Solar Controllers

Transferring heat from a hotter to a cooler tank in order to equalize the temperature in both tanks and increase total storage capacity is another common use for a differential controller.

Solar thermal systems generally use a special relay called a Differential Controller. As the name implies, this relay activates a pump or pumps when a span (or difference) between two temperatures is achieved. In other words, when the temperature at the solar collector is X degrees hotter than the temperature at the bottom of the solar storage tank, the differential controller activates the necessary pumps and draws that useful heat into the system.

The Differential Controller