BS EN ISO 12759-2015 pdf download.Fans 一 Efficiency classification for fans. 5.4 Tolerances At each stage of the fan design and manufacturing cycle, including conversion from prototype performance data or calculation, fabrication and testing of a purpose-designed fan, finite uncertainties prevail and acceptance tolerances shall be applied. Any test for fan performance is subject to error, and the range within which these testing errors can be expected to lie is defined numerically as the uncertainty of measurement. In addition, the true performance of the fan (if it can be ascertained) would be found to differ from that of another nominally identical fan, owing to inevitable variations in manufacture. The expected range of this manufacturing variation shall be added to the uncertainty of measurement to determine the minimum tolerance required for a performance specification. The tolerances given in ISO 13348:2007, Clause 5 (performance tolerances for purpose-designed fans and series-produced non-certified fans), and ISO 13348:2007, Clause 6 (performance tolerances for series- produced fans in certified ratings programmes), shall apply. 6 Ratings 6.1 General The variation of fan type and drive option leads to efficiency being derived in different ways. For grading purposes, the efficiency has been defined as a function of the size for bare shaft fans and as a function of input power for driven fans, Direct comparison shall not be made between driven fans rating (FMEG) and bare shaft fans rating (FEG). If the efficiency of the bare shaft fan is required on a driven unit (see 6.2), Figure 4 remains applicable. In this case, the motor efficiency shall be obtained from a dynamometer test or by calibrated motor performance curves, conforming to IEC 60034-2-1. This clause gives guidance on the optimum efficiency (best efficiency point) levels which are achievable by the fan types addressed in this International Standard. The minimum levels of acceptability are dependent on consultation between regulator and manufacturer’s representatives or local legislation, where this exists. The efficiency grade for a fan is based on its performance characteristics at a speed not higher than the maximum safe operating speed to obtain its best efficiency point. 6.2 Bare shaftfans The relationship between the FEG and fan size is shown in Figure 4. While the fan efficiency is a function of the operating point of the fan, the efficiency grades are based on the optimum (peak) efficiency of the fan as the characteristic of fan energy efficiency. A fan...
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