ÖNORM EN 17526

This document specifies requirements and tests for the construction, performance, safety and production of battery powered class 1,5 Capillary Thermal-Mass Flow sensor gas meters (hereinafter referred to as meter(s)). This applies to meters having co-axial single pipe, or two pipe connections, which are used to measure volumes of fuel gases of the 2nd and/or 3rd family, as given in EN 437:2021. In general, the term "thermal mass flow meters" applies to a flow-measuring device using heat transfer to measure and indicate gas flowrate, as defined in ISO 14511. NOTE Although the word "mass" is present in the definition of the measurement principle, gas meters covered by this document provide measurement of gas at base conditions of temperature and pressure. These meters have a maximum working pressure not exceeding 0,5 bar and a maximum flowrate not exceeding 160 m3/h over a minimum ambient temperature range of −10 °C to +40 °C and a gas temperature range as specified in the marking, with a minimum range of 40 °C. For meters designed for hydrogen measurement, the maximum flowrate is not exceeding 480 m3/h, whilst the other characteristics are as stated above. This document applies to meters indicating volume at base conditions, which are installed in locations with vibration and shocks of low significance. It applies to meters in: - closed locations (indoor or outdoor with protection, as specified in the instruction manual) with condensing humidity or with non-condensing humidity; or, if specified in the marking: - open locations (outdoor without any covering) both with condensing humidity or with non-condensing humidity; and in locations with electromagnetic disturbances likely to be found in residential, commercial and light industrial use. For meters which indicate unconverted volume, reference can be made to Annex C. Unless otherwise stated, all pressures given in this document are gauge pressures. Requirements for electronic indexes, valves and additional requirements for batteries incorporated in the meter and any other additional functionalities are given in EN 16314:2013. Unless otherwise stated in a particular test, the tests are carried out on meters that include additional functionality devices, as indicated in the instruction manual. Clauses 1 to 13 are for design and type testing only. For meters designed for blended gas and/or hydrogen measurement, refer to Annex E. This document refers only to hydrogen as specified in ISO 14687:2025 with a purity of type I grade A or better. Unless otherwise stated, all tests applicable to 2nd and 3rd family gases are applicable also to blended gas and hydrogen. Mixtures with a hydrogen concentration above 20 % and below 98 % by volume are not covered by this document.