Some netizens said that the compressor of the chiller was frozen! What's going on here? What to do with it?
The compressor return air inlet frosting
The frosting of the compressor return air port indicates that the compressor return air temperature is too low. So what will cause this situation?
It is known that if the volume and pressure of the same quality of the refrigerant change, the temperature will have a different performance. That is to say, if liquid coolant absorbs more heat, then the coolant with the same mass will show high pressure, temperature and volume; if there is less heat absorption, the pressure, temperature and volume will be low.
So in other words, if the compressor return air temperature is low, it will generally show the low return air pressure and the same volume of high refrigerant. The root cause of this situation is that the refrigerant flowing through the evaporator cannot fully absorb the heat required to expand itself to the predetermined pressure temperature value, resulting in low temperature and pressure volume values of the return gas.
There are two reasons cause this temperature:
- The throttle valve's liquid coolant supply is normal but the evaporator can't absorb heat and supply the coolant expansion normally.
- The evaporator's heat absorption works normally, but there are too much throttle valve refrigerant supply. In other words, it has excessive refrigerant flow, which is commonly understood as too much fluorine, means too much fluorine will also cause low pressure.
The lack of fluorine results in the frosting of the compressor
- As the extremely low flow of the refrigerant, will make that the refrigerant begin to expand from the first expansion space after it flows out of the rear end of the throttle valve. Most of the frost on the drain head at the back end of the expansion valve we seen is often caused by the lack of fluorine or the insufficient flow rate of the expansion valve. Too little coolant expansion will not be used to the entire area of the evaporator, will form a low temperature in the local evaporator. In some regions, the too low temperature is due to the rapid expansion of the low refrigerant quantity, that will result in the evaporator frosting phenomenon. After the partial frost formation, the heat transfer in this area is low due to the formation of heat insulation layer on the surface of the evaporator, the expansion of the refrigerant will be transferred to other areas, gradually occur the entire evaporator frost or ice phenomenon. The entire evaporator forms an insulating layer, and the expansion then spreads to the compressor return pipe leading to the compressor return gas frost.
- Due to the low refrigerant volume, low evaporating pressure of evaporator leads to low evaporator temperature, which will also gradually lead to evaporator condensation forming heat insulation layer and transfer expansion point to compressor return air, leading to compressor return air frost. The above two points will show the evaporator frosting before compressor returns air frosting.
Actually most cases for frost phenomenon,we just need to adjust the hot gas bypass valve. The specific method is to open the rear end cap of the hot air bypass valve, and then use the no. 8 hexagon wrench to clockwise rotate the inside adjustment nut. The adjustment process should not be too fast. Generally, it will be paused after a half turn, and the system will run for a period of time before deciding whether to continue the adjustment. After the operation is stable and the frosting phenomenon disappears, screw the end cover tightly.
Cylinder head frosting
Always caused by large amounts of wet steam or refrigerant sucked into the compressor (crankcase frosting in serious cases). The main causes of this situation are:
- The thermal expansion valve is opened too wide, the temperature sensor is installed incorrectly or is fixed loose, so that the temperature is too high and the valve core is unnormally opened.
The thermal expansion valve takes the degree of superheat at the evaporator outlet as the feedback signal, which produces the deviation signal after comparing with the given superheat value to adjust the direct acting proportional regulator of the refrigerant flows into the evaporator, which integrates the transmitter, regulator and actuator.
When the parameters measured by the transmitter deviate from the given value, the physical quantity of the transmitter changes, and sufficient energy is generated to directly drive the action of the actuator. The position change of the actuator is proportional to the parameter being tuned.
Thermal expansion valve can be divided into internal balance thermal expansion valve and external balance thermal expansion valve according to the different balance mode. The liquid coolant evaporates and absorbs heat in the evaporator. When it flows to the outlet of the evaporator, it has completely vaporized and has a certain degree of superheat. The thermodynamic expansion valve's temperature tube is close to the evaporator outlet pipe and feels the temperature of the evaporator outlet. If the liquid filled in the temperature bulb is the same as the coolant, the liquid pressure above the thermal expansion valve diaphragm is greater than the liquid pressure below the diaphragm, and the higher the temperature of the evaporator outlet is , which is also can be said the higher the superheat, the higher liquid pressure above the diaphragm is.
This pressure difference is balanced by the tension between the stem and the adjusting spring below the diaphragm. If change or adjust the spring tension can change the upward force of the pushing rod, further to change the opening degree of the needle valve. Obviously, the evaporator superheat level will also lead to changes of the opening of the needle valve. When the regulating spring is adjusted in a certain position, the expansion valve will automatically change the pin valve opening according to the temperature of the evaporator outlet, so that the superheat degree of the evaporator outlet can be kept at a certain value.
The opening of the thermal expansion valve is over-regulated, the temperature sensor package is installed incorrectly or is fixed loose, so the temperature is too high and the valve core is unnormally opened. This can make a lot of wet steam suction compressor to cause the cylinder head frosting. The thermal expansion valve is used to adjust the superheat when working with the evaporator.
If the evaporator outlet superheat degree is too large, the overheating section at the back of the evaporator is too long, the refrigerating capacity will be significantly reduced.
But if the superheat at the outlet is too small, it may cause the compressor liquid hammer or even frost on the cylinder head. Generally, expansion valve should adjust the evaporator outlet superheat degree to 3℃-8℃.
- When the feed flow solenoid valve is leaking or stops, the expansion valve is not closed tightly, resulting in a large amount of refrigerant liquid in the evaporator before starting. Temperature relay is used to combine with solenoid valve to control temperature of storage.
The temperature sensing package of the temperature relay is placed in the cold storage. When the temperature of the cold storage is higher than the setting value limit, the contact point of the temperature relay is connected, the electromagnetic valve coil is energized, the valve is opened, and the refrigerant enters the evaporator for cooling. When the temperature is below the lower limit of the set value, the temperature relay contacts are disconnected, the solenoid coil current is cut off, the solenoid closes, and the refrigerant stops entering the evaporator, thus the temperature can keep in the desired range.
- The suction stop valve opened too large or open large too early when starting the compressor.
- When there are too many refrigerants in the system, the liquid level in the condenser is high, and the heat transfer area of condensation is reduced, which increases the condensation pressure.
That is to say, the pressure before the expansion valve increases, and the cooling dose flowing into the evaporator increases. The liquid refrigerant cannot completely evaporate in the evaporator, so the compressor sucks in wet steam, the cylinder head is cold or even frosting, and may cause "liquid hammer", and the evaporation pressure will also on the high side.
The use rate of air conditioning increases in winter because of cold weather. However, various problems may occur when the air conditioning is used for a long time. A common cause of non - heating or poor heating effect of air conditioning in winter is lack of fluorine.
How to detect if the air conditioner is deficient in fluorine?
The most direct way to determine the lack of fluorine in winter is to see if the air conditioner does not produce heat, wind, or too small wind. The most direct method is to test the heating pressure of the air conditioner with the pressure gauge. Under normal heating, the working pressure is 1.6~ 2.1Mpa. If it is lower than this standard, it is fluorine deficiency.
For professionals, if they want to test the deficient in fluorine, turn on the air conditioner to start cooling, and let the air conditioner compressor run continuously for more than 15 minutes. If the refrigeration system is deficient in fluorine, the following phenomenon will occur:
- The return air pipe is dry, and there is no obvious cooling sensation when touch by hand ,or no dew condensation phenomenon.
- High pressure tube frosting. The reason is lack of fluorine, resulting in pressure inside the tube and boiling point decrease, make the valve temperature below freezing point.
- Open indoor machine face plate, take off screen, you can discover evaporator only have few frost or condensation. This is the result of a shortage of refrigerant and a corresponding reduction in cooling area.
- Outdoor air exhaust has no thermal sensation. The lack of refrigerant leads to the reduction of condensation pressure and temperature.
- Drain hoses drain very little or no water at all
- If the high pressure tube is frosted, it indicates serious fluorine deficiency, and if only the air tube valve is frosted, that means slight fluorine deficiency or too low ambient temperature.
Operation method of air conditioning fluoridation adding
Turn on the air conditioner and adjust it to the state of refrigeration, so that the fluorine can be added through the three-way valve.;
Because the winter is cold, air conditioning room temperature is likely to be lower than the set temperature, this time air conditioning will shut down;
How to make air conditioning run again?
Use the method of manual heating to raise the temperature of the heat detector!
- Cover the air conditioner heat detector with a hot towel to raise the temperature of the air conditioner heat detector;
- Put it in the cup with warm water;
- Use artificial palm to hold temperature probe and raise temperature
In the state of heating, you can unplug the four-way valve of the external machine. In this way, the compressor of the air conditioner will operate in the state of refrigeration and the refrigerant can be added.
The method of adding refrigerant is the same as that of refrigeration condition. Here is a brief description:
- Open the small nut of the external machine connecting with triangle valve(not the one with a hexagonal screw hole in the side);
- Use professional snow hose pipe to connect with(the yellow tube is connected with a refrigerant tank; The blue pipe is connected with the low pressure thick pipe; The red one is connected with a high-pressure thin pipe. )
- Connect the refueling hose to the refrigerant steel cylinder valve,connect one end to the refueling valve (with pressure gauge), turn on the gauge, connect the another end of refueling hose to the thick pipe valve refueling nozzle on the air conditioner outdoor machine, loosen the joint of the steel cylinder valve and release some air (exhaust air) before tightening.
Basis and method for accurately add fluorine
- Pressure method
According to the indoor temperature, estimate the condensation temperature of system (such as indoor temperature 20 ℃ around, condensation temperature we estimate about 40-50 ℃), the high pressure at this time should be:
- Current method:
Measure the running current of the compressor with the clamp meter. If it is close to the rated running current, the refrigerant is sufficient. If it is less than the rated current, the refrigerant needs to be continued to fill.
- Fluoridize by weight and quantity:
The most accurate method is: quantitative add fluorine, according to the nameplate on the machine. Need how many kilograms we add how many kilograms.
- Experience approach：
Determine whether the refrigerant is sufficient by air pipe and liquid pipe
During the process of fluoridation, touch the temperature of the two tubes from time to time. If the thin tube is hot, and the thick tube is a little hot for hand it’s OK.
Refrigerant add wrongly has safe hidden troubles
There are many kinds of freon refrigerants, such as R22, R410A, R320, R209, and R134. Different refrigerant has different characters, and they cannot be mixed. If adding different kinds of freon, the refrigerant used in the compressor will deteriorate, or the system is blocked, resulting in not refrigeration or poor refrigeration effect. If a false freon is added, there is also the possibility that the pressure is too high, causing the connection pipe to explode and so on.
The purpose of the filter is to collect solid impurities in the cooling system and lubricating oil, to prevent blocking of system, capillary or expansion valve, and ensure that the chiller's piping system is unobstructed.
The special drying filter for water chiller is mainly composed of desiccant and metal mesh. The outer shell is made of copper tube with two different meridians at both ends. At the inlet there is a thick metal mesh and at the outlet is a thin metal mesh. The internal desiccant is used to absorb the moisture in the refrigerant, to ensure the capillary and expansion valve is unblocked, and to ensure the normal operation of the industrial cold water refrigerating system.
No matter the air-cooled water chiller, water-cooled water chiller or screw type water chiller, the impurities in water or lubricating oil shall be effectively filtered by drying filter. If the time of using the filter is too long, and there is no regular cleaning and replacement,it will result in dirty and plugging phenomenon, and then affect the cooling effect of the chiller. Its failure mainly manifest as that the outer shell of the filter turns from warm to cold or frost condensation, which will lead to insufficient liquid supply of the evaporator.
If there’s no temperature difference, we can know that the filter is completely clogged up. It is the same as the failure phenomenon when the capillary tube is completely blocked. If the drying filter and filter are slightly blocked or completely blocked, the main performance is that the refrigeration cycle condenser has no hot air discharge, the air outlet becomes normal temperature, and the running of the compressor is tedious. If the air-cooled chiller or the water-cooled chiller or the screw chiller is stopped, disconnect the capillaries/connection pipes attached to the dryer. Sufficient gas can be discharged at the side of the capillaries/connection pipes but the dryer has no gas discharge, that is, the dryer is blocked. Otherwise. the capillary or connection pipe side is blocked.
If the dry filter or filters are blocked, a new filter should be replaced. And vacuumize according to the nameplate on the water chiller to fill with predetermined amount of refrigerant to do machine test and observation, ensure the unit refrigeration system operate normally. Since most users are directly cooling the tap water and the unit operates 24 hours a day, the operator should check the filter regularly to ensure the cold water chillers cooling fast and operation stable.