Has Ex nL been replaced by Ex ic?
Abstract
Yes. Energy-limited Ex nL was transferred to intrinsic safety as level of protection Ex ic in IEC 60079-11:2006, and IEC 60079-15:2010 removed nL. Installed Ex nL equipment remains a Zone 2 (EPL Gc) product under its certificate; new products are certified Ex ic.
Yes. The energy-limited type of protection "nL" from IEC 60079-15 was transferred into the intrinsic safety standard as level of protection "ic", first included in the fifth edition of IEC 60079-11 (2006). IEC 60079-15:2010 then removed the nL requirements. Equipment already certified and marked Ex nL remains suitable for Zone 2 (EPL Gc) under its certificate; new equipment is certified and marked Ex ic.
Short answer
- Where nL went: into IEC 60079-11 as intrinsic safety level "ic". An IEC interpretation sheet on IEC 60079-11:2011 says the aim of the transfer was not to revise the requirements substantially, apart from specific clauses.
- When: "ic" first appeared in IEC 60079-11 edition 5 (2006); the nL and [nL] requirements were removed from IEC 60079-15 edition 4 (2010).
- What changed: "ic" is intrinsic safety, so it covers both EPL Gc (gas, Zone 2) and Dc (dust, Zone 22), while nL was a Gc concept only. Some rules differ, for example larger separation distances at "ic" terminals and simpler component ratings.
- Old equipment: installed
Ex nLand associated[Ex nL]apparatus can stay in use in Zone 2 while it is in good condition and used as its certificate states. - New designs and purchases: specify
Ex ic(or "ib" or "ia", which always satisfy "ic").
What Ex nL was and why it moved
Type of protection "n" was a collection of Zone 2 techniques in IEC 60079-15: non-sparking "nA", enclosed break "nC", restricted breathing "nR" and energy-limited "nL". Energy limitation is the same principle as intrinsic safety: the voltage and current in the circuit are kept so low that a spark or hot surface cannot ignite the atmosphere, but only in normal operation, without counting faults. That made "nL" a natural lowest level of intrinsic safety.
IEC therefore moved it into IEC 60079-11 as "ic", next to "ia" (safe with two faults, EPL Ga) and "ib" (safe with one fault, EPL Gb). The other "n" techniques followed the same path over time: "nA" moved to increased safety as "ec" in IEC 60079-7:2015, enclosed break to IEC 60079-1, and IEC 60079-15:2017 keeps only "nC" and "nR".
| Ex nL (former) | Ex ic (current) | |
|---|---|---|
| Standard | IEC 60079-15 editions before 2010 | IEC 60079-11 since the 2006 edition |
| Principle | Energy limitation in normal operation | Intrinsic safety, assessed for normal operation |
| EPL | Gc only | Gc and Dc |
| Associated apparatus | [Ex nL] | [Ex ic] |
| Typical location | Zone 2 | Zone 2, Zone 22 |
Can existing Ex nL equipment stay in service?
Yes. A revision of a product standard does not make certified equipment unsafe. Ex nL equipment was placed on the market as category 3 (ATEX) or EPL Gc equipment, and Directive 1999/92/EC allows category 3 equipment in Zone 2. The plant must keep it in good condition, inspect it under IEC 60079-17 against its own certificate, and use it within its marked parameters.
Two practical points need care:
- Mixing nL and ic in one circuit. Old field devices and new associated apparatus can often be combined, but only after checking the parameters on both certificates, as for any energy-limited loop. IEC 60079-25:2010 explicitly allowed energy-limited "nL" apparatus with suitable parameters in an "ic" FISCO fieldbus system, with a label at the installation.
- Spares and repairs. Replacement units are now supplied as Ex ic. That is acceptable for a Zone 2 nL location, provided the gas group, temperature class and loop parameters still match.
Example: A Zone 2 analyser shelter has pressure transmitters marked II 3 G Ex nL IIC T4 fed from [Ex nL] interfaces. One interface fails and the replacement is marked [Ex ic Gc] IIC. The technician compares the new Uo, Io, Co and Lo with the transmitters' input and internal parameters plus the cable, documents the check and installs it. The transmitters themselves need not be replaced.
What changed in the requirements
An IEC interpretation sheet (ISH 3 of 2016 to IEC 60079-11:2011) lists clause by clause which requirements apply to "ic". Its guidance table notes that "ic" serves both Gc and Dc, and its background explains that separation distances at "ic" terminals were increased to align with the installation standard IEC 60079-14, and that rating rules for protective components were simplified. The 2023 edition of IEC 60079-11 states that "ia" and "ib" requirements are always sufficient for "ic", and that for "ic" faults are considered only for the spark ignition assessment and the determination of the entity parameters.
Common mistakes
- Rejecting Ex nL equipment at inspection only because the concept no longer exists. Check it against its own certificate.
- Using Ex nL or Ex ic in Zone 1. Both are EPL Gc only (ic also Dc); intrinsically safe equipment for Zone 1 needs at least "ib".
- Assuming any ic device fits any nL loop without a parameter check.
Related on excodex
- Ex ec, Ex nA and Ex nR: protection for Zone 2
- Intrinsic safety (Ex i): ia, ib and ic and the energy limitation principle
- Can Ex nA equipment still be installed now that Ex ec has replaced it?
- Is intrinsic safety needed in Zone 2, or is Ex ic enough?
- Standards spaces: IEC 60079-11, IEC 60079-15; tool: Ex marking check
Standards and further reading
- IEC 60079-11, intrinsic safety "i" (edition 7.0, 2023): sample with list of changes
- IEC 60079-11:2011 with interpretation sheet 3 (2016) on the transfer of "nL" to "ic": law.resource.org
- IEC 60079-15:2010, type of protection "n", abstract listing the removal of nL (withdrawn 2017): evs.ee
- IEC 60079-15:2017, type of protection "n" (nC and nR only): law.resource.org
- IEC 60079-25:2010, intrinsically safe systems, Annex I on "ic" FISCO systems: law.resource.org
- Directive 1999/92/EC, Annex II, equipment categories per zone: legislation.gov.uk
This article is general technical information prepared by the excodex editorial team. It does not replace the applicable standards, the equipment certificates and instructions, national regulations or the assessment of a competent person.