UL STANDARDS INCORPORATING IEC ZONING PRINCIPALS
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 |
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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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