Refrigeration System Troubleshooting Guide
There are five kinds of substances in the circulation of air conditioning and refrigeration systems: refrigerant, oil, water, air and other impurities. Refrigerant and oil are necessary to ensure the normal operation of the system. The latter three substances are harmful to the system, but they cannot Absolutely eliminate. At the same time, the refrigerant itself has three states: vapor phase, liquid phase, and vapor-liquid mixed phase. Therefore, once the air conditioning and refrigeration system fails, its symptoms and causes are more complicated. Below, eleven common faults of the air conditioning and refrigeration system are listed.
1. The fan does not turn:
There are two reasons why the fan does not run: one is an electrical failure, the control circuit is not connected; the other is a mechanical failure of the fan shaft. When the room air conditioner fan does not turn, the temperature of the air conditioner room will rise, and the suction pressure and discharge pressure of the compressor will drop to a certain extent. After the air-conditioning fan does not turn, the heat exchange efficiency of the heat exchange coil in the air-conditioning room decreases, and when the heat load of the air-conditioning room remains unchanged, the temperature of the air-conditioning room will rise.
Due to insufficient heat exchange, the temperature of the refrigerant in the heat exchange coil will decrease compared with the original temperature, that is, the evaporation temperature will decrease, and the refrigeration coefficient of the system will decrease. The outlet temperature of the evaporator felt by the thermal expansion valve also decreases, resulting in a smaller opening of the thermal expansion valve and a corresponding decrease in refrigerant, so both the suction and exhaust pressures are reduced. The overall effect of the reduction of the refrigerant flow rate and the reduction of the refrigeration coefficient is to reduce the cooling capacity of the system.
2. The cooling water inlet temperature is too low:
As the cooling water temperature decreases, the discharge pressure, discharge temperature and filter outlet temperature of the compressor all decrease. However, the temperature of the air-conditioned room remains unchanged, because the temperature of the cooling water has not dropped to the extent that it will affect the cooling effect. If the cooling water temperature drops to a certain level, the condensing pressure will also decrease, causing the pressure difference on both sides of the thermal expansion valve to decrease, the flow capacity of the thermal expansion valve will also decrease, and the refrigerant will also decrease, so the cooling effect will decrease. .
3. The cooling water inlet temperature is too high:
If the cooling water inlet temperature is too high, the refrigerant will be supercooled, the condensing temperature will be too high, and the condensing pressure will be too high accordingly. The pressure ratio of the compressor will increase, the shaft power will increase, and the gas transmission coefficient will decrease, thus reducing the cooling capacity of the system. Therefore, the overall cooling effect will be reduced, and the temperature of the air-conditioned room will rise.
4. The circulating water pump does not turn:
When debugging and running the refrigerating unit, the system circulating water pump should be turned on first. When the circulating water pump is not running, the cooling water outlet temperature and the condenser refrigerant outlet temperature rise most obviously. Due to the sharp decline in the cooling effect of the condenser, the suction temperature and exhaust temperature of the compressor also rise rapidly, and the condensation temperature The rise makes the evaporation temperature also rise, but the increase in the evaporation temperature is not as large as the increase in the condensation temperature, so the cooling efficiency is reduced, and the temperature of the air-conditioned room rises rapidly.
5. Filter clogging:
A clogged filter means that the system is dirty. Under normal circumstances, dirty blockage often occurs at the filter. This is because the filter screen of the filter blocks the cross section of the channel to filter out dirt and metal filings and other debris. After a long time, the refrigeration and air conditioner will be blocked. The consequence of filter clogging is the reduction of refrigerant circulation. Many of the reasons are similar to the expansion valve opening too small. The temperature at the outlet of the filter is getting lower and lower. This is because throttling begins at the filter, resulting in a decrease in the local temperature of the system, and in severe cases, local frosting or icing of the system will occur.
6. The load of the air-conditioning room is too large:
Due to the effect of internal and external disturbances in the room and the influence of various factors, the excessive load of the air-conditioned room will cause the temperature of the air-conditioned room to rise, and finally the temperature index that should be maintained in the normal air-conditioned room cannot be reached. At the same time, the two most affected parameters are compressor suction temperature and discharge temperature.
Due to the influence of the heat capacity of the air-conditioned room, it will take a certain period of time before the influence of other parameters becomes obvious.
7. Cooling water flow rate is too small:
Due to the relationship between the cooling water pipe and the cooling water valve, the configuration of the cooling tower in the system is too small or there is too much scale in the cooling tower, the cooling water flow rate is too small and the cooling water inlet temperature is too high are also common faults.
When the cooling water flow rate is too small, the heat exchange effect of the condenser decreases, so the temperature of the refrigerant at the outlet of the condenser rises, and the condensing temperature of the refrigerant rises, which reduces the refrigeration coefficient and affects the refrigeration effect.
When other conditions remain unchanged, the temperature of the air-conditioned room will also rise to a certain extent, and the suction temperature of the compressor will also rise. But the most obvious change is that the cooling water outlet temperature difference will become larger and larger.
8. The opening of the expansion valve is too small:
The opening of the expansion valve is too small in terms of the normal charge of refrigerant in the refrigeration system. In the fault of too small opening of the expansion valve, the circulating refrigerant in the whole system is insufficient. When other working conditions remain unchanged, it cannot fully Satisfied that the liquid preparation gasifies and absorbs heat at low pressure, so the superheat of the return air is very large, the suction and exhaust temperature and the temperature of the air-conditioned room rise, and the suction and exhaust pressure will drop.
The temperature of the refrigerant at the outlet of the condenser will drop (that is, the cooling capacity of the system will increase), because the heat transfer capacity of the condenser does not change, but the refrigerant flow rate circulating in the entire system is very small, although the refrigeration coefficient increases at this time, The unit cooling capacity has been increased. But the overall cooling capacity is reduced, so the temperature of the air-conditioned room will rise.
There is a small opening in the expansion valve. To adjust the opening of the expansion valve is to adjust the size of the small opening. The larger the opening and the larger the caliber, the more liquid will flow through.
9. Insufficient refrigerant
Too little refrigerant is usually caused by two reasons: one is that the charging amount of the product is not enough before leaving the factory, which is generally a small occurrence; Common glitches. There is no obvious difference between insufficient refrigerant and too small opening of the expansion valve.
10. Too much refrigerant:
Excess refrigerant results from blind refrigerant charging, which is not uncommon when servicing refrigeration systems. This will reduce the effective heat exchange area in the condenser, reduce the heat exchange effect, cause the condensation temperature to rise, the condensation pressure to increase, and the high pressure to be too high.
Too much refrigerant enters the evaporator and fails to fully vaporize, and is sucked by the compressor to cause low pressure and high pressure, condensation or frost on the cylinder head of the compressor, and in severe cases, a liquid impact cylinder accident occurs. Part of the liquid refrigerant enters the compressor, the load on the motor increases, it is difficult to start, and the current is overloaded during operation. In severe cases, the motor will be burned due to overload.
11. The suction and exhaust valves of the compressor are damaged:
For reciprocating compressors, damage to the suction and discharge valves of the compressor is a common mechanical failure. This experiment is simulated by bypassing the suction and discharge ports of the compressor. When a fault occurs, the suction temperature and suction pressure will rise, and the discharge temperature and discharge pressure will drop, which is equivalent to the actual air delivery volume of the compressor is reduced, so the cooling effect will be poor, and the temperature of the air-conditioned room will be very high. Rapid rise, when the situation is serious, the low voltage relay will stop the compressor.
