FprEN IEC 60335-2-21:2026
(Main)Household and similar electrical appliances - Safety - Part 2-21: Particular requirements for storage water heaters
- Abstract
IEC 60335-2-21:2022 deals with the safety of electric storage water heaters for household and similar purposes and intended for heating water below boiling temperature, their rated voltage being not more than 250 V for single-phase appliances and 480 V for other appliances including direct current (DC) supplied appliances and battery-operated appliances. This standard also deals with: – appliances not intended for normal household use, but which nevertheless possibly pose a source of danger to the public, such as appliances intended to be used by laymen in shops and on farms; – immersion heater units intended to be retrofitted in a heat exchange closed water heater having provision for retrofitting. Additional requirements are given in Annex AA. As far as is practicable, this standard deals with the common hazards presented by appliances that are encountered by all persons in and around the home. However, in general, it does not take into account – persons (including children) whose physical, sensory or mental capabilities, or lack of experience and knowledge prevents them from using the appliance safely without supervision or instruction; – children playing with the appliance. Attention is drawn to the fact that – for appliances intended to be used in vehicles or on board ships or aircraft, additional requirements can be necessary; – in many countries, additional requirements are specified by the national health authorities, the national authorities responsible for the protection of labour and similar authorities; – in many countries regulations exist for the installation of equipment connected to the water mains. This standard does not apply to – appliances for boiling water (IEC 60335-2-15); – instantaneous water heaters (IEC 60335-2-35); – commercial dispensing appliances and vending machines (IEC 60335-2-75); – appliances intended exclusively for industrial purposes; – appliances intended to be used in locations where special conditions prevail, such as the presence of a corrosive or explosive atmosphere (dust, vapour or gas). This seventh edition cancels and replaces the sixth edition published in 2012 and Amendment 1:2018. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a) the text has been aligned with IEC 60335-1:2020; b) some notes have been converted to normative text (Clause 1, 5.2, 15.3, 19.1, 19.2, 19.3, 19.4, 22.47, 22.104, 22.110, Annex AA introduction); c) updated requirement restricting use of appliance inlets (25.1). This part 2 is to be used in conjunction with the latest edition of IEC 60335-1 and its amendments unless that edition precludes it; in that case, the latest edition that does not preclude it is used. It was established on the basis of the sixth edition (2020) of that standard.
- Status
- Not Published
- Publication Date
- 02-May-2027
- Technical Committee
- CLC/TC 61 - Safety of household and similar electrical appliances
- Drafting Committee
- CLC/TC 61/WG 01 - Relation with standardization and legislation
- Current Stage
- 4599 - Dispatch of FV draft to CMC - Finalization for Vote
- Start Date
- 06-Oct-2026
- Due Date
- 06-Oct-2025
- Completion Date
- 06-Oct-2026
FprEN IEC 60335-2-21:2026 is a CENELEC draft European standard for the safety of electric storage water heaters. It specifies particular safety requirements for household and similar appliances that heat water below boiling temperature, and it also covers some non-household appliances that can still present a danger to the public. The document is used together with IEC 60335-1 and adds the special construction, marking, test, and installation rules for this appliance family.
What does FprEN IEC 60335-2-21:2026 specify?
FprEN IEC 60335-2-21:2026 covers the safety of electric storage water heaters for household and similar purposes, with rated voltage not more than 250 V for single-phase appliances and 480 V for other appliances, including direct current (DC) supplied and battery-operated appliances. It also covers immersion heater units intended for retrofit in a heat exchange closed water heater where retrofit is provided for.
The standard is written as a Part 2 to be used with IEC 60335-1. It supplements or modifies the general clauses of Part 1, and where a Part 1 subclause is not mentioned, that subclause applies as far as is reasonable.
It does not cover boiling water appliances, instantaneous water heaters, commercial dispensing appliances and vending machines, appliances intended exclusively for industrial purposes, or appliances for locations with special conditions such as corrosive or explosive atmospheres.
| Annex | What it covers |
|---|---|
| Annex A | Routine tests, including a pressure test |
| Annex R | Software evaluation for programmable electronic circuits |
| Annex AA | Additional requirements for immersion heater units intended for installation in heat exchange closed water heaters |
What are the key requirements of FprEN IEC 60335-2-21:2026?
FprEN IEC 60335-2-21:2026 focuses on how these water heaters are classified, marked, tested, and built so that pressure, overheating, leakage, and electrical hazards are controlled in normal use and foreseeable abnormal use.
Classification and enclosure protection
FprEN IEC 60335-2-21:2026 requires water heaters to be class I, class II or class III, and it sets minimum ingress protection for installation conditions. Water heaters installed outdoors shall be at least IPX4, while other water heaters shall be at least IPX1.
In practice, this tells the designer and buyer what insulation concept and enclosure protection are acceptable for the intended installation location.
Marking and instructions
FprEN IEC 60335-2-21:2026 requires the rated pressure and rated capacity to be marked, and it adds specific markings for closed water heaters, low-pressure water heaters, and open-outlet water heaters. The inlet and outlet also have to be identified, and blue and red are the stated colors if color coding is used.
The instructions for closed water heaters have to explain the pressure-relief device, the discharge pipe, regular operation of the device, and how the heater is drained. For heat exchange models, the instructions also have to cover control device installation and temperature settings so the thermal cut-out is not driven by heat from the exchanger.
This matters because installation errors are a major source of safety problems, especially where pressure relief, venting, and drainage are involved.
Heating and surface temperature checks
FprEN IEC 60335-2-21:2026 gives a temperature rise test for accessible surfaces and allows a probe from Figure 102 to be used where surfaces are suitably flat and accessible. Table 101 gives the permitted temperature rises for accessible surfaces under normal operating conditions.
The heater is operated until steady conditions are established or until the thermostat interrupts current for the first time after 16 h, whichever comes first. For a manufacturer, this means surface heating must be checked under a realistic long-run operating condition, not only at startup.
Abnormal operation and emptying scenarios
FprEN IEC 60335-2-21:2026 includes special abnormal-operation tests for closed water heaters, low-pressure water heaters and open-outlet water heaters. Some appliances not likely to be emptied in normal use are tested differently, while cistern-fed and cistern-type water heaters are not subjected to the same heating-element tests.
The abnormal-operation clauses also require that there be no leakage from the container during the tests. This is important because overheating and dry-running are credible service faults, and the standard checks that the appliance remains safe under those conditions.
Pressure resistance and pressure control
FprEN IEC 60335-2-21:2026 requires the container to withstand the relevant water pressure for its type, with separate pressure test conditions for closed, cistern-fed, low-pressure, open-outlet and cistern-type water heaters. Pressure-relief devices are rendered inoperative during the pressure test, and no leakage or permanent deformation that impairs compliance is allowed.
The construction clauses also limit the rated pressure of certain water heater types and require means to avoid excessive pressure in open-outlet, low-pressure and cistern-type designs. For the user, this means the product must be designed around the pressure condition it will actually see in service.
Thermal cut-out and control safety
FprEN IEC 60335-2-21:2026 requires closed water heaters to incorporate a thermal cut-out that provides all-pole disconnection and operates independently from the thermostat, with a neutral-conductor exception for fixed wiring. The cut-out must be non-self-resetting and arranged so it cannot simply reclose after a fault.
The operating temperature requirements are intended to keep the water temperature within safe limits or make the cut-out operate before its own temperature becomes too high. Where compliance depends on electronics, Annex R applies software evaluation and fault/error control measures.
That is important in practice because the cut-out is the last line of defence against dangerous overheating.
What terms does FprEN IEC 60335-2-21:2026 define?
- Storage water heater - A stationary appliance that heats and stores water in a container and includes devices that control water temperature.
- Closed water heater - An unvented storage water heater that operates at water-system pressure, with water flow controlled by valves in the outlet system.
- Cistern-fed water heater - A storage water heater vented to atmosphere and supplied by gravity from a separate cistern.
- Cistern-type water heater - A storage water heater with a cistern incorporated in the appliance, supplied by gravity.
- Open-outlet water heater - A storage water heater where flow is controlled only by a valve in the inlet pipe and expanded water leaves through the outlet.
- Low-pressure water heater - A vented storage water heater connected through a pressure reducing valve, with flow controlled by valves in the outlet system.
- Heat exchange water heater - A storage water heater that uses a heat exchanger immersed in the container to heat the water.
- Rated pressure - The water pressure assigned to the appliance by the manufacturer.
Who uses FprEN IEC 60335-2-21:2026?
FprEN IEC 60335-2-21:2026 is used by manufacturers of electric storage water heaters and immersion heater units, test laboratories, certification bodies, and safety engineers. It is also relevant to quality managers, compliance teams, and buyers who need to verify that a product design matches the intended installation type and pressure conditions.
Installers and technical specifiers use it when selecting pressure-relief devices, pressure reducing valves, venting arrangements, and mounting details. It is especially relevant in the domestic hot water, plumbing, water heating, and appliance safety sectors.
What changed in FprEN IEC 60335-2-21:2026 from the previous edition?
FprEN IEC 60335-2-21:2026 cancels and replaces the sixth edition published in 2012 and Amendment 1:2018. The stated technical changes are:
- the text has been aligned with IEC 60335-1:2020
- some notes have been converted to normative text in Clause 1, 5.2, 15.3, 19.1, 19.2, 19.3, 19.4, 22.47, 22.104, 22.110 and the Annex AA introduction
- the requirement restricting use of appliance inlets has been updated
Which standards are used with FprEN IEC 60335-2-21:2026?
FprEN IEC 60335-2-21:2026 is used with IEC 60335-1, which provides the general safety requirements that this Part 2 supplements and modifies. The document also depends on IEC 60584-1 for thermocouple EMF specifications and tolerances, which supports the temperature-measurement methods in the test clauses.
IEC 60730-1:2013, together with its amendments IEC 60730-1:2013/AMD1:2015 and IEC 60730-1:2013/AMD2:2020, contributes the control requirements used for thermal cut-outs and similar safety-related control functions.
What does the FprEN IEC 60335-2-21:2026 document contain?
FprEN IEC 60335-2-21:2026 contains the full Part 2 structure, from scope and references through construction, marking, tests, and Annexes. The main text includes test methods for heating, moisture resistance, abnormal operation, pressure resistance, mechanical strength, and thermal cut-out behaviour.
The document also includes Figure 101, which shows example storage water heater types, Figure 102, which shows the surface-temperature probe, and Figure 103, which shows thermocouple positions. Table 101 gives the temperature-rise limits for accessible surfaces under normal operation.
Annex A provides a routine pressure test, Annex R gives software evaluation rules for programmable electronic circuits, and Annex AA gives additional requirements for immersion heater units intended for retrofit in heat exchange closed water heaters. These annexes are the parts most likely to be used for product verification, routine production testing, and certification work.
Relations
- Effective Date
- 31-Oct-2023
- Effective Date
- 31-Oct-2023
- Effective Date
- 31-Oct-2023
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Frequently Asked Questions
FprEN IEC 60335-2-21:2026 is a draft published by CLC. Its full title is "Household and similar electrical appliances - Safety - Part 2-21: Particular requirements for storage water heaters". This standard covers: IEC 60335-2-21:2022 deals with the safety of electric storage water heaters for household and similar purposes and intended for heating water below boiling temperature, their rated voltage being not more than 250 V for single-phase appliances and 480 V for other appliances including direct current (DC) supplied appliances and battery-operated appliances. This standard also deals with: – appliances not intended for normal household use, but which nevertheless possibly pose a source of danger to the public, such as appliances intended to be used by laymen in shops and on farms; – immersion heater units intended to be retrofitted in a heat exchange closed water heater having provision for retrofitting. Additional requirements are given in Annex AA. As far as is practicable, this standard deals with the common hazards presented by appliances that are encountered by all persons in and around the home. However, in general, it does not take into account – persons (including children) whose physical, sensory or mental capabilities, or lack of experience and knowledge prevents them from using the appliance safely without supervision or instruction; – children playing with the appliance. Attention is drawn to the fact that – for appliances intended to be used in vehicles or on board ships or aircraft, additional requirements can be necessary; – in many countries, additional requirements are specified by the national health authorities, the national authorities responsible for the protection of labour and similar authorities; – in many countries regulations exist for the installation of equipment connected to the water mains. This standard does not apply to – appliances for boiling water (IEC 60335-2-15); – instantaneous water heaters (IEC 60335-2-35); – commercial dispensing appliances and vending machines (IEC 60335-2-75); – appliances intended exclusively for industrial purposes; – appliances intended to be used in locations where special conditions prevail, such as the presence of a corrosive or explosive atmosphere (dust, vapour or gas). This seventh edition cancels and replaces the sixth edition published in 2012 and Amendment 1:2018. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a) the text has been aligned with IEC 60335-1:2020; b) some notes have been converted to normative text (Clause 1, 5.2, 15.3, 19.1, 19.2, 19.3, 19.4, 22.47, 22.104, 22.110, Annex AA introduction); c) updated requirement restricting use of appliance inlets (25.1). This part 2 is to be used in conjunction with the latest edition of IEC 60335-1 and its amendments unless that edition precludes it; in that case, the latest edition that does not preclude it is used. It was established on the basis of the sixth edition (2020) of that standard.
IEC 60335-2-21:2022 deals with the safety of electric storage water heaters for household and similar purposes and intended for heating water below boiling temperature, their rated voltage being not more than 250 V for single-phase appliances and 480 V for other appliances including direct current (DC) supplied appliances and battery-operated appliances. This standard also deals with: – appliances not intended for normal household use, but which nevertheless possibly pose a source of danger to the public, such as appliances intended to be used by laymen in shops and on farms; – immersion heater units intended to be retrofitted in a heat exchange closed water heater having provision for retrofitting. Additional requirements are given in Annex AA. As far as is practicable, this standard deals with the common hazards presented by appliances that are encountered by all persons in and around the home. However, in general, it does not take into account – persons (including children) whose physical, sensory or mental capabilities, or lack of experience and knowledge prevents them from using the appliance safely without supervision or instruction; – children playing with the appliance. Attention is drawn to the fact that – for appliances intended to be used in vehicles or on board ships or aircraft, additional requirements can be necessary; – in many countries, additional requirements are specified by the national health authorities, the national authorities responsible for the protection of labour and similar authorities; – in many countries regulations exist for the installation of equipment connected to the water mains. This standard does not apply to – appliances for boiling water (IEC 60335-2-15); – instantaneous water heaters (IEC 60335-2-35); – commercial dispensing appliances and vending machines (IEC 60335-2-75); – appliances intended exclusively for industrial purposes; – appliances intended to be used in locations where special conditions prevail, such as the presence of a corrosive or explosive atmosphere (dust, vapour or gas). This seventh edition cancels and replaces the sixth edition published in 2012 and Amendment 1:2018. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a) the text has been aligned with IEC 60335-1:2020; b) some notes have been converted to normative text (Clause 1, 5.2, 15.3, 19.1, 19.2, 19.3, 19.4, 22.47, 22.104, 22.110, Annex AA introduction); c) updated requirement restricting use of appliance inlets (25.1). This part 2 is to be used in conjunction with the latest edition of IEC 60335-1 and its amendments unless that edition precludes it; in that case, the latest edition that does not preclude it is used. It was established on the basis of the sixth edition (2020) of that standard.
FprEN IEC 60335-2-21:2026 is classified under the following ICS (International Classification for Standards) categories: 13.120 - Domestic safety; 91.140.65 - Water heating equipment. The ICS classification helps identify the subject area and facilitates finding related standards.
FprEN IEC 60335-2-21:2026 has the following relationships with other standards: It is inter standard links to FprEN IEC 60335-2-21:2026/FprAA:2026, EN 60335-2-21:2021, EN 60335-2-21:2021/A1:2021. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
FprEN IEC 60335-2-21:2026 is associated with the following European legislation: EU Directives/Regulations: 2014/35/EU, 2014/53/EU; Standardization Mandates: M/511, M/536. When a standard is cited in the Official Journal of the European Union, products manufactured in conformity with it benefit from a presumption of conformity with the essential requirements of the corresponding EU directive or regulation.
FprEN IEC 60335-2-21:2026 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
01-september-2024
Gospodinjski in podobni električni aparati - Varnost - 2-21. del: Posebne zahteve
za akumulacijske grelnike vode
Household and similar electrical appliances - Safety - Part 2-21: Particular requirements
for storage water heaters
Sicherheit elektrischer Geräte für den Hausgebrauch und ähnliche Zwecke - Teil 2-21:
Besondere Anforderungen für Wassererwärmer (Warmwasserspeicher und
Warmwasserboiler)
Appareils électrodomestiques et analogues - Sécurité - Partie 2-21: Exigences
particulières pour les chauffe-eau à accumulation
Ta slovenski standard je istoveten z: prEN IEC 60335-2-21:2024
ICS:
13.120 Varnost na domu Domestic safety
91.140.65 Oprema za ogrevanje vode Water heating equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD DRAFT
prEN IEC 60335-2-21
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2024
ICS 13.120; 91.140.65 Will supersede EN 60335-2-21:2021; EN 60335-2-
21:2021/A1:2021
English Version
Household and similar electrical appliances - Safety - Part 2-21:
Particular requirements for storage water heaters
(IEC 60335-2-21:2022)
Appareils électrodomestiques et analogues - Sécurité - Sicherheit elektrischer Geräte für den Hausgebrauch und
Partie 2-21: Exigences particulières pour les chauffe-eau à ähnliche Zwecke - Teil 2-21: Besondere Anforderungen für
accumulation Wassererwärmer (Warmwasserspeicher und
(IEC 60335-2-21:2022) Warmwasserboiler)
(IEC 60335-2-21:2022)
This draft European Standard is submitted to CENELEC members for enquiry.
Deadline for CENELEC: 2024-09-06.
The text of this draft consists of the text of IEC 60335-2-21:2022.
If this draft becomes a European Standard, CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which
stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CENELEC in three official versions (English, French, German).
A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to
the CEN-CENELEC Management Centre has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.
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 supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and
shall not be referred to as a European Standard.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Project: 78879 Ref. No. prEN IEC 60335-2-21:2024 E
prEN IEC 60335-2-21:2024 (E)
1 European foreword
2 This document (prEN IEC 60335-2-21:2024) consists of the text of IEC 60335-2-21:2022 prepared by
3 IEC/TC 61 "Safety of household and similar electrical appliances".
4 This document is currently submitted to the Enquiry.
5 The following dates are proposed:
• latest date by which the existence of this (doa) dor + 6 months
document has to be announced at national
level
• latest date by which this document has to be (dop) dor + 12 months
implemented at national level by publication of
an identical national standard or by
endorsement
• latest date by which the national standards (dow) dor + 36 months
conflicting with this document have to be (to be confirmed or
withdrawn modified when voting)
6 This document is read in conjunction with prEN IEC 60335-2-21:2024/prAA:2024.
7 This document will supersede EN 60335-2-21:2021 and all of its amendments and corrigenda (if any).
8 This document has been prepared under a standardization request addressed to CENELEC by the European
9 Commission. The Standing Committee of the EFTA State subsequently approves these requests for its
10 Member States.
11 For relationship with EU legislation, see informative Annexes ZZA and ZZC, which are an integral part of
12 prEN IEC 60335-2-21:2024/prAA:2024.
IEC 60335-2-21 ®
Edition 7.0 2022-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Household and similar electrical appliances – Safety –
Part 2-21: Particular requirements for storage water heaters
Appareils électrodomestiques et analogues – Sécurité –
Partie 2-21: Exigences particulières pour les chauffe-eau à accumulation
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 13.120; 91.140.65 ISBN 978-2-8322-5858-3
– 2 – IEC 60335-2-21:2022 © IEC 2022
CONTENTS
FOREWORD . 4
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 9
3 Terms and definitions . 9
4 General requirement . 10
5 General conditions for the tests . 10
6 Classification . 10
7 Marking and instructions . 11
8 Protection against access to live parts . 12
9 Starting of motor-operated appliances . 12
10 Power input and current . 12
11 Heating . 12
12 Charging of metal-ion batteries . 13
13 Leakage current and electric strength at operating temperature . 13
14 Transient overvoltages . 13
15 Moisture resistance . 13
16 Leakage current and electric strength . 13
17 Overload protection of transformers and associated circuits . 14
18 Endurance . 14
19 Abnormal operation . 14
20 Stability and mechanical hazards . 15
21 Mechanical strength . 15
22 Construction . 15
23 Internal wiring . 17
24 Components . 18
25 Supply connection and external flexible cords . 19
26 Terminals for external conductors . 19
27 Provision for earthing . 19
28 Screws and connections . 19
29 Clearances, creepage distances and solid insulation . 20
30 Resistance to heat and fire . 20
31 Resistance to rusting . 20
32 Radiation, toxicity and similar hazards . 20
Annexes . 23
Annex A (informative) Routine tests . 23
Annex R (normative) Software evaluation . 24
Annex AA (normative) Additional requirement for immersion heater units intended for
the installation in heat exchange closed water heaters . 25
Bibliography . 28
IEC 60335-2-21:2022 © IEC 2022 – 3 –
Figure 101 – Examples of types of storage water heaters . 21
Figure 102 – Probe for measuring surface temperatures . 22
Figure 103 – Example of positions of the thermocouples . 22
Table 101 – Maximum temperature rises of external accessible surfaces under normal
operating conditions . 13
– 4 – IEC 60335-2-21:2022 © IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HOUSEHOLD AND SIMILAR ELECTRICAL APPLIANCES –
SAFETY –
Part 2-21: Particular requirements for storage water heaters
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,
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preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
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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.
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assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
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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.
IEC 60335-2-21 has been prepared by IEC technical committee 61: Safety of household and
similar electrical appliances. It is an International Standard.
This seventh edition cancels and replaces the sixth edition published in 2012 and
Amendment 1:2018. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the text has been aligned with IEC 60335-1:2020;
b) some notes have been converted to normative text (Clause 1, 5.2, 15.3, 19.1, 19.2, 19.3,
19.4, 22.47, 22.104, 22.110, Annex AA introduction);
c) updated requirement restricting use of appliance inlets (25.1).
IEC 60335-2-21:2022 © IEC 2022 – 5 –
The text of this International Standard is based on the following documents:
Draft Report on voting
61/6675/FDIS 61/6751/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.
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/standardsdev/publications.
A list of all parts of the IEC 60335 series, under the general title: Household and similar
electrical appliances – Safety, can be found on the IEC website.
This part 2 is to be used in conjunction with the latest edition of IEC 60335-1 and its
amendments unless that edition precludes it; in that case, the latest edition that does not
preclude it is used. It was established on the basis of the sixth edition (2020) of that standard.
NOTE 1 When "Part 1" is mentioned in this standard, it refers to IEC 60335-1.
This part 2 supplements or modifies the corresponding clauses in IEC 60335-1, so as to convert
that publication into the IEC standard: Particular requirements for storage water heaters.
When a particular subclause of Part 1 is not mentioned in this part 2, that subclause applies as
far as is reasonable. When this standard states "addition", "modification" or "replacement", the
relevant text in Part 1 is to be adapted accordingly.
NOTE 2 The following numbering system is used:
– subclauses, tables and figures that are numbered starting from 101 are additional to those in Part 1;
– unless notes are in a new subclause or involve notes in Part 1, they are numbered starting from 101, including
those in a replaced clause or subclause;
– additional annexes are lettered AA, BB, etc.
NOTE 3 The following print types are used:
– requirements: in roman type;
– test specifications: in italic type;
– notes: in small roman type.
Words in bold in the text are defined in Clause 3. When a definition concerns an adjective, the adjective and the
associated noun are also in bold.
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,
• replaced by a revised edition, or
• amended.
– 6 – IEC 60335-2-21:2022 © IEC 2022
NOTE 4 The attention of National Committees is drawn to the fact that equipment manufacturers and testing
organizations may need a transitional period following publication of a new, amended or revised IEC publication in
which to make products in accordance with the new requirements and to equip themselves for conducting new or
revised tests.
It is the recommendation of the committee that the content of this publication be adopted for implementation nationally
not earlier than 12 months or later than 36 months from the date of publication.
The following differences exist in the countries indicated below.
– Clause 1: Immersion heater units intended to be retrofitted in a heat exchange closed water
heater are not allowed unless:
• the immersion heater unit has been tested with the tank models and brands listed in the
instructions of the immersion heater unit;
• the tank models and brands list the models of the immersion heater units that can be
retrofitted (Australia, Netherlands, New Zealand).
– 6.1: Class 0I appliances are allowed (Japan).
– 6.2: IPX0 water heaters are allowed (France).
– 7.1: Additional markings are required (Australia, New Zealand and South Africa).
– 7.12.1: Additional instructions are required (South Africa).
– 13.2: An additional leakage current test is required (China).
– 22.101: Pressure reducing valves have to be designed for an inlet pressure of 2 MPa (South
Africa).
– 22.102: The temperature limit is 95 °C (South Africa).
– 22.101: The minimum rated pressure is 1,0 MPa (Denmark, Finland, Norway and Sweden).
– 22.103: Closed water heaters have to incorporate a pressure-relief device sensitive to both
pressure and temperature that operates before the water temperature reaches 99 °C (South
Africa).
– 22.103: Closed water heaters have to incorporate a temperature relief valve or a combined
temperature and pressure-relief valve that operates before the water temperature reaches
100 °C (United Kingdom).
– 22.106: The thermal cut-out of single-phase closed water heaters need only provide single-
pole disconnection (Japan).
– 22.106: For all closed water heaters, the thermal cut-out is to provide all-pole disconnection
(France).
– 22.110: Additional requirements apply to plastic or resin-based containers for open outlet,
cistern type and low pressure type (South Africa).
– 24.1.4 Additional requirements apply to thermal cut-outs (South Africa).
– 24.102: The maximum water temperature is 99 °C (Japan and Norway).
– 24.102: The temperature limit of 130 °C is only allowed for closed water heaters having a
rated pressure of at least 0,4 MPa (South Africa).
IEC 60335-2-21:2022 © IEC 2022 – 7 –
INTRODUCTION
It has been assumed in the drafting of this International Standard that the execution of its
provisions is entrusted to appropriately qualified and experienced persons.
Guidance documents concerning the application of the safety requirements for appliances can
be accessed via TC 61 supporting documents on the IEC website
https://www.iec.ch/tc61/supportingdocuments
This information is given for the convenience of users of this International Standard and does
not constitute a replacement for the normative text in this standard.
This standard recognizes the internationally accepted level of protection against hazards such
as electrical, mechanical, thermal, fire and radiation of appliances when operated as in normal
use taking into account the manufacturer's instructions. It also covers abnormal situations that
can be expected in practice and takes into account the way in which electromagnetic
phenomena can affect the safe operation of appliances.
This standard takes into account the requirements of IEC 60364 as far as possible so that there
is compatibility with the wiring rules when the appliance is connected to the supply mains.
However, national wiring rules can differ.
If an appliance within the scope of this standard also incorporates functions that are covered
by another part 2 of IEC 60335, the relevant part 2 is applied to each function separately, as
far as is reasonable. If applicable, the influence of one function on the other is taken into
account.
When a part 2 standard does not include additional requirements to cover hazards dealt with in
Part 1, Part 1 applies.
NOTE 1 This means that the technical committees responsible for the part 2 standards have determined that it is
not necessary to specify particular requirements for the appliance in question over and above the general
requirements.
This standard is a product family standard dealing with the safety of appliances and takes
precedence over horizontal and generic standards covering the same subject.
NOTE 2 Horizontal publications, basic safety publications and group safety publications covering a hazard are not
applicable since they have been taken into consideration when developing the general and particular requirements
for the IEC 60335 series of standards.
An appliance that complies with the text of this standard will not necessarily be considered to
comply with the safety principles of the standard if, when examined and tested, it is found to
have other features that impair the level of safety covered by these requirements.
An appliance employing materials or having forms of construction differing from those detailed
in the requirements of this standard may be examined and tested according to the intent of the
requirements and, if found to be substantially equivalent, may be considered to comply with the
standard.
NOTE 3 Standards dealing with non-safety aspects of household appliances are:
– IEC standards published by TC 59 concerning methods of measuring performance;
– CISPR 11, CISPR 14-1 and relevant IEC 61000-3 series standards concerning electromagnetic emissions;
– CISPR 14-2 concerning electromagnetic immunity;
– IEC standards published by TC 111 concerning environmental matters.
– 8 – IEC 60335-2-21:2022 © IEC 2022
HOUSEHOLD AND SIMILAR ELECTRICAL APPLIANCES –
SAFETY –
Part 2-21: Particular requirements for storage water heaters
1 Scope
This clause of Part 1 is replaced by the following.
This part of IEC 60335 deals with the safety of electric storage water heaters for household
and similar purposes and intended for heating water below boiling temperature, their rated
voltage being not more than 250 V for single-phase appliances and 480 V for other appliances
including direct current (DC) supplied appliances and battery-operated appliances.
This standard also deals with:
– appliances not intended for normal household use, but which nevertheless possibly pose a
source of danger to the public, such as appliances intended to be used by laymen in shops
and on farms;
– immersion heater units intended to be retrofitted in a heat exchange closed water heater
having provision for retrofitting. Additional requirements are given in Annex AA.
As far as is practicable, this standard deals with the common hazards presented by appliances
that are encountered by all persons in and around the home. However, in general, it does not
take into account
– persons (including children) whose
• physical, sensory or mental capabilities, or
• lack of experience and knowledge
prevents them from using the appliance safely without supervision or instruction;
– children playing with the appliance.
Attention is drawn to the fact that
– for appliances intended to be used in vehicles or on board ships or aircraft, additional
requirements can be necessary;
– in many countries, additional requirements are specified by the national health authorities,
the national authorities responsible for the protection of labour and similar authorities;
– in many countries regulations exist for the installation of equipment connected to the water
mains.
This standard does not apply to
– appliances for boiling water (IEC 60335-2-15);
– instantaneous water heaters (IEC 60335-2-35);
– commercial dispensing appliances and vending machines (IEC 60335-2-75);
– appliances intended exclusively for industrial purposes;
– appliances intended to be used in locations where special conditions prevail, such as the
presence of a corrosive or explosive atmosphere (dust, vapour or gas).
IEC 60335-2-21:2022 © IEC 2022 – 9 –
2 Normative references
This clause of Part 1 is applicable except as follows:
Addition:
IEC 60584-1, Thermocouples – Part 1: EMF specifications and tolerances
IEC 60730-1:2013, Automatic electrical controls – Part 1: General requirements
IEC 60730-1:2013/AMD1:2015
IEC 60730-1:2013/AMD2:2020
3 Terms and definitions
This clause of Part 1 is applicable except as follows.
3.1 Definitions relating to physical characteristics
3.1.9 Addition:
operation of the appliance after installation in accordance with the instructions and filled with
cold water
3.1.101
rated pressure
water pressure assigned to the appliance by the manufacturer
3.5 Definitions relating to types of appliances
3.5.101
storage water heater
stationary appliance for heating and storing water in a container and incorporating devices to
control the water temperature
3.5.102
closed water heater
unvented storage water heater intended to operate at the pressure of the water system, the
flow of water being controlled by one or more valves in the outlet system
Note 1 to entry: A closed water heater is shown in Figure 101a).
Note 2 to entry: The operating pressure may be the output pressure of a reducing or boosting device.
3.5.103
cistern-fed water heater
storage water heater that is vented to atmosphere and intended to be supplied by water under
gravity from a separate cistern, the flow of water being controlled by one or more valves in the
outlet system
Note 1 to entry: A cistern-fed water heater is shown in Figure 101d).
Note 2 to entry: The water heater may be installed so that the expanded water returns to the cistern.
Note 3 to entry: In a cistern-fed water heater, the pressure in the container results from the column of water in
the cistern.
– 10 – IEC 60335-2-21:2022 © IEC 2022
3.5.104
cistern-type water heater
storage water heater having a container supplied by water under gravity from a cistern
incorporated in the appliance
Note 1 to entry: The expanded water can return to the cistern, the flow of water being controlled by one or more
valves in the outlet system.
Note 2 to entry: A cistern-type water heater is shown in Figure 101c).
Note 3 to entry: In a cistern-type water heater, the surface of the water is always at atmospheric pressure.
3.5.105
open-outlet water heater
storage water heater in which the flow of water is only controlled by a valve in the inlet pipe
and in which the expanded or displaced water flows through the outlet
Note 1 to entry: An open-outlet water heater is shown in Figure 101b).
Note 2 to entry: In an open-outlet water heater, the static pressure at the outlet is always at atmospheric pressure.
3.5.106
low-pressure water heater
storage water heater that is vented to atmosphere and intended to be connected to the water
mains through a pressure reducing valve, the flow of water being controlled by one or more
valves in the outlet system
Note 1 to entry: A low-pressure water heater is shown in Figure 101e).
3.5.107
heat exchange water heater
storage water heater in which heated water is fed into a heat exchanger, such as a coiled tube
or similar device, which is itself immersed in a container with the water to be heated
Note 1 to entry: The heated water fed into the heat exchanger is heated from a pri
...