Non-invasive Thermal Energy Metering within Industrial Environments

The FLUXUS F721TE is specially designed for heating and cooling Thermal Energy measurement, with all measurements – Flowmeter, Temperature, and BTU computer, contained in one device. Temperature and BTU calculations are done in accordance with EN 1434 Thermal Energy meter standard.

Like all measuring systems of the FLUXUS series, the F721TE 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 sensors or by use of insertion temperature probes.
From the temperature difference as well as the measured volume flow rate and on the basis of the physical media parameters (liquid enthalpy data stored in the meter), the heating or cooling performance is calculated.

Further, the F721TE can also be equipped with two measurement channels to:
- Simultaneously measure two pipes e.g. chilled and hot water submetering in a building, two chillers at the chiller plant, etc.,
- Allow for a complete monitoring of a chiller – chilled water and condenser water,
- to allow accurate measurements even at locations that have very little straight run – dual mount on one pipe averages profile disturbance.

An important advantage of the FLUXUS F721TE lies with its very high zero point stability and unrivalled accuracy even at very low flow rates.
In submetering it is necessary to capture very low flow rates during off peak seasons – like hot water delivery to a building in the summer months – or this becomes free energy. Many meters have zero drift that is hidden by a zero cut-off setting, and some metering technologies just cannot measure the low velocities associated with Thermal Energy off peak flow rates.

Another important aspect of FLEXIM's BTU meter is that every meter is WET FLOW CALIBRATED in a NIST traceable and ISO 17025 accredited flow calibration laboratory. This is a true calibration not a certificate of a bench tested meter that others might supply as an accuracy certification. BTU meters are used for billing allocation; your BTU meters need solid documentation of accuracy.

A critical and sometimes overlooked aspect of the BTU meter combined performance is the temperature accuracy. Unmatched RTD’s can have a 1o F uncertainty on the temperature accuracy. For a chilled water system with a delta T of 10F this can represent a 10% uncertainty (error) in measurement. FLEXIM RTD’s are 4-wire matched pair with an extremely high match of 0.03F at 50° F (chilled water temperature). FLEXIM also adheres to EN 1434 for temperature accuracy for the full range of temperature measurement.

MAINTENANCE FREE metering is now the standard that FLEXIM has achieved. The first aspect of zero maintenance is that the sensors are not in contact with the liquid, there is nothing to get fouled up. The second aspect of zero maintenance is achieved by utilizing Flexim’s non grease transducer COUPLING PADS. These pads can handle temperatures up to 390F. FLEXIM has a huge installed base (over 100 Universities and over 10,000 metering points), and a history since the 2006 implementation with the coupling pads of never having a transducer signal failure.    

High Accuracy – Low installation cost – No maintenance


  • Reliable and wearfree measurement from outside
  • Virtually unlimited application range - even at extreme applications (from -190 °C uo to +630 °C)
  • 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 at night time
  • Simple, cost-effective retrofitting without any disruption to supply
  • Tamper-proof storage of measuring data
  • Ready for Advanced Meter Verification


Industry Applications

Technical Facts

Measurement uncertainty of the measuring system (volumetric flow rate)
± 1 % of reading ±0.02 ft/s
Measurement uncertainty at the measuring point (volumetric flow rate)
0.15 % of reading ±0.02 ft/s
Flow velocity range
0.03 to 82 ft/s
Ex zone transmitter
ATEX/IECEx Zone 2, FM Class I /Div 2
Power supply
100-230VAC, 24DC, 12DC
Available transducers
Shear wave
for Ex zones
ATEX/IECEx Zone 1/Zone 2
FM Class I - Div2
for pipe sizes range
0.24 inch to 255.9 inch
for temperature range
-40°C ... +240°C
4-20mA active/passive
4-20mA HART active/passive
4-20mA active/passive
Binary input
Digital communication
Modbus RTU/TCP
Profibus PA
Foundation Fieldbus
Advanced Meter Verification (AMV)
Additional Information
For more detailed Information please download the Technical Specifications