James asks this question, which concerns EExd electric motors, none of which have an external earth link from the SWA cable banjo to the external motor earth stud. It has been answered by the NICEIC (Theme – Fire, Safety and Security):
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Question: We are carrying out periodic checks on EExd electric motors and none of them have an external earth link from the SWA cable banjo to the external motor earth stud.
I can’t find a reference in the manufacture’s data as to whether it is essential for certification.
We are wondering whether it is only essential under certain conditions, and can be omitted if using SWA cable with a dedicated earth…what do you think?
Otherwise it means de-glanding all the motors.
Answer: Thank you for your enquiry regarding the earthing of EExd motors. Presumably, the SWA cables will have appropriate flameproof glands and the SWA armour itself forms the circuit protective conductor - 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 carried out 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 often believed by contractors. A local reliable earth connection can be used for this purpose. We trust that the above information is helpful.
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