BTU Meter &
Temperature Differential Controller

USDT 2004A controller has the following functions:

  • Digital display of power in kW
  • Digital display of energy in kWh
  • Digital display of flow rate in gpm
  • Digital display of supply temperatureDigital display of return temperature
  • Adjustable Delta T (∆T) differential from  1 oF to 50 oFManual override of outputs for system testing
  • Programmable hysteresis
  • Status screen for indication of the current state of the system


NOTE: The information presented in this page is for guidance only - no part of this may be used for any agreement, whether express or implied, or to form any contract. THERMO TECHNOLOGIES reserves the right to change specifications and prices without prior notice.

Universal Differential  Controller and Energy Calculator

USDT 2004A calculates energy collection (or consumption) by multiplying the flow volume by the difference in water temperature between the supply and return lines. These results appear on the LCD window. It ensures the highest level of accuracy by using adjustable (on unit calibration) temperature sensors and microprocessor calculations. The unit is an advanced temperature differential controller with energy calculation capabilities. 


The standard unit includes two thermistor sensors. The system diagnostics are powerful and accurate; they display potential system problems such as sensor or pump failures.

The suggested retail price for a controller and two sensors is $179.00.

The USDT 2004 monitors and displays supply and return temperatures. When the supply temperature exceeds the return temperature by a programmable temperature difference (∆T), an internal relay can power a ¼ HP pump or an auxiliary relay.
To avoid overheating the controlled system, the pump stops when the supply temperature reaches a programmable maximum temperature (TMAX).  Frost or cooling protection is regulated through return temperature monitoring. Regardless of the temperature difference (∆T), the pump runs when the return temperature is below a programmable minimum temperature (Tmin).  The system offers an adjustable temperature hysteresis to avoid pump cycling.

Power Connection
  • Power supply 120 V AC
  • Maximum load 3.15 A (75 W)
  • Phantom load max. 2 W
  • A surge arrester at the collector sensor reduces lightning damages to the controller internal electronics 

Sensor Characteristics

  • The unit is supplied with two thermistor sensors
  • Sensor cables can be extended up to 500 feet using standard two wire cables
  • Collector sensor is supplied with a weather resistant terminal box and EMI impedance protector
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