IEC 60079-14 Explained: Design, Selection and Installation of Electrical Installations

Correct equipment selection and installation help maintain the protection provided by explosion-protected electrical equipment.

Having certified Ex equipment is only part of a hazardous-area electrical installation. The equipment must also be selected for the correct location and installed in accordance with its certification, applicable standards, and manufacturer's instructions.

Cable glands, cable entries, wiring systems, earthing, bonding, circuit segregation, and equipment installation details can all affect whether the intended protection is maintained.

IEC 60079-14 addresses the design of electrical installations, selection and installation of equipment, and the required initial inspection in explosive atmospheres. The current sixth edition, IEC 60079-14:2024, also addresses installation documentation and personnel competency. Official IEC publication details.

This guide explains how the standard fits into hazardous-area projects and what engineers, EPC contractors, installers, and procurement teams should verify.

1. What IEC 60079-14 Covers

IEC 60079-14 specifies requirements for electrical installation design, equipment selection, installation, and initial inspection for electrical Ex equipment in or associated with explosive atmospheres. It applies alongside the requirements for electrical installations in non-hazardous areas.

Key engineering activities include:

• Selection of equipment suitable for the classified hazardous area.
• Design and installation of electrical wiring systems.
• Selection and installation of cable glands and cable entries.
• Earthing, bonding, and electrical separation.
• Installation requirements for different Ex protection concepts.
• Initial inspection and installation documentation.
• Personnel competency for relevant installation activities.

The standard covers new installations as well as applicable modifications and extensions. Its scope is not unlimited: IEC 60079-14:2024 identifies exclusions, including certain mines susceptible to firedamp, medical rooms, flammable-mist hazards, and installations of non-electrical Ex equipment outside the specified assembly context. Project requirements and applicable national regulations must also be considered.

2. Where It Fits in a Hazardous-Area Project

IEC 60079-14 connects hazardous-area design decisions with the installed electrical system. A typical project sequence includes:

1. Classify areas where explosive atmospheres may occur.
2. Define equipment protection and environmental requirements.
3. Select suitable certified Ex equipment.
4. Design the electrical installation and wiring arrangements.
5. Install equipment and verify that the installation follows the design and applicable requirements.
6. Complete the required initial inspection before placing the installation into service.
7. Apply the applicable inspection and maintenance requirements during operation.

For example, an Ex d enclosure may have suitable certification, but an unsuitable cable-entry arrangement can compromise the installed protection. Similarly, an intrinsically safe instrument loop can be affected by incorrect circuit segregation or incompatible connected apparatus.

Certification of individual equipment does not, by itself, demonstrate that the complete installation is correct.

3. Start With Hazardous-Area Classification

Equipment selection begins with the area classification and the conditions in which the equipment will operate. The Ex marking must be checked against the intended location rather than treated as a general approval for all hazardous areas.

Review the following information:

• Gas or dust hazardous-area zone.
• Gas group or dust group, as applicable.
• Required Equipment Protection Level (EPL).
• Temperature classification or maximum surface temperature.
• Ambient temperature limits.
• Environmental conditions, including water ingress, corrosion, and mechanical exposure.
• Complete equipment marking, certification, and any special conditions of use.

IEC 60079-10-1 addresses classification of areas where explosive gas atmospheres may occur. The relevant dust-area classification standard and project basis should be consulted for combustible-dust installations.

4. EPL and Equipment Selection

Equipment Protection Level is one factor used to establish whether equipment is suitable for a classified area. The following table shows common relationships between gas or dust zones and EPLs; it is not a substitute for the complete equipment marking or the project-specific selection requirements.

Atmosphere	Zone	Common associated EPL
Gas	Zone 0	Ga
Gas	Zone 1	Gb
Gas	Zone 2	Gc
Dust	Zone 20	Da
Dust	Zone 21	Db
Dust	Zone 22	Dc

These are common selection relationships, not the only consideration in every installation. The appropriate protection concept, certification, gas or dust group, temperature limits, ambient conditions, and any applicable local requirements must also be verified.

5. From Certified Equipment to Installed Equipment

Ex equipment is certified against defined requirements and conditions. During installation, those conditions must be respected.

Examples of installation-sensitive requirements include:

• Ex d: cable entries, glands, stopping plugs, and interfaces must be suitable for the certified flameproof arrangement.
• Ex e: terminal connections, conductor selection, enclosure integrity, and installation practices must follow the equipment requirements.
• Ex i: circuit segregation, identification, associated apparatus, and system compatibility must be verified.
• Ex p: protective-gas supply, purge arrangements, monitoring, and protective functions must be installed as specified.
• Ex t: dust ingress protection and temperature-related requirements must be maintained.

The exact installation requirements depend on the equipment certification, the applicable standard clauses, and the manufacturer's instructions. Do not assume that a method suitable for one protection concept is acceptable for another.

6. Cable Glands and Cable Entries

Cable entries are a critical interface between the electrical installation and the Ex enclosure. An incorrect gland, stopping plug, thread connection, or sealing arrangement can affect the intended protection.

During engineering and installation review, check:

• Gland and entry suitability for the protection concept and equipment certification.
• Thread type, size, and compatibility with the enclosure entry.
• Cable construction and the gland's suitability for that cable.
• Required ingress protection and sealing arrangements.
• Mechanical retention and strain relief where required.
• Correct treatment of unused entries using suitable certified stopping plugs.
• Compliance with the equipment certificate and installation instructions.

For Ex d equipment, the cable-entry method is particularly important because the entry forms part of the installed flameproof arrangement. The appropriate solution depends on the certified equipment, cable type, entry design, and applicable installation requirements. A generic rule should not replace the manufacturer's documentation.

Procurement teams should therefore confirm cable-entry requirements before ordering glands and accessories. A product can be certified and still be unsuitable for the intended installation interface.

7. Wiring Systems

The wiring system must be suitable for the hazardous environment and must not compromise the connected Ex equipment.

Consider:

• Cable type and electrical ratings.
• Mechanical protection and routing.
• Environmental exposure, including temperature, moisture, and corrosive conditions.
• Conduit or other wiring methods where applicable.
• Support, termination, and protection against damage.
• Separation requirements for different circuit types.

Wiring-system suitability must be evaluated against the installation conditions and the requirements applicable to the equipment and protection concept. Cable selection should not be based only on conductor size or voltage rating.

8. Earthing and Bonding

Earthing and bonding are essential parts of the electrical installation. The design should address protective earthing, bonding continuity, and any additional arrangements required by the equipment or protection concept.

Review the following where applicable:

• Protective earthing connections.
• Bonding of conductive enclosures and associated metalwork.
• Continuity of the earthing and bonding system.
• Earthing requirements for associated apparatus and intrinsically safe circuits.
• Measures addressing electrostatic hazards.
• Special arrangements identified by the manufacturer or project design.

Some intrinsically safe arrangements have specific earthing requirements, particularly where barrier designs depend on a defined connection to earth. Other arrangements use galvanic isolation. The actual requirements must be taken from the equipment documentation and applicable installation design.

9. Installing Intrinsically Safe Circuits

Intrinsic safety relies on limiting the energy capable of causing ignition. Installation errors can undermine the assessed circuit arrangement even when the individual devices are certified.

Installation checks may include:

• Segregation of intrinsically safe and non-intrinsically safe circuits.
• Identification and routing of intrinsically safe wiring.
• Correct installation of barriers or galvanic isolators.
• Prevention of inadvertent interconnection with other circuits.
• Verification of associated apparatus and field-device compatibility.
• Earthing and screening arrangements where required.
• Compliance with approved control drawings and equipment instructions.

IEC 60079-11 Explained: Intrinsic Safety "i" addresses the equipment protection concept. IEC 60079-14 addresses the installation requirements. The design and assessment of complete intrinsically safe electrical systems are also addressed by IEC 60079-25.

10. Initial Inspection Before Energization

IEC 60079-14:2024 explicitly includes the required initial inspection in its title and scope. This is an important distinction from treating the standard as a design-and-installation guide alone.

Before an installation is placed into service, the required inspection and documentation should confirm that the installed equipment and wiring conform to the design, applicable requirements, and manufacturer's instructions.

A practical review can include:

• Equipment marking and suitability for the classified location.
• Condition and compatibility of cable glands, entries, and stopping plugs.
• Wiring installation and circuit segregation.
• Earthing and bonding arrangements.
• Protection-concept-specific installation details.
• Compliance with certificates, control drawings, and special conditions of use.
• Completion of required installation records and documentation.

The applicable inspection extent, method, and acceptance criteria must be established from the current standard, project requirements, and the installation's circumstances. This summary is not a substitute for the standard's full inspection requirements.

11. Common Installation Problems

Installation deficiencies can occur even when the installed equipment itself has valid certification. Common examples include:

• Incorrect cable gland or stopping plug selection.
• Thread incompatibility or incorrect entry installation.
• Damaged enclosure entries or sealing interfaces.
• Equipment that is unsuitable for the classified location or ambient conditions.
• Incorrect segregation of intrinsically safe and non-intrinsically safe circuits.
• Incomplete earthing or bonding arrangements.
• Failure to follow manufacturer installation instructions.
• Missing or incomplete installation documentation.

These issues should be resolved against the applicable requirements before the installation is accepted. The corrective action depends on the specific equipment, certification, installation method, and project basis.

12. Competency and Documentation

Hazardous-area installation involves decisions that depend on understanding Ex protection concepts, equipment markings, and the installation requirements relevant to each protection method.

IEC 60079-14:2024 includes requirements relating to documentation and personnel competency. Project teams should establish responsibilities and ensure that personnel undertaking design, selection, installation, and inspection tasks have the appropriate competence for their assigned work.

Installation documentation should be sufficient to demonstrate the design basis, equipment selection, installation arrangement, and completion of the required verification and inspection activities. The exact documentation required depends on the applicable standard and project requirements.

13. What IEC 60079-14 Does Not Replace

IEC 60079-14 forms one part of the hazardous-area lifecycle. Other standards address related activities.

Activity	Relevant standard
General Ex equipment requirements	IEC 60079-0
Explosive gas atmosphere area classification	IEC 60079-10-1
Electrical installation design, selection, installation, and initial inspection	IEC 60079-14
Inspection and maintenance of electrical installations	IEC 60079-17
Repair, overhaul, and reclamation of Ex equipment	IEC 60079-19
Intrinsically safe electrical systems	IEC 60079-25

These standards have related but distinct roles. In particular, the initial inspection required for an installation should not be confused with the ongoing inspection and maintenance addressed by IEC 60079-17.

14. IEC 60079-14 in Procurement and Technical Bid Evaluation

Installation requirements should be considered before equipment is ordered. A technical bid evaluation can identify whether a proposed product is compatible with the project's hazardous-area classification and the intended installation arrangement.

Depending on the equipment and project, review:

• Required protection concept and EPL.
• Complete equipment marking and certification documentation.
• Gas or dust group and temperature requirements.
• Ambient temperature and environmental limits.
• Cable-entry threads and compatible gland arrangements.
• Earthing, bonding, and terminal requirements.
• Special installation conditions and accessories.
• Manufacturer installation instructions and control drawings.

Where a vendor proposes an alternative, assess its suitability for the actual installation rather than accepting it solely because its headline Ex marking appears similar. This can reduce construction delays caused by incompatible entries, missing accessories, or installation conditions that were not identified during procurement.

Related Reading

• IEC 60079 Series Explained
• IEC 60079-0 Explained: General Requirements for Ex Equipment
• IEC 60079-1 Explained: Flameproof Enclosures "d"
• IEC 60079-7 Explained: Increased Safety "e"
• IEC 60079-11 Explained: Intrinsic Safety "i"
• How to Read IECEx Equipment Markings

References

• IEC 60079-14:2024 – Electrical installation design, selection and installation of equipment, including initial inspection
• IEC 60079 series – Explosive atmospheres standards catalogue
• IECEx – International certification system for equipment used in explosive atmospheres

This article is an engineering overview. For design approval, installation, and inspection, consult the applicable edition of the standards, project specifications, equipment certificates, and manufacturer's instructions.