UL STANDARDS INCORPORATING IEC ZONING PRINCIPALS

Article 505 of the NEC code, permits the use of the Zone method of Classified Areas.ul

This means that products can be approved by :-

Class, Division, & Gas Group,
e.g. Class I, Division I,A,B,C,D or

Class, Zone, & Gas Group
e.g. Class I, Zone 1 AEx d IIC

Although the code permits the approval of products for the Zone classification, in a similar way to IEC practice, this does not mean that mixing of different forms of equipment approval across zones or divisions is acceptable. eg. products approved for Zone 1 do not necessarily meet the requirements of Division 1 which also encompasses Zone 0.

IEC Standards are also being adopted into the NEC, however, in some cases the IEC Standard is amended to suit the requirements of the NEC. e.g. IEC 60079 vs UL 60079 Hazardous Area Cable Glands. Cable glands that comply with IEC 60079 MUST meet the requirements of UL514B before they can be used on NEC Zone Classified Installations.

For Canada, Zone classified products are tested to IEC Standards with no national deviations.

The correlation between IEC standards adopted in North America, and the associated forms of protection is shown below :-

EQUIPMENT FORMS OF PROTECTION CENELEC IEC NORTH AMERICAN STANDARDS
Protection Method Code of Protection Protection Principle ATEX CATEGORY CENELEC Standard # IEC Standard Code of Protection Permitted in Zone UL Standards FM Standards
Flameproof Ex d Contains the explosion and quenches the flame 2 EN 50018 IEC 60079-1 AEx d 1 or 2 UL 60079-1 FM3600 (ISA 12.22.01*)
Intrinsic Safety Ex ia Limit energy of sparks, limits the temperature 1 EN 50020 IEC 60079-11 AEx ia 0, 1, 2 UL 60079-11 FM3610 (ISA 12.12.01)
Ex b Limit energy of sparks, limits the temperature 2 EN 50039 AEx ib 1 or 2 UL 60079-7 FM3600 (ISA 12.16.01)
Increased Safety Ex e No arcs, sparks or hot surfaces 2 EN 50019 IEC 60079-7 AEx e 1 or 2 UL 60079-7 FM3600 (ISA 12.16.01*)
 
Encapsulated Ex m Keep the flammable gas away from any hot surfaces and ignition capable equipment 2 EN 50028 IEC 60079-18 AEx m 1 or 2 UL 60079-18 FM3600 (ISA 12.23.01*)
Immersed in oil Ex o 2 EN 50015 IEC 60079-6 AEx o 1 or 2 UL 60079-6 FM3600 (ISA 12.16.01*)
Pressurised Ex p 2 EN 50016 IEC 60079-2 Ex p 1 or 2 NFPA 496 FM3620
Quartz/Sand Filled Ex q Contains the explosion and quenches the flame 2 EN 50017 IEC 60079-5 Ex p 1 or 2 UL 60079-5 FM3600 (ISA 12.25.01)
 
Non-Sparking Ex nA No arcs, sparks or hot surfaces 3 EN 50021 IEC 60079-15 AEx nA 2 UL 60079-15 FM3600 (ISA 12.12.02)
Enclosed Break Ex nC Contains the explosion and quenches the flame AEx nC
Energy Limitation Ex nL Limits energy of sparks, limits the ­temperature AEx nL
Restricted Breathing Ex nR   AEx nR

Note: CENELEC Standards # may be withdrawn since EN60079 replaced EN500 series but are included for cross comparision or references purposes only

Note: Items with * also required to comply with ISA 12.00.01

There is a similarity if not a direct equivalent between current IEC and North American Codes of Protection and Area Classification. It is envisaged any differences will be eliminated with the developing acceptance of IEC Standards in North America and vice versa. Here is a simple representative cross relationship between North American and IEC classifications :-

EQUIVALENT ZONE / DIVISION
NEC IEC
Division I Zone 0
Zone 1
Division II Zone 2

The opposite cannot be assumed. For example Flameproof Ex d equipment certified under IEC rules is not automatically suitable for NEC / CEC Division 1 areas.

IEC / NEC-CEC Deployment Comparison

Mixing of Codes is Usually Not Permitted, and this equally applies to cable glands or cable connectors.

Accepting that Flameproof is not Explosion Proof and vice versa is very important, and whilst some confusion frequently occurs between both the terminology and understanding of the principles involved, the two concepts follow distinctly different testing and installation standards. For this reason alone great care should be taken when indulging in selection and installation from differing codes of practice.

Here is a comparison of the testing methods adopted for Ex d IIC Cable Glands to IEC 60079-1 & Class I Division 1 ABCD (NEC) Explosion Proof Cable Connectors to UL 2225 intended for use in hazardous locations, specifically for use with Ex d IIC (IEC) & Class I Division 1 (NEC or CEC) Explosion Proof apparatus.

CABLE ENTRY DEVICES - PRODUCT CERTIFICATION TESTS
Protection method Ex d Explosion Proof
STANDARD IEC 60079-1 UL2225, CSA 22.2
HYDROSTATIC PRESSURE TEST AT 450 PSI FOR 2 MINUTES UP TO 2000 PSI FOR 2 MINUTES
ENCLOSURE TYPE / SIZE USED FOR EXPLOSION TESTING NOT APPLICABLE EXPLOSION PROOF 29 LITRES ENCLOSURE VOLUME

A compound barrier type (seal type) cable gland must always be used, under the NEC / CEC wiring code rules, for any Class I Division 1 or Division 2 explosion proof equipment installed in hazardous locations.

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