Enclosed Differential Controller

 This rugged little differential controller is easy to install and easy to adjust with a single adjustment potentiometer that integrates both the differential on and differential off setting for the pump. This controller can power pumps that require less than 300 Watts of power yet the basic controller itself consumes less than 0.1 Watt of power per hour. The pump indicator lamp comes on when the pump is activated and the heat indicator lamp changes intensity in proportion the the temperature difference between the solar collector and solar heat storage tank. The differential adjustment is made through a hole in the top cover plate. 

A single differential pot adjustment allows the user to easily strike a balance between heat gain and energy conservation. Heat transfer only takes place when there’s a difference in temperature. As the temperature differential increases the heat transfer rate also increases. Sooo we’re left with the question...  What is the best differential adjustment for a system?



As you can see the connections and the adjustments have been greatly simplified. As a matter of fact the pump connections to a PV system with a battery back up may be further simplified by placing a jumper between J1 pin 2 and J1 pin 3. If you are using this controller to drive an AC pump the connections illustrated are the ones you will use. All you'll need to power the controller is a small 12VDC wall wart DC adapter. 

The most important thing to remember when connecting the DC power supply is the polarity. The positive terminal of the power supply connects with J1pin 3... and as you can see the Collector probe and the Storage probe have a common junction at J2 pin 2.  BUT how is the differential adjusted?

This is where the heat indicator lamp comes to the rescue. Rather than calculating the differential with temperature monitors you’ll be able estimate it directly by observing the intensity of the heat indicator lamp.  When the heat indicator lamp starts to glow heat is available for collection and the pump indicator might be activated. The point at which the pump is activated or deactivated is controlled by the user, with the differential adjustment.  It's as simple as that...

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