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IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
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IEC 60079-0
Edition 6.0 2011-06
EXPLOSIVE ATMOSPHERES –
Part 0: Equipment – General requirements
INTERPRETATION SHEET 4
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:
DISH Report on voting
31/1454/DISH 31/1465/RVDISH
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.
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Interpretation sheet of Subclause 16.6 of IEC 60079-0:2011
The TC 31/CAG requested (Resolution 2 of 2018-04-19) that WG 22 prepare an interpretation
sheet based on IECEx Decision Sheet DS2018/002 addressing the assignment of entry point
and branching point temperatures of electrical rotating machines.
This interpretation is made available for Edition 6 of this standard due to the current use of
that standard by manufacturers, conformity assessment schemes and national bodies by
means of this “Interpretation Sheet” as follows:
ICS 29.260.20
IEC 60079-0:2011-06/ISH4:2019-04(en)
– 2 – IEC 60079-0:2011/ISH4:2019
IEC 2019
Details of interpretation:
IEC 60079-0:2011 (Ed. 6), Explosive atmospheres – Part 0: Equipment – General
requirements
Interpretation of Subclause 16.6, Temperature at branching point and entry point:
Question: Subclause 16.6 of IEC 60079-0:2011 (Ed. 6) states “When the temperature under
rated conditions is higher than 70 °C at the entry point or 80 °C at the branching point of the
conductors, information shall be marked on the equipment exterior to provide guidance to the
user on the proper selection of cable and cable gland or conductors in conduit.”
It is not normal practice for electrical rotating machines to be tested with the cable entry
devices and cables that might be used in an actual installation, but with the cables available
at the manufacturer’s test area. In many cases, there will be no formal entry device as the
cables will enter via the space reserved for fixing of a gland plate.
How shall the relevant entry point and branching point temperatures be determined?
Interpretation: The use of the maximum internal air space temperature to represent the
maximum service temperature of terminal box gaskets and seals, the cable branching point
temperature, and the entry point temperature reflects the normal practice of testing electrical
rotating machines without prior knowledge of the actual glands and cables to be used for
installation. The production of heat from the electrical rotating machine connections is
generally insignificant with respect to the production of heat from the machine windings and
core.
Further amplification:
1) The entry point of the cable where the temperature is measured should be sealed so far
as possible to ensure that there is minimum air-circulation which can reduce the measured
temperature.
2) This is not intended to apply to any gasket between the terminal box and the frame of the
electrical rotating machine, where higher temperatures may be recorded, but only to the
gasket between the terminal box and its lid.
Although written in the context of electrical rotating machines, there may be other types of
equipment where an equivalent approach is applicable.
IEC 2019
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
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IEC 60079-0
Edition 6.0 2011-06
ATMOSPHERES EXPLOSIVES –
Partie 0: Matériel – Exigences générales
FEUILLE D'INTERPR É T AT I O N 4
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