IEC 60364-4-42

NORME CEI
INTERNATIONALE IEC
60364-4-42
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
2001-08
Installations électriques des bâtiments –
Partie 4-42:
Protection pour assurer la sécurité –
Protection contre les effets thermiques
Electrical installations of buildings –
Part 4-42:
Protection for safety –
Protection against thermal effects
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60364-4-42 © IEC:2001 – 3 –
CONTENTS
FOREWORD . 5
420.1 Scope . 7
420.2 Normative references . 7
421 Protection against fire . 9
422 Measures for protection against fire . 11
422.1 General . 11
422.2 Conditions of evacuation in an emergency . 11
422.3 Nature of processed or stored materials . 13
422.4 Combustible constructional materials . 15
422.5 Fire propagating structures . 15
423 Protection against burns. 17
424 Protection against overheating . 17
424.1 Forced air heating systems . 17
424.2 Appliances producing hot water or steam . 17
Annex A (informative) IEC 60364 – Parts 1 to 6: Restructuring . 19
Table 42A – Temperature limits in normal service for accessible parts of equipment
within arm’s reach . 17
Table A.1 – Relationship between restructured and original parts . 19
Table A.2 – Relationship between new and old clause numbering. 23

60364-4-42 © IEC:2001 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL INSTALLATIONS OF BUILDINGS –
Part 4-42: Protection for safety –
Protection against thermal effects
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60364-4-42 has been prepared by IEC technical committee 64:
Electrical installations and protection against electric shock.
The IEC 60364 series (parts 1 to 6), is currently being restructured, without any technical
changes, into a more simple form (see annex A).
According to a unanimous decision by the Committee of Action (CA/1720/RV (2000-03-21)),
the restructured parts of IEC 60364 have not been submitted to National Committees for
approval.
The text of this second edition of IEC 60364-4-42 is compiled from and replaces
– part 4-42, first edition (1980),
– part 4-482, first edition (1982).
This publication has been drafted, as close as possible, in accordance with the ISO/IEC
Directives, Part 3.
Annex A is for information only.
The committee has decided that the contents of this publication will remain unchanged
until 2004. At this date, the publication will be
 reconfirmed;
 withdrawn;
 replaced by a revised edition, or
 amended.
60364-4-42 © IEC:2001 – 7 –
ELECTRICAL INSTALLATIONS OF BUILDINGS –
Part 4-42: Protection for safety –
Protection against thermal effects
420.1 (421) Scope
Persons, fixed equipment, and fixed materials adjacent to electrical equipment shall be
protected against harmful effects of heat developed by electrical equipment, or thermal
radiation, particularly the following effects:
• combustion or degradation of materials;
• risk of burns;
• impairment of the safe function of installed equipment.
NOTE  Protection against overcurrent is dealt with in IEC 60364-4-43.
420.2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this part of IEC 60364. For dated references, subsequent amendments
to, or revisions of, any of these publications do not apply. However, parties to agreements
based on this part of IEC 60364 are encouraged to investigate the possibility of applying the
most recent editions of the normative documents indicated below. For undated references, the
latest edition of the normative document referred to applies. Members of IEC and ISO maintain
registers of currently valid International Standards.
IEC 60079-14:1996, Electrical apparatus for explosive gas atmospheres – Part 14: Electrical
installations in hazardous areas (other than mines)
IEC 60332-1:1993, Tests on electric cables under fire conditions – Part 1: Tests on a single
vertical insulated wire or cable
IEC 60332-3-10:2000, Tests on electric cables under fire conditions – Part 3-10: Test for
vertical flame spread of vertically-mounted bunched wires or cables – Apparatus
IEC 60332-3-21:2000, Tests on electric cables under fire conditions – Part 3-21: Test for
vertical flame spread of vertically-mounted bunched wires or cables – Category A F/R
IEC 60332-3-22:2000, Tests on electric cables under fire conditions – Part 3-22: Test for
vertical flame spread of vertically-mounted bunched wires or cables – Category A
IEC 60332-3-23:2000, Tests on electric cables under fire conditions – Part 3-23: Test for
vertical flame spread of vertically-mounted bunched wires or cables – Category B
IEC 60332-3-24:2000, Tests on electric cables under fire conditions – Part 3-24: Test for
vertical flame spread of vertically-mounted bunched wires or cables – Category C
________
In this standard, references in brackets refer to the previous numbering system.

60364-4-42 © IEC:2001 – 9 –
IEC 60332-3-25:2000, Tests on electric cables under fire conditions – Part 3-25: Test for
vertical flame spread of vertically-mounted bunched wires or cables – Category D
IEC 60364-4-41: Electrical installations of buildings – Part 4-41: Protection for safety –
Protection against electric shock
IEC 60364-4-43: Electrical installations of buildings – Part 4-43: Protection for safety –
Protection against overcurrent
IEC 60364-5-51: Electrical installations of buildings – Part 5-51: Selection and erection of
electrical equipment – Common rules
IEC 60614 (all parts), Conduits for electrical installations
421 (422)  Protection against fire
NOTE  Fire terms and related tests are under consideration by co-operation between ISO and IEC. The terms used
in this clause are provisional.
421.1 (422.1)  Electrical equipment shall not present a fire hazard to adjacent materials
Any relevant manufacturer’s erection instructions shall be observed in addition to the
requirements of IEC 60364.
421.2 (422.2)  Where fixed equipment may attain surface temperatures which could cause a
fire hazard to adjacent materials, the equipment shall either:
• be mounted on or within materials which will withstand such temperatures and are of low
thermal conductance, or
• be screened from elements of building construction by materials which will withstand such
temperatures and are of low thermal conductance, or
• be mounted to allow safe dissipation of heat at a sufficient distance from any material on
which such temperatures could have deleterious thermal effects, any means of support
being of low thermal conductance.
)  Where arcs or sparks may be emitted by permanently connected equipment in
421.3 (422.3
normal service, the equipment shall either:
• be totally enclosed in arc-resistant material, or
• be screened by arc-resistant material from building elements on which the arcs could have
deleterious thermal effects, or
• be mounted to allow safe extinction of the arc at a sufficient distance from building
elements on which the arc could have deleterious thermal effects.
Arc-resistant material used for this protective measure shall be non-combustible, of low
thermal conductivity, and of adequate thickness to provide mechanical stability.
421.4 (422.4)  Fixed equipment causing a focusing or concentration of heat shall be at a
sufficient distance from any fixed object or building element so that the object or element, in
normal conditions, cannot be subjected to a dangerous temperature.

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421.5 (422.5)  Wherever electrical equipment in a single location contains flammable liquid in
significant quantity, precautions shall be taken to prevent burning liquid and the products of
combus tion of the liquid (flame, smoke, toxic gases) spreading to other parts of the building.
NOTE 1  Examples of such precautions are
– a drainage pit to collect leakages of liquid and ensure their extinction in the event of fire, or
– installation of the equipment in a chamber of adequate fire resistance and the provision of sills or other means
of preventing burning liquid spreading to other parts of the building, such a chamber being ventilated solely to
the external atmosphere.
NOTE 2  The generally accepted lower limit for a significant quantity is 25 l.
NOTE 3  For less than 25 l, an arrangement to prevent the escape of liquid will suffice.
NOTE 4  It is desirable to switch off supply at the onset of a fire.
421.6 (422.6)  The materials of enclosures arranged around electrical equipment during
erection shall withstand the highest temperature likely to be produced by the electrical
equipment.
Combustible materials are not suitable for the construction of these enclosures unless
preventive measures against ignition are taken, such as covering with non-combustible or not
readily combustible material of low thermal conductivity.
422 (482)  Measures for protection against fire
422.1 (482.0)  General
The requirements of this clause shall be observed in addition to those of clause 421 for
installations in locations where the conditions of external influences described in 422.2 exist.
422.2 (482.1)  Conditions of evacuation in an emergency
Condition BD2: Low density occupation, difficult conditions of evacuation
BD3: High density occupation, easy conditions of evacuation
BD4: High density occupation, difficult conditions of evacuation
(according to table 51A of IEC 60364-5-51).
NOTE  Authorities responsible for building construction, public gatherings, fire prevention, etc. may specify
which BD condition is applicable.
422.2.1 (482.1.1)  In conditions BD2, BD3 and BD4, wiring systems shall not encroach on
escape routes unless the wiring is provided with sheaths or enclosures which, either during
the time authorized by regulations for building elements of the escape route or for 2 h in the
absence of such a regulation,
• will not contribute to, or propagate a fire, and
• will not attain a temperature high enough to ignite adjacent material.
NOTE  Tests on cables under fire conditions are given in IEC 60332-1, IEC 60332-3-10, IEC 60332-3-21,
IEC 60332-3-22, IEC 60332-3-23, IEC 60332-3-24 and IEC 60332-3-25. Tests on conduit under fire conditions are
given in IEC 60614.
Wiring systems encroaching on escape routes shall not be within arm's reach unless they are
provided with protection against mechanical damage likely to occur during an evacuation. Any
wiring systems in escape routes shall be as short as practicable.

60364-4-42 © IEC:2001 – 13 –
422.2.2 (482.1.2)  In conditions BD3 and BD4, switchgear and controlgear devices, except
certain devices to facilitate evacuation, shall be accessible only to authorized persons. If they
are placed in passages, they shall be enclosed in cabinets or boxes constructed of non-
combustible or not readily combustible material.
NOTE  Definitions for "non-combustible" and "not readily combustible" are under consideration.
422.2.3 (482.1.3)  In conditions BD3 and BD4 and in escape routes, the use of electrical
equipment containing flammable liquids is prohibited.
NOTE  Individual auxiliary capacitors incorporated in apparatus are not subject to this requirement. This exception
principally concerns discharge lamps and capacitors of motor starters.
422.3 (482.2)  Nature of processed or stored materials
Condition BE2: Fire risk (according to table 51A of IEC 60364-5-51).
NOTE 1  Quantities of flammable materials, surface or volume, of the locations may be regulated by national
authorities.
NOTE 2  For explosion risks, see IEC 60079-14.
422.3.1 (482.2.1)  Electrical equipment shall be restricted to that necessary to the use of these
locations, except wiring systems according to 422.3.6
422.3.2 (482.2.2)  Where it is expected that dust sufficient to cause a fire hazard could
accumulate on enclosures of electrical equipment, measures shall be taken to prevent the
enclosures from attaining excessive temperatures.
422.3.3 (482.2.3)  Electrical equipment shall be so selected and erected that its normal
temperature rise and foreseeable temperature rise during a fault cannot cause a fire.
These arrangements may be effected by the construction of equipment or its conditions of
installation.
Special measures are not necessary where the temperature of surfaces is unlikely to cause
combustion of nearby substances.
422.3.4 (482.2.4)  Switchgear for protection, control and isolation shall be placed outside
locations presenting BE2 conditions, unless it is in an enclosure providing a degree of
protection appropriate for such a location but at least IP4X.
422.3.5 (482.2.5)  Where wiring is not embedded in non-combustible material, precautions
shall be taken to
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