In many industrial productions, the establishment of a stable constant temperature dehumidification system is an indispensable important link in the production process. At present, the constant temperature control technology is relatively mature, but to achieve the dehumidification effect under constant temperature conditions, the realization of its control is relatively complicated. Using the NA200 series PLC, we can better control the energy-saving constant temperature dehumidification system.

Hardware Configuration:

The whole system adopts NA200 series PLC and touch screen as the control core of the whole system. The PLC is connected with the host computer to enable the system to achieve remote control and monitoring functions. The temperature and humidity sensor senses the temperature and humidity of the supply air, and controls the temperature and humidity of the dehumidification room through the controller and the actuator.

Control plan:

(1) Temperature control:

Control the refrigerator and electric heating according to the return air temperature. The actual temperature is higher than the set value of the controller, and the refrigerator is turned on. The actual temperature is lower than the set value of the controller, the cold machine is turned on, and the electric heating is turned on.　

(2) Humidity control:

Control the dehumidifier according to the return air humidity. The actual humidity is higher than the set value of the controller, and the dehumidification wheel is on. When the actual humidity is lower than the set value, the dehumidification wheel is closed.

(3) Control of regenerative fan and regenerative electric heating:

Determine the dehumidification effect of the dehumidifier based on the difference between the supply air humidity and the return air humidity. If the humidity difference is small, the dehumidification effect is judged to be good, and the regenerative fan and regenerative electric heating can be started. When the difference is greater than the set value, the regenerative electric heating is turned off, and at the same time, the regenerative fan is turned off for a period of time to remove the residual heat.

(4) Filter detection:Install differential pressure switches on the primary and intermediate effect filters to monitor the dust suction effect of the filter. Determine whether the filter is clogged according to the pressure difference, and alarm on the controller to prompt to take measures.　

(5) Fan status detection:

Monitor the running status of the fan (such as on/off, normal/fault, etc.). Provide corresponding protection measures according to operating conditions. When the fan stops or the fault stops, the controller alarms, prompts the fan to fail, and immediately stops all controlled equipment to protect the air conditioning unit.

(6) Air valve and fan linkage:

When the fan runs, the air valve opens; when the fan stops, the air valve closes.