ISO 21684:2025

International
Standard
ISO 21684
First edition
Fans — Laboratory test methods for
2025-09
air circulating fans
Reference number
© ISO 2025
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Published in Switzerland
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Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Air circulating fans .2
3.2 Fan performance variables .3
3.3 Force .3
3.4 General definitions.3
3.5 Psychrometrics .4
3.6 Test configuration.4
4 Symbols, abbreviated terms and subscripts . 5
4.1 Symbols and abbreviated terms .5
4.2 Subscripts . .5
5 Instruments and methods of measurement . 6
5.1 Accuracy .6
5.1.1 General .6
5.1.2 Instrument accuracy .6
5.1.3 Measurement uncertainty .6
5.1.4 Uncertainty of a result .6
5.2 Measurements to determine thrust and airflow rate .7
5.2.1 Airflow rate .7
5.2.2 Thrust .7
5.2.3 Dimensional measurements .7
5.3 Power .7
5.3.1 General .7
5.3.2 Meters .7
5.3.3 Calibration . . .8
5.3.4 Averaging .8
5.4 Fan speed .8
5.5 Air density .8
5.5.1 General .8
5.5.2 Thermometers .8
5.5.3 Barometers .8
6 Equipment and Setups . 9
6.1 Allowable test setups .9
6.2 Load cell orientation . .9
6.3 Minimum testable configuration .9
7 Observations and Conduct of Test . 9
7.1 General test requirements .9
7.1.1 Equilibrium .9
7.1.2 Extraneous airflow .10
7.1.3 Run-in requirements.10
7.2 Data to be recorded .10
7.2.1 Test unit .10
7.2.2 Test setup .10
7.2.3 Instruments .10
7.2.4 Test data .10
7.3 Test procedures .11
8 Calculations .11
8.1 Calibration correction .11
8.2 Ambient air density .11

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8.3 Thrust . 12
8.4 Area . 12
8.5 Airflow rate . 12
8.6 Power . 12
8.7 Fan total pressure . 13
8.8 Overall efficiency . 13
8.9 Circulating fan efficacy . 13
8.10 Ceiling Fan Energy Index (C) . 13
8.11 Thrust efficiency ratio .14
9 Report and results of test . 14
9.1 Test report and results of test . .14
9.2 Personnel .16
10 Figures . 17
Annex A (informative) Air circulating fan subcategories .
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