# IEC 60079-7 — Equipment Protection by Increased Safety 'e'

> IEC 60079-7 specifies 'increased safety' (Ex e) protection — applied to equipment that does not produce arcs, sparks or hot surfaces in normal operation. Used primarily for terminals, junction boxes, motors without slip rings, and lighting fixtures.

- Source : https://industryhub.site/en/standards/iec-60079-7
- Body : IEC
- Family : Hazardous Areas
- Status : current
- First published : 1976
- Latest revision : 2017 (Edition 6)
- Edition : 6
- Next revision : Active maintenance
- Access : Paid (IEC webstore — ~200 CHF)
- Language : English

## Document structure

- **IEC 60079-7:2017** — Equipment protection by increased safety 'e' : Specifies enhanced construction requirements for non-sparking equipment : insulation distances, temperature limits, IP rating, mechanical strength. Less expensive than flameproof but more limited (no normal-operation arcs allowed).

## Key concepts

- **Increased safety principle** : Engineer the equipment so that it does NOT produce ignition sources during normal operation (no arcs, no sparks, no hot surfaces > T-class). Then add safety margin in clearances, creepage distances, materials, mechanical strength.
- **Ex eb vs ec** : Ex eb = standard increased safety, suitable for Zone 1 (EPL Gb). Ex ec = relaxed requirements for Zone 2 only (EPL Gc), introduced in 2015 to replace the deprecated 'nA' protection method.
- **Limiting temperature rise** : Critical for Ex e motors : the motor must not exceed its T-class even when stalled or under fault conditions. Manufacturers specify a t_E time : maximum time a stalled motor can remain energized before exceeding limits. Tripped before t_E by thermal overload protection.
- **Where you find Ex e** : Terminal boxes (most common — junction boxes on Ex d motors etc.), squirrel-cage motors WITHOUT brushes/slip rings, lighting fixtures (LEDs, fluorescent), some space heaters, transformers.

## Where Ex e fits in the Ex protection toolkit

Ex e occupies the **middle ground** between IS (low power, Zone 0) and flameproof (any power, Zone 1+). Specifically :

- **Higher power than IS** : can handle motor terminals, lighting circuits
- **Lower cost than Ex d** : no need for explosion containment construction
- **Limited to non-arcing equipment** : ruled out for relays, contactors, switches with normal-operation arcing

In practice, the most common Ex e application is the **terminal compartment** of an industrial motor. The motor body itself is **Ex d** (the rotor brushes / commutator could spark, must be contained), but the connection terminals don't arc in normal operation — they get Ex e (lighter, easier to access for maintenance). The marking becomes **Ex de** (compound : 'd' for motor body, 'e' for terminal box).

Junction boxes are another major application — distributing power to multiple Ex devices, with no internal arcing under normal operation.

## Ex e motor protection

The catch with Ex e motors : the **stall current** must not heat the windings beyond the T-class. Manufacturers specify :
- `tE time` : time at stall before T-class exceeded (typically 5-40 seconds)
- `IA/IN` : starting-current-to-rated-current ratio

The thermal overload relay protecting the motor must trip in less than `tE` even under worst-case stall. This is documented and verified at commissioning.

## Ex ec — the new Zone 2 option

The 2017 edition reorganized Zone 2 protection methods. The old **"Ex nA" (non-sparking)** classification was merged into **"Ex ec"**, the relaxed Ex e variant for Zone 2 only.

Effect : Ex e equipment for Zone 2 became slightly easier to certify (less rigorous environmental testing) while keeping the basic non-arcing principle. New designs use Ex ec for Zone 2. Legacy nA designations are still seen on older equipment.

## Applicable industries

Oil & Gas (terminal boxes everywhere), Petrochemical (junction boxes, lighting), Chemical industry, Marine and offshore

## References & further reading

- [IEC 60079-7:2017 — official](https://webstore.iec.ch/publication/61425)