System Controller

Solar Water Heater System Controller - StecaThe system controller constantly compares the temperatures between the collector (T1) and the lower area of the storage tank (T2) via temperature sensors.  Once the sun heats the collector and there is a temperature difference of 16 diff. °F (constant fixed value) between the collector and the storage tank, the collector and tank pumps are switched on.   The tank pump pulls water from the bottom of the tank, through the heat exchanger and back to the tank.   The collector pump circulates distilled water through the collector loop and the other side of the heat exchanger.   The heat from the collectors is transferred through the heat exchanger to the domestic water in the tank.

The Steca model TR0301U differential temperature control provides automatic, safe and reliable operation of domestic solar water heating systems.   The 110v electrical output is pre-wired to two pumps that circulate water on each side of the heat exchanger.   The microprocessor-based TR0301U utilizes two RTD (resistance temperature detector) type sensors to monitor collector and tank temperatures with digital accuracy.   The LCD provides a variety of real time information including system temperatures at up to three separate locations.  The consistent use of simple pictograms ensures ease of operation and troubleshooting. In addition to the primary function of turning the circulating pumps on and off during the day, the TR0301U provides important diagnostic and safety functions. For example, the LCD pictograms will indicate fault conditions such as sensor shorts or pump failures.   Varistors protect the sensor inputs against high voltage spikes. The load side is fuse protected.


  • Digital accuracy

  • LCD provides real time operating temperatures

  • Animated representation of system operation

  • Sophisticated monitoring and fault diagnostics

  • Fused output protection for pump circuit • Varistor high voltage spike protection

  • Adjustable high limit temperature of storage tank

  • Accessible side-mounted on, off, auto switch