This differential thermostat is fully assembled and fully guaranteed and ready to go. It comes with a set of probes and a DC wall transformer and the shipping is FREE. You'll need a 9 Volt DC wall transformer when powering an AC pump, but If you're are using the controller to power a DC pump with a PV supply and you don't need a a DC wall transformer power supply let me know and I'll send you a $10 refund. I know this controller looks small, but size is not everything. Although it only consumes only1 watt of power per hour it can regulate either AC or DC pumps that consume up to 500 Watts per hour.
Soooooo what makes this Differential Controller
special besides, low cost, durability, versatility and ease of construction.
Well besides regulating 500 Watt AC or DC pumps this controller is safe and stable.
SAFETY...The 5 Volt regulator, built into the circuit supplies power to the probes. If the probe wires are ever shorted out the current supplied by the voltage regulator is limited, so there is no need to worry about a melt down because of an accidental short.
STABILITY... The 5 Volt regulator supplies the temperature sensors with a stable voltage reference. If 12 Volt PV power supply is used to power a DC pump the feedback voltage to the controller drops as the sunlight intensity drops. This feature allows the relay to turn off sooner than normal and increase the life expectancy of a back up battery in a PV system by preventing an unnecessary power drain leading to a dead battery. A 9 Volt DC wall transformer is is used to supply power to the controller when the controller is used to regulate an AC pump. If for some reason the wall transformer is damaged so that the DC supply voltage drops the pump will also shut down sooner than normal. This is both a SAFETY & STABILITY feature of this basic differential thermostat.
A simple adjustment of the differential pot is all that's required to maximize a solar heat harvest. Bigger is better when it comes to the surface area of collectors, but it's not necessarily better when it comes to the size a controller.
The hook ups for AC and DC pumps are illustrated below.
Could it be any simpler?
To power an AC pump you will need a 9VDC Wall transformer (actual voltage 12Volts to 14Volts) Features of the basic Differential Thermostat
When mounted the
Basic Differential Thermostat would appear as illustrated above. If you need a differential
controller that displays temperature check out the AC/DC
If your good with a soldering iron and would like to save a little money you may be interested in the Differential Controller Kit
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