To keep the pump from running when the ground is frozen or while it's raining this sensor will do that. The sensor and adapter must be ordered when the unit is being built. It cannot be added on after the initial purchase.
Price includes installation of the wiring harness and the Rain & Freeze Sensor.
TurboRain Accessory, Soil Sensor for the TurboRain Automatic
Freeze / Rain - sensor keeps the pump from running when it is raining or temps below freezing