Why DN is not enough
The connection diameter determines mechanical fit, not the heat meter’s optimal measuring range. A heat meter combines a flow measurement, a matched temperature-sensor pair and a calculator to determine transferred thermal energy. Thermal energy meters fall under the MI-004 section of the EU Measuring Instruments Directive, but compliance claims must always be confirmed for the exact model and variant.
Estimate flow from the design thermal load
For water circuits, a useful engineering approximation is P(kW) ≈ 1.163 × q(m³/h) × ΔT(K), where P is thermal power, q is volumetric flow and ΔT is the supply-to-return temperature difference. The coefficient approximates water properties and is not a substitute for the heat meter’s certified energy calculation. For 60 kW at ΔT = 20 K, the flow estimate is q ≈ 60/(1.163 × 20) = 2.58 m³/h.
Why the design temperature difference matters
If the same 60 kW load operates at ΔT = 10 K, required flow rises to approximately 5.16 m³/h. Thus a 60 kW label alone cannot establish the correct Qp. Consider pump characteristics, actual operating flow, valve control and heating-system temperature regimes together.
Interpret Qi, Qp and Qs correctly
Qi is the minimum specified flow rate; Qp is the permanent rated flow rate; Qs is the short-duration overload flow rate. The expected continuous design flow must remain compatible with the meter’s approved operating range, and temporary peaks must respect Qs. Oversizing the meter may place low-load operation close to Qi. A matching DN does not guarantee a suitable metrological selection.
Sensor pairing and installation
The energy result depends on both measured flow and the temperature difference determined by the matched pair of sensors. Sensor pockets, insertion geometry, supply/return position and preservation of the matched pair are essential. Small temperature differences can make sensor-related deviations especially important. Verify each model’s installation manual and permitted minimum ΔT.
Seven checks before procurement
Record heating capacity and design supply/return temperatures.
Derive minimum, continuous and peak flows from circuit, pump and valve calculations.
Compare all flow points with the selected model’s certified Qi, Qp and Qs values.
Verify connection size, pressure loss and permitted installation orientation.
Check rated temperature range, minimum ΔT and sensor installation details.
Request relevant MI-004/EN 1434 records for the precise meter variant.
Specify M-Bus, LoRaWAN or other reading interfaces separately from the metrological parameters.
Practical conclusion
Sizing Qp from pipe diameter or nominal boiler output alone creates avoidable uncertainty. Establish the actual operating flows and validate the Qi–Qp–Qs range from the model-specific documents. ATLAS ultrasonic heat meters can then be reviewed against the design data without assuming undocumented specifications.
Technical support: Submit thermal capacity, supply/return temperatures and a design-flow schedule to request an appropriate heat-meter selection.
Kaynak başlıkları / References: MID 2014/32/EU, EN 1434 / Thermal meter technical manual, EU 2025/1939 harmonised standards