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can you certify an installation which has two core red and black singles wiring in conduits approx 50 years old with no cpcs

Dave O'Malley

the clients expect me to certifcate an installation with red and black singles cables in conduit thats approx 50 -60  years old with no cpcs 

my take is i cannot touch this with a barge pole 

dave O'Malley 

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    I started in 1981 in a large factory. We didnt fit a CPC in the conduit or trunking, as the CPC WAS the conduit and trunking. Benefits of that was that pretty much every machine was at the same potential, and, no chance of getting a loose connection from a single cable, these were large machine and conveyors, all bolted together at some point. The fault current was huge, as the substation was inside the factory, with 5Mw furnaces the other side of the wall.

    When tested, it would give a far lower Zs than an equivalent CPC using a cable to each machine.

    I would say test it, then see how low the Zs is, and be amazed that people 60 years actually knew what they were doing, and find out that the Zs and R2 are far lower than you could ever achieve by adding a copper CPC to each circuit.

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  • 0

    I started in 1981 in a large factory. We didnt fit a CPC in the conduit or trunking, as the CPC WAS the conduit and trunking. Benefits of that was that pretty much every machine was at the same potential, and, no chance of getting a loose connection from a single cable, these were large machine and conveyors, all bolted together at some point. The fault current was huge, as the substation was inside the factory, with 5Mw furnaces the other side of the wall.

    When tested, it would give a far lower Zs than an equivalent CPC using a cable to each machine.

    I would say test it, then see how low the Zs is, and be amazed that people 60 years actually knew what they were doing, and find out that the Zs and R2 are far lower than you could ever achieve by adding a copper CPC to each circuit.

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