IEC 63522-37:2025

IEC 63522-37 ®
Edition 1.0 2025-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical relays – Tests and measurements –
Part 37: Terminal temperature rise at rated load

Relais électriques – Essais et mesurages –
Partie 37: Échauffement des bornes à la charge assignée
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 Secretariat Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
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
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform IEC Products & Services Portal - products.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews, graphical symbols and the glossary.
committee, …). It also gives information on projects, replaced With a subscription you will always have access to up to date
and withdrawn publications. content tailored to your needs.

IEC Just Published - webstore.iec.ch/justpublished
Electropedia - www.electropedia.org
Stay up to date on all new IEC publications. Just Published
The world's leading online dictionary on electrotechnology,
details all new publications released. Available online and once
containing more than 22 500 terminological entries in English
a month by email.
and French, with equivalent terms in 25 additional languages.

Also known as the International Electrotechnical Vocabulary
IEC Customer Service Centre - webstore.iec.ch/csc
(IEV) online.
If you wish to give us your feedback on this publication or need

further assistance, please contact the Customer Service
Centre: sales@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Recherche de publications IEC -  IEC Products & Services Portal - products.iec.ch
webstore.iec.ch/advsearchform Découvrez notre puissant moteur de recherche et consultez
La recherche avancée permet de trouver des publications IEC gratuitement tous les aperçus des publications, symboles
en utilisant différents critères (numéro de référence, texte, graphiques et le glossaire. Avec un abonnement, vous aurez
comité d’études, …). Elle donne aussi des informations sur les toujours accès à un contenu à jour adapté à vos besoins.
projets et les publications remplacées ou retirées.

Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
Le premier dictionnaire d'électrotechnologie en ligne au monde,
Restez informé sur les nouvelles publications IEC. Just
avec plus de 22 500 articles terminologiques en anglais et en
Published détaille les nouvelles publications parues.
français, ainsi que les termes équivalents dans 25 langues
Disponible en ligne et une fois par mois par email.
additionnelles. Egalement appelé Vocabulaire

Electrotechnique International (IEV) en ligne.
Service Clients - webstore.iec.ch/csc

Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-nous:
sales@iec.ch.
IEC 63522-37 ®
Edition 1.0 2025-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical relays – Tests and measurements –

Part 37: Terminal temperature rise at rated load

Relais électriques – Essais et mesurages –

Partie 37: Échauffement des bornes à la charge assignée

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.120.70  ISBN 978-2-8327-0359-5

– 2 – IEC 63522-37:2025 © IEC 2025
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 6
4 Test procedure . 6
4.1 Purpose . 6
4.2 Procedure . 6
4.2.1 Test set-up . 6
4.2.2 Test procedure . 7
4.3 Conditions to be specified . 7
5 Evaluation . 8
5.1 General . 8
5.1.1 Process monitoring . 8
5.1.2 Visual inspection . 8
5.1.3 Final checking . 8
5.2 Test report . 8
Annex A (normative) Heating test arrangement . 9
Bibliography . 10

Figure A.1 – Test arrangement . 9

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL RELAYS –
TESTS AND MEASUREMENTS –
Part 37: Terminal temperature rise at rated load

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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC 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, IEC 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 https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 63522-37 has been prepared by IEC technical committee 94: Electrical relays. It is an
International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
94/1131/FDIS 94/1145/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.

– 4 – IEC 63522-37:2025 © IEC 2025
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
This International Standard is to be used in conjunction with IEC 63522-0:— .
A list of all parts of IEC 63522 series, published under the general title Electrical relays – Tests
and measurements, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
___________
Under preparation: Stage at the time of publication: IEC/CDV 63522-0:2024.

ELECTRICAL RELAYS –
TESTS AND MEASUREMENTS –
Part 37: Terminal temperature rise at rated load

1 Scope
This part of lEC 63522 is used for testing all kinds of electrical relays and for evaluating their
ability to perform under expected conditions of transportation, storage and all aspects of
operational use.
NOTE Examples for electrical relays in the sense of this document include electromechanical relays, reed relays,
reed contacts, reed switches, solid state relays, time relays and technology combinations of these.
The object of this document is to define a standard test method to measure terminal temperature
rise at rated load, included solder terminals, flat quick-connect terminations, screw and
screwless type terminals, alternative termination types and sockets.
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.
IEC 60584-1, Thermocouples – Part 1: EMF specifications and tolerances
IEC 60998-1, Connecting devices for low-voltage circuits for household and similar purposes –
Part 1: General requirements
IEC 60999-1, Connecting devices – Electrical copper conductors – Safety requirements for
screw-type and screwless-type clamping units – Part 1: General requirements and particular
2 2
requirements for clamping units for conductors from 0,2 mm up to 35 mm (included)
IEC 61810-1:2015, Electromechanical elementary relays – Part 1: General and safety
requirements
IEC 63522-0:—, Electrical relays – Tests and measurements – Part 0: General and guidance
IEC 63522-7, Electrical relays – Tests and measurements – Part 7: Functional tests
___________
Under preparation: Stage at the time of publication: IEC/CDV 63522-0:2024.
Under preparation: Stage at the time of publication: IEC/BPUB 63522-7:2024.

– 6 – IEC 63522-37:2025 © IEC 2025
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 63522-0 apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
4 Test procedure
4.1 Purpose
Terminal temperature rise at rated load test is to check that the relay terminals do not exceed
a given temperature rise, with the relay permanently energized and the contact(s) loaded with
maximum rated resistive load.
4.2 Procedure
4.2.1 Test set-up
The requirements of the test set-up shall be as follows.
a) Test procedure A – Group mounting: The test is carried out with three relays mounted side
by side in the same direction according to Annex A.
NOTE 1 See IEC 61810-1:2015, Table 5, test procedure A.
Test procedure B – Single mounting: The test is carried out with one relay.
NOTE 2 See IEC 61810-1:2015, Table 5, test procedure B.
Unless specifically designed otherwise, the DUTs are tested in the horizontal position with
the terminals pointing downwards. The mounting distance shall be stated by the
manufacturer.
b) Terminal screws and nuts or terminal screws are tightened with a torque equal to two-thirds
of that specified in IEC 60998-1 or IEC 60999-1.
NOTE 3 For relays for low-voltage circuits for household and similar purposes, use IEC 60998-1, and for relays
for other purposes, use IEC 60999-1.
c) In case of screwless terminals, ensure that the conductors are correctly fitted to the
terminals in accordance with IEC 60998-1 or IEC 60999-1.
NOTE 4 For relays for low-voltage circuits for household and similar purposes, use IEC 60998-1, and for relays
for other purposes, use IEC 60999-1.
d) The DUTs shall be mounted in a sufficiently large heat chamber without forced convection.
When an air circulating test chamber is used for testing, baffles shall be provided within the
test chamber, unless all other conditions in 4.2.1 are met.
e) The DUTs shall be protected from air draughts, solar influences and the like and it is not
allowed to be subjected to any artificial cooling.
f) During the test, the predetermined ambient temperature of the heat chamber shall not be
influenced by the DUT.
g) The ambient temperature shall be constantly at room temperature or alternatively equal to
the upper limit of the operating temperature range.

4.2.2 Test procedure
This test shall be performed at the maximum ambient temperature and altitude (if applicable)
specified for the DUTs being tested.
NOTE If the maximum altitude cannot be met, the test can be conducted by reducing atmospheric pressure. The
relationship between altitude and atmospheric pressure refers to IEC 60664-1.
The electrical interconnections between the relays or between the relays and the load shall be
made with conductors with a cross-sectional area according to IEC 63522-0:—, 4.7.
Temperature at the terminals is determined by means of fine wire thermocouples which are
positioned so that they have negligible effect on the temperature being determined. The
thermocouples shall be selected by the manufacturer in accordance with IEC 60584-1.
Generally, thermocouples with diameter of 0,320 mm (28 AWG) or 0,254 mm (30 AWG) are
recommended. The measuring points are positioned on the terminals as close as possible to
the body of the relay. During the test, thermocouples shall be positioned on every contact
terminal.
Other test methods than thermocouples are permitted, provided they show equivalent test
results.
The contacts shall be loaded with a nominal current or as specified by the manufacturer for the
contact set until thermal equilibrium.
The test procedure shall be as the following three steps, and terminal temperature rise shall be
monitored throughout the test.
1) During the first 3 h of this test, the relay coil shall not be energized. Break contacts shall be
loaded with the highest rated current.
2) During the next portion of the test, the coil of the relay shall be energized continuously for
97 h. The coil voltage shall be set to the maximum specified value. Make contacts shall
carry the highest rated resistive current at any convenient voltage.
3) Immediately following the operating period and with the relay still at the thermal equilibrium,
the relay shall be tested to determine that the energized function is completed when operate
voltage is applied. The lower limit of the operate voltage range shall be used for operating
function test.
4.3 Conditions to be specified
The conditions to be specified are the following:
a) ambient conditions;
b) energization value;
c) contact load: the load conditions of make contact and break contact shall be explained
separately, if they are not consistent;
d) mounting of the DUT;
e) method of determining temperature:
– thermocouple; or
– other method.
f) maximum permissible temperature rise of the terminals.

– 8 – IEC 63522-37:2025 © IEC 2025
5 Evaluation
5.1 General
5.1.1 Process monitoring
a) During the test, the temperature of relay terminals shall not exceed a maximum permissible
temperature rise. For elementary relay, the maximum permissible temperature rise given in
IEC 61810-1:2015, Clause 8, shall apply.
b) Immediately following the operating period and with the DUT still at the thermal equilibrium,
the DUT is energized by the lower limit of the operate voltage range or specified coil voltage
and the DUT works properly or sets/resets position for bi-stable relay.
5.1.2 Visual inspection
After the test, the appearance of the DUT shall be inspected, and both the relay case and plastic
parts near the relay body shall not be melted.
5.1.3 Final checking
a) After the test, the DUT is cooled down to approximately room temperature. The measured
final parameters shall be in accordance with IEC 63522-7 within the limits defined by the
manufacturer product specification.
b) Any other measurement, if required.
5.2 Test report
If this document is executed as a part of a test record of another standard, then the results shall
be reported as required in the other standard.
Otherwise, it is recommended to issue a dedicated test report according to this document.
The test report shall contain all the information necessary to reproduce the test. I
...