BS EN 437:2021 pdf download.Test gases — Test pressures — Appliance categories.
4.2 Test gases The composition and principal characteristics of the different test gases corresponding to the gas families or groups are given in Tables 2 and 3. In particular cases specified in the individual appliance standards, gas G 24, whose characteristics are given in Table 3, may be used but only at the normal test pressure. The calorific values of the third family gases, expressed in mega joules per cubic metre in Table 2, may also be expressed in mega joules per kilogram of dry gas, as shown in Table 3. The values in Tables 2 and 3, measured and expressed at 15 °C, are derived from EN ISO 6976:2016. The conditions for the preparation of the test gases are given in Annex A. NOTE The characteristics of second family gases at reference conditions other than 15 °C for metering and 15 °C for combustion can be calculated using the coefficients given in EN ISO 13443:2005, Annex A (normative). As an example, the characteristics of the reference gases of the second family at 0 °C for metering and for combustion and 1 013,25 mbar (dry gas) are given in Table 4.
5 Test pressures The values of the test pressures, i.e. the static pressure to be applied at the gas inlet connection to the appliance whilst in operation, are given in Tables 5 and 6. NOTE The test conditions are specified in the individual appliance standards. However: — for the combustion test in still air with G 21 the appliance is first adjusted on G 20 to give an increase of 5 % in the nominal heat input where a gas pressure governor exists, and an increase of 7,5 % in the absence of a governor. Gas G 21 is then substituted for G 20 without altering this adjustment; — tests for ignition and crosslighting should be carried out at an inlet pressure of 0,7 times the normal pressure (p n ) using the reference gas(es) for the first and second families.BS EN 437 pdf download.