The core problem of compressor oper
The frosting direction of the refrigeration system is exquisite, do you know
1. If the frosting direction is the compressor return port, it will gradually frost toward the evaporator. The possible reasons are:
1. The throttle valve is opened too large, and the appearance is that the temperature and pressure of the condensing return liquid are normal or slightly higher, and frost starts to gradually form towards the evaporator from the compressor return port.
2. The evaporator cannot absorb heat normally, or the cold generated by the evaporator cannot be taken away. The appearance is that the return liquid temperature and pressure are normal or slightly lower, and the frosting starts from the compressor air return port to the evaporator gradually. After a long time, the compressor returns to the evaporator and the throttle valve to the evaporator section. , And finally there is low pressure. The check method is:
· Check if the air filter is clean;
· Check whether the fan speed is normal;
· Whether the evaporator is clean;
· Whether the air supply system is blocked;
· Is the belt too loose?
2. If the frosting direction is from the expansion valve to the evaporator, the possible reasons are:
1. The refrigerant is too small (leakage). The appearance is that the return liquid temperature of the condenser is too high but the pressure is not high, and the frost begins to gradually form at the throttle valve toward the evaporator.
2. The opening of the expansion valve is too small, and the appearance is that the temperature and pressure of the condensed return liquid are normal or slightly lower, and frost begins to gradually form at the throttle valve toward the evaporator.
3. Check the sight glass to see the refrigerant situation. The bubble is serious, which may be a system leak; the refrigerant in the sight glass does not bubbling or seldom bubbling, it may be that the expansion valve is opened too small or blocked. There will be a large temperature difference before and after the blockage.
The surface of the evaporator fin is frosted, and the evaporator temperature at the frosted part is lower than 0℃, and the frosting speed is related to the ambient temperature and humidity. There are two phenomena of evaporator frosting:
1) A phenomenon is that frost starts from the outlet of the evaporator and forms over the entire surface of the evaporator over time. This phenomenon is a manifestation of excessive liquid supply for the evaporator (obvious response of the capillary system). For the entire refrigeration system of the household air conditioner, it may be a problem with the return air system and the control system:
A. The return air filter is blocked by dust, the surface of the evaporator fin is blocked, the capacitor of the fan is broken or the capacitance is reduced, the fan motor does not rotate, the speed is slow, etc., which cause the heat exchange load of the evaporator to decrease.
B. Cooling operation for a long time when the ambient temperature is low or the return air temperature sensor resistance changes. In household air conditioners, if the control system has anti-freezing protection function, after the refrigeration system runs for a period of time, when the control system detects that the temperature of the evaporator coil is lower than 0℃, the controller automatically turns off the compressor and outdoor fan for protection. The fan runs with high-speed wind. During the protection period, when the indoor evaporator coil temperature is greater than 10°C, the protection will be cancelled and the refrigeration operation will resume. If it is found that the evaporator surface does not retreat for a long time, the evaporator coil sensor and return air temperature sensor of the control system may be faulty or the control system does not have the anti-freezing protection function.
C. Some air conditioners have continuous operation function. When the continuous operation function is turned on, the operation of the refrigeration system is not controlled by the temperature sensor, and frost on the surface of the evaporator will appear after the operation time is long. Just turn off the continuous operation function. During maintenance, check the evaporator fins, fan system, controller return air temperature and coil temperature sensor, and the ambient temperature at the time of operation, and confirm that there is no problem with the inspected components to determine whether the system has too much fluorine. The high fluorine content rate is generally a phenomenon that may only appear after the system has been refilled with refrigerant. One point to note here is that the fluorine content rate of the system may not be frosted on the surface of the evaporator when the ambient temperature is high, and frost on the surface of the evaporator may occur when the ambient temperature is low.
2) Another phenomenon is that frosting begins after capillary throttling. As time goes by, part of the surface of the evaporator is severely frosted, and most of the surface of the evaporator has no condensation. This phenomenon will affect the evaporator of the refrigeration system. It is the performance of insufficient liquid supply. For the entire refrigeration system of a household air conditioner, it may be that the system is leaking or the throttling system is half blocked. Distinguish whether the system is leaky or the throttling system is half blocked:
A. The condenser outlet temperature is high, the current is large, and the evaporator inlet is partly frosted without cooling, and most of the throttling system has a half-block phenomenon. The filter in front of the capillary inlet of the fault location is dirty or the connecting liquid pipe (thin pipe) inside and outside is squashed to form a secondary throttling.
B. The air outlet temperature of the condenser is not high, the current is small, and there is some frost at the inlet of the evaporator, which is not cooling. Most of the refrigeration system pipelines have leaks. Faulty parts of the system pipelines, welding points, interface sockets, valve cores, bonnets, especially the oily parts of the system pipelines. There should be a system capability protection function in the household air conditioner control system. In refrigeration mode, after the compressor runs continuously for 30 minutes, the indoor evaporator coil temperature ≥ 25℃ (some manufacturers use indoor ambient temperature-indoor coil temperature ≤ 4℃), stop the compressor, external fan, and indoor fan Run at the set wind speed. Access protection generally needs to be powered off to exit. Some control systems do not have the ability to protect, and compressor overheat protection may occur when the compressor is running continuously.
3. The evaporator freezes
The entire evaporator freezes because the refrigerant in the evaporator is vaporizing and absorbing heat! Did not get more calories! Just reduce the temperature in the limited space on the outer wall of the copper pipe to below 0 degrees! That is, after the temperature of the cooling medium (air) is lower than the dew point temperature, dewdrops will form on the outer wall of the evaporator! The temperature dropped below 0 degrees! Cause icing!
Why the temperature is below 0 degrees! It is because the amount of treated air on the outer surface of the evaporator is small! So the heat transfer is more sufficient! Therefore, the first two analyses of the owner are all around why the air volume is not enough to discuss! As for the third point: if the evaporator outlet freezes and the return air superheat is reduced! It is possible that there is too much refrigerant! Because one of the necessary conditions for the evaporator to freeze is that the evaporation temperature must be below 0 degrees! And more refrigerant will cause the evaporation temperature to rise!
Add an impossible factor: the enthalpy value of the air entering the evaporator is small! That is, the inlet air temperature is low or the humidity is low! In addition, the evaporator manufacturing process does not use hydrophilic treatment! As a result, the condensed water cannot leave the evaporator smoothly! The heat exchange time is too long!
1. Less refrigerant.
In the absence of refrigerant, the pressure in the system will decrease accordingly, and the decrease in pressure leads to a decrease in the evaporation temperature of the refrigerant, usually below zero degrees Celsius, which causes the water in the air to directly condense into frost. , Instead of the normal water state, at the same time, in this case, the temperature sensor of the coil of the split air conditioner indoor unit (detecting the temperature of the indoor evaporator coil) can also detect that the coil has a certain temperature drop (if not, the air conditioner (Protective machine). In this case, the split air conditioner indoor unit will freeze, and the process should be to turn on-the high-pressure pipe of the external unit is frosted-the entrance of the internal unit evaporator is frosted-the internal unit is frozen Ice-ice cubes are blown out from the tuyere (in severe cases)-the internal fan is stuck (in severe cases).
2, the evaporator is dirty.
When the internal unit evaporator is very dirty, the air volume of the internal unit will be severely reduced, so that the heat needed to absorb the refrigerant when the internal unit evaporates cannot be replenished from the indoor hot air. Under the circumstances, the evaporating temperature change is not well understood, and I look forward to someone to add), at this time, the internal machine evaporator will slowly start from condensation to icing. And the process should be booting-the wind is small (the air outlet is effective, but the indoor temperature can't drop, and the air outlet sometimes has misty water vapor blowing out. This phenomenon usually occurs in places with poor operating environment, such as bars , Karaoke, barber shop (hair blocking) restaurant, etc.
3. The fan speed is slow.
The situation is very similar to that of the dirty evaporator, but the operating environment is good when actually observed, the evaporator is clean, and the human body feels that the wind speed is low.
4. The continuous operation time of the air conditioner is too long.
This situation is especially common in some enterprises and institutions, but it mostly occurs in larger cabinet-type internal machines. This situation usually does not occur in small split hang-ups (estimated to be related to low cooling capacity). In larger ones, Especially for 5P air conditioners, they will freeze after a long time of operation, but the freezing part is different from the above situations. The freezing part is generally near the end of the steamer, especially in the return pipe of the outdoor unit. (Low pressure, inhalation), sometimes ice will form very thick and thick. However, this state does not affect its cooling effect.
5. The indoor humidity is too high and the running time is too long.
is similar to the previous situation, but it mostly occurs on the split hanger, especially in some hotel kitchens, cold dishes, etc., which require long-term operation and the environment is humid.
6. The copper pipes connecting the internal and external machines are folded flat.
This kind of situation also happens frequently, and its manifestation is mostly frost or icing from the collapsed place (longer running time is icing), explore the reason. It should be that the refrigerant has undergone secondary throttling at the place where it flows through the flattening, and it has evaporated unexpectedly at the place of throttling, and most of the flattened places cannot exchange heat with the outside air, which leads to The temperature at the fold becomes lower and lower, and eventually freezes.
