IEC 60079-7:2015

IEC 60079-7 ®
Edition 5.1 2017-08
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 7: Equipment protection by increased safety "e"
Atmosphères explosives –
Partie 7: Protection du matériel par sécurité augmentée «e»
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IEC 60079-7 ®
Edition 5.1 2017-08
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 7: Equipment protection by increased safety "e"

Atmosphères explosives –
Partie 7: Protection du matériel par sécurité augmentée «e»

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-4708-2

IEC 60079-7 ®
Edition 5.1 2017-08
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
Explosive atmospheres –
Part 7: Equipment protection by increased safety "e"

Atmosphères explosives –
Partie 7: Protection du matériel par sécurité augmentée «e»

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
IEC 60079-7
Edition 5.0  2015-06
EXPLOSIVE ATMOSPHERES –
Part 7: Equipment protection by increased safety 'e'

INTERPRETATION SHEET 1
This interpretation sheet has been prepared by IEC technical committee 31: Equipment for
explosive atmospheres.
The text of this interpretation sheet is based on the following documents:
ISH Report on voting
31/1258/ISH 31/1272/RVD
Full information on the voting for the approval of this interpretation sheet can be found in the
report on voting indicated in the above table.
___________
increased safety “e”
Question:
Do the requirements given in 5.2.3 prohibit the use of a terminal box opened to the interior of
a motor rated 1 kV or greater, provided the interior of the machine has an ingress protection
of IP54 or greater?
5.2.3 Degrees of protection provided by electrical machines, Level of Protection “ec”
The requirements of 4.10 apply, except that terminal boxes attached to electrical machines
operating at voltages up to 1 kV, may be opened to the interior of the machine, only when the
degree of protection of the electrical machine is at least IP44. Covers and entries of the
terminal box shall provide at least degree of protection IP54.
ICS 29.260.20
– 2 – IEC 60079-7:2015/ISH1:2016  IEC 2016
Answer:
No. As long as the interior of the machine has an ingress protection of IP54 or greater,
determined in accordance with IEC 60079-0, there is no limitation to less than 1 kV. If the
interior of the machine has an ingress rating of IP44 or lower, the use of a terminal box open
to the interior of a motor rated 1 kV or greater is not permitted.
NOTE Many manufacturers opt to declare IP44 for the machine for certification purposes, whilst claiming a rating
of IP54 or higher, by assessment, for contractual purposes in order to avoid the difficult testing required for
certification of the IP of larger machines. As such, this additional IP rating need only comply with IEC 60529 or
IEC 60034-5 as applicable, and not with any of the testing detailed in IEC 60079-0.

– 2 – IEC 60079-7:2015+AMD1:2017 CSV
© IEC 2017
CONTENTS
FOREWORD . 8
1 Scope . 14
2 Normative references . 15
3 Terms and definitions . 17
4 Constructional requirements . 21
4.1 Level of Protection . 21
4.2 Electrical connections . 21
4.2.1 General . 21
4.2.2 Field wiring connections . 22
4.2.3 Factory connections. 23
4.2.4 External plug and socket connections for field wiring connection . 25
4.3 Clearances . 26
4.4 Creepage distances . 26
4.5 Printed wiring boards with conformal coating, Level of Protection “ec” . 32
4.6 Solid electrical insulating materials . 33
4.6.1 Specification . 33
4.6.2 Long-term thermal stability . 33
4.7 Windings . 34
4.7.1 General . 34
4.7.2 Insulated conductors . 34
4.7.3 Winding impregnation . 34
4.7.4 Conductor dimensions . 34
4.7.5 Sensing elements . 35
4.8 Temperature limitations . 35
4.8.1 General . 35
4.8.2 Conductors . 35
4.8.3 Insulated windings . 36
4.9 Wiring internal to equipment . 37
4.10 Degrees of protection provided by enclosures . 37
4.11 Fasteners . 38
5 Supplementary requirements for specific electrical equipment . 38
5.1 General . 38
5.2 Electrical machines . 38
5.2.1 General . 38
5.2.2 Degrees of protection provided by electrical machines, Level of
Protection “eb” . 39
5.2.3 Degrees of protection provided by electrical machines, Level of
Protection “ec” . 39
5.2.4 Connection facilities for external conductors . 39
5.2.5 Internal fans . 40
5.2.6 Minimum air gap . 40
5.2.7 Rotating electrical machines with cage rotors . 41
5.2.8 Limiting temperature . 43
5.2.9 Machines with permanent magnet rotors . 46
5.2.10 Stator winding insulation system . 46
5.2.11 Supplemental winding requirements Level of Protection “eb” . 47

© IEC 2017
5.2.12 Bearing seals and shaft seals . 47
5.2.13 Neutral point connections . 48
5.3 Luminaires, hand lights, or caplights . 48
5.3.1 General . 48
5.3.2 Light source . 49
5.3.3 Minimum distance between lamp and protective cover . 50
5.3.4 Electrical spacings . 50
5.3.5 Lampholders and lamp caps . 51
5.3.6 Auxiliaries for Luminaires in Level of Protection “ec” . 54
5.3.7 Surface temperatures . 55
5.3.8 Limiting temperatures . 56
5.3.9 Luminaires for tubular fluorescent bi-pin lamps . 56
5.3.10 Tests for resistance to impact . 57
5.4 Analog measuring instruments and instrument transformers . 57
5.4.1 General . 57
5.4.2 Limiting temperature . 57
5.4.3 Short-circuit currents . 57
5.4.4 Short time thermal current . 58
5.4.5 Measuring instruments supplied by current transformers . 58
5.4.6 Moving coils . 58
5.4.7 External secondary circuits . 58
5.5 Transformers other than instrument transformers . 58
5.6 Supplementary requirements for equipment incorporating cells and batteries . 59
5.6.1 Type of cells and batteries . 59
5.6.2 Requirements for cells and batteries ≤25 Ah . 60
5.6.3 Requirements for valve-regulated or vented cells or batteries >25 Ah . 63
5.6.4 Charging of cells and batteries . 66
5.7 General purpose connection and junction boxes . 67
5.8 Resistance heating equipment (other than trace heating systems) . 67
5.8.1 General . 67
5.8.2 Heating resistors . 67
5.8.3 Temperature coefficient . 68
5.8.4 Insulating material . 68
5.8.5 Cold-start current . 68
5.8.6 Electrical safety device . 68
5.8.7 Electrically conductive covering . 68
5.8.8 Exclusion of explosive atmosphere . 69
5.8.9 Conductor cross-section . 69
5.8.10 Limiting temperature . 69
5.8.11 Safety device . 69
5.9 Supplementary requirements for fuses . 70
5.9.1 General . 70
5.9.2 Temperature class of equipment . 71
5.9.3 Fuse mounting . 71
5.9.4 Fuse enclosures . 71
5.9.5 Replacement fuse identification . 71
5.10 Other electrical equipment . 71
6 Type verifications and type tests. 71
6.1 Dielectric strength . 71

– 4 – IEC 60079-7:2015+AMD1:2017 CSV
© IEC 2017
6.2 Rotating electrical machines . 72
6.2.1 Determination of starting current ratio I / I and the time t . 72
A N
E
6.2.2 Mounting of machine for test . 72
6.2.3 Additional tests for machines . 72
6.2.4 Overspeed test of cemented magnets . 74
6.3 Luminaires . 74
6.3.1 Battery operated luminaires . 74
6.3.2 Impact and drop tests . 74
6.3.3 Mechanical tests for screw lampholders other than E10 . 75
6.3.4 Abnormal operation of luminaires . 76
6.3.5 Sulphur dioxide test for Level of Protection “eb” for the connection of bi-
pin lamp caps to lampholders . 77
6.3.6 Vibration test for Level of Protection “eb” for luminaires with bi-pin
lamps . 78
6.3.7 Test for wiring of luminaires subject to high-voltage impulses from
ignitors . 79
6.3.8 Tests for electronic starters for tubular fluorescent lamps and for
ignitors in Level of Protection “ec” for discharge lamps . 79
6.3.9 Test for starter holders for luminaires in Level of Protection “ec” . 80
6.4 Measuring instruments and instrument transformers . 80
6.5 Transformers other than instrument transformers . 81
6.6 Verification and tests for cells and batteries of Level of Protection “eb” . 81
6.6.1 General . 81
6.6.2 Insulation resistance . 81
6.6.3 Mechanical shock test . 81
6.6.4 Test for ventilation of Level of Protection “eb” battery container . 82
6.7 Verification and tests for cells and batteries of Level of Protection “ec” . 83
6.7.1 General . 83
6.7.2 Insulation resistance . 83
6.7.3 Mechanical shock test . 83
6.7.4 Test for ventilation of Level of Protection “ec” battery container . 83
6.8 General purpose connection and junction boxes . 84
6.8.1 General . 84
6.8.2 Maximum dissipated power method . 84
6.8.3 Defined arrangement method . 84
6.9 Resistance heating equipment . 84
6.10 Terminal insulating material tests . 85
7 Routine verifications and routine tests . 86
7.1 Dielectric tests . 86
7.2 Dielectric tests for batteries . 87
7.3 Inter-turn overvoltage tests . 87
8 Ex Component certificates . 87
8.1 General . 87
8.2 Terminals . 87
9 Marking and instructions . 88
9.1 General marking . 88
9.2 Ex Component enclosures . 89
9.3 Instructions for use . 89
9.3.1 Battery operated equipment . 89

© IEC 2017
9.3.2 Terminals . 89
9.3.3 Luminaires . 89
9.3.4 Machines . 90
9.4 Warning markings . 90
10 Documentation . 91
Annex A (normative) Temperature determination of electrical machines – Methods of
test and of calculation . 92
A.1 General . 92
A.2 Determination of maximum service temperatures . 92
A.2.1 Rotor temperature – normal operation . 92
A.2.2 Winding temperature – normal operation . 92
A.3 Determination of maximum surface temperatures . 93
A.3.1 General . 93
A.3.2 Locked rotor tests . 93
A.4 Optional calculation of maximum surface temperature . 94
A.4.1 General . 94
A.4.2 Rotor temperature . 94
A.4.3 Stator temperature . 94
A.5 Determination of t time . 94
E
A.6 Arduous starting conditions . 95
A.7 Motors operated with a converter . 95
Annex B (normative) Type tests for specific forms of resistance heating devices or
resistance heating units (other than trace heater) . 96
B.1 Resistance heating devices subjected to mechanical stresses . 96
B.2 Resistance heating devices or units intended for immersion . 96
B.3 Resistance heating devices or units having hygroscopic insulating material . 96
B.4 Verification of limiting temperature of resistance heating devices (other than
trace heaters) . 96
B.4.1 General . 96
B.4.2 Safety devices . 96
B.4.3 Resistance heating unit of stabilized design. 97
B.4.4 Heating device with temperature self-limiting characteristic . 97
Annex C (informative) Cage motors – Thermal protection in service . 98
Annex D (informative) Resistance heating devices and units – Additional electrical
protection . 99
D.1 Objective . 99
D.2 Method of protection . 99
Annex E (informative) Combinations of terminals and conductors for general purpose
connection and junction boxes . 100
E.1 General . 100
E.2 Maximum dissipated power method. 100
E.3 Defined arrangement method . 100
Annex F (normative) Dimensions of copper conductors . 103
Annex G (normative) Test procedure for T5 (only 8 W),T8, T10 and T12 lamps. 104
G.1 Asymmetric pulse test . 104
G.1.1 General . 104
G.1.2 Test procedure . 104
G.2 Asymmetric power test . 105
G.2.1 General . 105

– 6 – IEC 60079-7:2015+AMD1:2017 CSV
© IEC 2017
G.2.2 Test procedure . 106
Annex H (normative) Alternative separation distances for Level of Protection “ec”
equipment under controlled environments . 109
H.1 General . 109
H.2 Specific Conditions of Use . 109
H.3 Control of pollution access . 110
H.4 Voltage limitation . 110
H.5 Control of overvoltages and transient protection . 110
H.6 Alternative separation distances . 110
Annex I (informative) Application, installation, and testing considerations for Level of
Protection “ec” asynchronous machines . 112
I.1 Surface temperature . 112
I.2 Starting . 112
I.3 Rated voltage and surface discharges . 113
Annex J (informative) Luminaires incorporating LEDs . 114
J.1 LEDs for EPL Gb . 114
J.2 LEDs for EPL Gc . 114
Bibliography . 115

Figure 1 – Determination of creepage distances and clearances . 32
Figure 2 – Minimum values of the time t (in seconds) of motors in relation to the
E
starting current ratio I /I . 44
A N
Figure 3 – Arrangement for the luminaire vibration test . 78
Figure A.1 – Diagram illustrating the determination of time t . 95
E
Figure E.1 – Example of defined terminal/conductor arrangement table . 102
Figure G.1 – Asymmetric pulse test circuit . 105
Figure G.2 – Asymmetric power detection circuit . 107
Figure G.3 – Flow Chart – Asymmetric power Test for T8, T10, T12 and T5 (8 W
lamps) . 108

Table 1 – Tracking resistance of insulating materials . 27
Table 2 – Minimum Creepage distances, clearances and separations . 28
Table 3 – Conditions for the determination of maximum surface temperature . 35
Table 4 – Maximum temperatures for insulated windings . 36
Table 5 – Potential air gap sparking risk assessment for cage rotor ignition risk factors . 43
Table 6 – Stator insulation system tests of Level of Protection “ec” machines . 47
Table 7 – Assumed voltage of neutral points . 48
Table 8 – Minimum distance between lamp and protective cover . 50
Table 9 – Creepage distances and clearances at peak values of pulse voltages greater

than 1,5 kV . 51
Table 10 – Creepage distances and clearances for screw lampholder and lamp cap . 52
Table 11 − Resistance to the effect of short-circuit currents . 58
Table 12 – Types and use of cells and batteries . 60
Table 13 – Explosion test mixtures . 73
Table 14 – Tests for resistance to impact . 75
Table 15 – Insertion torque and minimum removal torque . 75

© IEC 2017
Table 16 – Power dissipation of cathodes of lamps supplied by electronic ballasts . 77
Table 17 – Value for pull-out tests . 86
Table 18 – Creepage distances and clearances for screw lamp caps . 90
Table 19 − Text of warning markings. 90
Table 20 – Separation in compound-filled cable sealing boxes . 40
Table F.1 – Standard cross-sections of copper conductors . 103
Table H.1 – Alternative separation distances for equipment under controlled
environments . 111

– 8 – IEC 60079-7:2015+AMD1:2017 CSV
© IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 7: Equipment protection
by increased safety ''e''
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,
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6) All users should ensure that they have the latest edition of this publication.
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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.
This consolidated version of the official IEC Standard and its amendment(s) has been
prepared for user convenience.
IEC 60079-7 edition 5.1 contains the fifth edition (2015-06) [documents 31/1182/FDIS and
31/1194/RVD], its interpretation sheet (2016-09), and its amendment 1 (2017-08)
[documents 31/1301/CDV and 31/1324/RVC].
In this Redline version, a vertical line in the margin shows where the technical
content is modified by amendment 1. Additions are in green text, deletions are in
strikethrough red text. A separate Final version with all changes accepted is
available in this publication.

© IEC 2017
International Standard IEC 60079-7 has been prepared by IEC Technical Committee 31:
Equipment for explosive atmospheres.
This fifth edition cancels and replaces the fourth edition published in 2006, and constitutes a
technical revision.
The requirements for Type of Protection “nA” have been relocated from IEC 60079-15. To
assist the user of this document, the significant changes with respect to the previous edition
are shown below in two separate tables, one showing the changes from IEC 60079-7, Edition
4 (2006) for “e” to IEC 60079-7, Edition 5 (2014) for “eb”; and the other showing the changes
from IEC 60079-15, Edition 4 (2010) for “nA” to IEC 60079-7, Edition 5 (2014) for “ec”.
The significance of the changes between IEC Standard, IEC 60079-7, Edition 5 (2014) (for
“eb”) and IEC 60079-7, Edition 4 (2006) (for “e”) are as listed below:
for “e” to “eb” Type
Explanation of the significance of the changes Clause Minor and Extension Major
editorial technical
changes changes
Scope 1 X
Clarification of applicability
Notes added to address short circuits and short-term
thermal excursions
Clarification of resistance heating definitions 3.13 X
Addition of terminal insulation material tests 4.2.2.4 C1
Soldered Connections 4.2.2.5 C2
4.2.3.3
Silver-Soldered connections 4.2.3.3 X
Clarification of “duplicated” contacts 4.2.3.4a) X
External plug and socket connections for field wiring 4.2.4 X
connection of batteries
Clarification of conditions for the determination of 4.8.1 X
maximum surface temperature
Table 3
Maximum temperatures for insulated windings Table 4 X
Degrees of protection provided by enclosures 4.10.1 x C3
Clarification of applicability 5.2.1 X
Minimum air gap for motors 5.2.6 X
Devices for limiting winding temperature protection 5.2.8.2 X
5.2.8.3
Permanent magnet motors 5.2.9 X
6.2.4
9.3.4c)
Added Tungsten-Halogen lamp 5.3.2.2 X
5.3.2.3
5.3.2.4
5.3.3 X
Added spacings for < 10 W lamps
Permission added for re-lamping outside of hazardous 5.3.5.2.2 X
area
Added bayonet lamps 5.3.5.4.2 X
Added contact requirements for bayonet lamps 5.3.5.5 X

– 10 – IEC 60079-7:2015+AMD1:2017 CSV
© IEC 2017
for “e” to “eb” Type
Explanation of the significance of the changes Clause Minor and Extension Major
editorial technical
changes changes
Renaming of “Type” of cells and batteries 5.6.2 X
Clarification of approaches for general purpose 5.7 X
junctions boxes
6.9
Annex E
Clarified temperature monitoring and control 5.8 X
Clarification of testing of battery powered luminaires 6.3.1 X
Clarification of impact tests 6.3.2.2 X
Added abnormal tests for discharge lamps 6.3.4.1  C4
Added T5 8W 6.3.4.3 X
Table 16
To maintain T4 temperature class, cathode power or 6.3.4.3  C5
ambient temperature reduced
Table 16
Clarification of routine tests for terminal boxes 7.1 X
Marking of “e” replaced by “eb” 9.1 See “Information about the background
of Changes”
Ex Component enclosures 9.2  C6
Highlight essential documentation for rotating 10 X
electrical machines
Temperature tests Annex A X
The significance of the changes between IEC Standard, IEC 60079-7, Edition 5 (2015) (fo
...

IEC 60079-7 ®
Edition 5.0 2015-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 7: Equipment protection by increased safety «e»

Atmosphères explosives –
Partie 7: Protection du matériel par sécurité augmentée «e»

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IEC 60079-7 ®
Edition 5.0 2015-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 7: Equipment protection by increased safety «e»

Atmosphères explosives –
Partie 7: Protection du matériel par sécurité augmentée «e»

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-2885-2

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
IEC 60079-7
Edition 5.0  2015-06
EXPLOSIVE ATMOSPHERES –
Part 7: Equipment protection by increased safety 'e'

INTERPRETATION SHEET 1
This interpretation sheet has been prepared by IEC technical committee 31: Equipment for
explosive atmospheres.
The text of this interpretation sheet is based on the following documents:
ISH Report on voting
31/1258/ISH 31/1272/RVD
Full information on the voting for the approval of this interpretation sheet can be found in the
report on voting indicated in the above table.
___________
increased safety “e”
Question:
Do the requirements given in 5.2.3 prohibit the use of a terminal box opened to the interior of
a motor rated 1 kV or greater, provided the interior of the machine has an ingress protection
of IP54 or greater?
5.2.3 Degrees of protection provided by electrical machines, Level of Protection “ec”
The requirements of 4.10 apply, except that terminal boxes attached to electrical machines
operating at voltages up to 1 kV, may be opened to the interior of the machine, only when the
degree of protection of the electrical machine is at least IP44. Covers and entries of the
terminal box shall provide at least degree of protection IP54.
ICS 29.260.20
– 2 – IEC 60079-7:2015/ISH1:2016  IEC 2016
Answer:
No. As long as the interior of the machine has an ingress protection of IP54 or greater,
determined in accordance with IEC 60079-0, there is no limitation to less than 1 kV. If the
interior of the machine has an ingress rating of IP44 or lower, the use of a terminal box open
to the interior of a motor rated 1 kV or greater is not permitted.
NOTE Many manufacturers opt to declare IP44 for the machine for certification purposes, whilst claiming a rating
of IP54 or higher, by assessment, for contractual purposes in order to avoid the difficult testing required for
certification of the IP of larger machines. As such, this additional IP rating need only comply with IEC 60529 or
IEC 60034-5 as applicable, and not with any of the testing detailed in IEC 60079-0.

– 2 – IEC 60079-7:2015 © IEC 2015
CONTENTS
FOREWORD . 8
1 Scope . 14
2 Normative references . 15
3 Terms and definitions . 17
4 Constructional requirements . 21
4.1 Level of Protection . 21
4.2 Electrical connections . 21
4.2.1 General . 21
4.2.2 Field wiring connections . 22
4.2.3 Factory connections. 23
4.2.4 External plug and socket connections for field wiring connection . 25
4.3 Clearances . 26
4.4 Creepage distances . 26
4.5 Printed wiring boards with conformal coating, Level of Protection “ec” . 32
4.6 Solid electrical insulating materials . 33
4.6.1 Specification . 33
4.6.2 Long-term thermal stability . 33
4.7 Windings . 34
4.7.1 General . 34
4.7.2 Insulated conductors . 34
4.7.3 Winding impregnation . 34
4.7.4 Conductor dimensions . 34
4.7.5 Sensing elements . 35
4.8 Temperature limitations . 35
4.8.1 General . 35
4.8.2 Conductors . 35
4.8.3 Insulated windings . 36
4.9 Wiring internal to equipment . 36
4.10 Degrees of protection provided by enclosures . 37
4.11 Fasteners . 38
5 Supplementary requirements for specific electrical equipment . 38
5.1 General . 38
5.2 Electrical machines . 38
5.2.1 General . 38
5.2.2 Degrees of protection provided by electrical machines, Level of
Protection “eb” . 39
5.2.3 Degrees of protection provided by electrical machines, Level of
Protection “ec” . 39
5.2.4 Connection facilities for external conductors . 39
5.2.5 Internal fans . 39
5.2.6 Minimum air gap . 39
5.2.7 Rotating electrical machines with cage rotors . 40
5.2.8 Limiting temperature . 42
5.2.9 Machines with permanent magnet rotors . 45
5.2.10 Stator winding insulation system . 45
5.2.11 Supplemental winding requirements Level of Protection “eb” . 46

5.2.12 Bearing seals and shaft seals . 46
5.2.13 Neutral point connections . 47
5.3 Luminaires, hand lights, or caplights . 47
5.3.1 General . 47
5.3.2 Light source . 48
5.3.3 Minimum distance between lamp and protective cover . 49
5.3.4 Electrical spacings . 49
5.3.5 Lampholders and lamp caps . 50
5.3.6 Auxiliaries for Luminaires in Level of Protection “ec” . 53
5.3.7 Surface temperatures . 54
5.3.8 Limiting temperatures . 55
5.3.9 Luminaires for tubular fluorescent bi-pin lamps . 55
5.3.10 Tests for resistance to impact . 56
5.4 Analog measuring instruments and instrument transformers . 56
5.4.1 General . 56
5.4.2 Limiting temperature . 56
5.4.3 Short-circuit currents . 56
5.4.4 Short time thermal current . 57
5.4.5 Measuring instruments supplied by current transformers . 57
5.4.6 Moving coils . 57
5.4.7 External secondary circuits . 57
5.5 Transformers other than instrument transformers . 57
5.6 Supplementary requirements for equipment incorporating cells and batteries . 58
5.6.1 Type of cells and batteries . 58
5.6.2 Requirements for cells and batteries ≤25 Ah . 59
5.6.3 Requirements for valve-regulated or vented cells or batteries >25 Ah . 62
5.6.4 Charging of cells and batteries . 65
5.7 General purpose connection and junction boxes . 66
5.8 Resistance heating equipment (other than trace heating systems) . 66
5.8.1 General . 66
5.8.2 Heating resistors . 66
5.8.3 Temperature coefficient . 67
5.8.4 Insulating material . 67
5.8.5 Cold-start current . 67
5.8.6 Electrical safety device . 67
5.8.7 Electrically conductive covering . 67
5.8.8 Exclusion of explosive atmosphere . 68
5.8.9 Conductor cross-section . 68
5.8.10 Limiting temperature . 68
5.8.11 Safety device . 68
5.9 Supplementary requirements for fuses . 69
5.9.1 General . 69
5.9.2 Temperature class of equipment . 70
5.9.3 Fuse mounting . 70
5.9.4 Fuse enclosures . 70
5.9.5 Replacement fuse identification . 70
5.10 Other electrical equipment . 70
6 Type verifications and type tests. 70
6.1 Dielectric strength . 70

– 4 – IEC 60079-7:2015 © IEC 2015
6.2 Rotating electrical machines . 71
6.2.1 Determination of starting current ratio I / I and the time t . 71
A N
E
6.2.2 Mounting of machine for test . 71
6.2.3 Additional tests for machines . 71
6.2.4 Overspeed test of cemented magnets . 73
6.3 Luminaires . 73
6.3.1 Battery operated luminaires . 73
6.3.2 Impact and drop tests . 73
6.3.3 Mechanical tests for screw lampholders other than E10 . 74
6.3.4 Abnormal operation of luminaires . 75
6.3.5 Sulphur dioxide test for Level of Protection “eb” for the connection of bi-
pin lamp caps to lampholders . 76
6.3.6 Vibration test for Level of Protection “eb” for luminaires with bi-pin
lamps . 77
6.3.7 Test for wiring of luminaires subject to high-voltage impulses from
ignitors . 78
6.3.8 Tests for electronic starters for tubular fluorescent lamps and for
ignitors in Level of Protection “ec” for discharge lamps . 78
6.3.9 Test for starter holders for luminaires in Level of Protection “ec” . 79
6.4 Measuring instruments and instrument transformers . 79
6.5 Transformers other than instrument transformers . 80
6.6 Verification and tests for cells and batteries of Level of Protection “eb” . 80
6.6.1 General . 80
6.6.2 Insulation resistance . 80
6.6.3 Mechanical shock test . 80
6.6.4 Test for ventilation of Level of Protection “eb” battery container . 81
6.7 Verification and tests for cells and batteries of Level of Protection “ec” . 82
6.7.1 General . 82
6.7.2 Insulation resistance . 82
6.7.3 Mechanical shock test . 82
6.7.4 Test for ventilation of Level of Protection “ec” battery container . 82
6.8 General purpose connection and junction boxes . 83
6.8.1 General . 83
6.8.2 Maximum dissipated power method . 83
6.8.3 Defined arrangement method . 83
6.9 Resistance heating equipment . 83
6.10 Terminal insulating material tests . 84
7 Routine verifications and routine tests . 85
7.1 Dielectric tests . 85
7.2 Dielectric tests for batteries . 86
7.3 Inter-turn overvoltage tests . 86
8 Ex Component certificates . 86
8.1 General . 86
8.2 Terminals . 86
9 Marking and instructions . 87
9.1 General marking . 87
9.2 Ex Component enclosures . 88
9.3 Instructions for use . 88
9.3.1 Battery operated equipment . 88

9.3.2 Terminals . 88
9.3.3 Luminaires . 88
9.3.4 Machines . 89
9.4 Warning markings . 89
10 Documentation . 90
Annex A (normative) Temperature determination of electrical machines – Methods of
test and of calculation . 91
A.1 General . 91
A.2 Determination of maximum service temperatures . 91
A.2.1 Rotor temperature – normal operation . 91
A.2.2 Winding temperature – normal operation . 91
A.3 Determination of maximum surface temperatures . 92
A.3.1 General . 92
A.3.2 Locked rotor tests . 92
A.4 Optional calculation of maximum surface temperature . 93
A.4.1 General . 93
A.4.2 Rotor temperature . 93
A.4.3 Stator temperature . 93
A.5 Determination of t time . 93
E
A.6 Arduous starting conditions . 94
A.7 Motors operated with a converter . 94
Annex B (normative) Type tests for specific forms of resistance heating devices or
resistance heating units (other than trace heater) . 95
B.1 Resistance heating devices subjected to mechanical stresses . 95
B.2 Resistance heating devices or units intended for immersion . 95
B.3 Resistance heating devices or units having hygroscopic insulating material . 95
B.4 Verification of limiting temperature of resistance heating devices (other than
trace heaters) . 95
B.4.1 General . 95
B.4.2 Safety devices . 95
B.4.3 Resistance heating unit of stabilized design. 96
B.4.4 Heating device with temperature self-limiting characteristic . 96
Annex C (informative) Cage motors – Thermal protection in service . 97
Annex D (informative) Resistance heating devices and units – Additional electrical
protection . 98
D.1 Objective . 98
D.2 Method of protection . 98
Annex E (informative) Combinations of terminals and conductors for general purpose
connection and junction boxes . 99
E.1 General . 99
E.2 Maximum dissipated power method. 99
E.3 Defined arrangement method . 99
Annex F (normative) Dimensions of copper conductors . 102
Annex G (normative) Test procedure for T5 (only 8 W),T8, T10 and T12 lamps. 103
G.1 Asymmetric pulse test . 103
G.1.1 General . 103
G.1.2 Test procedure . 103
G.2 Asymmetric power test . 104
G.2.1 General . 104

– 6 – IEC 60079-7:2015 © IEC 2015
G.2.2 Test procedure . 105
Annex H (normative) Alternative separation distances for Level of Protection “ec”
equipment under controlled environments . 108
H.1 General . 108
H.2 Specific Conditions of Use . 108
H.3 Control of pollution access . 109
H.4 Voltage limitation . 109
H.5 Control of overvoltages and transient protection . 109
H.6 Alternative separation distances . 109
Annex I (informative) Application, installation, and testing considerations for Level of
Protection “ec” asynchronous machines. 111
I.1 Surface temperature . 111
I.2 Starting . 111
I.3 Rated voltage and surface discharges . 112
Annex J (informative) Luminaires incorporating LEDs . 113
J.1 LEDs for EPL Gb . 113
J.2 LEDs for EPL Gc . 113
Bibliography . 114

Figure 1 – Determination of creepage distances and clearances . 32
Figure 2 – Minimum values of the time t (in seconds) of motors in relation to the
E
starting current ratio I /I . 43
A N
Figure 3 – Arrangement for the luminaire vibration test . 77
Figure A.1 – Diagram illustrating the determination of time t . 94
E
Figure E.1 – Example of defined terminal/conductor arrangement table . 101
Figure G.1 – Asymmetric pulse test circuit . 104
Figure G.2 – Asymmetric power detection circuit . 106
Figure G.3 – Flow Chart – Asymmetric power Test for T8, T10, T12 and T5 (8 W
lamps) . 107

Table 1 – Tracking resistance of insulating materials . 27
Table 2 – Minimum Creepage distances, clearances and separations . 28
Table 3 – Conditions for the determination of maximum surface temperature . 35
Table 4 – Maximum temperatures for insulated windings . 36
Table 5 – Potential air gap sparking risk assessment for cage rotor ignition risk factors . 42
Table 6 – Stator insulation system tests of Level of Protection “ec” machines . 46
Table 7 – Assumed voltage of neutral points . 47
Table 8 – Minimum distance between lamp and protective cover . 49
Table 9 – Creepage distances and clearances at peak values of pulse voltages greater

than 1,5 kV . 50
Table 10 – Creepage distances and clearances for screw lampholder and lamp cap . 51
Table 11 − Resistance to the effect of short-circuit currents . 57
Table 12 – Types and use of cells and batteries . 59
Table 13 – Explosion test mixtures . 72
Table 14 – Tests for resistance to impact . 74
Table 15 – Insertion torque and minimum removal torque . 74

Table 16 – Power dissipation of cathodes of lamps supplied by electronic ballasts . 76
Table 17 – Value for pull-out tests . 85
Table 18 – Creepage distances and clearances for screw lamp caps . 89
Table 19 − Text of warning markings. 89
Table F.1 – Standard cross-sections of copper conductors . 102
Table H.1 – Alternative separation distances for equipment under controlled
environments . 110

– 8 – IEC 60079-7:2015 © IEC 2015
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 7: Equipment protection
by increased safety ''e''
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) 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 60079-7 has been prepared by IEC Technical Committee 31:
Equipment for explosive atmospheres.
This fifth edition cancels and replaces the fourth edition published in 2006, and constitutes a
technical revision.
The requirements for Type of Protection “nA” have been relocated from IEC 60079-15. To
assist the user of this document, the significant changes with respect to the previous edition
are shown below in two separate tables, one showing the changes from IEC 60079-7, Edition
4 (2006) for “e” to IEC 60079-7, Edition 5 (2014) for “eb”; and the other showing the changes
from IEC 60079-15, Edition 4 (2010) for “nA” to IEC 60079-7, Edition 5 (2014) for “ec”.

The significance of the changes between IEC Standard, IEC 60079-7, Edition 5 (2014) (for
“eb”) and IEC 60079-7, Edition 4 (2006) (for “e”) are as listed below:
for “e” to “eb” Type
Explanation of the significance of the changes Clause Minor and Extension Major
editorial technical
changes changes
Scope 1 X
Clarification of applicability
Notes added to address short circuits and short-term
thermal excursions
Clarification of resistance heating definitions 3.13 X
Addition of terminal insulation material tests 4.2.2.4  C1
Soldered Connections 4.2.2.5  C2
4.2.3.3
Silver-Soldered connections 4.2.3.3 X
Clarification of “duplicated” contacts 4.2.3.4a) X
External plug and socket connections for field wiring 4.2.4 X
connection of batteries
Clarification of conditions for the determination of 4.8.1 X
maximum surface temperature
Table 3
Maximum temperatures for insulated windings Table 4 X
Degrees of protection provided by enclosures 4.10.1 x C3
Clarification of applicability 5.2.1 X
Minimum air gap for motors 5.2.6 X
Devices for limiting winding temperature protection 5.2.8.2 X
5.2.8.3
Permanent magnet motors 5.2.9 X
6.2.4
9.3.4c)
Added Tungsten-Halogen lamp 5.3.2.2 X
5.3.2.3
5.3.2.4
Added spacings for < 10 W lamps 5.3.3 X
Permission added for re-lamping outside of hazardous 5.3.5.2.2 X
area
Added bayonet lamps 5.3.5.4.2 X
Added contact requirements for bayonet lamps 5.3.5.5 X
Renaming of “Type” of cells and batteries 5.6.2 X
Clarification of approaches for general purpose 5.7 X
junctions boxes
6.9
Annex E
Clarified temperature monitoring and control 5.8 X
Clarification of testing of battery powered luminaires 6.3.1 X
Clarification of impact tests 6.3.2.2 X
Added abnormal tests for discharge lamps 6.3.4.1  C4
Added T5 8W 6.3.4.3 X
Table 16
– 10 – IEC 60079-7:2015 © IEC 2015
for “e” to “eb” Type
Explanation of the significance of the changes Clause Minor and Extension Major
editorial technical
changes changes
To maintain T4 temperature class, cathode power or 6.3.4.3  C5
ambient temperature reduced
Table 16
Clarification of routine tests for terminal boxes 7.1 X
Marking of “e” replaced by “eb” 9.1 See “Information about the background
of Changes”
Ex Component enclosures 9.2  C6
Highlight essential documentation for rotating 10 X
electrical machines
Temperature tests Annex A X
The significance of the changes between IEC Standard, IEC 60079-7, Edition 5 (2015) (for
“ec”) and IEC 60079-15, Edition 4 (2010) (for “nA”) are as listed below:
for “nA” to “ec” Type
Explanation of the significance of the changes Clause Minor and Extension Major
editorial technical
changes changes
Scope 1 X
Clarification of applicability
Notes added to address short circuits and short-term
thermal excursions
Clarification of resistance heating definitions 3.13 X

Soldered Connections 4.2.2.5 C7

4.2.3.3
Silver-Soldered connections 4.2.3.3 X

Evaluation of pluggable connections 4.2.3.5a) X

External plug and socket connections for field wiring 4.2.4 X

connection
Minimum separation distances for encapsulated or 4.3 X

sol
...