IEC 60335-2-73:2024

IEC 60335-2-73 ®
Edition 3.0 2024-03
EXTENDED VERSION
INTERNATIONAL
STANDARD
colour
inside
This extended version of IEC 60335-2-73:2024 includes the content of the references made to
IEC 60335-1:2020
Household and similar electrical appliances – Safety –
Part 2-73: Particular requirements for fixed immersion heaters
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IEC 60335-2-73 ®
Edition 3.0 2024-03
EXTENDED VERSION
INTERNATIONAL
STANDARD
colour
inside
This extended version of IEC 60335-2-73:2024 includes the content of the references made to
IEC 60335-1:2020
Household and similar electrical appliances – Safety –
Part 2-73: Particular requirements for fixed immersion heaters
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 01.140.65 ISBN 978-2-8322-8548-0

IEC 60335-1:2020/ISH1:2021 – 1 –
© IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
IEC 60335-1
Edition 6.0  2020-09
HOUSEHOLD AND SIMILAR ELECTRICAL APPLIANCES – SAFETY –

Part 1: General requirements
INTERPRETATION SHEET 1
This interpretation sheet has been prepared by IEC technical committee 61: Safety of
household and similar electrical appliances.
The text of this Interpretation Sheet is based on the following documents:
Draft Report on voting
61/5999/DISH 61/6009/RVDISH
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
___________
INTRODUCTION
Edition 6 of IEC 60335-1:2020 defines and introduces requirements for a detachable
power supply part of an appliance. In the document, 24.2 prohibits the use of a power
supply in a flexible cord.
QUESTION:
Does Subclause 24.2 prohibit the use of a detachable power supply part?
ANSWER
No, a "detachable power supply part" is a defined term and is not captured by the term
"power supply" as used in Subclause 24.2.
NOTE A detachable power supply part is captured by the defined term when the output of the power supply
part is detachable from the class III construction part of the appliance at:
– the power supply part, or
– the class III construction part of the appliance.
However, the supply cord (if any) does not have to be detachable from the detachable power supply part.
ICS 13.120; 97.030
IEC 60335-1:2020-09/ISH1:2021-11(en)

– 2 – IEC 60335-2-73:2024 EXV © IEC 2024
CONTENTS
FOREWORD . 6
INTRODUCTION . 9
1 Scope . 10
2 Normative references . 11
3 Terms and definitions . 16
4 General requirement . 27
5 General conditions for the tests . 27
6 Classification . 31
7 Marking and instructions . 32
8 Protection against access to live parts . 40
9 Starting of motor-operated appliances . 42
10 Power input and current . 42
11 Heating . 45
12 Charging of metal-ion batteries . 51
13 Leakage current and electric strength at operating temperature . 52
14 Transient overvoltages . 55
15 Moisture resistance . 56
16 Leakage current and electric strength . 58
17 Overload protection of transformers and associated circuits . 60
18 Endurance . 61
19 Abnormal operation . 61
20 Stability and mechanical hazards . 71
21 Mechanical strength . 72
22 Construction . 74
23 Internal wiring . 87
24 Components . 89
25 Supply connection and external flexible cords . 94
26 Terminals for external conductors . 102
27 Provision for earthing . 104
28 Screws and connections . 106
29 Clearances, creepage distances and solid insulation . 109
30 Resistance to heat and fire . 118
31 Resistance to rusting . 121
32 Radiation, toxicity and similar hazards . 122
Annex A (informative) Routine tests . 137
Annex B (normative) Battery-operated appliances, separable batteries and detachable
batteries for battery-operated appliances . 139
Annex C (normative) Ageing test on motors . 160
Annex D (normative) Thermal motor protectors . 161
Annex E (normative) Needle-flame test . 162
Annex F (normative) Capacitors . 163
Annex G (normative) Safety isolating transformers . 165

Annex H (normative) Switches . 166
Annex I (normative) Motors having basic insulation that is inadequate for the rated
voltage of the appliance . 168
Annex J (normative) Coated printed circuit boards . 170
Annex K (informative) Overvoltage categories . 171
Annex L (informative) Guidance for the measurement of clearances and creepage
distances . 172
Annex M (informative) Pollution degree . 175
Annex N (normative) Proof tracking test . 176
Annex O (informative) Selection and sequence of the tests of Clause 30 . 177
Annex P (informative) Guidance for the application of this standard to appliances
used in tropical climates . 182
Annex Q (informative) Sequence of tests for the evaluation of electronic circuits . 184
Annex R (normative) Software evaluation . 187
Annex S (informative) Guidance for the application of this standard on measurement
of power input and current based on the requirements of 10.1 and 10.2 concerning the
representative period . 201
Annex T (normative) UV-C radiation effect on non-metallic materials . 202
Annex U (normative) Appliances intended for remote communication through public
networks . 205
Bibliography . 209
Index of defined terms . 212

Figure 1 – Circuit diagram for leakage current measurement at operating temperature
for single-phase connection of class II appliances and for parts of class ll construction . 123
Figure 2 – Circuit diagram for leakage current measurement at operating temperature
for single-phase connection of other than class II appliances or parts of class ll
construction . 124
Figure 3 – Circuit diagram for leakage current measurement at operating temperature
for three-phase with neutral class II appliances and for parts of class ll construction . 125
Figure 4 – Circuit diagram for leakage current measurement at operating temperature
for three-phase with neutral appliances other than those of class II or parts of class ll
construction . 126
Figure 5 – Small part . 127
Figure 6 – Example of an electronic circuit with low-power points . 127
Figure 7 – Test finger nail . 128
Figure 8 – Flexing test apparatus . 129
Figure 9 – Constructions of cord anchorages . 130
Figure 10 – An example of parts of an earthing terminal . 131
Figure 11 – Examples of clearances . 132
Figure 12 – Example of the placement of the cylinder . 133
Figure 13 – Small parts cylinder . 134
Figure 14 – Example of a specified operating region of a lithium-ion cell during
charging . 135
Figure 101 – Probe for measuring surface temperatures . 136
Figure B.1 – Examples of battery-operated appliance constructions and application of
normative Annex B (1 of 2) . 157

– 4 – IEC 60335-2-73:2024 EXV © IEC 2024
Figure B.2 – Examples of correct polarity connection marking representing three
batteries . 159
Figure I.1 – Simulation of faults . 169
Figure L.1 – Sequence for the determination of clearances . 172
Figure L.2 – Sequence for the determination of creepage distances . 173
Figure L.3 – Measurement of clearances . 174
Figure O.1 – Tests for resistance to heat . 177
Figure O.2 – Selection and sequence of tests for resistance to fire in hand-held
appliances . 178
Figure O.3 – Selection and sequence of tests for resistance to fire in attended
appliances . 178
Figure O.4 – Selection and sequence of tests for resistance to fire in unattended
appliances . 179
Figure O.5 – Some applications of the term "within a distance of 3 mm" . 181
Figure Q.1 – Flowchart outlining the sequence of tests for the evaluation of electronic

circuits (1 of 2) . 185
Figure S.1 – Flowchart giving guidance on measurement of power input and current
concerning the representative period . 201

Table 1 – Power input deviation . 43
Table 2 – Current deviation . 44
Table 101 – Maximum temperature rises for specified external accessible surfaces
under normal operating conditions . 47
Table 3 – Maximum normal temperature rises . 48
Table 4 – Voltage for electric strength test . 54
Table 5 – Characteristics of high-voltage sources . 55
Table 6 – Impulse test voltage . 55
Table 7 – Test voltages. 60
Table 8 – Maximum winding temperature . 64
Table 9 – Maximum abnormal temperature rise . 69
Table 10 – Dimensions of cables and conduits . 95
Table 11 – Minimum cross-sectional area of conductors . 97
Table 12 – Pull force and torque . 99
Table 13 – Nominal cross-sectional area of conductors . 103
Table 14 – Torque for testing screws and nuts . 108
Table 15 – Rated impulse voltage . 110
Table 16 – Minimum clearances . 110
Table 17 – Minimum creepage distances for basic insulation . 114
Table 18 – Minimum creepage distances for functional insulation . 116
Table 19 – Minimum thickness for accessible parts of reinforced insulation consisting
of a single layer . 117
Table A.1 – Test voltages . 138
Table B.1 – Artificial source characteristics . 141
Table B.2 – Total area of openings for metal-ion cells . 149
Table B.3 – Volume of air injected at 2 070 kPa . 149
Table C.1 – Test conditions . 160

Table R.1 – General fault/error conditions . 189
Table R.2 – Specific fault/error conditions . 191
Table R.3 – Semi-formal methods . 197
Table R.4 – Software architecture specification . 197
Table R.5 – Module design specification . 198
Table R.6 – Design and coding standards . 199
Table R.7 – Software safety validation . 199
Table T.1 – Minimum property retention limits after UV-C exposure . 203
Table T.2 – Minimum electric strength for internal wiring after UV-C exposure . 204
Table U.1 – Examples of acceptable measures against unauthorised access and
transmission fault/error modes . 207

– 6 – IEC 60335-2-73:2024 EXV © IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HOUSEHOLD AND SIMILAR ELECTRICAL APPLIANCES –
SAFETY –
Part 2-73: Particular requirements for fixed immersion 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
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
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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
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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
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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.
This extended version (EXV) of the official IEC Standard provides the user with the
comprehensive content of the Standard.
made to IEC 60335-1:2020.
The specific content of IEC 60335-2-73:2024 is displayed on a blue background.

IEC 60335-2-73 has been prepared by IEC technical committee 61: Safety of household and
similar electrical appliances. It is an International Standard.
This third edition cancels and replaces the second edition published in 2002, Amendment 1:
2006 and Amendment 2: 2009. 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, 19.2);
c) addition of external accessible surface temperatures (Clause 11).
The text of this International Standard is based on the following documents:
Draft Report on voting
61/6954/CDV 61/7055A/RVC
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/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 fixed immersion 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.
– 8 – IEC 60335-2-73:2024 EXV © IEC 2024
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, or
• revised.
NOTE 4 The attention of National Committees is drawn to the fact that equipment manufacturers and testing
organizations can 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 the amendment 2 be adopted for implementation
nationally not earlier than 12 months or later than 36 months from the date of publication.

IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

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.

– 10 – IEC 60335-2-73:2024 EXV © IEC 2024
HOUSEHOLD AND SIMILAR ELECTRICAL APPLIANCES –
SAFETY –
Part 2-73: Particular requirements for fixed immersion heaters

1 Scope
This part of IEC 60335 deals with the safety of fixed electric immersion heaters for household
and similar purposes that are intended for installation in a water tank open to the atmosphere
for heating water to a temperature below its boiling point with a rated voltage of not more than
250 V for single-phase appliances and 480 V for other appliances including direct current (DC)
supplied appliances.
NOTE 101 The water tank can have alternative means for heating water, such as the circulation of hot water
supplied from a separate boiler.
Immersion heaters having a rated power input up to 25 kW for incorporation as an alternative
heating source in central heating boilers are also within the scope of this standard.
Appliances not intended for normal household use but which nevertheless can be a source of
danger to the public, such as appliances intended to be used by laypersons in shops, in light
industry and on farms, are within the scope of this standard.
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, the national water supply
authorities and similar authorities.
This standard does not apply to
– 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);
– heating elements incorporated in appliances such as
• appliances for heating liquids (IEC 60335-2-15);
• storage water heaters (IEC 60335-2-21);
• instantaneous water heaters (IEC 60335-2-35);
– aquarium heaters (IEC 60335-2-55);
– portable immersion heaters (IEC 60335-2-74);

– engine preheaters such as those for cars and buses.
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 60034-1, Rotating electrical machines – Part 1: Rating and performance
IEC 60061-1, Lamp caps and holders together with gauges for the control of interchangeability
and safety – Part 1: Lamp caps
IEC 60065:2014, Audio, video and similar electronic apparatus – Safety requirements
IEC 60068-2-2, Environmental testing – Part 2-2: Tests – Test B: Dry heat
IEC 60068-2-31, Environmental testing – Part 2-31: Tests – Test Ec: Rough handling shocks,
primarily for equipment-type specimens
IEC 60068-2-75, Environmental testing – Part 2-75: Tests – Test Eh: Hammer tests
IEC 60068-2-78, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat, steady state
IEC TR 60083, Plugs and socket-outlets for domestic and similar general use standardized in
member countries of IEC
IEC 60085:2007, Electrical insulation – Thermal evaluation and designation
IEC 60112:2003, Method for the determination of the proof and the comparative tracking indices
of solid insulating materials
IEC 60112:2003/AMD1:2009
IEC 60127 (all parts), Miniature fuses
IEC 60227 (all parts), Polyvinyl chloride insulated cables of rated voltages up to and including
450/750 V
IEC 60227-5:2011, Polyvinyl chloride insulated cables of rated voltages up to and including
450/750 V – Part 5: Flexible cables (cords)
IEC 60238, Edison screw lampholders
IEC 60245 (all parts), Rubber insulated cables – Rated voltages up to and including 450/750 V
IEC 60252-1:2010, AC motor capacitors – Part 1: General – Performance, testing and rating –
Safety requirements – Guidance for installation and operation
IEC 60252-1:2010/AMD1:2013
___________
There exists a consolidated edition 4.1:2009 that includes edition 4 and its Amendment 1.
There exists a consolidated edition 2.1:2013 that includes edition 2 and its Amendment 1.

– 12 – IEC 60335-2-73:2024 EXV © IEC 2024
IEC 60309-2, Plugs, socket-outlets and couplers for industrial purposes – Part 2: Dimensional
interchangeability requirements for pin and contact-tube accessories
IEC 60320 (all parts), Appliance couplers for household and similar general purposes
IEC 60320-1, Appliance couplers for household and similar general purposes – Part 1: General
requirements
IEC 60320-2-3, Appliance couplers for household and similar general purposes – Part 2-3:
Appliance couplers with a degree of protection higher than IPX0
IEC 60320-3, Appliance couplers for household and similar general purposes – Part 3: Standard
sheets and gauges
IEC 60384-14:2013, Fixed capacitors for use in electronic equipment – Part 14: Sectional
specification – Fixed capacitors for electromagnetic interference suppression and connection
to the supply mains
IEC 60384-14:2013/AMD1:2016
IEC 60417, Graphical symbols for use on equipment
IEC 60445:2017, Basic and safety principles for man-machine interface, marking and
identification – Identification of equipment terminals, conductor terminations and conductors
IEC 60529:1989, Degrees of protection provided by enclosures (IP Code)

IEC 60529:1989/AMD1:1999
IEC 60529:1989/AMD2:2013
IEC 60584-1, Thermocouples – Part 1: EMF specifications and tolerances
IEC 60598-1:2014, Luminaires – Part 1: General requirements and tests
IEC 60598-1:2014/AMD1:2017
IEC 60603-11, Connectors for frequencies below 3 MHz for use with printed boards – Part 11:
Detail specification for concentric connectors (dimensions for free connectors and fixed
connectors)
IEC 60664-1:2007, Insulation coordination for equipment within low-voltage systems – Part 1:
Principles, requirements and tests
IEC 60664-3:2016, Insulation coordination for equipment within low-voltage systems – Part 3:
Use of coating, potting or moulding for protection against pollution
IEC 60664-4:2005, Insulation coordination for equipment within low-voltage systems – Part 4:
Consideration of high-frequency voltage stress
IEC 60691, Thermal-links – Requirements and application guide
IEC 60695-2-11:2014, Fire hazard testing – Part 2-11: Glowing/hot-wire based test methods –
Glow-wire flammability test method for end-products (GWEPT)
___________
There exists a consolidated edition 4.1:2016 that includes edition 4 and its Amendment 1.
There exists a consolidated edition 2.2:2013 that includes edition 2 and its Amendment 1 and Amendment 2.
There exists a consolidated edition 8.1:2017 that includes edition 8 and its Amendment 1.

IEC 60695-2-12, Fire hazard testing – Part 2-12: Glowing/hot-wire based test methods – Glow-
wire flammability index (GWFI) test method for materials
IEC 60695-2-13, Fire hazard testing – Part 2-13: Glowing/hot-wire based test methods – Glow-
wire ignition temperature (GWIT) test method for materials
IEC 60695-10-2, Fire hazard testing – Part 10-2: Abnormal heat – Ball pressure test
IEC 60695-11-5:2016, Fire hazard testing – Part 11-5: Test flames – Needle-flame test method
– Apparatus, confirmatory test arrangement and guidance
IEC 60695-11-10, Fire hazard testing – Part 11-10: Test flames – 50 W horizontal and vertical
flame test methods
IEC 60730-1:2013, Automatic electrical controls – Part 1: General requirements
IEC 60730-1:2013/AMD1:2015
IEC 60730-2-8:2018, Automatic electrical controls – Part 2-8: Particular requirements for
electrically operated water valves, including mechanical requirements
IEC 60730-2-9:2015, Automatic electrical controls – Part 2-9: Particular requirements for
temperature sensing controls
IEC 60730-2-9:2015/AMD1:2018
IEC 60730-2-10, Automatic electrical controls for household and similar use – Part 2-10:
Particular requirements for motor-starting relays
IEC 60738-1, Thermistors – Directly heated positive temperature coefficient – Part 1: Generic
specification
IEC 60799, Electrical accessories – Cord sets and interconnection cord sets
IEC 60906-1, IEC system of plugs and socket-outlets for household and similar purposes –
Part 1: Plugs and socket-outlets 16 A 250 V a.c.
IEC 60934, Circuit-breakers for equipment (CBE)
IEC 60990:2016, Methods of measurement of touch current and protective conductor current
IEC 60999-1:1999, 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 61000-4-2, Electromagnetic compatibility (EMC) – Part 4-2: Testing and measurement
techniques – Electrostatic discharge immunity test
IEC 61000-4-3, Electromagnetic compatibility (EMC) – Part 4-3: Testing and measurement
techniques – Radiated, radio-frequency, electromagnetic field immunity test
___________
There exists a consolidated edition 5.1:2015 that includes edition 5 and its Amendment 1.
There exists a consolidated edition 4.1:2018 that includes edition 4 and its Amendment 1.

– 14 – IEC 60335-2-73:2024 EXV © IEC 2024
IEC 61000-4-4, Electromagnetic compatibility (EMC) – Part 4-4: Testing and measurement
techniques – Electrical fast transient/burst immunity test
IEC 61000-4-5, Electromagnetic compatibility (EMC) – Part 4-5: Testing and measurement
techniques – Surge immunity test
IEC 61000-4-6, Electromagnetic compatibility (EMC) – Part 4-6: Testing and measurement
techniques – Immunity to conducted disturbances, induced by radio-frequency fields
IE
...

IEC 60335-2-73 ®
Edition 3.0 2024-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Household and similar electrical appliances – Safety –
Part 2-73: Particular requirements for fixed immersion heaters

Appareils électrodomestiques et analogues – Sécurité –
Partie 2-73: Règles particulières pour les thermoplongeurs installés à poste fixe
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IEC 60335-2-73 ®
Edition 3.0 2024-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Household and similar electrical appliances – Safety –

Part 2-73: Particular requirements for fixed immersion heaters

Appareils électrodomestiques et analogues – Sécurité –

Partie 2-73: Règles particulières pour les thermoplongeurs installés à poste fixe

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 91.140.65  ISBN 978-2-8322-8459-9

– 2 – IEC 60335-2-73:2024 © IEC 2024
CONTENTS
FOREWORD . 3
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 8
3 Terms and definitions . 8
4 General requirement . 8
5 General conditions for the tests . 8
6 Classification . 8
7 Marking and instructions . 9
8 Protection against access to live parts . 9
9 Starting of motor-operated appliances . 9
10 Power input and current . 9
11 Heating . 9
12 Charging of metal-ion batteries . 10
13 Leakage current and electric strength at operating temperature . 10
14 Transient overvoltages . 10
15 Moisture resistance . 10
16 Leakage current and electric strength . 11
17 Overload protection of transformers and associated circuits . 11
18 Endurance . 11
19 Abnormal operation . 11
20 Stability and mechanical hazards . 11
21 Mechanical strength . 11
22 Construction . 11
23 Internal wiring . 12
24 Components . 12
25 Supply connection and external flexible cords . 12
26 Terminals for external conductors . 12
27 Provision for earthing . 12
28 Screws and connections . 12
29 Clearances, creepage distances and solid insulation . 12
30 Resistance to heat and fire . 12
31 Resistance to rusting . 13
32 Radiation, toxicity and similar hazards . 13
Annexes . 14
Bibliography . 15

Figure 101 – Probe for measuring surface temperatures . 13

Table 101 – Maximum temperature rises for specified external accessible surfaces
under normal operating conditions . 10

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HOUSEHOLD AND SIMILAR ELECTRICAL APPLIANCES –
SAFETY –
Part 2-73: Particular requirements for fixed immersion 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,
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 60335-2-73 has been prepared by IEC technical committee 61: Safety of household and
similar electrical appliances. It is an International Standard.
This third edition cancels and replaces the second edition published in 2002, Amendment 1:
2006 and Amendment 2: 2009. 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, 19.2);
c) addition of external accessible surface temperatures (Clause 11).

– 4 – IEC 60335-2-73:2024 © IEC 2024
The text of this International Standard is based on the following documents:
Draft Report on voting
61/6954/CDV 61/7055A/RVC
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/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 fixed immersion 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, or
• revised.
NOTE 4 The attention of National Committees is drawn to the fact that equipment manufacturers and testing
organizations can 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 the amendment 2 be adopted for implementation
nationally not earlier than 12 months or later than 36 months from the date of publication.

– 6 – IEC 60335-2-73:2024 © IEC 2024
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.

HOUSEHOLD AND SIMILAR ELECTRICAL APPLIANCES –
SAFETY –
Part 2-73: Particular requirements for fixed immersion heaters

1 Scope
This clause of Part 1 is replaced by the following.
This part of IEC 60335 deals with the safety of fixed electric immersion heaters for household
and similar purposes that are intended for installation in a water tank open to the atmosphere
for heating water to a temperature below its boiling point with a rated voltage of not more than
250 V for single-phase appliances and 480 V for other appliances including direct current (DC)
supplied appliances.
NOTE 101 The water tank can have alternative means for heating water, such as the circulation of hot water
supplied from a separate boiler.
Immersion heaters having a rated power input up to 25 kW for incorporation as an alternative
heating source in central heating boilers are also within the scope of this standard.
Appliances not intended for normal household use but which nevertheless can be a source of
danger to the public, such as appliances intended to be used by laypersons in shops, in light
industry and on farms, are within the scope of this standard.
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, the national water supply
authorities and similar authorities.
This standard does not apply to
– 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);
– heating elements incorporated in appliances such as
• appliances for heating liquids (IEC 60335-2-15);
• storage water heaters (IEC 60335-2-21);
• instantaneous water heaters (IEC 60335-2-35);

– 8 – IEC 60335-2-73:2024 © IEC 2024
– aquarium heaters (IEC 60335-2-55);
– portable immersion heaters (IEC 60335-2-74);
– engine preheaters such as those for cars and buses.
2 Normative references
This clause of Part 1 is applicable except as follows.
Addition:
IEC 60584-1, Thermocouples – Part 1: EMF specifications and tolerances
3 Terms and definitions
This clause of Part 1 is applicable except as follows.
3.1 Definitions relating to physical characteristics
3.1.9 Modification:
normal operation
Replace the first paragraph with the following:
operation of the appliance after installation in the smallest tank specified, the tank being
thermally insulated and filled with water
NOTE 101 to entry Accessible parts of the appliance are not thermally insulated.
4 General requirement
This clause of Part 1 is applicable.
5 General conditions for the tests
This clause of Part 1 is applicable except as follows.
5.2 Addition:
NOTE 101 Additional appliances can be required for the tests of Clause 19.
6 Classification
This clause of Part 1 is applicable except as follows.
6.1 Addition:
Immersion heaters shall be class I, class II or class III.

7 Marking and instructions
This clause of Part 1 is applicable except as follows.
7.1 Addition:
Appliances for multiple supply shall be marked with their rated power input for each supply
circuit.
Appliances shall be marked with the substance of "Do not cover".
7.12.1 Addition:
The installation instructions shall include the following:
– the type and dimensions of the tank in which the immersion heater can be installed;
– the positioning of the immersion heater within the tank;
– a statement that the installer must check that there is water in the tank before the immersion
heater is first switched on;
– a statement that the immersion heater is to be installed only in a system where the heating
element is always below water level, such as in a cistern-fed tank, if applicable.
8 Protection against access to live parts
This clause of Part 1 is applicable.
9 Starting of motor-operated appliances
This clause of Part 1 is not applicable.
10 Power input and current
This clause of Part 1 is applicable.
11 Heating
This clause of Part 1 is applicable except as follows.
11.3 Addition:
Where the external accessible surfaces are suitably flat and access permits, then the test probe
of Figure 101 is used to measure the temperature rises of external accessible surfaces specified
in Table 101. The probe is applied with a force of 4 N ± 1 N to the surface in such a way that
the best possible contact between the probe and the surface is ensured. The measurement is
performed after a contact period of 30 s.
The probe may be held in place using a laboratory stand clamp or similar device. Any measuring
instrument giving the same results as the probe may be used.

– 10 – IEC 60335-2-73:2024 © IEC 2024
11.7 Modification:
Replace the first paragraph with the following:
Appliances are operated until steady conditions are established. However, the test is terminated
after 24 h provided that a thermal control has operated.
11.8 Modification:
Replace the first paragraph with the following:
During the test, the temperature rises are monitored continuously and shall not exceed the
values shown in Table 3 and Table 101.
Table 101 – Maximum temperature rises for specified external accessible
surfaces under normal operating conditions
a
Surface
Temperature rise of external accessible surfaces
K
Bare metal 42
b
Coated metal
Glass and ceramic 56
c, d
Plastic and plastic coating > 0,4 mm
NOTE The temperature rise limits of handles, knobs, grips, keyboards, keypads and similar parts are specified in
Table 3.
a
Temperature rises are not measured on surfaces that are immersed during normal use or inaccessible to a
75 mm diameter probe having a hemispherical end.
b
Metal is considered coated when a coating having a minimum thickness of 90 µm made of enamel, powder or
non-substantially plastic coating is used.
c
The temperature rise limit of plastic also applies for plastic material having a metal finish of thickness less than
0,1 mm.
d
When the thickness of the plastic coating does not exceed 0,4 mm, the temperature rise limits of coated metal
for underlying metal apply or the temperature rise limits for glass or ceramic material for underlying glass or
ceramic material apply.
12 Charging of metal-ion batteries
This clause of Part 1 is applicable.
13 Leakage current and electric strength at operating temperature
This clause of Part 1 is applicable.
14 Transient overvoltages
This clause of Part 1 is applicable.
15 Moisture resistance
This clause of Part 1 is applicable.

16 Leakage current and electric strength
This clause of Part 1 is applicable.
17 Overload protection of transformers and associated circuits
This clause of Part 1 is applicable.
18 Endurance
This clause of Part 1 is not applicable.
19 Abnormal operation
This clause of Part 1 is applicable except as follows.
19.2 Addition:
Appliances are operated with the tank empty, any thermal control that operates during the test
of Clause 11 being short-circuited.
If more than one thermal control operates during the test of Clause 11, they are short-circuited
in turn.
The test is not carried out on immersion heaters intended to be installed in a system where the
heating element is always below water level, such as in a cistern-fed tank.
19.4 Addition:
Appliances are operated with the tank filled with water to at least 10 mm above the highest
point of the heating element, or the highest level allowed by the construction.
The water temperature shall not exceed 98 °C.
20 Stability and mechanical hazards
This clause of Part 1 is applicable.
21 Mechanical strength
This clause of Part 1 is applicable.
22 Construction
This clause of Part 1 is applicable except as follows.
22.101 Appliances shall be supplied with a seal or other means to ensure that there is no
leakage from the tank after installation.
Compliance is checked by inspection during the test of Clause 11.

– 12 – IEC 60335-2-73:2024 © IEC 2024
22.102 The compartment containing the supply terminals shall be prevented from rotating by
more than 180° with respect to the fixed part of the immersion heater.
Compliance is checked by inspection.
23 Internal wiring
This clause of Part 1 is applicable.
24 Components
This clause of Part 1 is applicable except as follows.
24.101 Thermal cut-outs incorporated for compliance with Clause 19 shall not be self-
resetting. They shall operate independently of the thermostat.
Compliance is checked by inspection.
25 Supply connection and external flexible cords
This clause of Part 1 is applicable.
26 Terminals for external conductors
This clause of Part 1 is applicable.
27 Provision for earthing
This clause of Part 1 is applicable except as follows.
27.1 Addition:
Metal parts of class I immersion heaters that are in contact with water shall be permanently
connected to the earthing terminal.
28 Screws and connections
This clause of Part 1 is applicable.
29 Clearances, creepage distances and solid insulation
This clause of Part 1 is applicable.
30 Resistance to heat and fire
This clause of Part 1 is applicable except as follows.
30.2.2 Not applicable.
31 Resistance to rusting
This clause of Part 1 is applicable.
32 Radiation, toxicity and similar hazards
This clause of Part 1 is applicable.

Key
A adhesive
B thermocouple wires 0,3 mm diameter to IEC 60584-1 Type K
C handle arrangement permitting a contact force of 4 N ± 1 N
D polycarbonate tube: inside diameter 3
...