IEC 61666:2010

Industrial systems, installations and equipment and industrial products - Identification of terminals within a system

IEC 61666:2010 establishes general principles for the identification of terminals of objects within a system, applicable to all technical areas (for example mechanical engineering, electrical engineering, construction engineering, process engineering). They can be used for systems based on different technologies or for systems combining several technologies. This second edition cancels and replaces the first edition of IEC 61666 published in 1997 and edition constitutes a technical revision. It includes the following substantial changes with respect to the previous edition:
- the terminology used in the publication has been adapted to the one used in IEC 81346-1 Ed. 2;
- a more comprehensive description of the designation principles is provided;
- additional examples illustrating terminal designations related to the function aspect and location aspect are provided;
- an additional example illustrating the use of terminal designation sets is provided;
- the former informative Annex A has been turned into a clause in the standard.
IEC 61666:2010 has the status of a horizontal standard in accordance with IEC Guide 108

Systèmes industriels, installations et appareils, et produits industriels - Identification des bornes dans le cadre d'un système

L'IEC 61666:2010 établit les principes généraux en vue de l'identification des bornes des objets à l'intérieur d'un système, applicables à tous les domaines techniques (par exemple l'ingénierie mécanique, l'ingénierie électrique, l'ingénierie de la construction, l'ingénierie des procédés). Ils peuvent être appliqués à des systèmes reposant sur des techniques différentes ou combinant plusieurs techniques. Les exigences relatives au marquage des désignations de bornes sur les produits ne font pas partie de la présente publication. Cette deuxième édition annule et remplace la première édition publiée en 1997. Cette édition constitue une révision technique. Cette édition inclut les modifications substantielles suivantes par rapport à l'édition précédente:
- la terminologie utilisée dans la publication a été adaptée à celle utilisée dans l'IEC 81346-1 Ed. 2;
- une description plus complète des principes de désignation est fournie;
- des exemples additionnels illustrant des désignations de bornes se rapportant à l'aspect de fonction et l'aspect d'emplacement sont fournis;
- un exemple additionnel illustrant l'utilisation des ensembles de désignation de bornes est fourni;
- l'ancienne Annexe A (informative) a été transformée en un article de la norme.
L'IEC 61666:2010 a le statut de norme horizontale conformément au Guide IEC 108.

General Information

• Status: Published
• Publication Date: 15-Jun-2021
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 01.080.30 - Graphical symbols for use on mechanical engineering and construction drawings, diagrams, plans, maps and in relevant technical product documentation
• Technical Committee: TC 3 - Documentation, graphical symbols and representations of technical information
• Drafting Committee: MT 18 - TC 3/MT 18
• Current Stage: PPUB - Publication issued
• Start Date: 31-Aug-2010
• Completion Date: 19-Aug-2010

Relations

• Amended By: IEC 61666:2010/AMD1:2021 - Amendment 1 - Industrial systems, installations and equipment and industrial products - Identification of terminals within a system
• Effective Date: 05-Sep-2023
• Revises: IEC 61666:1997 - Industrial systems, installations and equipment and industrial products - Identification of terminals within a system
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 61666 ®
Edition 2.0 2010-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
HORIZONTAL STANDARD
NORME HORIZONTALE
Industrial systems, installations and equipment and industrial products –
Identification of terminals within a system

Systèmes industriels, installations et appareils, et produits industriels –
Identification des bornes dans le cadre d’un système

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by
any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either IEC or
IEC's member National Committee in the country of the requester.
If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,
please contact the address below or your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
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et les microfilms, sans l'accord écrit de la CEI ou du Comité national de la CEI du pays du demandeur.
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International Standards for all electrical, electronic and related technologies.

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IEC 61666 ®
Edition 2.0 2010-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
HORIZONTAL STANDARD
NORME HORIZONTALE
Industrial systems, installations and equipment and industrial products –
Identification of terminals within a system

Systèmes industriels, installations et appareils, et produits industriels –
Identification des bornes dans le cadre d’un système

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 01.080.30 ISBN 978-2-88912-148-9
– 2 – 61666 © IEC:2010
CONTENTS
FOREWORD.3
1 Scope.5
2 Normative references .5
3 Terms and definitions .5
4 Terminal designation .7
4.1 General .7
4.2 Designation of terminals with respect to the product aspect.8
4.3 Designation of terminals with respect to the function aspect .9
4.4 Designation of terminals with respect to the location aspect .10
4.5 Terminal designation set .11
5 Classification of terminals.13
Annex A (informative) Examples of terminal designations not specified by a
manufacturer .14
Bibliography.16

Figure 1 – Principle of terminal designation .7
Figure 2 – Example of designation of terminals for a 3-phase squirrel-cage motor .9
Figure 3 – A device shown with function labels on which the terminal designations
related to the function aspect are based, as well as terminal designations (pins) related
to the product aspect .10
Figure 4 – Example of a symbol for a motor starter provided with terminal designations
related to the function aspect.10
Figure 5 – Example of a terminal board for cross-connection where the terminals are
designated related to their location aspect .11
Figure 6 – Example of a terminal designation set.12
Figure 7 – Example of a design with terminal designations related to the function
aspect.12
Figure 8 – Example of an implemented design based on Figure 7 with terminal
designations related to the product aspect.13
Figure 9 – Example of an implemented design based on Figure 7 with terminal
designation sets related to the function and product aspects .13
Figure A.1 – Four terminal blocks composing one terminal assembly (each terminal

block is considered as an object) .14
Figure A.2 – One terminal block with eight terminals (the complete unit is an object) .15
Figure A.3 – One terminal block with eight terminals with two entry points each .15

61666  IEC:2010 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL SYSTEMS, INSTALLATIONS
AND EQUIPMENT AND INDUSTRIAL PRODUCTS –
IDENTIFICATION OF TERMINALS WITHIN A SYSTEM

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61666 has been prepared by IEC technical committee 3:
Information structures, documentation and graphical symbols
It has the status of a horizontal standard in accordance with IEC Guide 108.
This second edition cancels and replaces the first edition of IEC 61666 published in 1997.
This edition constitutes a technical revision.
This edition includes the following substantial changes with respect to the previous edition:
 the terminology used in the publication has been adapted to the one used in IEC 81346-1 Ed.2;
 a more comprehensive description of the designation principles is provided;
 additional examples illustrating terminal designations related to the function aspect and
location aspect are provided;
 an additional example illustrating the use of terminal designation sets is provided;
 the former informative Annex A has been turned into a clause in the standard.

– 4 – 61666 © IEC:2010
The text of this standard is based on the following documents:
FDIS Report on voting
3/1001/FDIS 3/1008/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
61666 © IEC:2010 – 5 –
INDUSTRIAL SYSTEMS, INSTALLATIONS
AND EQUIPMENT AND INDUSTRIAL PRODUCTS –
IDENTIFICATION OF TERMINALS WITHIN A SYSTEM

1 Scope
This International Standard establishes general principles for the identificatio
...

IEC 61666 ®
Edition 2.1 2021-06
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
HORIZONTAL PUBLICATION
PUBLICATION HORIZONTALE
Industrial systems, installations and equipment and industrial products –
Identification of terminals within a system

Systèmes industriels, installations et appareils, et produits industriels –
Identification des bornes dans le cadre d’un système

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
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IEC 61666 ®
Edition 2.1 2021-06
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
HORIZONTAL PUBLICATION
PUBLICATION HORIZONTALE
Industrial systems, installations and equipment and industrial products –

Identification of terminals within a system

Systèmes industriels, installations et appareils, et produits industriels –

Identification des bornes dans le cadre d’un système

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 01.080.30 ISBN 978-2-8322-9912-8

IEC 61666 ®
Edition 2.1 2021-06
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
HORIZONTAL PUBLICATION
PUBLICATION HORIZONTALE
Industrial systems, installations and equipment and industrial products –
Identification of terminals within a system

Systèmes industriels, installations et appareils, et produits industriels –
Identification des bornes dans le cadre d’un système

– 2 – IEC 61666:2010+AMD1:2021 CSV
 IEC 2021
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Terminal designation . 7
4.1 General . 7
4.2 Designation of terminals with respect to the product aspect. 8
4.3 Designation of terminals with respect to the function aspect . 9
4.4 Designation of terminals with respect to the location aspect . 10
4.5 Terminal designation set . 11
5 Classification of terminals . 14
Annex A (informative) Examples of terminal designations not specified by a
manufacturer . 15
Bibliography . 17

Figure 1 – Principle of terminal designation . 7
Figure 2 – Example of designation of terminals for a 3-phase squirrel-cage motor . 9
Figure 3 – A device shown with function labels on which the terminal designations
related to the function aspect are based, as well as terminal designations (pins) related
to the product aspect . 10
Figure 4 – Example of a symbol for a motor starter provided with terminal designations
related to the function aspect . 10
Figure 5 – Example of a terminal board for cross-connection where the terminals are
designated related to their location aspect . 11
Figure 6 – Example of a terminal designation set . 12
Figure 7 – Example of a design with terminal designations related to the function
aspect . 12
Figure 8 – Example of an implemented design based on Figure 7 with terminal
designations related to the product aspect . 13
Figure 9 – Example of an implemented design based on Figure 7 with terminal
designation sets related to the function and product aspects . 14
Figure A.1 – Four terminal blocks composing one terminal assembly (each terminal
block is considered as an object) . 15
Figure A.2 – One terminal block with eight terminals (the complete unit is an object) . 16
Figure A.3 – One terminal block with eight terminals with two entry points each . 16

 IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL SYSTEMS, INSTALLATIONS
AND EQUIPMENT AND INDUSTRIAL PRODUCTS –
IDENTIFICATION OF TERMINALS WITHIN A SYSTEM

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This consolidated version of the official IEC Standard and its amendment has been
prepared for user convenience.
IEC 61666 edition 2.1 contains the second edition (2010-08) [documents 3/1001/FDIS
and 3/1008/RVD] and its amendment 1 (2021-06) [documents 3/1487/FDIS and
3/1514/RVD].
In this Redline version, a vertical line in the margin shows where the technical content
is modified by amendment 1. Additions are in green text, deletions are in strikethrough
red text. A separate Final version with all changes accepted is available in this
publication.
– 4 – IEC 61666:2010+AMD1:2021 CSV
 IEC 2021
International Standard IEC 61666 has been prepared by IEC technical committee 3:
Information st
...