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Nanjing Haizhizhou Heating and Cooling Equipment Co., Ltd
The function and selection of buffer water tank for air conditioning heat pump
Date: 2025-10-12Read: 5
1、 The function of buffer water tank
Buffer water tank is an important auxiliary equipment in air conditioning heat pump system, which mainly functions in stabilizing system operation, improving energy efficiency, protecting equipment, and optimizing user experience. The following is the specific function and principle analysis:
1. If a buffer water tank is not used, it will result in frequent start stop of the host. Due to the limited circulating water volume in the loop, the host will reach the design temperature in a very short period of time, and the host will stop working. Then, in a very short period of time, the water temperature will reach the starting conditions of the host, and the host will start again. Frequent starting will greatly reduce the service life of the host and waste electricity. Not only does it require a buffer water tank, but it is also best to have a larger capacity for the water tank.
2. Efficient defrosting with short defrosting time. When used in harsh winter, especially between -3 ℃ and 5 ℃, the frost on the host is very obvious, and the impact of defrosting on indoor temperature is a headache. Because the unit requires the consumption of heat in the pipeline during reverse cooling, if the water volume in the water system is low, the defrosting time will increase and the water temperature in the pipeline will be low, resulting in poor defrosting effect. If a buffer water tank is installed, during the defrosting process, due to the temperature inside the tank, defrosting can be completed in a short period of time with minimal heat consumption, avoiding fluctuations in indoor temperature caused by the defrosting of the main unit. This has a significant impact on stabilizing the system's end effect.
3. It can ensure smooth water flow in the system, complete automatic exhaust, and avoid unit failure. We know that when the water tank is placed in the return system, circulating water enters from the upper part of the tank and is discharged from the lower part. As a result, gas in the water will accumulate in the upper space of the tank, and the pressure in the closed system will automatically force the gas to be discharged from the upper exhaust valve. In this way, the bottom outlet of the buffer tank connected to the water tank's suction port can not only protect the impeller of the water pump, but also ensure that the system is free of gas and the main engine works normally because there is no gas. If there is no buffer water tank, the presence of gas may cause the flow switch of the host to malfunction and high pressure alarm at times.
4. Can make the system's sewage discharge more efficientgoodTo prevent system blockage. There are a large number of impurities in our system, which will slowly accumulate at the bottom of the buffer tank through circulation. When passing through the Y-shaped filter, the water quality of the pump will improve, thereby reducing the cleaning of the Y-shaped filter.
2、 Selection of buffer water tank size
Method 1: Buffer tank capacity=required water volume for system stability - actual water volume of the system.
Firstly, calculate the amount of water required for system stability, denoted as M1, where M1=QT/(C △ T), where Q is the heating capacity of the unit in KW, T is the defrosting time in seconds, C is the specific heat capacity of water, taken as 4.187, and △ T is the maximum allowable decrease in water supply temperature, taken as 3 ℃.
The actual water volume of the system is equal to the water capacity per meter of the underfloor heating pipe multiplied by the total length of the system pipeline. If the end is a radiator, the water capacity of the radiator should also be taken into account.
Taking a certain brand of machine in Beijing as an example, with an area of 150 square meters and equipped with a 7P low-temperature heat pump heating machine, the heating capacity is 20KW. Therefore, the required water volume for the system is 20 × 4 × 60 ÷ (4.187 × 3)=382 (L).
Actual water capacity of the system: Taking the commonly used 20 pipes in the north as an example, the water capacity per meter of 20 pipes is about 0.314L. Based on an area of about 5 meters of pipes, the actual water capacity of the system is about 235L.
So, a buffer water tank with a capacity of 382L-235L=147 (L) is required, and 150L is sufficient for actual installation.
Method 2: If you are new to household heating and don't know how to calculate it, you can use 100L and 150L unified configuration, that is, regardless of the size of the system, the buffer water tank is uniformly equipped with 100L or 150L. These two models are usually available to meet the needs of most projects.