Low-voltage electrical installations - Part 4-42: Protection for safety - Protection against thermal effects

IEC 60364-4-42:2010 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.
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.
- 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.

Installations électriques basse tension - Partie 4-42: Protection pour assurer la sécurité - Protection contre les effets thermiques

La CEI 60364-4-42:2010 s'applique aux installations électriques pour ce qui concerne les mesures de protection des personnes, du bétail et des biens contre
- les effets thermiques, la combustion ou la dégradation des matériaux, et le risque de brûlure provoqués par un matériel électrique,
- la propagation des flammes en cas de danger d'incendie, depuis les installations électriques vers d'autres compartiments feu séparés par des barrières se trouvant à proximité, et
- les atteintes à la sécurité de fonctionnement des matériels électriques, y compris les services de sécurité.
Cette troisième édition annule et remplace la seconde édition, publiée en 2001, et constitue une révision technique. Les principales modifications par rapport à l'édition précédente sont les suivantes:
- Le domaine d'application inclut désormais la protection contre tous les effets thermiques et la propagation des flammes en cas d'incendie, depuis les installations électriques vers d'autres compartiments feu séparés par des barrières se trouvant à proximité.
- Les exigences associées aux chemins d'évacuation en cas d'urgence ont été développées/modifiées.
- Les exigences associées à la nature des matériaux traités ou stockés ont été développées et modifiées.
- Les exigences associées aux matériaux de construction combustibles ont été développées/modifiées.
- Les exigences associées aux structures propagatrices du feu ont été légèrement modifiées.
- De nouvelles exigences pour le choix et la mise en oeuvre des installations dans des emplacements comportant un danger pour les biens irremplaçables ont été ajoutées.
- La protection contre les surchauffes inclut désormais les appareils de chauffage.

General Information

Status
Published
Publication Date
18-May-2010
Current Stage
PPUB - Publication issued
Start Date
19-May-2010
Completion Date
19-May-2010
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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
IEC 60364-4-42:2010
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
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---------------------- Page: 2 ----------------------
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
CODE PRIX
ICS 29.120.50; 91.140.50 ISBN 978-2-88910-942-5
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 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

---------------------- Page: 4 ----------------------
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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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.
---------------------- Page: 5 ----------------------
– 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.
---------------------- Page: 6 ----------------------
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.
---------------------- Page: 7 ----------------------
– 6 – 60364-4-42 © IEC:2010
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.
---------------------- Page: 8 ----------------------
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.
---------------------- Page: 9 ----------------------
– 8 – 60364-4-42 © IEC:2010
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

---------------------- Page: 10 ----------------------
60364-4-42 © IEC:2010 – 9 –

are placed in passages, they shall be enclosed in cabinets or boxes constructed of non-

combustible or not readily combustible material.

NOTE This clause does not prohibit plastic enclosures that are not readily combustible.

422.2.3 In conditions BD3 and BD4 and in escape routes, electrical equipment containing

flammable liquids shall not be installed.

NOTE Individual capacitors incorporated in equipment are not subject to this requirement. This exception

principally concerns discharge luminaires and capacitors of motor starters.
422.3 Locations with risks of fire due to the nature of processed or stored
materials
Condition BE2: Fire risk (according to Table 51A of IEC 60364-5-51:2005).

NOTE 1 Quantities of flammable materials or the surface or volume of the location may be regulated by national

authorities.
NOTE 2 For explosion risks, see IEC 60079-14.

422.3.1 Luminaires shall be kept at an adequate distance from combustible materials. If no

other information is given by manufacturers, spotlights and projectors shall be installed at the

following minimum distances from combustible materials:
≤ 100 W 0,5 m
> 100 W to 300 W 0,8 m
> 300 W to 500 W 1,0 m
> 500 W greater distances can be necessary.

NOTE In the absence of manufacturers’ instructions, the above distances imply all directions.

Lamps and other components of luminaires shall be protected against foreseeable mechanical

stresses. Such protective means shall not be fixed on lampholders unless they form an

integral part of the luminaire. Modifications to luminaires are not acceptable.

A luminaire with a lamp that could eject flammable materials in case of failure shall be

installed with a safety protective shield for the lamp in accordance with the manufacturer’s

instructions.

NOTE Luminaires suitable for direct mounting on normally flammable surfaces were earlier marked with the

symbol
according to IEC 60598-1:2003 (sixth edition).

With the publication of IEC 60598-1:2008 , luminaires suitable for direct mounting have no special marking and

only luminaires not suitable for mounting on normally flammable surfaces are marked with symbols

and/or
(see Clause N.4 of IEC 60598-1:2008 for further explanations).
———————
This seventh edition cancelled and replaced the sixth edition.
---------------------- Page: 11 ----------------------
– 10 – 60364-4-42 © IEC:2010

422.3.2 Measures shall be taken to prevent an electrical enclosure of equipment such as a heater or

resistor from exceeding the following temperatures:
• 90 °C under normal conditions, and
• 115 °C under fault conditions.

Where materials such as dust or fibres sufficient to cause a fire hazard could accumulate on

an enclosure of electrical equipment, adequate measures shall be taken to prevent that

enclosure from exceeding the temperatures stated above.

NOTE Luminaires marked in compliance with IEC 60598-2-24 are designed to provide limited surface

temperature.

422.3.3 Switchgear for protection, control and isolation shall be placed outside locations

presenting condition BE2, unless it is in an enclosure providing a degree of protection

appropriate for such a location of at least IP4X or, in the presence of dust, IP5X or, in the

presence of conductive dust, IP6X, except where 422.3.11 applies.

422.3.4 Except where wiring and wiring systems are embedded in non-combustible material,

only non-flame-propagating wiring systems shall be used.

As a minimum, equipment shall be selected in accordance with the following requirements:

– cables shall satisfy the test under fire conditions specified in the IEC 60332 series;

– conduit systems shall satisfy the test for resistance to flame propagation specified in the

IEC 61386 series;

– cable trunking systems and cable ducting systems shall satisfy the test for resistance to

flame propagation specified in the IEC 61084 series;

– cable tray systems and cable ladder systems shall satisfy the test for resistance to flame

propagation specified in the IEC 61537 series;

– powertrack systems shall satisfy the test for resistance to flame propagation specified in

the IEC 61534 series.

NOTE 1 Where the risk of flame propagation is high, e.g. in long vertical runs of bunched cables, cables should

meet the flame propagation characteristics of the appropriate part in the IEC 60332-3 series.

NOTE 2 Flame propagation tests for cable management systems are always performed in a vertical configuration.

422.3.5 Wiring systems which traverse these locations, but are not necessary for the use of

the locations, shall satisfy the following conditions:
• the wiring systems shall meet the requirements of 422.3.4;

• they have no connection along the route inside the locations, unless these connections

are placed in fire-resistant enclosures;
• they are protected against overcurrent in accordance with 422.3.10;
• ba
...

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