Abstract
Central air-conditioning system is one of the indispensable supporting facilities in modern large buildings, of which energy consumption is huge, accounting for about 50% of the total power consumption of buildings. In fact, the system runs under full load only a maximum of more than 10 days a year, or even only more than 10 hours. Most of the time, it runs almost 70% under load. Generally speaking, the load of the frozen host in the central air-conditioning system can automatically adjust with the seasonal temperature changing. While, the frozen pumps and cooling pumps matched with the frozen host can not adjust the load automatically. They almost run 100% under load all the time, which causes a great waste of energy. This situation also deteriorates the environment and quality of operation of central air-conditioning.
With the increasing maturity of variable frequency technology, the application of frequency converter, PLC, digital-to-analog conversion module and temperature sensor is widely used. The combination of these devices constitutes a system of temperature closed-loop automatic control, which can adjust the output flows of the pump. It offers a reliable technical condition to energy-saving.
This paper will elaborate from the aspects of indoor parameters setting, status of multi-district, and water circulation system of central air-conditioning to discuss the energy saving facilities and running of the central air-conditioning.The emphases will be put on the energy-saving control system of water circulation in central air-conditioning.The controller of this system is Panasonic PLC,which uses PWM pulse output with frequency conversion control technology to control.This paper gives a detailed introduction of the hardware and software structures of the water cycle energy-saving system. The specific hardware circuit and software flow chart are also given in this paper.
Keywords: central air-conditioning, PLC, transducer, temperature control
