AC/DC Differential Controller

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. A 12VDC photo-voltaic panel with a battery back up may be used to power a DC pump as well as this AC/DC differential controller.

An AC pump may also be regulated with this controller by using a tiny 12 VDC wall transformer instead of a PV power supply. 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 more than 600 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 shuts off. 

 PV Systems with 12 Volt Battery :
Another feature of the AC/DC controller is battery protection used with PV power supplies. If the differential is set too low or the sunlight is insufficient to keep a battery charged the controller shuts down before the battery is depleted.  The controller will shut down when the voltage drops below 8 volts and will not come back on until  the battery has been sufficiently recharged (around 14 volts). The differential off adjustment allows the user to adjust the maximum heat gain with minimum power requirements. The best adjustment will depend on the size of the PV power supply and the demands made on the pump. Closed loop systems generally require less power than open loop systems. A PV panel with a maximum power output between 10 and 100 watts is good for most applications. I am using a 50 watt PV panel with my MTD solar heating system.

WITHOUT A BATTERY BUFFER between a PV panel and a pump the supply voltage could fluctuate between 0 volts and 18 volts. This extreme voltage fluctuation puts undue stress on most DC pumps. Some people think that a PV panel alone is sufficient to regulate pump speed with sunlight intensity. HOWEVER, total dependence on sunlight intensity for regulation is not a good idea. Scattered clouds can turn off a pump before heat is collected from a collector.  Bright sunlight in winter is another consideration. Without a differential controller bright sunlight turns on a pump at full speed before the collector has had time to warm up. This bright/cold condition could circulate cold water through a heat storage system and diminishes net heat gain. This is why differential controllers should be used with PV power supplies with battery back up systems. Since battery protection is built into the circuit expensive deep cycle batteries are not required.

If you are using a 12VDC photo-voltaic power supply with a battery back up you can use the same 12VDC supply to power your pump as you use to power the differential controller. Battery protection is built into the circuit so if the supply voltage drops below 8 VDC the controller will be deactivated to prevent battery damage. After the battery has recharged up to 14 VDC the pump will be allowed to come back on if the collector temp is 10* F above the storage temp.
If you are powering an AC pump you will need a 9 VDC wall transformer to power the controller.

 

 

AC/DC Differential Controller with two monitors and two temperature probes   USA only                   $150

AC/DC Differential Controller with two monitors and two temperature probes international                $150

    9VDC Wall Transformer   (actual Voltage 12VDC to 14VDC)                                                                       $  7

Calibrated Temperature Probe                                                                                                                              $10  

 

 

Controllers with one monitor for both Collector and Storage... $125

A BASIC Differential Controller Kit is a low cost alternative but it does not come with monitors.

PLEASE CHOOSE GRAY OR NATURAL WHEN ORDERING the AC/DC Differential Controller.
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