ISO 18501:2025
(Main)Performance rating of positive displacement refrigerant compressor
Performance rating of positive displacement refrigerant compressor
This document specifies normative references, terms and definitions, rating requirements, published rating, tolerance and marking provisions of positive displacement refrigerant compressors. This document applies to positive displacement refrigerant compressors and their performance in air-conditioning, heating, refrigeration and dehumidification applications. Single stage, two-stage and refrigerant-injected compressors without intermediate temperature load (only one evaporator) are included in this document. Subcritical operation and transcritical operation are also included in this document. Compressors for other applications, compression types and operations can also refer to this document. The manufacturer is solely responsible for the determination of values to be used in the published product information. This document is intended as guidance for the industry, including manufacturers, engineers, installers and service contractors. It defines the minimum amount of information in a standard form to enable the evaluation and comparison of different compressors for use in an application.
Détermination des performances des compresseurs frigorifiques à déplacement positif
General Information
- Status
- Published
- Publication Date
- 19-Mar-2025
- Technical Committee
- ISO/TC 86/SC 4 - Testing and rating of refrigerant compressors
- Drafting Committee
- ISO/TC 86/SC 4 - Testing and rating of refrigerant compressors
- Current Stage
- 6060 - International Standard published
- Start Date
- 20-Mar-2025
- Due Date
- 03-Oct-2025
- Completion Date
- 20-Mar-2025
Overview - ISO 18501:2025 (Performance rating of positive displacement refrigerant compressor)
ISO 18501:2025 provides a standardized framework for the performance rating and publication of data for positive displacement refrigerant compressors used in air‑conditioning, heating, refrigeration and dehumidification. It defines the minimum information, rating requirements, tolerances and marking provisions manufacturers should use so that compressors can be evaluated and compared for real applications. The document covers single‑stage, two‑stage and refrigerant‑injected compressors (with one evaporator), and includes subcritical and transcritical operation modes.
Key topics and technical requirements
- Scope and definitions: Terms for fixed and modulating compressors, economizer operation, superheat/subcooling, intermediate/interstage ports, VFDs, etc.
- Test basis: All published ratings must be based on tests conducted in accordance with ISO 18976.
- Rating conditions: Standardized rating points and application envelopes are defined (suction/ discharge conditions, superheat/subcooling, return gas), enabling consistent comparisons across compressors.
- Published rating data: Individual published ratings must include, at minimum, power input, refrigerating or heating capacity, refrigerant mass flow and current. Ratings may be provided as single points or via polynomial equations covering an application envelope.
- Modulating compressors: Requirements differ for fixed displacement, discrete modulating and continuous modulating compressors (number and form of published ratings).
- Economizer and liquid injection: Special reporting rules - e.g., controlled discharge temperature for liquid‑injected compressors and liquid temperatures for economized operation.
- Ambient and electrical conditions: Ratings are established with an ambient around the compressor of 35 °C and using nameplate rated voltage/frequency (guidance for dual‑voltage and voltage ranges).
- Tolerances and marking: The standard specifies tolerance provisions and minimum marking/data that must accompany published ratings.
- Informative annexes: Methods for handling zeotropic mixtures and superheat correction.
Practical applications - who uses ISO 18501:2025
- Compressor manufacturers - to publish consistent, comparable product data and comply with industry expectations.
- System designers and OEMs - to select compressors based on standardized performance metrics for HVACR systems.
- Engineers and consultants - for accurate load and performance calculations, including transcritical and economized systems.
- Installers and service contractors - to verify expected operating points, labeling and tolerance claims during installation and maintenance.
- Test laboratories and regulators - to align test reports and conformity checks with ISO testing/rating norms.
Related standards and keywords
- Related: ISO 18976 (Testing of refrigerant compressors), ISO 817 (refrigerant designation/safety), IEC 60038 (voltages).
- Relevant keywords for search and discovery: ISO 18501:2025, positive displacement refrigerant compressor, performance rating, refrigerant compressors, rating conditions, published rating, economizer, subcritical, transcritical, compressor tolerances, compressor marking.
Frequently Asked Questions
ISO 18501:2025 is a standard published by the International Organization for Standardization (ISO). Its full title is "Performance rating of positive displacement refrigerant compressor". This standard covers: This document specifies normative references, terms and definitions, rating requirements, published rating, tolerance and marking provisions of positive displacement refrigerant compressors. This document applies to positive displacement refrigerant compressors and their performance in air-conditioning, heating, refrigeration and dehumidification applications. Single stage, two-stage and refrigerant-injected compressors without intermediate temperature load (only one evaporator) are included in this document. Subcritical operation and transcritical operation are also included in this document. Compressors for other applications, compression types and operations can also refer to this document. The manufacturer is solely responsible for the determination of values to be used in the published product information. This document is intended as guidance for the industry, including manufacturers, engineers, installers and service contractors. It defines the minimum amount of information in a standard form to enable the evaluation and comparison of different compressors for use in an application.
This document specifies normative references, terms and definitions, rating requirements, published rating, tolerance and marking provisions of positive displacement refrigerant compressors. This document applies to positive displacement refrigerant compressors and their performance in air-conditioning, heating, refrigeration and dehumidification applications. Single stage, two-stage and refrigerant-injected compressors without intermediate temperature load (only one evaporator) are included in this document. Subcritical operation and transcritical operation are also included in this document. Compressors for other applications, compression types and operations can also refer to this document. The manufacturer is solely responsible for the determination of values to be used in the published product information. This document is intended as guidance for the industry, including manufacturers, engineers, installers and service contractors. It defines the minimum amount of information in a standard form to enable the evaluation and comparison of different compressors for use in an application.
ISO 18501:2025 is classified under the following ICS (International Classification for Standards) categories: 27.200 - Refrigerating technology. The ICS classification helps identify the subject area and facilitates finding related standards.
You can purchase ISO 18501:2025 directly from iTeh Standards. The document is available in PDF format and is delivered instantly after payment. Add the standard to your cart and complete the secure checkout process. iTeh Standards is an authorized distributor of ISO standards.
Standards Content (Sample)
International
Standard
ISO 18501
First edition
Performance rating of positive
2025-03
displacement refrigerant
compressor
Détermination des performances des compresseurs frigorifiques à
déplacement positif
Reference number
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication 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’s member body in the country of the requester.
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
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Rating requirements . 4
4.1 General requirements .4
4.2 Rating conditions .4
5 Published rating . 5
5.1 General requirements .5
5.2 Individual published rating .6
5.3 Number of individual published ratings requirement .6
5.4 Polynomial equations .6
5.5 Published data.7
5.6 Application envelope .8
6 Tolerance . . 8
7 Marking provisions .10
Annex A (informative) Method to handle zeotropic mixtures .11
Annex B (informative) Superheat correction .13
Bibliography . 14
iii
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.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 86, Refrigeration and air-conditioning,
Subcommittee SC 4, Testing and rating of refrigerant compressors.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
International Standard ISO 18501:2025(en)
Performance rating of positive displacement refrigerant
compressor
1 Scope
This document specifies normative references, terms and definitions, rating requirements, published
rating, tolerance and marking provisions of positive displacement refrigerant compressors. This document
applies to positive displacement refrigerant compressors and their performance in air-conditioning,
heating, refrigeration and dehumidification applications. Single stage, two-stage and refrigerant-injected
compressors without intermediate temperature load (only one evaporator) are included in this document.
Subcritical operation and transcritical operation are also included in this document.
Compressors for other applications, compression types and operations can also refer to this document.
The manufacturer is solely responsible for the determination of values to be used in the published product
information.
This document is intended as guidance for the industry, including manufacturers, engineers, installers
and service contractors. It defines the minimum amount of information in a standard form to enable the
evaluation and comparison of different compressors for use in an application.
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
ISO 817, Refrigerants — Designation and safety classification
IEC 60038, IEC standard voltages
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18976 and the following 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
positive displacement refrigerant compressor
machine that increases the pressure of a refrigerant vapour by reducing the compression chamber volume
3.2
fixed displacement compressor
compressor with only one displacement capacity
3.3
modulating compressor
compressor with more than one displacement capacity, either continuous or discrete modulating capacities
3.3.1
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.
3.3.2
discrete modulating compressor
compressor with two to four discrete displacement capacities
3.4
subcooling
difference between the bubble point temperature of the refrigerant corresponding to its pressure and the
temperature of the liquid refrigerant
3.5
superheat
difference between the temperature of the vapour refrigerant and its dew-point temperature corresponding
to its pressure
3.6
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
3.7
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
3.8
power input
time rate of energy usage of the compressor plus any accessories required to sustain operation of the
compressor at the rating condition
3.9
refrigerating coefficient of performance
ratio of the refrigerating capacity to the power input
3.10
heating coefficient of performance
ratio of heating capacity (3.7) to the power input
3.11
intermediate port
inlet port for vapour or liquid within a compression chamber at a pressure between suction and discharge
pressure
3.12
interstage port
inlet port for vapour or liquid between two stages of compression
3.13
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
3.14
economized operation
system operation mode which reduces the specific enthalpy of the refrigerant entering the evaporator and
produces vapour which is injected into the compression process
Note 1 to entry: For economized operation with heat exchanger economizer, partial high-pressure liquid refrigerant is
throttled to intermediate pressure to subcool the remaining refrigerant. The vapourized refrigerant can be piped to
the intermediate port or interstage port of the compressor.
Note 2 to entry: For economized operation with flash tank economizer, all refrigerant at outlet condenser is throttled
to intermediate pressure in the flash tank. The saturated liquid goes to evaporator loop and saturated vapour can be
piped to the intermediate port or interstage port of the compressor.
3.15
variable frequency drive
VFD
power electronic device supplying an electric motor with a variable frequency and voltage
3.16
subcritical operation
operating condition with discharge pressure below the critical pressure of the refrigerant
3.17
transcritical operation
operating condition with discharge pressure above and the suction pressure below the critical pressure
3.18
liquid injection
injection of high-pressure side liquid refrigerant into the compressor
3.19
step
level of modulation achieved by changing the displacement capacity
EXAMPLE Compressor operating frequency, compressor rotation speed, frequency of variable frequency drive
and mechanical unloading setting.
3.19.1
maximum step
step producing the highest displacement capacity of the modulating compressor defined by the manufacturer
3.19.2
minimum step
step producing the lowest displacement capacity of the modulating compressor defined by the manufacturer
3.19.3
reduced step
step producing less displacement capacity than the maximum step of the modulating compressor
3.20
fluid
liquid, gas or vapour including the state of appearance close to and above the critical pressure
3.21
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 around the compressor and its
accessories of 35 °C. If rating at ambient temperatures other than 35 °C, the actual ambient temperature
used to establish the rating shall be stated by the manufacturer.
Published ratings shall be established using the nameplate rated voltage and frequency. For dual nameplate
voltage ratings, published ratings shall be established using both voltages, or using the higher of the two
voltages, if only a single rating is to be published. For compressors with a voltage range, the rated voltage
should be published.
For liquid-injected compressors, the manufacturer shall report the controlled discharge temperature.
For economized compressors, refrigerating capacity including the increased refrigeration effect by the
subcooling or gas cooling provided by economizer operation shall be reported.
For economized operation compressors with manufacturer mounted or specified heat exchanger, the liquid
temperature leaving the heat exchanger shall be stated, if the refrigerant leaving at intermediate pressure is
not fully evaporated.
For economized operation compressors without a manufacturer specified intermediate heat exchanger, the
liquid refrigerant leaving the economizer shall be 5 K above the refrigerant temperature corresponding to
the pressure at the intermediate port or interstage port of the compressor and the specific enthalpy at the
outlet of the condenser.
For economized operation compressors with flash tank, liquid temperature leaving the flash tank shall be
equal to the bubble point temperature corresponding to the pressure at the intermediate port or interstage
port of the compressor.
4.2 Rating conditions
Rating conditions shown in Table 1 are provided for manufacturers to publish performance for the ease
of comparing with other compressors. If there is no applicable application or type, the manufacturer can
specify the rating conditions.
...
ISO 18501:2025は、ポジティブディスプレイスメント冷媒コンプレッサの性能評価に関する標準であり、非常に重要な文書です。この標準は、ポジティブディスプレイスメント冷媒コンプレッサの規範的参照、用語と定義、評価要件、公開された評価、許容差、マーク付けに関する規定を明確に定めています。また、エアコン、暖房、冷却、除湿の用途におけるポジティブディスプレイスメント冷媒コンプレッサの性能に適用されます。 この標準の強みは、その包括性にあります。単段、二段、および中間温度負荷なし（エバポレーターが1つのみ）の冷媒注入コンプレッサが対象となっており、サブクリティカルおよびトランスクリティカルな運転も含まれています。このような幅広い適用範囲により、さまざまなメーカーやエンジニア、インストーラー、サービス請負業者は、異なるコンプレッサを評価し、比較するための指針を得ることができます。 また、製造業者が公開する製品情報に使用する値の決定について責任を持つことが明記されているため、業界全体において透明性と一貫性が確保されます。このことは、信頼性の高いデータをもとにした意思決定をサポートし、業界全体の品質向上に寄与します。 ISO 18501:2025は、標準化された形式で必要な最小限の情報を提供し、異なるコンプレッサの性能を評価しやすくするための有用な文書であり、ポジティブディスプレイスメント冷媒コンプレッサの運用と選択において非常に relevant です。
Die ISO 18501:2025 bietet eine umfassende Norm für die Leistungsbewertung von positiv verdrängenden Kältemittelkompressoren und ist von hoher Relevanz für die Branche. Der Anwendungsbereich dieser Norm erstreckt sich über eine Vielzahl von Anwendungen, einschließlich Klimatisierung, Heizung, Kühlung und Entfeuchtung. Dies gewährleistet, dass die Norm für Einzelstufen-, Zwei-Stufen- und Kältemittel-injizierte Kompressoren ohne Zwischen-Temperaturbelastung anwendbar ist, was ihre Vielseitigkeit unterstreicht. Ein hervorstechendes Merkmal der ISO 18501:2025 ist die klare Definition und Festlegung von Normen, Begriffen und Bewertungsanforderungen. Diese präzisen Vorgaben ermöglichen eine einheitliche Bewertung und den Vergleich von Kompressoren, was für Hersteller, Ingenieure, Installateure und Servicedienstleister von immenser Bedeutung ist. Dank der normativen Verweise und der detaillierten Toleranz- und Kennzeichnungsbestimmungen bietet die Norm einen strukturierten Rahmen, der die Qualität und Zuverlässigkeit der Produkte sichert. Die Einbeziehung von subkritischen und transkritischen Betriebsbedingungen zeigt zudem, dass die Norm anpassungsfähig ist und moderne Anforderungen in der Kältetechnik berücksichtigt. Dies stellt sicher, dass auch innovative Technologien integriert werden können. Trotz der umfassenden Anforderungen ist der Hersteller für die Festlegung der Werte verantwortlich, die in den veröffentlichten Produktinformationen verwendet werden. Diese Regelung fördert die Verantwortung und Transparenz innerhalb der Branche. Die ISO 18501:2025 ist somit nicht nur eine technische Richtlinie, sondern auch ein wichtiges Instrument zur Gewährleistung eines hohen Standards in der Fertigung und Anwendung von Kältemittelkompressoren, was ihre Relevanz unterstreicht und zur Optimierung der Effizienz in der Industrie beiträgt.
ISO 18501:2025 표준은 긍정 변위 냉매 압축기의 성능 평가에 관한 포괄적인 지침을 제공합니다. 이 표준은 긍정 변위 냉매 압축기의 성능을 평가하기 위한 필수적인 참조사항, 용어 및 정의, 등급 요구사항, 발표된 등급, 허용 오차 및 마킹 규정을 명확히 합니다. 특히, 이 문서는 공기 조절, 난방, 냉동 및 탈습 응용 분야에서 사용되는 긍정 변위 냉매 압축기에 적용됩니다. 이 표준의 주요 강점은 단일 단계, 이단계 및 중간 온도 하중이 없는 냉매 주입 압축기를 포함하여 다양한 압축기의 작동 방식을 포괄적으로 정의하여 사용자의 선택을 돕는 것입니다. 또한, 기준을 제공함으로써 제조업체가 발표된 제품 정보를 작성하는 데 필요한 최소한의 정보를 규정하여 사용자가 다양한 압축기의 성능을 평가하고 비교할 수 있도록 지원합니다. ISO 18501:2025는 또한 아등급 작동 및 초급 작동까지 다루며, 이는 다양한 응용 프로그램에서의 압축기 성능을 고려할 수 있는 유연성을 제공합니다. 이 표준은 제조업체, 엔지니어, 설치자 및 서비스 계약자를 포함한 산업 전반에 유용한 지침을 제공합니다. 따라서 이 표준은 HVAC 산업의 발전에 매우 중요한 역할을 하며, 냉매 압축기 성능 평가의 표준화 뿐만 아니라, 시장의 투명성과 효율성을 증대시키는 데 기여할 것입니다.
La norme ISO 18501:2025 se positionne comme un document essentiel pour l'évaluation des performances des compresseurs de réfrigérant à déplacement positif. Son champ d'application est clairement défini, englobant non seulement les compresseurs utilisés dans le conditionnement d'air, le chauffage, la réfrigération et la déshumidification, mais aussi les compresseurs à un étage, à deux étages et ceux injectant un réfrigérant, sans charge thermique intermédiaire. Cela démontre une pertinence indéniable dans divers contextes d'application, tant pour les professionnels que pour les entreprises évoluant dans ces secteurs. L'un des points forts de la norme ISO 18501:2025 réside dans ses références normatives, ainsi que dans ses définitions de termes et exigences de notation qui favorisent la clarté et l'uniformité au sein de l'industrie. Cela permet non seulement aux fabricants d'élaborer des documents d'information sur leurs produits conformes, mais également aux ingénieurs et installateurs de réaliser des comparaisons plus faciles entre les différents modèles de compresseurs. L'inclusion d'opérations subcritiques et transcritiques renforce encore la fonctionnalité de la norme, la rendant appropriée pour une gamme élargie d'applications. En précisant que le fabricant est responsable de la détermination des valeurs à utiliser dans l'information publiée, la norme ISO 18501:2025 établit une responsabilisation qui encourage la transparence et la rigueur dans la communication des performances des produits. Cette approche non seulement garantit la fiabilité des informations, mais elle soutient également les utilisateurs finaux dans leur processus de décision. En somme, la norme ISO 18501:2025 constitue un cadre vital pour le secteur des compresseurs de réfrigérant à déplacement positif. En standardisant les exigences de notation et en assurant une compréhension claire des performances, elle renforce la compétitivité et l'innovation dans une industrie en constante évolution.
The ISO 18501:2025 standard presents a comprehensive framework for the performance rating of positive displacement refrigerant compressors. Its scope is meticulously defined, addressing key areas such as normative references, terms and definitions, and rating requirements applicable to a range of refrigeration applications including air-conditioning, heating, refrigeration, and dehumidification. One of the notable strengths of ISO 18501:2025 is its inclusion of both single-stage and two-stage compressors, as well as refrigerant-injected compressors that operate without an intermediate temperature load. This broad applicability ensures that a diverse range of systems can be assessed under a unified standard, facilitating easier comparisons across various technologies and methodologies. Moreover, the standard’s provisions for both subcritical and transcritical operation add to its relevance, as it aligns with current practices and innovations within the refrigeration industry. Furthermore, ISO 18501:2025 establishes specific guidelines for published ratings, tolerances, and marking provisions, which are crucial for maintaining clarity and consistency in product information. The emphasis on providing a standard form for manufacturers to present compressor performance data promotes transparency and fosters trust among stakeholders including engineers, installers, and service contractors. This is particularly relevant in helping end-users make informed decisions based on reliable and comparable performance metrics. The responsibility assigned to manufacturers for determining the values used in published information highlights the standard’s practical application within the industry. However, it also places an onus on manufacturers to ensure accuracy and compliance, thus encouraging a culture of accountability that can drive improvements in product quality and performance. Overall, the relevance of ISO 18501:2025 in the evolving landscape of refrigeration technology cannot be overstated. As the industry continues to innovate and optimize its processes, this standard serves as a vital resource for aligning operational practices with recognized benchmarks, ultimately enhancing the effectiveness and efficiency of positive displacement refrigerant compressors.
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.
Loading comments...