SIST HD 60364-4-42:2011

SLOVENSKI STANDARD
01-maj-2011
Nadomešča:
SIST HD 384.4.42 S1:2000
SIST HD 384.4.42 S1:2000/A1:2000
SIST HD 384.4.42 S1:2000/A2:2000
SIST HD 384.4.482 S1:2002
Nizkonapetostne električne inštalacije - 4-42. del: Zaščitni ukrepi - Zaščita pred
toplotnimi učinki (IEC 60364-4-42:2010, spremenjen)
Low voltage electrical installations - Part 4-42: Protection for safety - Protection against
thermal effects
Errichten von Niederspannungsanlagen - Teil 4-42: Schutzmaßnahmen - Schutz gegen
thermische Einflüsse
Installations électriques basse tension - Partie 4- 42: Protection pour assurer la sécurité -
Protection contre les effets thermiques
Ta slovenski standard je istoveten z: HD 60364-4-42:2011
ICS:
29.120.50 Varovalke in druga Fuses and other overcurrent
nadtokovna zaščita protection devices
91.140.50 Sistemi za oskrbo z elektriko Electricity supply systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

HARMONIZATION DOCUMENT
HD 60364-4-42
DOCUMENT D'HARMONISATION
March 2011
HARMONISIERUNGSDOKUMENT
ICS 29.120.50; 91.140.50 Supersedes HD 384.4.42 S1:1985 + A1:1992 + A2:1994

English version
Low voltage electrical installations -
Part 4-42: Protection for safety -
Protection against thermal effects
(IEC 60364-4-42:2010, modified)

Installations électriques basse tension -  Errichten von Niederspannungsanlagen -
Partie 4- 42: Protection pour assurer la Teil 4-42: Schutzmaßnahmen -
sécurité - Schutz gegen thermische Einflüsse
Protection contre les effets thermiques (IEC 60364-4-42:2010, modifiziert)
(CEI 60364-4-42:2010, modifiée)

This Harmonization Document was approved by CENELEC on 2011-02-14. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for implementation of this
Harmonization Document at national level.

Up-to-date lists and bibliographical references concerning such national implementations may be obtained on
application to the Central Secretariat or to any CENELEC member.

This Harmonization Document exists in three official versions (English, French, German).

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, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2011 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. HD 60364-4-42:2011 E
Foreword
The text of the International Standard IEC 60364-4-42:2010, prepared by IEC TC 64, Electrical installations
and protection against electric shock, together with common modifications prepared by the Technical
Committee CENELEC TC 64, Electrical installations and protection against electric shock, was submitted to
the formal vote and was approved by CENELEC as HD 60364-4-42 on 2011-02-14.

This European Standard supersedes HD 384.4.42 S1:1985 + A1:1992 + A2:1994.
The main changes with respect to HD 384.4.42 S1:1985 + A1:1992 + A2:1994 are listed below:
– The scope now includes protection against all thermal effects and flames in case of a fire hazard being
propagated from electrical installations to other fire compartments segregated by barriers which are in the
vicinity.
– Requirements associated with escape routes for evacuation in an emergency have been
expanded/modified.
– Requirements associated with the nature of processed or stored materials have been expanded/modified.
– Requirements associated with combustible constructional materials have been expanded/modified.
– Requirements associated with fire propagating structures have been modified slightly.
– New requirements for the selection and erection of installations in locations which might endanger
precious goods have been added.
– Protection against overheating now includes space heating appliances.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent rights.
The following dates were fixed:

– latest date by which the HD has to be implemented
at national level by publication of a harmonized
national standard or by endorsement (dop) 2012-02-14

– latest date by which the national standards conflicting
with the HD have to be withdrawn (dow) 2014-02-14
Annexes ZA to ZD have been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60364-4-42:2010 was approved by CENELEC as a Harmonization
Document with agreed common modifications as given below.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
[2] IEC 60079-14:1996 NOTE  Harmonized as EN 60079-14:1997 (not modified).
[5] IEC 60332-1-2:2004 NOTE  Harmonized as EN 60332-1-2:2004 (not modified).
[6] IEC 60332-3-21:2000 NOTE  Harmonized as EN 60332-3-21:2009 (modified).
[7] IEC 60332-3-22:2000 NOTE  Harmonized as EN 60332-3-22:2009 (not modified).

- 3 - HD 60364-4-42:2011
[8] IEC 60332-3-23:2000 NOTE  Harmonized as EN 60332-3-23:2009 (not modified).
[9] IEC 60332-3-24:2000 NOTE  Harmonized as EN 60332-3-24 (not modified).
[10] IEC 60332-3-25:2000 NOTE  Harmonized as EN 60332-3-25:2009 (not modified).
[11] IEC 60364-4-43 NOTE  Harmonized as HD 60364-4-43.
[13] IEC 60364-5-52 NOTE  Harmonized as HD 60364-5-52.
[16] IEC 60598 series NOTE  Harmonized in EN 60598 series (partially modified).
[17] IEC 60598-1:2003 NOTE  Harmonized as EN 60598-1:2004 (modified).
[18] IEC 60598-1:2008 NOTE  Harmonized as EN 60598-1:2008 (modified).
[19] IEC 60670-1 NOTE  Harmonized as EN 60670-1.
[20] IEC 60695-4 NOTE  Harmonized as EN 60695-4.
[21] IEC 60702-1 NOTE  Harmonized as EN 60702-1.
[22] IEC 60947-2 NOTE  Harmonized as EN 60947-2.
[23] IEC 61034-2 NOTE  Harmonized as EN 61034-2.
[25] IEC 61386-1 NOTE  Harmonized as EN 61386-1.
[26] IEC 61439-1 NOTE  Harmonized as EN 61439-1.
[27] IEC 62020 NOTE  Harmonized as EN 62020.
[28] IEC 62305 series NOTE  Harmonized in EN 62305 series (partially modified).

COMMON MODIFICATIONS
422 Precautions where particular risks of fire exist

422.3
Add the following note:
NOTE 3 Other locations having similar risk as those mentioned in IEC 60364-5-51, Table 51A, BE2 should also be considered, for
example commercial kitchens.
422.3.1
Modify the Note as follows:
F
Luminares marked    in accordance with EN 60598-1 are suitable for mounting on a normally flammable
surface.
422.3.9
Modify first line as follows:
Final circuits supplying or traversing the location and current using equipment, shall be protected against
insulation faults as follows:
422.3.12
Modify text as follows:
PEN conductors are not allowed in locations where condition BE2 applies, except for circuits traversing such
locations and having no connection between their traversing PEN conductor and any conductive part in this
location and erected in such a way as to reduce the risk of a fault between the pen conductor and any
conductive part in the location to a minimum.

Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application 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.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year

IEC 60332 Series Tests on electric and optical fibre cables under EN 60332 Series
fire conditions
IEC 60364-4-41 2005 Low-voltage electrical installations - HD 60364-4-41 2007
(mod) Part 4-41: Protection for safety - Protection + corr. July 2007
against electric shock
IEC 60364-5-51 2005 Electrical installations of building - HD 60364-5-51 2009
(mod) Part 5-51: Selection and erection of electrical
equipment - Common rules
IEC 60598-2-24 - Luminaires - EN 60598-2-24 -
(mod) Part 2: Particular requirements -
Section 24: Luminaires with limited surface
temperatures
IEC 61084 Series Cable trunking and ducting systems for - -
electrical installations
IEC 61386 Series Conduit systems for cable management EN 61386 Series

IEC 61534 Series Powertrack systems EN 61534 Series

IEC 61537 - Cable management - Cable tray systems EN 61537 -
and cable ladder systems
- 5 - HD 60364-4-42:2011
Annex ZB
(normative)
Special national conditions
Special national condition: National characteristic or practice that cannot be changed even over a long
period, e.g. climatic conditions, electrical earthing conditions.

NOTE If it affects harmonization, it forms part of the Harmonization Document.

For the countries in which the relevant special national conditions apply these provisions are normative, for
other countries they are informative.

Country Clause Wording
No.
420.1 In Germany the following additional requirements to the scope apply to
the second indent of clause 420.1 - against flames and smoke in case of
Germany
a fire hazard being propagated from electrical installations to other fire
compartments segregated by barriers which are in the vicinity, and
421.3 In Germany the following additional requirements for protection against
arcing apply:
421.3 Protective devices shall be installed for protection in case of
arcing where the electrical installation shall meet a high degree of
reliability.
Protective devices for the protection against arcing shall detect the light
effect of the arc and the increase of current in the line conductors.
Furthermore, they shall extinguish the arc within a time of 5 ms and
disconnect the electrical installation from the supply. The extinguishing

of the arc may not be generated before the set limiting values regarding
the light and current detection are exceeded.

Slowly acting protective devices are not able to prevent damage of
goods and that can make it impossible to put the electrical installation in
to operation again within a short time.

In general a separation by use of a metal sheet does not provide the
required arc withstand capability.

421.7 Where in case of a fire hazard from switchgear assemblies heavy smoke
generation in escape corridors may be assumed a sealed fire barrier for
the erection of the switchgear assembly is necessary.

This requirement is fulfilled if the switchgear assembly is placed in an
enclosure of non-combustible material or in a separate location. Ceilings
and walls of the separating location shall have a fireresisting capability
for a time of at least 90 min and doors for a time of at least 30 min.

422.1.2 Additional requirements apply in Germany:
“In Germany for the selection and erection of electrical equipment

Chapter 53 “Erection of low voltage installations –
Part 530: Selection and erection of electrical equipment – Switchgear and
controlgear” applies in addition.”
422.3 Section 422.3 includes, for example, the selection and erection of
installations in locations with risks of fire due to the nature of processed
or stored materials like the manufacturing, processing, storage of
combustible materials, including the accumulation of dust in barns,

wood working factories, paper mills, textile factories or similar.

NOTE  The nature and allowed quantities of combustible materials, or surface or
volume of the locations may be regulated by national authorities.

Country Clause Wording
No.
422.3 Additional requirements apply in Germany:
In Germany the classification in fire-hazard areas is in the response of
the operator/user of the electrical installation, taking into account, if
necessary, the accident prevention regulation BGV A1 by the employers'
liability insurance association/EU-directive 89/654/EWG.
He should consult an expert for the classification. The publication
VdS 2033 „Feuergefährdete Betriebsstätten und diesen gleichzustellende
Risiken“, published by the German Insurance Association (GDV),
contains suitable case studies. Thereafter fire hazard areas are rooms or
places in the rooms or outside in which the danger insists that after local
and operational relations easily flammable materials in hazardous
amount comes closer to the electrical equipment in such a way, that
higher temperatures or arcs form a fire hazard. These can be areas like
work rooms, dry rooms and storerooms, hay camps, straw camps, jute
camps and flax camps as well as such sites outside, e.g., in paper,
textiles or wooden processing companies.
„Easily flammable“ are ignitable firm materials which burn, exposed to
the flame of a match for 10 s, and after removing the ignition source burn
and glow further by itself. Those materials are like hay or straw, straw
dust, shavings, loose wood-wool, magnesium filings, brushwood, loose
paper, tree and cell woollen fibres.
422.3.4 Additional requirements apply in Germany:
NOTE 3  PVC-jacketed cables, e.g., NYM and NYY, and the cable types in Table 1 fulfil the

requirements.
NOTE 4  The recommendation to use cable with improved fire characteristics, is fulfilled,
if the types are according to Table 1. This cable types have also an improved protection
against corrosion damages with halogens and smoke damages.

Table 1 − Halogen-free cable with improved fire characteristics

Type short- Standard
sign
NHXMH DIN VDE 0250-214
(VDE 0250 Teil 214)
NHMH DIN VDE 0250-215
(VDE 0250 Teil 215)
NSHXA DIN VDE 0250-606
(VDE 0250 Teil 606)
H05Z-U DIN VDE 0282-9
H05Z-K (VDE 0282 Teil 9)
H07Z-U
H07Z-R
H07Z-K
H07ZZ-F DIN VDE 0282-13
(VDE 0282 Teil 13)
NHXH DIN VDE 0266 (VDE
0266)
NHXHX
NHXH FE
NHXCHX FE
NHXCH
NHXCHX
NHXCH FE
N2XH DIN VDE 0276-604
(VDE 0276 Teil 604)
N2XCH
- 7 - HD 60364-4-42:2011
Country Clause Wording
No.
Where an RCD may not be used, e.g. in the case of high operating
422.3.9a
currents, it is recommended to apply an equivalent protective measure,
e.g. a power switch with a coordinated RCD independent of the supply
voltage according to IEC 60947-2 - Residual current monitoring (RCM)
according to IEC 60020.
NOTE 1  This requirement is generally fulfilled if the disconnection occurs in a
time not exceeding 5 s. In electrical installations with a rated voltage 230/400 V

AC for this purpose RCD with a rated residual operating current not exceeding
300 mA are used.
NOTE 2  In the case of panel heating systems this requirement is fulfilled if the
disconnection occurs at a power of not more than 7 W at the place of the
insulation fault. In electrical installations with a rated voltage 230/400 V AC for
this purpose, RCDs with a rated residual operating current not exceeding 30 mA
are used.
422.3.9c Disconnection is not necessary where provisions are taken to prevent
Germany the occurrence of a fire hazard by short circuits or earth faults caused by
external influences like mechanical stresses.
422.3.9d Disconnection is not required for circuits which are erected in a short-
circuit and earth leakage proof manner.

NOTE 3  For short-circuit and earth leakage proof installation methods of wiring
systems see IEC 60364-5-52 and IEC 60439-1.

In every circuit the protective conductor shall be installed in close
422.3.9e
proximity to the live conductors and shall be introduced in equipment of

class II construction.
NOTE 4  For further requirements for floor and ceiling heating systems see
IEC 60364-7-753.
422.3.13 Delete Subclause 422.3.13
422.3.9 In Norway, RCDs with a rated residual operating current not exceeding
Norway 30 mA shall be used in IT installations connected to a public low voltage
distribution network.
424.1 In Norway, the following additional requirements apply:
In Norway it is required that one of the temperature limiting devices is a

thermal release. The thermal release shall disconnect all live conductors
and shall have manual resetting.
422.3.9 Additional requirements apply in the Czech Republic: the first sentence of
422.3.9 is as follows:
“Final circuits and current-using equipment, with the exception of wiring
Czech
systems enclosed in enclosures having degree of protection at least IP4X, shall
Republic
be protected against insulation faults as follows:”

422.4.1 Connections in junction boxes in a hollow combustible wall shall
Ireland comply with 526, and shall in addition be provided with a means of
strain-relief:
Ireland 422.2 Not applicable in Ireland
In Ireland, the following applies:
422.4.1
Ireland Connections in junction boxes in a hollow wall shall comply with 526,
and in addition shall be provided with a means of strain-relief.
Sweden 422.3.9 "In Sweden the common modification of 422.3.9 does not apply."
In Italy, the following additional requirement applies to 422.2.1:
422.2.1
Italy
Transfer the content of the subclause into a subclause of 422.1.

Country Clause Wording
No.
In Italy, the following additional requirement applies: to 422.2.2:
422.2.2
Transfer the content of the subclause into a subclause of 422.1.
In Italy, the following additional requirement applies to 422.2.3:
422.2.3
Transfer the content of the subclause, except for the first paragraph, with the
addition of the words “BD 2” conditions”, into a subclause of 422.1.
In Italy, the following additional requirements applies to 422.3:
Transfer the content of the subclause, except for the first paragraph, into a
subclause of 422.1.
Add the following:
422.3.3
This clause applies also to SELV and PELV systems.
The requirement concerning IP degrees of protection does not refer to
socket-outlets for household and similar use, to switches for circuits for
lighting and similar applications neither to circuit-breakers having rated
current not higher than 16 A and rated short-circuit capacity not higher than
3 000 A, in the case where they are used in a location where a particular risk
of fire exists.
In Italy, the following additional requirements apply to 422.3.4:
422.3.4
Precautions may be one of the following:
a) wiring with cable enclosed in a metal conduit or other metal enclosures,
having a degree of protection of at least IP 4X; or wiring with mineral
insulated cables without external non-metallic sheath;
b) wiring with multicore cables provided with concentric metallic sheath, or
metallic screen, or with cores provided with metallic sheaths, suitable to
perform the protective conductors function; or wiring with mineral insulated
cables with external non metallic sheath;
c) wiring with multicore cables incorporating a protective conductor; or wiring
with cables enclosed in metal conduit or other metal enclosures without a
particular degree of protection, or wiring with cables enclosed in insulating
enclosures having a degree of protection at least IP 4X.
In Italy, the following additional requirement applies to 422.3.4:
422.3.4
Transfer the content of the subclause into a subclause of 422.1,deleting
Note 1 and introducing, after the first indent, the following text:
“In particular for wiring described under b) and c), cables shall satisfy the test
under the conditions specified in IEC 60332-1 where installed individually or
at adequate distance within them. Alternatively, the cables shall meet the
flame propagation characteristics as defined in IEC 60332-3, provided that
the quantity of non-metallic materials does not exceed that specified in the
above-mentioned standard: otherwise, adequate fire barriers shall be
provided. In the case where the above precautions are not applied, fire
barriers shall be used”.
In Italy, the following additional requirement applies to 422.3.5:
422.3.5
Transfer the content of the subclause into a subclause of 422.1.
In Italy, the following additional requirement applies to 422.3.10:
422.3.10
Transfer into a subclause of 422.1 the content of the subclause, modified to
read as follows:
“Circuits supplying or traversing locations with a particular risk of danger of
fire shall be protected against overloads and short-circuits by overcurrent
protective devices located outside and on the supply side of these locations.
Circuits originating inside these locations shall be protected against
overcurrent by protective devices located at their origin."
In Italy, transfer the content of the subclause into a subclause of 422.1.
422.3.12
In Spain, UNE 201006 and its standard sheaths require the use of screws as the only
421.1
Spain
fixing means of the accessory with its enclosure.

- 9 - HD 60364-4-42:2011
Annex ZC
(informative)
A-deviations
A-deviation: National deviation due to regulations, the alteration of which is for the time being outside the
competence of the CENELEC national member.
This Harmonization Document does not fall under any Directive of the EC.
In the relevant CENELEC countries these A-deviations are valid instead of the provisions of the
Harmonization Document until they have been removed.

422.2 Additional requirements apply in Germany:
For wiring in escape routes there are special conditions established by
Germany
federal state authorities on the basis of the “Muster-Richtlinie über
brandschutztechnische Anforderungen an Leitungsanlagen (Muster-
Leitungsanlagen-Richtlinien MLAR)”
In Germany the following additional requirements for highly fire-retarding
422.4
components in timber-frame construction manner apply to 422.4.
For wiring in connection with highly fire-retarding components in timber-frame

construction manner, special conditions established by federal state authorities
on the basis of the Muster-Richtlinie über “Brandschutztechnische
Anforderungen an hochfeuerhemmnende Bauteile in Holzbauweise“ – M-
HFHHolzR.
Annex ZD
(informative)
B-deviations
B-deviation: National deviation from an HD due to particular technical requirements, permitted for a
specified transitional period.

422.3.1 Additional requirements apply in Germany:
Luminaires marked D in accordance with IEC 60598-1 are suitable for

mounting on normally flammable surfaces. For luminaires marked with
the symbol D, protection against deposition of dust and other
substances shall be provided also inside the luminaire. For compliance
Germany
with this requirement the luminaire is covered in the direction of the spot
light with a protective glass cover or a tube of IP5X.

Table ZB.1 in HD 60364-5-559 deals with the selection of luminaires and
lamp control gear in dependency of the location and surface of
installation.
422.5 Additional requirements apply in Germany:

422.5.2 Electrical equipment like outlets and switches, shall not be
fastened with claws.
IEC 60364-4-42 ®
Edition 3.0 2010-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Low-voltage electrical installations –
Part 4-42: Protection for safety – Protection against thermal effects

Installations électriques basse tension –
Partie 4-42: Protection pour assurer la sécurité – Protection contre les effets
thermiques
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
S
CODE PRIX
ICS 29.120.50; 91.140.50 ISBN 978-2-88910-942-5
– 2 – 60364-4-42 © IEC:2010
CONTENTS
FOREWORD.3
420.1 Scope .5
420.2 Normative references .5
420.3 Terms and definitions.5
421 Protection against fire caused by electrical equipment .6
421.1 General requirements .6
422 Precautions where particular risks of fire exist.8
422.1 General .8
422.2 Conditions of evacuation in an emergency.8
422.3 Locations with risks of fire due to the nature of processed or stored
materials .9
422.4 Locations with combustible constructional materials .11
422.5 Fire propagating structures.12
422.6 Selection and erection of installations in locations with endangering
of irreplaceable goods .12
423 Protection against burns .13
424 Protection against overheating .13
424.1 Forced air heating systems.13
424.2 Appliances producing hot water or steam .13
424.3 Space heating appliances.14
Annex A (informative) List of notes concerning certain countries.15
Bibliography.19

Table 42.1 – Temperature limits in normal service for accessible parts of equipment
within arm’s reach.13

60364-4-42 © IEC:2010 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LOW-VOLTAGE ELECTRICAL INSTALLATIONS –

Part 4-42: Protection for safety –
Protection against thermal effects

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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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.
International Standard IEC 60364-4-42 has been prepared by IEC technical committee 64:
Electrical installations and protection against electric shock.
This third edition cancels and replaces the second edition, published in 2001, and constitutes
a technical revision.
The main changes with respect to the previous edition are listed below:
– The scope now includes protection against all thermal effects and flames in case of a fire
hazard being propagated from electrical installations to other fire compartments
segregated by barriers which are in the vicinity.
– Requirements associated with escape routes for evacuation in an emergency have been
expanded/modified.
– Requirements associated with the nature of processed or stored materials have been
expanded/modified.
– 4 – 60364-4-42 © IEC:2010
– Requirements associated with combustible constructional materials have been
expanded/modified.
– Requirements associated with fire propagating structures have been modified slightly.
– New requirements for the selection and erection of installations in locations which might
endanger precious goods have been added.
– Protection against overheating now includes space heating appliances.
The text of this standard is based on the following documents:
FDIS Report on voting
64/1725/FDIS 64/1729/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The reader's attention is drawn to the fact that Annex A lists all of the "in-some-country"
clauses on differing practices of a less permanent nature relating to the subject of this
standard.
A list of all parts in the IEC 60364 series, under the general title Low-voltage electrical
installations, can be found on the IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
60364-4-42 © IEC:2010 – 5 –
LOW-VOLTAGE ELECTRICAL INSTALLATIONS –

Part 4-42: Protection for safety –
Protection against thermal effects

420.1 Scope
This part of IEC 60364 applies to electrical installations with regard to measures for the
protection of persons, livestock and property against
– thermal effects, combustion or degradation of materials, and risk of burns caused by
electrical equipment,
– flames in case of a fire hazard being propagated from electrical installations to other fire
compartments segregated by barriers which are in the vicinity, and
– the impairment of the safe functioning of electrical equipment including safety services.
NOTE 1 For protection against thermal effects, national statutory requirements may be applicable.
NOTE 2 Protection against overcurrent is dealt with in IEC 60364-4-43.
420.2 Normative references
The following referenced documents are indispensable for the application 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 60332 (all parts), Tests on electric and optical fibre cables under fire conditions
IEC 60364-4-41:2005, Low-voltage electrical installations – Part 4-41: Protection for safety –
Protection against electric shock
IEC 60364-5-51:2005, Electrical installations of buildings – Part 5-51: Selection and erection
of electrical equipment – Common rules
IEC 61084 (all parts), Cable trunking and ducting systems for electrical installations
IEC 61386 (all parts), Conduit systems for cable management
IEC 61534 (all parts), Power track systems
IEC 61537, Cable management – Cable tray systems and cable ladder systems
IEC 60598-2-24, Luminaires – Part 2-24: Particular requirements – Luminaires with limited
surface temperatures
420.3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

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420.3.1
combustible
capable of burning
420.3.2
fire
– a process of combustion characterized by the emission of heat and effluent accompanied
by smoke, and/or flame and/or glowing
– rapid combustion spreading uncontrolled in time and space
420.3.3
flammability
ability of a material or product to burn with a flame under specified test conditions
420.3.4
ignitability
measure of the ease with which a specimen can be ignited due to the influence of an external
source, under specified test conditions
420.3.5
ignition
initiation of combustion
NOTE For more information see IEC 60695-4.
420.3.6
non-flame propagating component
component which is liable to ignite, as a result of an applied flame, but in which the flame
does not propagate and which extinguishes itself within a limited time after the flame is
removed
[IEC 60050-442:1998, 442-01-12]
421 Protection against fire caused by electrical equipment
421.1 General requirements
Persons, livestock and property shall be protected against damage or injury caused by heat or
fire which may be generated or propagated in electrical installations by taking into account the
requirements of this standard and the instructions of equipment manufacturers.
The heat generated by electrical equipment shall not cause danger or harmful effects to
adjacent fixed material or to material which may foreseeably be in proximity to such
equipment. Electrical equipment shall not present a fire hazard to adjacent materials.
NOTE Damage, injury or ignition may be caused by effects such as
– heat accumulation, heat radiation, hot elements,
– reduction of the safe function of electrical equipment, e.g. protective devices such as protective switchgear,
thermostats, temperature limiters, seals of cable penetrations and wiring systems,
– overcurrent,
– insulation faults and/or arcs causing interference,
– harmonic currents,
– lightning strikes, see the IEC 62305 series,
– overvoltages, see Clause 443 of IEC 60364-4-44:2007,
– inappropriate selection or erection of equipment.
Any relevant manufacturer’s erection instructions shall be taken into account in addition to the
requirements of the IEC 60364 series.

60364-4-42 © IEC:2010 – 7 –
421.2 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 that 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 so as 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.
421.3 Where arcs or sparks may be emitted by permanently connected equipment in normal
service, the equipment shall either
• be totally enclosed in arc-resistant material, or
• be screened by arc-resistant material from materials on which the emission could have
harmful effects, or
• be mounted so as to allow safe extinction of the emissions at a sufficient distance from
material upon which the emissions could have harmful effects.
Arc-resistant material used for this protective measure shall be non-ignitable, of low thermal
conductivity, and of adequate thickness to provide mechanical stability.
NOTE For example, a sheet made of fibreglass silicone of 20 mm thickness may be considered as arc-resistant.
421.4 Fixed equipment causing a 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, is not
subjected to a dangerous temperature. For example, a temperature in excess of its ignition
temperature.
NOTE Any information from the manufacturer of the equipment should be taken into account.
421.5 Where electrical equipment in a single location contains flammable liquid in significant
quantity, adequate precautions shall be taken to prevent the spread of liquid, flame and the
products of combustion.
NOTE 1 Examples of such precautions include:
• a retention pit to collect any leakage of liquid and ensure extinction in the event of fire;
• installation of the equipment in a chamber of adequate fire resistance and the provision of sills or other means
of preventing 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 quantities less than 25 l, it is sufficient to take precautions to prevent the escape of liquid.
NOTE 4 Products of combustion of liquid are considered to be flame, smoke and gas.
NOTE 5 It is desirable to switch off the supply at the onset of a fire.
421.6 The materials of enclosures installed 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.

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422 Precautions where particular risks of fire exist
422.1 General
422.1.1 Electrical equipment shall be restricted to that necessary for the use of these
locations, except wiring systems according to 422.3.5.
422.1.2 Electrical equipment shall be so selected and erected that its temperature in normal
use 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
ignition of nearby substances.
422.1.3 Thermal cut-out devices shall have manual resetting only.
422.2 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 60364-5-51:2005).
NOTE Authorities responsible for building construction, public gatherings, fire prevention, etc. may specify which
BD condition is applicable.
422.2.1 In conditions BD2, BD3 and BD4, wiring systems shall not encroach on escape
routes unless the wiring in the wiring system is provided with sheaths or enclosures, provided
by the cable management system itself or by other means.
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.
Wiring systems in escape routes shall be as short as practicable and shall be non-flame
propagating.
NOTE 1 Compliance with this requirement may be achieved by using the following products:
– cables fulfilling tests under fire conditions of IEC 60332-1-2, and appropriate fire conditions as follows:
IEC 60332-3-21, IEC 60332-3-22, IEC 60332-3-23, IEC 60332-3-24 and IEC 60332-3-25;
– conduit systems classified as non-flame propagating according to IEC 61386-1;
– cable trunking systems classified as non-flame propagating according to IEC 61084-1;
– cable tray systems and cable ladder systems classified as non-flame propagating according to IEC 61537;
– for powertrack systems: the IEC 61534 series.
In conditions BD2, BD3 and BD4, wiring systems that are supplying safety circuits shall have
a resistance to fire rating of either the time authorized by regulations for building elements or
1 h in the absence of such a regulation.
NOTE 2 For the requirements for maintaining the function of wiring systems of safety services under fire
conditions, refer to Part 56.
Wiring within escape routes shall have a limited rate of smoke production.
NOTE 3 In the absence of any detailed requirement provided by cable standards, it is recommended that a value
of 60 % light transmittance is adopted as a minimum for any cable tested against IEC 61034-2.
422.2.2 In conditions BD2, BD3 and BD4, switchgear and controlgear devices, except
certain devices to facilitate evacuation, shall be accessible only to authorized persons. If they

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