Variable flow system at the end of the device (such as fan coil, air conditioner box combination, air handler, etc.) plus electric control valve, the indoor temperature controller to adjust the opening of the electric valve, from the main regulation of the flow through the coil, To ensure that the indoor temperature fluctuations in the allowable range. The change of the system flow is realized by adding the frequency converter on the pump to adjust the speed. At the same time, we must note that the valve opening changes, and can not guarantee the flow of change in accordance with the requirements of the allocation, so there must be appropriate control equipment to make the system more efficient operation. In variable flow operation of the system, the control device to solve three problems. 1. Balance the system cold source side of the loop; so that the water flow through the chiller unit is fixed. 2. Balance the system side of the transmission ring; to ensure that all load cases, control valves and end devices to meet the actual requirements of the design flow. 3. Balance control loop; ensure that the control valve is operating under good working conditions. In order to improve the control accuracy of the system, to achieve stable operation of the system. Must meet the following requirements: 1. All control devices have Kvs values ​​calculated by the system designer. 2. All pumps should provide accurate pump head. 3. The pressure drop across all end devices meets the designer's requirements. In practical applications only in the standard model selection of control valves, pumps and end devices. Control Valve: Kvs values ​​for most manufacturer control valves, each Kvs value about 60% higher than the previous file, so it is unlikely to choose exactly the required Kvs value. Pump: Depending on the model, the flow rate of the pump for selection may differ from the requirement by 10 to 40%. In order to ensure adequate flow, the pump is usually used more than 10% higher than the requirement and sometimes up to 25%. Fan Coil and Other End Devices: These devices are also available only for market availability. In fact, no one is going to choose a smaller fan coil and end device because of the risk of under-flow. In short, in order to avoid excessive traffic, improve system stability. The application of self-operated pressure control valve can easily limit the maximum flow to achieve the design flow. At the end of the electric control valve, although after careful calculation, you will find the required Kvs value of the control valve is not found in the market, the results of most of the control valve is too large. In many cases, the control valve should be fully open. For example: in the start-up process; a major fluctuations; heating supply water temperature is too low (refrigeration supply water temperature is too high); temperature control device is the maximum or minimum; or fan coil is too small. Under these conditions, overcurrent will occur in some circuits and undercurrent in other circuits when there is no balance in equipment control. Fluid circulation heating or cooling systems control the flow of the system through rigorous and precise control of balancing valves to provide adequate heating or cooling capacity to all sections of the building with optimal efficiency. And reduce energy consumption, so that the entire building to get a comfortable uniform temperature, creating a comfortable indoor environment. Balance valve in the air-conditioning system plays a balance of the resistance of the loop, constant and regulate the flow of the role, which promotes the system to run at the most economical flow to ensure that air-conditioning terminal equipment to obtain satisfactory output. Therefore, it is an energy-saving component that can improve the transmission efficiency of air-conditioning water system. The primary function of the balancing valve is to ensure that the system does operate according to the technical parameters, and the designer's original intention. During the balanced commissioning, some threats to system functions can be detected and eliminated: Incorrect balancing calculations implemented, pure installation errors such as wrong check valves or blocked filters, excessive pump head, etc. HVAC Online Find problems immediately, find the root cause and take corrective action during the balancing process to ensure that the system offers the best possible comfort with the lowest possible energy costs.