ISO 18483:2025

International
Standard
ISO 18483
First edition
Performance rating of centrifugal
2025-04
refrigerant compressor
Détermination des performances des compresseurs frigorifiques
centrifuges
Reference number
© ISO 2025
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Rating requirements . 3
4.1 General requirements .3
4.2 Rating methods .4
4.3 Rating conditions .4
4.4 Power supply requirements .5
5 Published rating . 5
5.1 Reference rating .5
5.2 Performance data .5
5.3 Application envelope .5
5.4 Published data.6
5.5 Tolerance .6
6 Marking provisions . 8
Annex A (informative) Example for the performance data . 9
Bibliography .10

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 86, Refrigeration and air-conditioning,
Subcommittee SC 4, Testing and rating of refrigerant compressors.
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iv
International Standard ISO 18483:2025(en)
Performance rating of centrifugal refrigerant compressor
1 Scope
This document specifies the rating requirements, published ratings and marking provisions of centrifugal
refrigerant compressors. This document applies to centrifugal compressors and their performance in
heating, ventilation and air-conditioning applications.
This document provides guidance and requirements for the industry, including manufacturers, engineers,
installers and contractors. It defines the minimum amount of information in a standardized form to enable
the evaluation and comparison of different compressors for use in an application and suggests a method to
be used to guarantee the accuracy of that information.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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 18976, Testing of refrigerant compressors
IEC 60038, IEC standard voltages
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
centrifugal refrigerant compressor
compressor relying on the impeller to increase the pressure and kinetic energy of the refrigerant vapour
before a portion of the kinetic energy is converted into pressure in the diffuser
Note 1 to entry: In this document, the term compressor implies centrifugal refrigerant compressor.
3.2
refrigerating capacity
product of the refrigerant mass flow at the compressor inlet port and the difference between the specific
refrigerant enthalpy at the compressor inlet port and the specific enthalpy of fluid entering the evaporator
expansion device
3.3
economizer
heat exchanger or flash tank that is used to lower the liquid specific enthalpy of the refrigerant entering the
evaporator while producing vapour that is reintroduced to the compression process

3.4
head factor
HF
ratio of isentropic enthalpy rise at each stage of the compressor to the square of suction sonic velocity
Note 1 to entry: This is a dimensionless parameter.
3.5
heating capacity
product of the refrigerant mass flow leaving the compressor discharge port and the difference of the specific
refrigerant enthalpy at the discharge port and the outlet of the condenser or gas cooler
3.6
heating coefficient of performance
C
OPh
ratio of heating capacity (3.5) to the power input
Note 1 to entry: This is a dimensionless parameter.
3.7
application envelope
allowable operation range of the compressor based on the suction dew-point and discharge dew-point
3.8
overall compressor efficiency
η
all
ratio of the isentropic enthalpy rise multiplied by the mass flow to the power input of the compressor
Note 1 to entry: This is a dimensionless parameter.
3.9
power input
time rate of energy usage of the compressor plus any accessories required to sustain operation of the
compressor at the rating condition
3.10
pressure ratio
π
ratio of the absolute discharge pressure to the absolute suction pressure of the compressor or compression stage
Note 1 to entry: This is a dimensionless parameter.
3.11
refrigerating coefficient of performance
C
OPr
ratio of refrigerating capacity to the power input
3.12
refrigerant flow factor
FF
ratio of suction volumetric flow of the compressor to the suction sonic velocity
Note 1 to entry: The flow coefficient excludes an impeller diameter squared term in the denominator to avoid exposing
proprietary dimensional information, therefore the units of measure are area (expressed in m ).
Note 2 to entry: This is a dimensionless parameter.
3.13
stage
basic unit of centrifugal compressor, which is composed of an impeller and its matching fixed elements that
works on the gas and realizes an energy increase

3.14
subcooling
difference between the bubble point temperature of the refrigerant corresponding to its pressure and the
temperature of the liquid refrigerant
3.15
superheat
difference between the temperature of the vapour refrigerant and its dew-point temperature corresponding
to its pressure
3.16
continuous modulating compressor
compressor with more than four displacement capacities or infinitely variable displacement capacities
Note 1 to entry: This includes but is not limited to variable speed, continuously variable mechanical unloading or
cyclic modulation of discrete.
3.17
discrete modulating compressor
compressor with two to four discrete displacement capacities
3.18
fixed modulation compressor
compressor with only one step
3.19
step
level of modulation achieved by changing the manufacturer defined operational setpoints
3.20
maximum step
maximum level of modulation defined by the manufacturer
3.21
minimum step
minimum level of modulation defined by the manufacturer
3.22
reduced step
level of modulation defined by the manufacturer which is less than the maximum step
3.23
publish
transfer information to any entity decided by the manufacturer
4 Rating requirements
4.1 General requirements
All published ratings shall be based on tests conducted in accordance with ISO 18976.
Published ratings shall be established with an ambient temperature of 35 °C around the compressor and
its accessories. If rating at ambient temperatures other than 35 °C, the actual ambient temperature used to
establish the rating shall be stated by the manufacturer.
The manufacturer is solely responsible for the determination of values to be used in published product
information.
4.2 Rating methods
Compressor performance data are provided in the context of a vapour compression cycle with the following
assumptions and requirements.
a) For all methods, other than mechanical sub-cooling in the economizer, parasitic heat gain or loss in the
liquid line shall be assumed to be zero.
b) Liquid temperature leaving the condenser shall be assumed to have 0 K subcooling unless otherwise
stated by the manufacturer.
c) The manufacturer shall specify the outlet liquid temperature of the economizer or the temperature
difference between the liquid leaving the economizer and the injected refrigerant entering the
intermediate heat exchanger.
d) Vapour temperature leaving the economizer shall be assumed to have superheat corresponding to the
pressure at the intermediate or interstage port of the compressor as follows:
1) superheat as declared by the manufacturer when rated with a specified heat exchanger as
economizer;
2) 5 K superheat when rated with a non-specified heat exchanger as economizer;
3) 0 K superheat when rated with a flash tank as economizer.
Unless otherwise
...