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.
This
12 VDC PV solar
powered differential thermostatic controller works in harmony with a photovoltaic power
supply and does not require a battery backup. As long as your pump does not
require more than 20 watts of power and your PV panel can supply at least
twice as much power as the pump needs the PV controller is an ideal
solution to your PV powered solar hot water system.
This
enclosed, differential controller is identical to the basic controller except
the electronic components are enclosed. It's easy to install and easy to adjust with a single
potentiometer that integrates both the differential on and
differential off setting for the pump. Like the other basic controllers the
enclosed controller can regulate AC or DC pumps requiring up to 300 watts of
power. One LED comes on when the pump is activated and the other LED becomes
brighter as more heat becomes available. The differential adjustment
is made through a tiny hole in the top cover plate.
Enclosed
Differential Controller with probes USA shipping only $99
The
Thermostatic
Differential Controller is like other differential controllers that
use thermistors to sense temperature, but these controllers use a bar graph
indicator to display either collector temperature or storage temperature with an
accuracy of +/-5*F.
Differential Thermostat with bar graph + probes..................................$125
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.
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