Choosing a Controller
Differential thermostatic controllers are also called differential solar controllers because they control pumps and fans that harvest heat from sunlight. Choosing the right controller for a solar thermal project is an important consideration since there are so many to choose from. For the last 30 years a popular controller has been the GL30 I have used them in the past, but I now make my own controllers that are easier to use for both AC and DC pump applications. Since price is an important consideration in today's economy I decided to list my controllers by price. For more information about them click on the illustrations.
The AC/DC Differential Controller will turn an AC or DC pump on and off to maximize solar heat gain from a solar collector just like all the other controllers... EXCEPT this controller is also capable of simultaneously monitoring the temperature in both the collector and the heat storage tank. An AC pump may be regulated with this controller by using a tiny 12 VDC wall transformer to power the controller. If the controller is used to drive a DC pump with PV power the PV power may be used directly to power the controller.. It's rugged and dependable and it consumes less than one watt per hour yet it can drive pumps that consume up to 300 Watts per hour.. Two temperature monitors continuously monitor and display both collector and storage temperatures. The differential potentiometer is used to adjust the temperature at which the pump turns off. The differential on temperature is set at 15* F.