SPECIFIC REQUIREMENTS

The values of the rated operating conditions shall be specified by the manufacturer as follows: For the temperature of the liquid: θ_(max), θ_(min), for the temperature differences: Δθ_(max), Δθ_(min), subject to the following restrictions: Δθ_(max)Δθ_(min) 10; Δθ_(min) = 3 K or 5 K or 10 K. For the pressure of the liquid: The maximum positive internal pressure that the thermal energy meter can withstand permanently at the upper limit of the temperature. For the flow rates of the liquid: q_(s), q_(p), q_(i), where the values of q_(p) and q_(i) are subject to the following restriction: q_(p)q_(i) 10. For the thermal power: P_(s). The following accuracy classes are defined for thermal energy meters: 1, 2, 3. The maximum permissible relative errors applicable to a complete thermal energy meter, expressed in percent of the true value for each accuracy class, are: For class 1: EE_(f) E_(t) E_(c), with E_(f), E_(t), E_(c) according to points 7.1 to 7.3. For class 2: EE_(f) E_(t) E_(c), with E_(f), E_(t), E_(c) according to points 7.1 to 7.3. For class 3: EE_(f) E_(t) E_(c), with E_(f), E_(t), E_(c) according to points 7.1 to 7.3. The complete thermal energy meter shall not exploit the MPEs or systematically favour any party. The instrument shall not be influenced by static magnetic fields and by electromagnetic fields at mains frequency. The influence of an electromagnetic disturbance shall be such that the change in the measurement result is not greater than the critical change value as laid down in requirement 4.3 or the indication of the measurement result is such that it cannot be interpreted as a valid result. The critical change value for a complete thermal energy meter is equal to the absolute value of the MPE applicable to that thermal energy meter (see point (3). After an appropriate test, taking into account the period of time estimated by the manufacturer, has been performed, the following criteria shall be satisfied: Flow sensors: The variation of the measurement result after the durability test, when compared with the initial measurement result, shall not exceed the critical change value. Temperature sensors: The variation of the measurement result after the durability test, when compared with the initial measurement result, shall not exceed 0,1 °C. Accuracy class Limits of flow rate Limits of temperature Limits of temperature difference Place of the flow sensor installation: flow or return Indication of the direction of flow The provisions for sub-assemblies may apply to sub-assemblies manufactured by the same or different manufacturers. Where a thermal energy meter consists of sub-assemblies, the essential requirements for the thermal energy meter apply to the sub-assemblies as relevant. In addition, the following apply: 7.1. The relative MPE of the flow sensor, expressed in %, for accuracy classes: Class 1: E_(f)(1 0,01 q_(p)q), but not more than 5 %, Class 2: E_(f)(2 0,02 q_(p)q), but not more than 5 %, Class 3: E_(f)(3 0,05 q_(p)q), but not more than 5 %, where the error E_(f) relates the indicated value to the true value of the relationship between flow sensor output signal and the mass or the volume. 7.2. The relative MPE of the temperature sensor pair, expressed in %: E_(t)(0,5 3 Δθ_(min)Δθ), where the error E_(t) relates the indicated value to the true value of the relationship between temperature sensor pair output and temperature difference. 7.3. The relative MPE of the calculator, expressed in %: E_(c)(0,5 Δθ_(min)Δθ), where the error E_(c) relates the value of the thermal energy indicated to the true value of the thermal energy. 7.4. The critical change value for a sub-assembly of a thermal energy meter is equal to the respective absolute value of the MPE applicable to the sub-assembly (see points 7.1, 7.2 or 7.3). Flow sensor: Accuracy class Limits of flow rate Limits of temperature Nominal meter factor (e.g. litres/pulse) or corresponding output signal Indication of the direction of flow Temperature sensor pair: Type identification (e.g. P_(t) 100) Limits of temperature Limits of temperature difference Calculator: Type of temperature sensors Limits of temperature Limits of temperature difference Required nominal meter factor (e.g. litres/pulse) or corresponding input signal coming from the flow sensor Place of the flow sensor installation: flow or return

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Source: EUR-Lex (Cellar) · retrieved 2026-11-06 · Text as adopted (Official Journal); later amendments are not incorporated in this text.