The SC4D Solar Controller model comes with updated features and includes new sensor cables, which must be used with the controller provided in the box. The SC3D is now discontinued and has been replaced by the SC4D.
This Solar Controller is micro-processor based and works by sensing the temperature on the roof and the temperature of the pool. This controller is suitable for both integrated and independent systems, and will work with your solar pool heating system whether you have pool heating provisions or not.
The SC4D controller will turn on your solar heating system when there is a 7 degree differential between your pool water temperature and the roof temperature, if the pool temperature is below the set temperature. If the pool temperature rises to the set temperature, or the roof temperature falls to within 2 degrees of the pool water temperature, then the controller will switch off the solar pump and stop the water from heating any further.