Large greenhouse exhaust fan automatic control circuit

Circuit working principle: In the figure, A and B are XMTD-2002 0~150 qc
digital temperature display regulator. When working, close the switch sw. and SW2, turn on
the AC220 V power supply, then set the numerical control DIP switch of instrument
A to the required lower limit temperature value (assumed to be 26°C), and set the numerical control temperature setting DIP switch of instrument B to the
upper limit setting. at a certain temperature value (assumed to be 28°C). When the temperature in the greenhouse or greenhouse
reaches the upper limit temperature value (28°C), the relay switching contacts "total" and "high" of the digital temperature control instrument B
are connected, and the relay K2 is energized, attracts and self-locks, and its contact
K2:, K2 is closed, the motor M starts to run, and the electric fan exhaust cools down; when the temperature
drops to the lower limit set value (26°C),
    the circuit working principle of the conversion relay of the digital temperature control instrument A: In the figure, A and B are XMTD-2002 type 0~150 qc
digital temperature display regulator. When working, close the switch sw. and SW2, turn on
the AC220 V power supply, then set the numerical control DIP switch of instrument A to the required lower limit temperature
value (assumed to be 26°C), and set the numerical control temperature setting DIP switch of instrument B to the
upper limit setting. at a certain temperature value (assumed to be 28°C). When the temperature in the greenhouse or greenhouse
reaches the upper limit temperature value (28°C), the relay switching contacts "total" and "high" of the digital temperature control instrument B
are connected, and the relay K2 is energized, attracts and self-locks, and its contact
K2:, K2 is closed, the motor M starts to run, and the electric fan exhaust cools down; when the temperature
drops to the lower limit setting value (26°C), the conversion relay of the digital temperature control instrument A