Hitachi PLC Application in Central Air Conditioning Energy Saving System

First, the system consists of:

The central air-conditioning energy-saving system is mainly composed of touch screens, Hitachi inverters, Hitachi PLCs, control instruments, temperature sensors, and other low-voltage protection and control electrical components. The control system adopts advanced industrial automation, measurement and control, frequency conversion and communication network technologies to perform automatic optimization control of the system, effectively reducing energy consumption, reducing labor intensity, increasing economic efficiency and extending the service life of the equipment. The various alarms and protection functions of the equipment are complete, and the safety factor is greatly improved. After the heating (refrigeration) equipment information is collected, displayed, and processed, it is used as the basis for achieving automatic control, in which the control equipment is a drag-and-drop three-control method, namely, one inverter drives three circulating water pumps (one for two), The heating (cooling) pipeline temperature sensor collects data on the temperature of the heating (refrigeration) pipeline and centrally controls the system equipment, and more intuitively displays various operating condition data of the on-site system during operation, which improves the reliability of the system.

Second, the system network structure:

Third, the system achieves:

u touch screen system interface shown in Figure 1:

figure 1

In the system interface, there is a control system and a data display button.

Explanation:

1: Control system button. When the control system button is clicked, the control system interface is entered.

2: The system displays the button. When the system display button is clicked, the data display interface is entered.

u system control interface shown in Figure 2

figure 2

In the main interface, there are four operation indicators, a system start, a system stop, and the button to return to the initial interface.

Explanation:

1: When the 1# circulating pump is in the power frequency operation, the 1# pump power frequency running indicator flashes.

2: When the 1# circulation pump is in frequency conversion operation, the 1# pump variable frequency operation indicator flashes.

3: When the 2# circulating pump is in the power frequency operation, the 2# pump power frequency running indicator flashes.

4: When the 2# circulation pump is in frequency conversion operation, the 2# pump frequency conversion running lamp flashes.

5: When the system control mode selection switch of the control panel of the control cabinet is in the automatic operation mode, the system will automatically start when the system startup button is clicked.

6: When the system control mode selection switch of the control panel of the control cabinet is in the automatic operation mode, the system stops when the system stop button is clicked.

7: Return to the initial interface button. When you click to return to the initial interface button, the system returns to the initial interface.

u data display interface as shown in Figure 3

image 3

In the data display interface, there is a 1# temperature display, a 2# temperature display, a system temperature target setting, and a button to return to the initial interface.

Explanation:

1: The system returns the temperature measurement to set up two temperature sensors, two temperature sensors are mutually redundant.

2:1# temperature display shows 1# temperature sensor measurement.

3:2# Temperature Display Displays the 2# temperature sensor measurement.

4: System temperature target setting. Users can set the operating status of the system to set the optimal return water temperature control target value.

5: Return to the initial interface button. When you click to return to the initial interface button, the system returns to the initial interface.

IV. Conclusion:

The central air-conditioning energy-saving control system has been inspected and used by the Tianjin Armed Police Medical College since its acceptance. The normal operation proves that the entire system is reasonably designed and advanced; the operation is simple; the reliability is high; and it fully meets the requirements of the user and achieves the effect of energy saving.