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HVAC means the field of Heating Ventilation and Air Conditioning. The differential pressure flow switch is designed according to the curve of resistance and flow of HVAC equipment. We know that the heat exchanger, water filter, water pump, valve and other devices of HVAC equipment have their resistance and flow performance curves. By detecting the water pressure difference between the two ends of the device, and comparing with the preset value of the device, the flow can be accurately controlled. Compared with the target paddle type flow switch, the differential pressure flow switch is an accurate flow control mode, which has accurate flow control value.
The differential pressure at the inlet and outlet of the heat exchanger is measured by connecting two copper pipes from the differential pressure type flow switch, which reflects the flow. The installation is very easy, which avoids the potential trouble of unit failure, which caused by inaccurate installation of target paddle water flow switch.
The electric parts and action parts of the differential pressure flow switch are designed with non-metallic materials, which can be used in the liquid as low as - 20 ℃. It can be used as the liquid flow detection in the liquid as low as - 100 ℃, by winding the electric heating wire in the pressure measuring connecting pipe,
In view of many problems of target type flow switch in ice storage unit, we started to replace the original target type flow switch of water chiller with differential pressure type flow switch as early as 1992, including double working condition water chiller , and adjusted the water flow of users, which has received remarkable economic benefits.
The replacement steps are as follows:
We take out the original target type flow switch and seal it with a plug, connect a three-way connector at the position where the inlet and outlet of the heat exchanger are connected with a pressure gauge, and the extra pressure tap is provided to the differential pressure type flow switch. The additional pressure tap at the inlet and outlet of the heat exchanger is respectively connected to the "high" and "low" pressure ports of the differential pressure switch.
In order to be fully responsible for the users, we use portable ultrasonic flowmeter to measure the flow protection value, adjust the set value of differential pressure flow switch to make it reset to 60% of the rated flow, that is, when the flow of water through the heat exchanger is less than 60%, the water flow switch will not reset, avoiding the decline or failure of water pump performance, insufficient opening of field valve or closing of end coil to press When the differential bypass is abnormal, the water flow drops, which leads to the hidden trouble of the main engine failure.
When the water flow suddenly drops to 50% of the rated flow when the main air conditioner is running, the differential pressure water flow switch is immediately protected. The function of precise water flow protection of differential pressure flow switch is incomparable to that of target flow switch.
For the condenser, proper cooling water flow can ensure that the refrigeration system of the air conditioning host works in a better state, and ensure the working efficiency of the unit. When the water flow is too small, not only the condensation pressure increases, but also the refrigeration capacity decreases. In serious cases, the compressor may fail. If the air conditioning unit does not get proper cooling water flow, the compressor will not work, which can fully protect the compressor from failure.
Reset flow can detect whether the flow of the water system meets the design requirements. Correct setting of the reset flow of the differential pressure switch can ensure the water flow required through the heat exchanger. Generally, the reset flow is 60-80% of the rated flow.
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