Notes on the use of parallel chiller-refrigeration technology-shanghai huizhuo refrigeration equipme

2020-02-11 17:19

The system has matching parameters and the basic performance requirements are the same as those of the stand-alone system. In parallel systems, pay particular attention to the reliability check of the system's oil return, and pay more attention when it is connected multiple times.


Two points that must be paid attention to in parallel system:


Air balance between compressors used by HYZOE chiller in parallel system: It is necessary to ensure the suction pressure difference between parallel compressors used by HYZOE chiller △ P <0.2-0.3 kgf / cm2.



The advantages of HYZOE chiller when using compressors in parallel:


1. Effective capacity control can be performed by using compressors in the HYZOE chiller in the on / off group.


2, improve reliability, compared to a single HYZOE chiller using the compressor to stop the number of times less.


3. The starting load is reduced. The starting time of each HYZOE chiller using a compressor can be separated by a time delay method.


4, standby, if one of the HYZOE chiller used compressor is damaged, there is still some capacity.



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The oil balance between the compressors used by HYZOE chiller: the oil return process must not cause the phenomenon of stagnation lubricating oil to accumulate in one or several HYZOE chiller while the other HYZOE chiller uses the compressor. Filter should be set at the oil return port. Set temperature and pressure protection switches. Keeping the oil level is the most important issue.


1.1, keep the oil level


When using compressors of HYZOE chiller in parallel, the oil level of the compressor used by the HYZOE chiller and the oil return of the system will cause a long-term operation to cause the oil level of the compressor used by the HYZOE chiller to change (the oil level on one side will decrease , The oil level rises on one side). As shown below:


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When connecting compressors A and B of the same model HYZOE chiller, if HYZOE chiller uses compressor A with a large amount of oil and a small amount of oil return from the system, the oil level of A will continue to drop, and eventually there will be almost no oil, resulting in Bearing failure due to poor lubrication. HYZOE chiller uses a small amount of oil for compressor B, and when the system returns a large amount of oil, the oil level of B will continue to rise. Finally, the motor rotor is almost immersed in the oil, causing the input power to increase and the temperature of each part to rise. .



The phenomenon of oil level change when the parallel HYZOE chiller is operating with a compressor (= the amount of oil is biased to the other HYZOE chiller is using a compressor) is called [partial oil].



Tip: In the worst case, there will be no oil in the compressor of the other HYZOE chiller in tens of minutes, which will cause serious damage to the compressor of the HYZOE chiller.


1.2, keep the oil level


Try to make every HYZOE chiller use a compressor with equal oil load and equal oil return. The suction line can extend the time of oil-free state, but these measures can not completely eliminate the use of compressors in HYZOE chiller. Partial oil.



Design a system that is not prone to oil misalignment. After oil misalignment occurs, you must adopt a design that restores the oil volume of the compressor used by the HYZOE chiller to the original state.


1.3, keep the oil level


The countermeasures to avoid oil segregation are:


① The HYZOE chiller of the same model and capacity is connected by a compressor, so as to equalize the oil load / return oil amount as much as possible.


② The HYZOE chiller uses the compressor's exhaust pipe to the confluence section, and the branch of the suction pipe to the HYZOE chiller uses the compressor. Each system component must use the same shape. Two HYZOE chiller use compression The machine should try to maintain an equal flow of refrigerant + oil.


③ In order to further suppress the oiling amount of the system, an oil separator is designed on the exhaust pipe, and it is best to take the oil that has been separated from the two HYZOE chillers and use the compressor to return to the system.



The above three countermeasures ① and ② are necessary, and ③ are necessary when necessary. The effect is very obvious)


1.4, keep the oil level


After a certain period of time, run the oil equalization operation:


The typical oil-balance operation method is to turn on and off the HYZOE chiller on both sides of the compressor for a short time by using the following sequence (Note 1), and correct the oil deviation, as shown below:



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① Stop a HYZOE chiller using a compressor (OFF) for 2 minutes: The oil will move to the HYZOE chiller using a compressor through the oil equalizing pipe.



② Contrast ① ON-OFF relationship for 2 minutes: The oil will move to the HYZOE chiller using the compressor through the oil equalizing pipe.



③ Return to the original operating state (both sides return to the operating state (ON)).



Verify the oil level balance of each HYZOE chiller using compressor in various working conditions (long piping, high drop, low temperature heating, maximum cooling, etc.), and ensure that the oil level in each HYZOE chiller using compressor is above 400ml ( The oil level observed through the oil level mirror is above 1/3 mirror level).


   


The current protection value of the compressor used in the conventional parallel HYZOE chiller is set to 1.2 to 1.4 times the rated current value.


HYZOE chiller uses compressor installation: It is required to be installed on the same horizontal plane as much as possible; HYZOE chiller uses compressor center distance selection to facilitate the loading and unloading of HYZOE chiller. The piping layout is as symmetrical as possible, and a gas-liquid-liquid separator is provided.



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Oil separator: one compressor can be used for each HYZOE chiller, or it can be set on the exhaust manifold.


Gas-liquid separators generally have two structures:


"One in, one out" structure: refers to an intake manifold and a manifold, and then the manifold is connected to each parallel HYZOE chiller with a compressor suction pipe using a distributor such as a tee.



The advantages are: the structure of the steam fraction is simple, the manufacturing is convenient, and the versatility is good.



The disadvantage is that it needs to use a distributor such as a tee to connect with the compressor suction pipe of each HYZOE chiller. The split effect of the tee directly affects the suction and oil return of the compressor used by each HYZOE chiller, and the oil return hole of the gas component It is difficult to take into account the full opening and the oil return during the minimum operation.






"One input, multiple output" structure: refers to one intake manifold and multiple exhaust pipes.



The advantage is that each HYZOE chiller uses the compressor to return air more easily, and the size of the oil return hole of each pipe is only responsible for the return of oil to a HYZOE chiller using the compressor. When the HYZOE chiller uses a compressor, the reliability is better.



Disadvantages are: the processing technology is complex, the accuracy requirements are high, the requirements for the size of each hole are consistent, and the installation height of the outlet pipe needs to be strictly controlled and consistent.


The above are the main points of HYZOE engineers sharing with you about the use of the entire system. If you have more information about the normal use of chiller, please contact Shanghai HYZOE Refrigeration Equipment Co., Ltd. We will answer your questions at any time!