Temperature Difference Controller

The temperature difference controller is basically a motor-control switch that automatically starts and stops the circulating pump according to temperature measurements. Most models nowadays display the temperatures on a lcd display. The controller decides to turn on the pump based on temperature readings from sensors located at the solar collector and the hot water tank. The controller is called a differential temperature controller because it monitors the temperature difference between the water in the bottom of the storage tank and the fluid in the solar collectors. When the fluid in the collectors is 8 degrees warmer than the coolest water in the storage tank, there is usable heat to be collected. The controller starts the pump. When the temperature difference drops to within 4 degrees, the controller stops the pump. The pump remain off until a useful temperature difference exists again. The temperature range for starting and stopping the pump can be changed by the user.