Heat quantity measurement within:

  • Facility management - Thermal Energy monitoring in Heating & Chiller systems at:
    - Universities
    - Commercial and Aministrative Buildings
    - Shopping Malls
    - Hospitals
    - Airports, Stations, Sport Stadiusm, etc.
  • Refrigeration and air-conditioning systems
  • Refrigeration compressors (also in the gas phase)
  • Absorption chillers
  • District heating transport pipelines and transfer stations
  • Energy consulting / audits
  • Energy-Contracting
  • Geothermic Plants
Technical Datasheet
tsfluxus_f502bt - en-gb.pdf
Adobe Acrobat Document 390.9 KB

The FLUXUS F502 BTU is specially designed for heat and cold quantity metering in buildings and within the manufacturing industry.

Like all measuring systems of the FLUXUS series, the F502 BTU measures the volumetric flow rate non-invasively via its clamp-on ultrasonic transducers. Simultaneously temperature probes monitor the temperatures at the supply and return lines of the heating or cooling system - either non-invasively with clamp-on technology or by use of wetted temperature probes.
From the temperature difference as well as the measured volume flow rate and on the basis of the physical media parameters stored in the internal database of the transmitter, the heating or cooling performance is calculated. With the help of the built-in totalizer function the FLUXUS F502 BTU can also be used as an energy meter. The integrated Modbus RTU, BACnet MS / TP or M-Bus communication interfaces provide for data exchange with the building automation system.

Both the ultrasonic transducers and temperature probes are carefully paired and matchedby FLEXIM. Due to these processes, the system measures with a high degree of accuracy and repeatability - even in applications with only small temperature differences, such as in cooling water circuits.

An important advantage of FLUXUS F502 BTU lies within its high zero point stability and unrivalled accuracy even at very low flow rates - signal drift and significant measurement uncertainty, as it can often be observed at magnetive-inductive heat quantity meters when measuring at low flow rates, can be ruled out. Moreover, even potential mineral deposits on the inner pipe wall cannot influence the measurement.

Thus, the FLUXUS F502 BTU offers the best metrological basis in terms of precision, long-life time, maintenance-free as well as cost-effective monitoring of thermal energy flows in buildings and manufacturing plants and thus forms the foundation for further process optimization tasks within the scope of a holistic energy management system - e.g. according to DIN ISO 50001.


  • Reliable and wearfree measurement from outside
  • Accurate thermal energy measurement due to:
  • - highly accurate flow measurement with paired and traceable calibrated ultrasonic transducers
  • - highly accurate temperature measurement with paired and traceable calibrated temperature sensors (acc. to DIN EN 1434-1)
  • Extremely high measuring dynamics from the lowest to the highest flow velocities - captures even the slightest flows during night time
  • Simple, cost-effective retrofitting without any disruption to supply
  • Tamper-proof storage of measuring data


Measuring quantities

Heat Quantity, Volume Flow, Mass Flow, Flow Velocity


Water (up to 6% of gaseous or solid entrainments by volume)

Flow channels


Media temperature

-40°C ... 100°C

Operating temperature of the transmitter

-10°C ... 60°C

Pipe diameter range

10 mm ... 400 mm

Flow velocity range

0,01 ... 25 m/s

Measurement accuracy


Volume Flow: ± 2 % of reading, ±0.01 m/s

Measurement accuracy


Temperature: ± 0,01% of reading, ± 0,03 K


± 0,25% of reading, ±0,01 m/s

Degree of protection

Transmitter: IP66 / Transducers: IP67


1x (2x optional) current, 1x (2x optional) binary

Communication Protocol

RS485 or Modbus RTU or BACnet MS/TP or M-Bus