ISO/FDIS 18976
(Main)Testing of refrigerant compressors
Testing of refrigerant compressors
The provisions of this document apply to Single-Stage and economised refrigerant compressors of the positive displacement type. Selected test methods are described for the determination of the refrigerating capacity, the power, the isentropic efficiency and the coefficient of performance. These test methods provide results of sufficient accuracy to permit consideration of the suitability of a refrigerant compressor to operate satisfactorily under any set of basic test conditions required for a given refrigeration installation. Attention is drawn in particular to a number of special precautions necessary to reduce testing losses to a minimum. This document applies only to tests carried out at the manufacturer’s works, or wherever the necessary equipment for testing to the accuracy required can be made available. The accuracy of measurement are specified in Clause 4. NOTE - Tests on complete refrigeration installations are dealt with in ISO 916. Annexes B and C, which provide additional information, do not form integral parts of this document.
Essais des compresseurs pour fluides frigorigènes
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FINAL DRAFT
International
Standard
ISO/TC 86/SC 4
Testing of refrigerant compressors
Secretariat: SAC
Essais des compresseurs pour fluides frigorigènes
Voting begins on:
2025-09-26
Voting terminates on:
2025-11-21
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TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 86/SC 4
Testing of refrigerant compressors
Secretariat: SAC
Essais des compresseurs pour fluides frigorigènes
Voting begins on:
Voting terminates on:
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland Reference number
ii
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
3.1 Terms and definitions .1
3.2 Symbols .3
4 Uncertainty of measurement and test conditions . 5
4.1 Uncertainty of performance data .5
4.2 Uncertainty of measurement .5
4.3 Refrigerant circuit state points .6
4.4 Test conditions .6
5 General requirements . 7
5.1 Calculation methods .7
5.1.1 Principle .7
5.1.2 Specific enthalpy .8
5.1.3 Refrigerant mass flow .8
5.1.4 Power input .8
5.1.5 Basic formulae .8
5.2 Requirements for the selection of a test method .10
5.2.1 General .10
5.2.2 Second concurrent test .10
5.3 Test period .11
5.3.1 General .11
5.3.2 Steady state conditions . .11
5.3.3 Recording of measured data .11
5.4 Pressure and temperature measuring points .11
5.5 Oil circulation .11
5.6 Fractionation . 12
5.7 Calibration of calorimeters . . 12
5.7.1 Heat leakage . 12
5.7.2 Reference temperature . 12
5.7.3 Calibration procedure. 12
5.8 Source of refrigerant data . 13
5.9 Kinetic refrigerant properties . 13
6 Test methods .13
6.1 General . 13
6.2 List of test methods . 13
6.2.1 Calorimetric methods . 13
6.2.2 Flow meter methods . 13
6.3 Choice of test methods for test X and test Y .14
6.4 Method A: Secondary fluid calorimeter .14
6.4.1 Description .14
6.4.2 Calibration . . .17
6.4.3 Test procedure.17
6.4.4 Requirements .17
6.4.5 Additional information .17
6.4.6 Determination of refrigerant mass flow .17
6.5 Method B: Flooded system calorimeter .17
6.5.1 Description .17
6.5.2 Calibration . . .18
6.5.3 Test procedure.18
6.5.4 Requirements .18
6.5.5 Additional information .18
iii
6.5.6 Determination of refrigerant mass flow .18
6.6 Method C: Dry system refrigerant calorimeter .19
6.6.1 Description .19
6.6.2 Calibration . . . 23
6.6.3 Test procedure. 23
6.6.4 Requirements . 23
6.6.5 Additional information . 23
6.6.6 Determination of refrigerant mass flow . 23
6.7 Method G: Water-cooled condenser/gas cooler on the discharge side .24
6.7.1 Description .24
6.7.2 Calibration .
...
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ISO/DISFDIS 18976:2024(en)
ISO/TC 86/SC 4/WG 4
Secretariat: DIN SAC
Date: 2025-04-14
Formatted: English (United Kingdom)
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Testing of refrigerant compressors
Essais des compresseurs pour fluides frigorigènes
FDIS stage
ISO/DISFDIS 18976:20242025(en)
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All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
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may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO'sISO’s member body in the country of the requester.
ISO Copyright Officecopyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
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Phone: + 41 22 749 01 11
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and numbers
Email: copyright@iso.org
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E-mail: copyright@iso.org
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Published in Switzerland.
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iii
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Contents Formatted: Adjust space between Latin and Asian text,
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Foreword . viii
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
3.1 Terms and definitions . 1
3.2 Symbols . 3
4 Uncertainty of measurement and test conditions . 5
4.1 Uncertainty of performance data . 5
4.2 Uncertainty of measurement . 6
4.3 Refrigerant circuit state points . 6
4.4 Test conditions . 7
5 General requirements . 8
5.1 Calculation methods . 8
5.2 Requirements for the selection of a test method . 12
5.3 Test period . 12
5.4 Pressure and temperature measuring points . 13
5.5 Oil circulation . 13
5.6 Fractionation . 14
5.7 Calibration of calorimeters . 14
5.8 Source of refrigerant data . 15
5.9 Kinetic refrigerant properties . 15
6 Test methods . 15
6.1 General . 15
6.2 List of test methods . 15
6.3 Choice of test methods for test X and test Y . 16
6.4 Method A: Secondary fluid calorimeter . 16
6.5 Method B: Flooded system calorimeter . 22
6.6 Method C: Dry system refrigerant calorimeter . 23
6.7 Method G: Water-cooled condenser/gas cooler on the discharge side . 31
6.8 Method D: Refrigerant gas flow meter . 34
6.9 Method F: Refrigerant flow meter in the liquid line . 38
6.10 Method M: Energy balance on compressor . 41
7 Determination of the power input by the compressor . 46
7.1 Measurement . 46
7.2 Calculation . 46
8 Test report . 46
8.1 General . 46
8.2 Test results . 47
Annex A (normative) Conversion of measured performance data to specified test conditions for
compressors with intermediate pressure port . 49
Annex B (informative) Estimation of errors . 54
Bibliography . 58
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Foreword . v Formatted: Font: 11 pt
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1 Scope . 1
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iv © ISO #### 2025 – All rights reserved
iv
ISO/DISFDIS 18976:20242025(en)
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2 Normative references . 1
3 Terms, definitions and symbols . 1
3.1 Terms and definitions . 1
3.2 Symbols . 3
4 Uncertainty of measurement and test conditions . 6
4.1 Uncertainty of performance data . 6
4.2 Uncertainty of measurement . 6
4.3 Test conditions . 7
5 General requirements . 8
5.1 Calculation methods . 8
5.1.1 Principle . 8
5.1.2 Specific enthalpy . 8
5.1.3 Refrigerant mass flow . 8
5.1.4 Power input . 8
5.1.5 Basic formulae . 9
5.2 Requirements for the selection of test method . 10
5.2.1 General . 10
5.2.2 Second concurrent test . 11
5.3 Test period . 11
5.3.1 General . 11
5.3.2 Steady state conditions . 11
5.3.3 Recording of measured data . 11
5.4 Pressure and temperature measuring points . 11
5.5 Oil circulation . 12
5.6 Fractionation . 12
5.7 Calibration of calorimeters . 12
5.7.1 Heat leakage . 12
5.7.2 Reference temperature. 12
5.7.3 Calibration procedure . 12
5.8 Source of refrigerant data . 13
5.9 Kinetic refrigerant properties . 13
6 Test methods . 13
6.1 General . 13
6.2 List of test methods . 13
6.2.1 Calorimetric methods . 13
6.2.2 6.2.2
...
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