EN ISO 12759:2015

SLOVENSKI STANDARD
01-oktober-2015
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GRSROQLOR$
Fans - Efficiency classification for fans (ISO 12759:2010, including Amd 1:2013)
Ventilatoren - Effizienzklassifizierung für Ventilatoren (ISO 12759:2010, einschließlich
Amd 1:2013)
Ventilateurs - Classification du rendement des ventilateurs (ISO 12759:2010, y compris
Amd 1:2013)
Ta slovenski standard je istoveten z: EN ISO 12759:2015
ICS:
23.120 =UDþQLNL9HWUQLNL.OLPDWVNH Ventilators. Fans. Air-
QDSUDYH conditioners
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 12759
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2015
ICS 23.120
English Version
Fans - Efficiency classification for fans (ISO 12759:2010,
including Amd 1:2013)
Ventilateurs - Classification du rendement des ventilateurs Ventilatoren - Effizienzklassifizierung für Ventilatoren (ISO
(ISO 12759:2010, y compris Amd 1:2013) 12759:2010, einschließlich Amd 1:2013)
This European Standard was approved by CEN on 16 July 2015.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2015 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 12759:2015 E
worldwide for CEN national Members.

Contents Page
European foreword .3

European foreword
The text of ISO 12759:2010, including Amd 1:2013, has been prepared by Technical Committee ISO/TC 117
“Fans” of the International Organization for Standardization (ISO) and has been taken over as EN ISO
12759:2015 by Technical Committee CEN/TC 156 “Ventilation for buildings” the secretariat of which is held by
BSI
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by January 2016, and conflicting national standards shall be withdrawn at
the latest by January 2016.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 12759:2010, including Amd 1:2013, has been approved by CEN as EN ISO 12759:2015
without any modification.
INTERNATIONAL ISO
STANDARD 12759
First edition
2010-12-15
Fans — Efficiency classification for fans
Ventilateurs — Classification du rendement des ventilateurs

Reference number
ISO 12759:2010(E)
©
ISO 2010
ISO 12759:2010(E)
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ii © ISO 2010 – All rights reserved

ISO 12759:2010(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
3.1 Fans — General .2
3.2 Fan or test installation categories according to the arrangement of ducting .3
3.3 Fans — Definitions relating to calculations.3
3.4 Definitions relating to fan efficiency .5
3.5 Fan efficiency grades.6
4 Symbols and units.6
5 Fan installation, efficiency and tolerance.7
5.1 General .7
5.2 Use of installation categories .9
5.3 Calculation of efficiency .9
5.4 Tolerances.10
6 Ratings.10
6.1 General .10
6.2 Bare shaft fans.10
6.3 Driven fans .13
Annex A (normative) Energy efficiency grades for bare shaft fans .20
Annex B (normative) Calculation method to determine efficiency of component parts.21
Annex C (informative) Variation of fan performance between installation categories.26
Annex D (informative) Input power calculation for driven fans at design point.27
Annex E (informative) Selection of fans for best efficiency .35
Annex F (informative) Determination of efficiency grade for a driven fan.38
Annex G (informative) Explanatory note .40
Bibliography.42

ISO 12759:2010(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 12759 was prepared by Technical Committee ISO/TC 117, Fans.
iv © ISO 2010 – All rights reserved

ISO 12759:2010(E)
Introduction
The last decade has seen not only an escalation in the price, but also an increasing recognition of the finite life
of many of the fossil fuels in use. There is also a belief that climatic change is due to an increase in the levels
of carbon dioxide in the atmosphere. This has lead to many nations reviewing methods of energy generation
and usage.
Therefore, there is a need to promote energy efficiency in order to maintain economic growth. This requires
better selection of equipment by users and better design of this equipment by manufacturers.
Fans of all types are used for ventilation and air conditioning, process engineering (drying, pneumatic
conveying), combustion air supply and agriculture, etc. Indeed, the energy usage by fans has been calculated
as nearly 20 % of worldwide demand.
The fan industry is of a global nature, with a considerable degree of exporting and licensing. To ensure that
defined fan performance characteristics are common throughout the world, a series of International Standards
has been developed. It is the belief of the industry that there is a need for the recognition of minimum
efficiency standards. To encourage their implementation, a classification system is proposed which
incorporates a series of efficiency bands. With improvements in technology and manufacturing processes, the
minimum efficiency levels can be reviewed and increased over time.
This International Standard can be used by legislators or regulatory bodies for defining future energy saving
targets.
INTERNATIONAL STANDARD ISO 12759:2010(E)

Fans — Efficiency classification for fans
1 Scope
This International Standard establishes a classification of fan efficiency for all fan types driven by motors with
an electrical input power range from 0,125 kW to 500 kW. This International Standard is applicable to bare
shaft and driven fans, as well as fans integrated into products. Fans integrated into products are measured as
stand-alone fans.
This International Standard is not applicable to:
a) fans for smoke and emergency smoke extraction;
b) fans for industrial processes;
c) fans for automotive application, trains and planes;
d) fans for potentially explosive atmospheres;
e) box fans, powered roof ventilators and air curtains;
f) jet fans for use in car parks and tunnel ventilation.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 5801:2007, Industrial fans — Performance testing using standardized airways
ISO 13348:2007, Industrial fans — Tolerances, methods of conversion and technical data presentation
ISO 13349:2010, Fans — Vocabulary and definitions of categories
IEC 60034-2-1, Rotating electrical machines — Part 2-1: Standard methods for determining losses and
efficiency from tests (excluding machines for traction vehicles)
IEC 60034-30, Rotating electrical machines — Part 30: Efficiency classes of single-speed, three-phase, cage-
induction motors
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13349 and the following apply.
NOTE See, in particular, ISO 13349:2010, Tables 4 and 5, as well as the associated equations in Clause 5 of this
International Standard and ISO 5801.
ISO 12759:2010(E)
3.1 Fans — General
3.1.1
fan
rotary bladed machine which receives mechanical energy and utilizes it by means of one or more impellers
fitted with blades to maintain a continuous flow of air or other gas passing through it and whose work per unit
mass does not normally exceed 25 kJ/kg
NOTE 1 Fans are defined according to their installation category, function, fluid path and operating conditions.
NOTE 2 Adapted from ISO 13349:2010, definition 3.1.1.
3.1.2
fan size
maximum impeller tip diameter, D, on which the design of the fan is based
3.1.3
drive
〈transmission and motor/control system〉 device used to power the fan, including motor, mechanical
transmission and motor/control system
NOTE 1 Examples of mechanical transmission are belt drive and couplings.
NOTE 2 Examples of a motor or control system are variable frequency controller and electronic commutator.
3.1.4
bare shaft fan
fan without drives, attachments or accessories (appurtenance)
See Figure 1.
NOTE Adapted from ISO 13349:2010, definition 3.1.2.
3.1.5
driven fan
one or more impellers fitted to or connected to a motor, with or without a drive mechanism, a housing and a
means of variable speed drive
See Figure 2.
NOTE Adapted from ISO 13349:2010, definition 3.1.3.
3.1.6
air
abbreviated term for the expression “air or other gas”
[ISO 13349:2010, definition 3.2]
3.1.7
standard air
atmospheric air having a density of exactly 1,2 kg/m
NOTE 1 Atmospheric air at a temperature of 16 °C, a pressure of 100 000 Pa and a relative humidity of 65 %, has a
density of 1,2 kg/m , but these conditions do not form part of the definition.
NOTE 2 Adapted from ISO 13349:2010, definition 3.3.
2 © ISO 2010 – All rights reserved

ISO 12759:2010(E)
3.2 Fan or test installation categories according to the arrangement of ducting
See Figure 3 and ISO 13349.
3.2.1
installation category A
installation with free inlet and free outlet
3.2.2
installation category B
installation with free inlet and ducted outlet
3.2.3
installation category C
installation with ducted inlet and free outlet
3.2.4
installation category D
installation with ducted inlet and ducted outlet
3.3 Fans — Definitions relating to calculations
3.3.1
average density at fan inlet
ρ
fluid density calculated from the absolute pressure and the static temperature
3.3.2
atmospheric pressure
p
a
pressure, measured with respect to absolute zero pressure, which is exerted at a point at rest relative to the
air around it
3.3.3
fan pressure
p
f
difference between the stagnation pressure at the fan outlet and the stagnation pressure at the fan inlet
3.3.4
fan static pressure
p
sf
conventional quantity defined as the fan pressure minus the fan dynamic pressure at the fan outlet corrected
by the Mach factor
3.3.5
absolute stagnation pressure at a point
p
sg
absolute pressure which would be measured at a point in a flowing gas, if it were brought to rest via an
isentropic process
3.3.6
conventional dynamic pressure at a point
p
d
pressure calculated from the velocity and the density of the air at the point
ISO 12759:2010(E)
3.3.7
fan dynamic pressure at the fan outlet
p
d2
conventional dynamic pressure at the fan outlet calculated from the mass flow rate, the average gas density at
the outlet and the outlet area
3.3.8
mass flow rate
q
m
mean value, over time, of the mass of air which passes through the specified airway cross-section per unit of
time
3.3.9
inlet volume flow rate
q
v1
mass flow rate at the inlet divided by the corresponding mean value, over time, of the average density at the
inlet
3.3.10
fan work per unit mass
W
m
increase in mechanical energy per unit mass of fluid passing through the fan
3.3.11
compressibility coefficient
k
p
ratio of the mechanical work done by the fan on the air to the work that would be done on an incompressible
fluid with the same mass flow, inlet density and pressure ratio
3.3.12
fan air power
P
u
conventional output power which is the product of the mass flow rate and the fan work per unit mass, or the
product of the inlet volume flow rate, the compressibility coefficient and the fan pressure
3.3.13
fan static air power
P
us
conventional output power which is the product of the mass flow rate and the fan static work per unit mass, or
the product of the inlet volume flow rate, the compressibility coefficient and the fan static pressure
3.3.14
impeller power
P
r
mechanical power supplied to the fan impeller
NOTE This is applicable to direct driven impellers which are open (as in, for example, a plenum fan) or enclosed in a
housing.
3.3.15
nominal motor power
P
N
rated output power of an electric motor
3.3.16
fan shaft power
P
a
mechanical power supplied to the fan shaft
4 © ISO 2010 – All rights reserved

ISO 12759:2010(E)
3.3.17
motor output power
P
o
shaft power output of the motor or other prime mover
3.3.18
motor input power
P
e
electrical power supplied to the fan's motor
3.3.19
drive/control electrical input power
P
ed
electrical power supplied to the motor's drive or control
3.4 Definitions relating to fan efficiency
3.4.1
fan impeller efficiency
η
r
fan air power divided by the impeller power, P
r
3.4.2
fan shaft efficiency
η
a
fan air power divided by the fan shaft power, P
a
3.4.3
overall efficiency
η
e
fan air power divided by the input power for the fan and motor
3.4.4
overall static efficiency
η
es
fan static air power divided by the input power for the fan and motor
3.4.5
overall efficiency drive
η
ed
〈transmission and motor/control system〉 fan air power divided by the input power for the fan and motor
combination which include transmission or variable speed controls to take account of all losses within the fan
assembly
3.4.6
overall static efficiency drive
η
esd
〈transmission and motor/control system〉 fan static air power divided by the input power for the fan and motor
combination which include transmission or variable speed controls to take account of all losses within the fan
assembly
NOTE 1 The efficiency can be referred to the installation category (see Figure 3 and ISO 13349).
NOTE 2 Efficiency can be expressed as a proportion of unity. To obtain a per cent value, multiply the efficiency result
by 100.
ISO 12759:2010(E)
3.4.7
optimum efficiency
η
opt
maximum efficiency achieved on the fan air characteristic with all operational parameters, except the air
system resistance, being fixed
3.4.8
compensation factor
C
c
factor, used in the determination of efficiencies for fans incorporating or fitted with variable speed drives
See Figure 5.
3.5 Fan efficiency grades
3.5.1
fan efficiency grade
FEG
efficiency grade for a bare shaft fan
NOTE The definitions given in 3.4.1 and 3.4.2 can apply.
3.5.2
fan motor efficiency grade
FMEG
efficiency grade for a driven fan
NOTE The definitions given in 3.4.3, 3.4.4, 3.4.5 and 3.4.6 can apply.
3.5.3
grade number
N
G
integer of the FMEG
4 Symbols and units
For the purposes of this document, the symbols and primary units in Table 1 for the parameters listed apply.
Table 1 — Symbols and units
Symbol Description Unit
C Compensation factor to account for energy savings at part load —
c
C Compensation factor to account for suboptimal matching of components —
m
D Maximum impeller tip diameter (fan size) mm
k Compressibility coefficient —
p
N Grade number (integer) of the FMEG —
G
P Fan shaft power W
a
P Power loss in bearings W
b
P Motor input power W
e
P Drive/control electrical input power W
ed
P Nominal motor power W
N
P Motor output power W
o
6 © ISO 2010 – All rights reserved

ISO 12759:2010(E)
Table 1 (continued)
Symbol Description Unit
P Impeller power W
r
P Specific fan power kW/(m /s) or W/(l/s)
sf
P Fan air power W
u
P Fan static air power W
us
p Atmospheric pressure Pa
a
p Conventional dynamic pressure at a point Pa
d
p Fan dynamic pressure at the fan outlet Pa
d2
p Fan pressure Pa
f
p Fan static pressure Pa
sf
p Absolute stagnation pressure at a point Pa
sg
q Mass flow rate kg/s
m
q Inlet volume flow rate m /s
v1
W Fan work per unit mass J/kg
m
η Fan shaft efficiency Expressed as a decimal
a
η Fan bearing efficiency Expressed as a decimal
b
η Variable speed drive efficiency Expressed as a decimal
c
η Overall efficiency for fans without drives Expressed as a decimal
e
η Overall efficiency for fans with drives Expressed as a decimal
ed
η Overall static efficiency for fans without drives Expressed as a decimal
es
η Overall static efficiency for fans with drives Expressed as a decimal
esd
η Motor efficiency Expressed as a decimal
m
η Optimum efficiency Expressed as a decimal
opt
η Fan impeller efficiency Expressed as a decimal
r
η Drive mechanism (transmission efficiency) Expressed as a decimal
T
ρ Average density at fan inlet kg/m
NOTE Efficiency in per cent (%) divided by 100 equals the efficiency, expressed as a decimal.

5 Fan installation, efficiency and tolerance
5.1 General
Fans range from the purpose-built single fan to the series-produced certified ranges, which are manufactured
in large quantities. A fan can be an impeller on a shaft with no drive mechanism attached (i.e. bare shaft fan)
(see Figure 1), or a motor attached to a drive system attached to an impeller within an impeller housing. In
that case, it can be supplemented by a volume control, such as a variable speed control or guide vanes (i.e.
driven fan) (see Figure 2).
The variation in design has led to efficiency being defined in a number of ways to suit the demands of the fan
type and the market.
ISO 12759:2010(E)
Figure 1 — Example of a bare shaft centrifugal fan

Key
P fan air power
u
P drive/control electrical input power
ed
a
Variable speed device loss (heat). [The variable speed device can be fitted or not (see Clause 6).]
b
Motor losses (heat).
c
Belt losses (heat).
d
Bearing losses (heat).
e
Impeller and casing aerodynamic losses (heat).
Figure 2 — Example of a driven fan showing power losses

8 © ISO 2010 – All rights reserved

ISO 12759:2010(E)
5.2 Use of installation categories
Fan efficiency ratings are frequently specific for each standardized test installation category.
If a fan is designed for a single installation category, its rated efficiency grade shall refer to that particular test
installation category, and this shall be clearly identified.
If a fan is suitable for use with different installation categories, the fan efficiency grade shall be based on the
efficiency ratings referring to the most suitable category, and this shall be clearly identified.
To determine the operating point of the fan, four installation categories shall be considered (see Figure 3). For
details of test methods, see the following clauses of ISO 5801:2007:
a) category A installations — Clause 30;
b) category B installations — Clause 31;
c) category C installations — Clause 32;
d) category D installations — Clause 33.
The standardized installation category used for rating the fan shall be clearly stated (see Annex C).
The motor input power and motor output power may be measured or determined using the methods given in
ISO 5801. Installation category E is not included in this International Standard.

a)  Category A b)  Category B c)  Category C d)  Category D
Figure 3 — Installation categories
5.3 Calculation of efficiency
5.3.1 The fan air power and efficiency are calculated from fan work per unit mass in accordance with
ISO 5801:2007, 14.8.1.
5.3.2 For a bare shaft fan where bearing losses are excluded, the efficiency is given by Equation (1):
η = P /P (1)
r u r
5.3.3 For a bare shaft fan where bearing losses are included, the efficiency is given by Equation (2):
η = P /P (2)
a u a
5.3.4 For a driven fan that does not include a variable speed drive, where the input power can be
determined, the overall efficiency is given by Equation (3) or (4):
η = P /P (3)
e u e
η = P /P (4)
es us e
ISO 12759:2010(E)
5.3.5 For a driven fan that includes a variable speed drive, where the input power can be determined, the
overall efficiency is given by Equation (5) or (6):
η = C × P / P (5)
ed c u ed
P
us
η =×C (6)
esd c
P
ed
NOTE The use of fan pressure or fan static pressure determines the appropriate efficiency grade according to the
installation category.
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 shaft fans
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 belongs to an FEG grade (e.g. FEG85), if its efficiency, at best efficiency duty and maximum speed, is
higher than the calculated value, at the impeller diameter, along the boundary, calculated in accordance with
10 © ISO 2010 – All rights reserved

ISO 12759:2010(E)
Annex A from the level of the immediately lower efficiency grade (e.g. 80 from FEG80), and equal to or lower
than the value on the boundary calculated for the nominal efficiency grade (e.g. FEG85).
In simple terms, a fan belongs to an FEG grade (e.g. FEG85) if its efficiency, at best efficiency duty and
maximum speed, is below the curve according to its designation, but above the next curve beneath (e.g.
FEG80).
η
opt
FEG90
FEG85
FEG80
FEG75
FEG71
FEG67
FEG63
FEG60
FEG56
FEG53
FEG50
100 125 160 200 250 315 400 500 630 800 1 000 D
140 180 224 280 355 450 560 900

Key
D fan size (mm)
η optimum (peak) fan efficiency (%)
opt
Figure 4 — FEG for bare shaft fans

The incremental efficiency grades for bare shaft fans are given in Table 2. An explanation of how to determine
the FEG is given in the notes to Table 2. The FEG grade for a given fan size is assigned when the fan
optimum (peak) efficiency is equal or lower than the value of efficiency in the row for that label and higher than
the value of efficiency in the next row down.

ISO 12759:2010(E)
Table 2 — Fan efficiency grades (FEG) for bare shaft fans
a
Optimum (peak) fan efficiency
%
d,e
for fan size, D (mm) of:
FEG r
b,c
grade
125 132 140 150 160 170 180 190 200 212 224 236 250
FEG90 Optimum (peak) fan efficiency above the FEG85 grade
FEG85 42,5 44,8 47,2 50,1 52,7 55,2 57,4 59,4 61,3 63,3 65,2 66,9 68,6
FEG80 40,1 42,3 44,6 47,3 49,8 52,1 54,2 56,1 57,9 59,8 61,6 63,1 64,8
FEG75 37,8 39,9 42,1 44,7 47,0 49,2 51,1 53,0 54,6 56,5 58,1 59,6 61,2
FEG71 35,7 37,7 39,8 42,2 44,4 46,4 48,3 50,0 51,6 53,3 54,9 56,3 57,8
FEG67 33,7 35,6 37,5 39,8 41,9 43,8 45,6 47,2 48,7 50,3 51,8 53,1 54,5
FEG63 31,8 33,6 35,4 37,6 39,5 41,4 43,0 44,6 46,0 47,5 48,9 50,2 51,5
FEG60 30,1 31,7 33,4 35,5 37,3 39,0 40,6 42,1 43,4 44,8 46,2 47,3 48,6
FEG56 28,4 29,9 31,6 33,5 35,2 36,9 38,3 39,7 41,0 42,3 43,6 44,7 45,9
FEG53 26,8 28,2 29,8 31,6 33,3 34,8 36,2 37,5 38,7 40,0 41,1 42,2 43,3
FEG50 25,3 26,7 28,1 29,8 31,4 32,9 34,2 35,4 36,5 37,7 38,8 39,8 40,9
23,9 25,2 26,6 28,2 29,7 31,0 32,3 33,4 34,5 35,6 36,7 37,6 38,6
d,e
for fan size, D (mm) of:
FEG r
b,c
grade
265 280 300 315 335 355 375 400 425 450 475 500 530
FEG90 Optimum (peak) fan efficiency above the FEG85 grade
FEG85 70,3 71,8 73,5 74,6 75,9 77,0 77,9 78,9 79,7 80,4 81,0 81,5 81,9
FEG80 66,4 67,8 69,4 70,4 71,7 72,7 73,6 74,5 75,3 75,9 76,5 76,9 77,4
FEG75 62,7 64,0 65,5 66,5 67,6 68,6 69,5 70,3 71,1 71,7 72,2 72,6 73,0
FEG71 59,2 60,4 61,8 62,8 63,9 64,8 65,6 66,4 67,1 67,7 68,1 68,5 68,9
FEG67 55,9 57,0 58,4 59,3 60,3 61,2 61,9 62,7 63,3 63,9 64,3 64,7 65,1
FEG63 52,7 53,8 55,1 55,9 56,9 57,7 58,4 59,2 59,8 60,3 60,7 61,1 61,4
FEG60 49,8 50,8 52,0 52,8 53,7 54,5 55,2 55,9 56,5 56,9 57,3 57,7 58,0
FEG56 47,0 48,0 49,1 49,9 50,7 51,5 52,1 52,8 53,3 53,8 54,1 54,5 54,8
FEG53 44,4 45,3 46,4 47,1 47,9 48,6 49,2 49,8 50,3 50,7 51,1 51,4 51,7
FEG50 41,9 42,8 43,8 44,4 45,2 45,9 46,4 47,0 47,5 47,9 48,2 48,5 48,8
39,5 40,4 41,3 42,0 42,7 43,3 43,8 44,4 44,8 45,2 45,5 45,8 46,1
d,e
for fan size, D (mm) of:
r
FEG
b,c
grade
560 600 630 670 710 750 800 850 900 950 1 000
FEG90 Optimum (peak) fan efficiency above the FEG85 grade
FEG85 82,3 82,7 83,0 83,3 83,5 83,7 83,8 84,0 84,1 84,1 84,1
FEG80 77,7 78,1 78,4 78,6 78,8 79,0 79,1 79,3 79,3 79,4 79,4
FEG75 73,4 73,8 74,0 74,2 74,4 74,6 74,7 74,8 74,9 75,0 75,0
FEG71 69,3 69,6 69,8 70,1 70,3 70,4 70,5 70,6 70,7 70,8 70,8
FEG67 65,4 65,7 65,9 66,1 66,3 66,5 66,6 66,7 66,8 66,8 66,8
FEG63 61,7 62,1 62,2 62,4 62,6 62,7 62,9 63,0 63,0 63,1 63,1
FEG60 58,3 58,6 58,8 59,0 59,1 59,2 59,4 59,4 59,5 59,5 59,6
FEG56 55,0 55,3 55,5 55,7 55,8 55,9 56,0 56,1 56,2 56,2 56,2
FEG53 51,9 52,2 52,4 52,5 52,7 52,8 52,9 53,0 53,0 53,1 53,1
FEG50 49,0 49,3 49,4 49,6 49,7 49,8 49,9 50,0 50,1 50,1 50,1
46,3 46,5 46,7 46,8 47,0 47,0 47,1 47,2 47,3 47,3 47,3
The fan sizes in bold print in this table are in the R20 Series of preferred numbers (see ISO 13351). The values of efficiencies are
calculated for fan sizes in the preferred numbers in the R40 Series. If this method is used for a direct driven fan not having the shaft and
bearings integral to the fan, the fan efficiency is the impeller efficiency.
a
The optimum (peak) fan efficiency may be calculated from the fan total pressure (see ISO 5801:2007, Annex A).
b
The FEG grade for a given fan size is assigned when the fan optimum (peak) efficiency is equal to or lower than the value of
efficiency in the row for that grade and higher than the value of efficiency in the next row down.
c
No grade shall be considered for fans with optimum (peak) efficiency below FEG50.
d
The fan size is the maximum impeller tip diameter, D, in millimetres.
e
For any fan size larger than 1 000 mm, the values in the column for the size 1 000 mm apply.
12 © ISO 2010 – All rights reserved

ISO 12759:2010(E)
To evaluate the efficiency of a bare shaft fan combined with or fitted to a drive system, the method given in
Annex B shall be used. As previously stated, no direct comparison shall be made between this method and
that stated in 6.3.
6.3 Driven fans
6.3.1 General
The efficiency grades for driven fans are shown in Figures 6, 7 and 8; the variation of optimum efficiency and
FMEG grade is shown as a function of input power and design.
A fan belongs to a given FMEG grade (e.g. FMEG55) if its best (optimum) efficiency at full speed is equal to or
greater than the value calculated according to Annex F (see 6.3.2, 6.3.3 and 6.3.4), for the nominal efficiency
grade level, e.g. FMEG55, and relevant input power. Any efficiency line can be interpolated from those shown
in Figures 6, 7 and 8.
In cases where a volume control device is necessary, a variable speed drive is the best option, as it is the
most efficient method for adjustment to different operating points. Other options for volume control, such as
guide vanes and control valves, are less efficient.
Many fans are required for duties less than their maximum. The most efficient way of achieving this,
dependent on the system characteristic, is by speed reduction.
The curves of FMEGs are based on impeller and motor combinations. If a control device is used, the
efficiency data can be revised by the correction values, compensation factor, for controls given in Table 3 and
Figure 5. This is intended to put systems with variable speed drives on the same level as fixed speed systems
because it recognizes that there are energy-saving opportunities.
NOTE Built-in means constructed as a non-detachable part of a larger unit and also being an essential and
permanent part of the unit.
Table 3 — Compensation factor for fans fitted with variable speed drives
Drive/control electrical input power Compensation factor
P C
ed c
< 5 kW −0,03 × ln(P ) + 1,088
ed
W 5 kW 1,04
ISO 12759:2010(E)
C
c
1,16
1,15
1,14
1,13
1,12
1,11
1,10
1,09
1,08
1,07
1,06
1,05
1,04
1,03
1,02
1,01
1,00
01 234 56 300 400 500
P
ed
Key
P drive/control electrical input power (kW)
ed
C compensation factor
c
Figure 5 — Compensation factor for fans fitted with variable speed drives

6.3.2 Axial, forward curved or radial-bladed centrifugal driven fans
The graph in Figure 6 and Table 4 are generated by Equations (7), (8), (9) and (10).
a) For input power of less than or equal to 10 kW:
1) fan and motor
η = 2,74 × ln(P ) − 6,33 + N (7)
opt e G
2) fan, motor and drives
η = 2,74 × ln(P ) − 6,33 + N (8)
opt ed G
b) For input power greater than 10 kW:
1) fan and motor
η = 0,78 × ln(P ) − 1,88 + N (9)
opt e G
2) fan, motor and drives
η = 0,78 × ln(P ) − 1,88 + N (10)
opt ed G
14 © ISO 2010 – All rights reserved

ISO 12759:2010(E)
where
P is the input power, in kilowatts;
e
P is the drive/control electrical input power, in kilowatts;
ed
N is the grade number (integer) of the FMEG, e.g. N = 40 for FMEG40.
G G
Key
P defined input power (kW)
ed
η optimum efficiency (best efficiency point) (%)
opt
Figure 6 — Efficiency grades for axial, forward curved or radial-bladed centrifugal driven fans

ISO 12759:2010(E)
Table 4 — Efficiency grades for axial, forward curved or radial-bladed centrifugal driven fans
Input power 0,125 0,3 1,0 2,5 5 8 10 20 60 160 300 375 500
kW
Efficiency grade Optimum efficiency (best efficiency point)
%
FMEG27 15,0 17,4 20,7 23,2 25,1 26,4 27,0 27,5 28,3 29,1 29,6 29,7 30,0
FMEG31 19,0 21,4 24,7 27,2 29,1 30,4 31,0 31,5 32,3 33,1 33,6 33,7 34,0
FMEG35 23,0 25,4 28,7 31,2 33,1 34,4 35,0 35,5 36,3 37,1 37,6 37,7 38,0
FMEG39 27,0 29,4 32,7 35,2 37,1 38,4 39,0 39,5 40,3 41,1 41,6 41,7 42,0
FMEG42 30,0 32,4 35,7 38,2 40,1 41,4 42,0 42,5 43,3 44,1 44,6 44,7 45,0
FMEG46 34,0 36,4 39,7 42,2 44,1 45,4 46,0 46,5 47,3 48,1 48,6 48,7 49,0
FMEG50 38,0 40,4 43,7 46,2 48,1 49,4 50,0 50,5 51,3 52,1 52,6 52,7 53,0
FMEG53 41,0 43,4 46,7 49,2 51,1 52,4 53,0 53,5 54,3 55,1 55,6 55,7 56,0
FMEG55 43,0 45,4 48,7 51,2 53,1 54,4 55,0 55,5 56,3 57,1 57,6 57,7 58,0
FMEG58 46,0 48,4 51,7 54,2 56,1 57,4 58,0 58,5 59,3 60,1 60,6 60,7 61,0
FMEG60 48,0 50,4 53,7 56,2 58,1 59,4 60,0 60,5 61,3 62,1 62,6 62,7 63,0
FMEG62 50,0 52,4 55,7 58,2 60,1 61,4 62,0 62,5 63,3 64,1 64,6 64,7 65,0
FMEG64 52,0 54,4 57,7 60,2 62,1 63,4 64,0 64,5 65,3 66,1 66,6 66,7 67,0
FMEG66 54,0 56,4 59,7 62,2 64,1 65,4 66,0 66,5 67,3 68,1 68,6 68,7 69,0

6.3.3 Centrifugal backward-bladed fans (with and without housing) and mixed-flow driven fans
The graph in Figure 7 and Table 5 are generated by Equations (11), (12), (13) and (14):
a) For input power of less than or equal to 10 kW:
1) fan and motor
η = 4,56 × ln(P ) − 10,5 + N (11)
opt e G
2) fan, motor and drives
η = 4,56 × ln(P ) − 10,5 + N (12)
opt ed G
b) For input power greater than 10 kW:
1) fan and motor
η = 1,1 × ln(P ) − 2,6 + N (13)
opt e G
2) fan, motor and drives
η = 1,1 × ln(P ) − 2,6 + N (14)
opt ed G
where
P is the input power, in kilowatts;
e
P is the drive/control electrical input power, in kilowatts;
ed
N is the grade number (integer) of the FMEG, e.g. N = 40 for FMEG40.
G G
16 © ISO 2010 – All rights reserved

ISO 12759:2010(E)
Key
P defined input power (kW)
ed
η optimum efficiency (best efficiency point) (%)
opt
Figure 7 — Efficiency grades for centrifugal backward-bladed fans (with and without housing)
and mixed-flow driven fans
ISO 12759:2010(E)
Table 5 — Efficiency grades for centrifugal backward-bladed fans (with and without housing)
and mixed-flow driven fans
Input power 0,125 0,3 1,0 2,5 5 8 10 20 60 160 300 375 500
kW
Efficiency grade Optimum efficiency (best efficiency point)
%
FMEG35 15,0 19,0 24,5 28,7 31,8 34,0 35,0 35,7 36,9 38,0 38,7 38,9 39,2
FMEG39 19,0 23,0 28,5 32,7 35,8 38,0 39,0 39,7 40,9 42,0 42,7 42,9 43,2
FMEG42 22,0 26,0 31,5 35,7 38,8 41,0 42,0 42,7 43,9 45,0 45,7 45,9 46,2
FMEG46 26,0 30,0 35,5 39,7 42,8 45,0 46,0 46,7 47,9 49,0 49,7 49,9 50,2
FMEG50 30,0 34,0 39,5 43,7 46,8 49,0 50,0 50,7 51,9 53,0 53,7 53,9 54,2
FMEG53 33,0 37,0 42,5 46,7 49,8 52,0 53,0 53,7 54,9 56,0 56,7 56,9 57,2
FMEG55 35,0 39,0 44,5 48,7 51,8 54,0 55,0 55,7 56,9 58,0 58,7 58,9 59,2
FMEG58 38,0 42,0 47,5 51,7 54,8 57,0 58,0 58,7 59,9 61,0 61,7 61,9 62,2
FMEG60 40,0 44,0 49,5 53,7 56,8 59,0 60,0 60,7 61,9 63,0 63,7 63,9 64,2
FMEG62 42,0 46,0 51,5 55,7 58,8 61,0 62,0 62,7 63,9 65,0 65,7 65,9 66,2
FMEG64 44,0 48,0 53,5 57,7 60,8 63,0 64,0 64,7 65,9 67,0 67,7 67,9 68,2
FMEG66 46,0 50,0 55,5 59,7 62,8 65,0 66,0 66,7 67,9 69,0 69,7 69,9 70,2
FMEG68 48,0 52,0 57,5 61,7 64,8 67,0 68,0 68,7 69,9 71,0 71,7 71,9 72,2
FMEG70 50,0 54,0 59,5 63,7 66,8 69,0 70,0 70,7 71,9 73,0 73,7 73,9 74,2
FMEG72 52,0 56,0 61,5 65,7 68,8 71,0 72,0 72,7 73,9 75,0 75,7 75,9 76,2
FMEG74 54,0 58,0 63,5 67,7 70,8 73,0 74,0 74,7 75,9 77,0 77,7 77,9 78,2
FMEG76 56,0
...