Circulating water pump capacity is too large in our country is a common problem, its capacity often reaches the actual need of 2-4 times, resulting in a serious waste of project investment and operating costs. So what is the real cause? Next, the central air conditioning maintenance Xiaobian to share with you the Suzhou central air conditioning maintenance: chilled water circulation pump failure interpretation.

First, the important role of chilled water circulation pump in air conditioning water system

The chilled water system of the air conditioner uses the circulating pump to transport the chilled water from the refrigeration room to the air conditioning equipment, so as to realize the exchange and transfer of the cold heat of the air conditioner and achieve the purpose of air conditioning. Circulation pump is the link between the refrigeration host and the room with cold equipment, to provide power for the circulation of the water system, is an important part of the air conditioning system.

In the design and operation process, it is often found that the selection of pump is unreasonable, resulting in a non-ideal operation state such as "big horse trolley" or long-term overload operation of the pump. It is particularly important to reduce the unreasonable factors in the selection, design and operation of the pump, reduce the operation energy consumption, and improve the service life of the pump.

As an important part of the air conditioning system, the air conditioning circulating pump accounts for about 15% to 20% of the energy consumption of the entire air conditioning system. The high-power pump can not ignore the temperature rise of the air conditioning frozen water in the circulation process, so how to reduce waste and tap the potential in the cold water circulation pump will have great significance for the energy saving of the HVAC system.

Second, the cause of excessive failure of circulating pump capacity

1, the design cooling load is too large

The design of cooling load is the main basis for selecting equipment, so the correct calculation of building cooling load is very important for the design of the whole air conditioning system. At present, the calculation method of air conditioning load provided in textbooks and design manuals, whether it is to calculate the wall load of the envelope structure, or the load of doors and Windows, the calculation results are for a specific room. However, the equipment capacity of the air conditioning system is determined according to the cooling load of the entire building. Due to the different factors such as the orientation, location, use function and heating source of each room in the building, the time of cooling load in each room is often not the same. Therefore, the value of the building cooling load should be the value of the hourly load superimposed on each room. According to the survey, some designers in our country simply superposition the cooling load of each room when calculating the building cooling load, resulting in the calculation result is much greater than the actual demand load. Therefore, we must pay enough attention to this, so that the design load is more reasonable and correct.

2, the system circulation resistance is large

When calculating the cyclic resistance of the system, due to the lack of experience of the designer, the value of some calculation parameters is too conservative, resulting in the calculated value of the cyclic resistance is too large. What is more, the calculated cyclic resistance is more than twice the actual value by using the estimation method to determine the cyclic resistance in the design stage of the construction drawing. The air conditioning system can only run when it is full of water, and the inlet and outlet of the pump are subject to the same hydrostatic pressure. Therefore, the head of the selected pump can only overcome the resistance of the pipeline system. However, some designers also include the hydrostatic pressure in the circulation resistance, which will of course increase the capacity of the circulation pump.

3. System static pressure problem

The air conditioning system can only run when it is full of water, and the inlet and outlet of the pump are subject to the same hydrostatic pressure. Therefore, the head of the selected pump can only overcome the resistance of the pipeline system. However, some designers also include the hydrostatic pressure in the circulation resistance, which will of course increase the capacity of the circulation pump.

4. System hydraulic balance problem

Because the hydraulic balance calculation of the system is not carefully carried out during the design, and the complete debugging is not carried out according to the requirements after the completion of the project, the hydraulic imbalance of the system is often caused. Some technicians mistakenly believe that the reason for this phenomenon is that the capacity of the circulating pump is too small, and the result is simply to use the method of increasing the pump, which naturally increases the capacity of the pump.