Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This Question of the Day, about separate circuit protective conductors (CPCs) run in parallel with armour, is answered by BASEC:
Answer: In many applications, the amount of armouring present on an armoured cable will be of sufficiently low resistance to permit its use as an acceptable CPC.
However, where a full-conductor-sized CPC has been specified, or where other considerations apply, this will not be the case and a separate CPC should be installed. It will depend on the actual system design and should be specified by the designer. Calculations should be carried out whenever the armour is used as a CPC to make sure.
The armouring would, of course, need to be properly terminated through appropriate glands at both ends, and tested as normal for a CPC.
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