IEC 60079-11:2011/ISH2:2016

 IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION

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IEC 60079-11
Edition 6.0  2011-06
EXPLOSIVE ATMOSPHERES –
Part 11: Equipment protection by intrinsic safety "i"

INTERPRETATION SHEET 2
This interpretation sheet has been prepared by subcommittee 31G: Intrinsically-safe
apparatus, of IEC technical committee 31: Equipment for explosive atmospheres.
The text of this interpretation sheet is based on the following documents:
ISH Report on voting
31G/252/ISH 31G/254/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.

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Interpretation of 6.2.5 – Requirements for connections and accessories for IS apparatus
when located in the non-hazardous area
Question:
Does the first NOTE of 6.2.5 imply that equipment which may be connected to non-intrinsically
safe connection facilities of intrinsically safe apparatus restricted to use in non-hazardous
area need to be assessed applying IEC 60079-11, if the value of U is less than 250 V a.c.?
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Does this furthermore apply to equipment to be connected to non-intrinsically safe connection
facilities of associated apparatus, if the value of U is less than 250 V a.c.?
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Background:
The first NOTE of 6.2.5 requires in cases were U is specified less than 250 V a.c. that this
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should not be derived from unassessed equipment. This is sometimes read as if the
requirements of IEC 60079-11 should be applied for voltage limitation to guarantee U .
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Terminological entry 3.13.13 defines that U is the maximum voltage that can be applied to
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the non intrinsically safe connection facilities of associated apparatus without invalidating the
ICS 29.260.20
IEC 60079-11:2011-06/ISH2:2016-07(en-fr)

– 2 – IEC 60079-11:2011/ISH2:2016

 IEC 2016
type of protection. NOTE 1 of 3.13.13, as an example, explains that this may apply to

connection facilities used for charging batteries.

In IEC 60079-11 there are no measures required for limiting the voltage of non I.S. circuits to

the specified U value, except for the use of a single Zener diode protected by a fuse as an
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integral measure of an associated apparatus limiting the voltage which can appear at a

transformer (8.3) or a coupler (8.9.2).

IEC 60079-14: 2013, 16.2.1 states:

Where U marked on the associated apparatus is less than 250 V it shall be installed in
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accordance with one of the following:
a) where U does not exceed 50 V a.c. or 120 V d.c., in an SELV or PELV system, or
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b) via a safety isolating transformer complying with the requirements of IEC 61558-2-6, or
technically equivalent standard, or
c) directly connected to apparatus complying with the IEC 60950 series, IEC 61010-1, or a
technically equivalent standard, or
d) fed directly from cells or batteries.
Answer
No
IEC 60079-11 does not require measures to limit U where it is specified as 250 V a.c. which
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is guaranteed by the public power supply using standards other than IEC 60079-11. Similarly,
IEC 60079-14 allows measures not compliant with IEC 60079-11 for limiting U to below
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250 V a.c.
Therefore no assessment of the voltage supply according to IEC 60079-11 is necessary
where U is specified less than 250 V a.c. provided that one of the measures allowed by
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IEC 60079-14:2013, 16.2.1 are applied.
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NOTE This does not alter the requirement of the 3 paragraph of 6.2.5 to assess, in accordance with IEC 60079-
11, any protective circuitry located in the non-hazardous area accessory.

 IEC 2016
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE

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IEC 60079-11
Edition 6.0  2011-06
ATMOSPHÈRES EXPLOSIVES –
Partie 11: Protection de l'équipement par sécurité intrinsèque "i"

FEUILLE D'INTERPR É TA TI O N 2

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