrigerant leakage in the air conditioning refrigeration system
When the air conditioning refrigeration system is tested with a meter, if no pressure is displayed, it means that the refrigerant in the refrigeration system has completely leaked. However, if there is still pressure at this time and the refrigeration system can barely operate, then after adding refrigerant, the pressure will rise immediately, which also reminds us that there is a refrigerant leak.
Solution: First, it is necessary to comprehensively inspect all parts of the refrigeration system, especially to find signs of oil leakage, and focus on using detergent to carefully check the suspected oil leakage location. If necessary, the refrigeration system can be tested for segmented pressure maintenance to further locate the leak. After finding the leak, welding should be used to repair the leak and re-debug the refrigeration system.
10. The heat dissipation effect of the condenser in the air conditioning refrigeration system is too good.
This usually occurs when the ambient temperature is low and the air conditioning outdoor fan does not have a speed regulation function.
Solution: This problem can be effectively solved by increasing the starting pressure of the air conditioner, or by improving the outdoor fan so that it has a speed regulation function.