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.
IEC 60079-7:2017 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).
Ex e occupies the middle ground between IS (low power, Zone 0) and flameproof (any power, Zone 1+). Specifically :
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.
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 ratioThe thermal overload relay protecting the motor must trip in less than tE even under worst-case stall. This is documented and verified at commissioning.
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.