ISO 12759-3:2019/DAM 1:2026(en)

ISO/TC 117/WG 11

Secretariat: BSI

Date: 2025-12-24

Fans — Efficiency classification for fans —

Part 3:

Fans without drives at maximum operating speed

AMENDMENT 1

© ISO 2026

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This document was prepared by Technical Committee ISO/TC 117, Fans.

This first edition cancels and replaces ISO 12759:2010, which has been technically revised. It also incorporates the Amendment ISO 12759:2010/Amd.1:2013.

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Fans — Efficiency classification for fans —
Part 3:
Fans without drives at maximum operating speed
AMENDMENT 1

Clause 6

Fifth paragraph

Replace “A number of fixed efficiency grades are defined based on fan diameter and optimum efficiency.” with “A number of fixed efficiency grades are defined based on fan diameter and optimum efficiency calculated according to Annex A.”

Figure 3

Replace Figure 3 with following:

Key

NOTE 1 Fan size is the nominal impeller diameter.

NOTE 2 The optimum (peak) fan efficiency shall be calculated from the fan (total) pressure (see ISO 5801:2017, 3.50).

NOTE 3 The FEG label for a given fan size is assigned when the optimum (peak) fan efficiency is equal to or lower than the efficiency at the grade upper limit and higher than the efficiency at the grade lower limit for the fan size.

NOTE 4 No label is considered for fans with an optimum (peak) efficiency below FEG50.

NOTE 5 For any fan size larger than 1 000 mm the values of the grade limits are the same as for a fan size of 1 000 mm.

NOTE 6 If this method is used for a direct driven fan without the shaft and bearings integral to the fan, the fan efficiency is the impeller efficiency.

Figure 3 — Fan efficiency grades (FEGs) for fans without drives

Annex A

Change Annex A from “informative” to “normative”.

A.1

Change Formula (A.1) from

to

(A.1)

A.2   Fan efficiency grades

Replace A.2 with the following.

Table A.2 — Fan efficiency grades (FEG) for fans without drives

A simple method of calculating the upper efficiency limit for an efficiency grade, N_G, for those defined in Table A.2 is given in Formula (A.3).

(A.3)

Where Z is defined in Table A.3.

Table A.3 — The coefficient Z for calculation of upper efficiency limit of a FEG for fans without drives

EXAMPLE: Determining the upper efficiency limit of FEG56 for an 800 mm diameter fan.