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Non-Invasive Thermal Energy Metering

The FLUXUS F502 Thermal Energy 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 Thermal Energy 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 Thermal Energy 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 matched by 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 Thermal Energy 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 Thermal Energy 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


Technical Facts

Measurement uncertainty of the measuring system (volumetric flow rate)
±1.5 % v. MW ±0.01 m/s
0.25 % v. MW ±0.01 m/s
Flow velocity range
0.01...25 m/s
Ex zone transmitter
only safe area
Power supply
230VAC, 12/24VDC
Available transducers
for pipe sizes range
DN25 ... DN500
for temperature range
-40°C ... 130°C
2x 4-20mA active
2x pulse/binary
2x Pt100/Pt1000
Digital communication
Modbus RTU