Published: 19 May 2014
Category: Q&A
Darren asks this question, which is about EEx 'd' electric motors sited in a hazardous area, and whether they need an external earth link from the SWA banjo to the external motor earth stud. It has been answered by the NICEIC (Theme – Fire, Safety & Security):
This Q & A is one of thousands posted in our Technical Expertise area, and answered on a daily basis by our Voltimum Experts.
Question: We are carrying out periodic checks on EEx 'd' motors and none of them have an external earth link from the SWA banjo to the external motor earth stud.
I can’t find a reference as to whether this is essential for certification in the manufacture’s data.
We are wondering whether it is only essential under certain conditions, and whether it can be omitted if using SWA cables with a dedicated earth?
Otherwise, it means de-glanding all of the motors.
Answer: Presumably the SWA cables will have appropriate flameproof glands and the SWA armour itself forms the circuit protective conductor (CPC), or possibly by the use of an internal core.
In any event, the SWA armour should be earthed. If this is the case then it may not be necessary for an additional link if the gland is making a good connection with the motor case itself, subject to a satisfactory earth continuity test.
This can most effectively be done using the wander lead R2 method subject to any hazardous area restrictions. It is not necessary to run the test lead back to the MET as is often believed by electrical contractors. A local reliable earth connection can be used for this purpose.
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