Why Heat Metering in Heat Pumps is key
May 15, 2025, 12 minute read
May 15, 2025, 12 minute read
In heating and cooling applications, accurate Energy and Heat Metering is a key feature to establish the efficiency of any system.
In the domain of Heat Pumps, heat metering will become a mandatory requirement in the near future. The “Eco design Directive 2009/125/EG” will be replaced soon by a new “Eco design for Sustainable Products Regulation”. The current drafts show that the requirements for transparency towards end customers regarding the energy efficiency of heating systems are increasing significantly.
What does the Regulation say about Heat Metering in Heat Pumps?
| Temperature difference range Δθ |
Δθ ≤ 5K | 5K < Δθ ≤ 10K | Δθ ≥ 10K |
|---|---|---|---|
| Tolerance± | 15% | 10% | 7,5% |
How can Allengra’s solution help to meet the requirements in heat pumps?
These upcoming accuracy requirements can only be achieved with an integrated heat meter that determines both the flow rate and the temperature difference in one device.
Using Allengra’s ALSONIC flow sensors meets these new requirements, as the flowmeters offer ultrasonic flow measurement and integrated differential temperature measurement. For continuous heat metering, by already paired the two PT1000 temperature sensors for flow and return in production. As a result, a measurement accuracy of ±0.3 K can be achieved for the temperature difference.
This, in combination with the flow measurement accuracy of ±2 %, the following heat quantity measurement accuracies are achieved:
| Temperature difference Δϑ | 3K | 4K | 5K | 10K | 20K |
| Tolerance ± | ± 12 % | ± 9.5 % | ± 8 % | ± 5 % | ± 3.5 % |
In conclusion, not only are the minimum requirements met, but the solution also offers many other advantages, for example:
By collecting the 3 measured values in just one device:
One device, with only one hydraulic and one electronic interface, is sufficient in the heat pump to perform all accurate calculations.
This saves costs, speeds up the installation time of the heat pump and reduces the complexity of procurement and warehousing.
Otherwise, heat pump manufacturers would have to pair temperature sensors during their production process, which only works accurately if the sensors are immersed in a liquid medium. This is an effort that is unlikely to be desirable given the increasing competitive pressure in the heat pump market.
The integrated microcontroller can calculate the instantaneous heat energy directly, sum it up over time and run additional evaluations.
For example, heating and cooling energy can easily be considered separately for winter and summer operation. A single bus communication link is sufficient to transmit all data to the controller, along with additional diagnostic information.
Thanks to this multifunctionality, the ultrasonic sensor outshines other flow measurement principles such as vortex or turbine sensors. Integrating a heat metering feature into a vortex or turbine solution is ultimately inferior to ultrasonic sensors in terms of price and performance.
The updated Eco design requirements also clarify that indirect volume flow measurement via the circulation pump is unsuitable. Using electrical power, speed, and pressure difference to determine flow is too imprecise for accurate heat quantity measurement.
Sources:
