Solar Differential Control

 

Differential thermostatic control is the best way to insure a net heat gain from the sun. Some controllers not only regulate heat flow but they also monitor collector and storage temperatures. Some controllers use multiple relays that control pumps and electronic valves� AND some controllers use separate controls for both the differential on and differential off settings. All of these things are fine� BUT remember the most important job of any solar controller involves the activation of a pump when heat is available for collection. For this reason I have developed a rugged basic differential controllers that respond to solar heat availability. 

Conventional on demand heaters rely on the convenience of fossil fuel energy concentrates. Only one temperature sensor is needed to activate the combustion process within a furnace. Solar heating systems are a bit more complicated. They rely on the intermittent nature of sunlight and two temperature sensors.

The solar heat available for collection is the driving force behind the differential controller. Metering the actual collector and storage temperatures can be interesting but it�s not an essential part of the heat collection process.

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The AC/DC Differential Controller is sometimes called a solar controller because it controls the heat flow from a solar collector. It will turn an AC or DC pump on and off to maximize solar heat gain from a solar collector with a minimum expenditure of electrical power. An AC pump may be regulated with this controller by using a tiny 12 VDC wall transformer instead of a PV power supply for the controller. A simple jumper wire between terminal 2 and 3 changes the AC pump differential controller into a DC pump differential controller so the AC/DC controller can be used to drive either an AC or DC pumps... 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. A differential potentiometer is used to adjust the temperature at which the pump turns off.

 




 














This is a basic differential controller with most of the components enclosed. There are two indicator lamps. One turns on when the pump is activated and the other one glows in proportion to the heat that's available.

Pins 1 and 2 are used to connect the relay to the pump. Pins 3 and 4 are used to connect either a PV supply or a Wall Wart 12VDC supply. The last three pins are used to connect thermistor probes to the enclosed differential controller. 

Remember the main function of a differential controller involves the regulation of a circulator pump based on the temperature difference between the heat collector area and the heat storage area. Heat is monitored with a single LED that glows in proportion to that heat availability.









.This Basic Differential Controller is identical to the one above in every way except that it's not enclosed. It's available as a kit for $65 and it comes fully assembled with a set of probes for $85. 

The relay can handle up to 300 watts of power and it may be used to regulate either AC or DC pumps. 

The differential pot adjustment is used to strike a balance between heat gain and energy conservation.

Polarity protection is also included incase the user mistakenly reverses the power supply.

This is a tough little differential controller designed to simplify the the hook up connections as well as the differential settings.

I also have a few controller kits left that only use one LED to indicate when the pump is on





     




 

     Basic Differential Controller Kit  + probes    FREE SHIPPING...........................................$65

 

    Basic Differential Controller assembled + probes...FREE SHIPPING...............................$85

    Differential Thermostat with bar graph + probes...........................................................$125

     Differential Thermostat with one monitor + probes.........................................................$125

     Differential Thermostat with two monitors + probes......................................................$150

    Temperature Monitoring Station....................................................................................$75

    Fahrenheit Temperature Probes.....................................................................................$10

    Thermistor Temperature Probes....................................................................................$10

    DC 9 volt Wall Adapter....................................................................................................$10


 

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