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Modifying existing power

James Edward Duncan

A client of mine needs to re-route part of a number of small power circuits (230v, low amps). It is preferred not to replace the circuits in their entirety, due to hazardous materials in the location.

So, cutting the circuits and jointing the now 2 new ends with a new cable is the option available.

For me I would test the entire circuit end to end, however my client only seems to want to test the new section! How would I persuade them that this is the wrong thing to do?

Also, the older parts of the circuits are potentially 20+ years old. So when I do the insulation test, do I still test to current regs? 

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    I am not at all sure that I understand the concept. 2 new ends implies that there will be a new segment from DB to old cable; the old cable; and a further new piece to the loads. It may be possible to test CPC continuity of the separate parts, but I am at a loss as to how Zs could be measured without a complete circuit.

    IR testing is mandatory - 643.1. It is to be conducted with final circuits connected - 643.3.2.

    So I think that James is right and the client is wrong.

    And yes, this is initial verification, so test to BS 7671:2018+1. It might be argued that these are not new circuits and a MEIWC is all that is required. That still has places for IR and Zs.

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    I am not at all sure that I understand the concept. 2 new ends implies that there will be a new segment from DB to old cable; the old cable; and a further new piece to the loads. It may be possible to test CPC continuity of the separate parts, but I am at a loss as to how Zs could be measured without a complete circuit.

    IR testing is mandatory - 643.1. It is to be conducted with final circuits connected - 643.3.2.

    So I think that James is right and the client is wrong.

    And yes, this is initial verification, so test to BS 7671:2018+1. It might be argued that these are not new circuits and a MEIWC is all that is required. That still has places for IR and Zs.

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