Our customer has a greenhouse. The greenhouse temperature is controlled by opening and closing the roof vents using a forward and reverse motor. When the temperature rises above the setpoint, the vent actuator motor operates for a programmed ON-time opening the vents 10 degrees.

After a programmed OFF-time, if the temperature is above the high / high setpoint, the vents open in 20 degree increments until the temperature falls below the high setpoint.

If the temperature in the greenhouse falls below the low setpoint, the vents progressively close keeping the greenhouse temperature within required limits.

Note: The relays are programmed in the repeat mode (programmable ON/OFF-time).

Greenhouse Ventilation Controller