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Legacy Installation EICR

Owelly

Greetings all.

Hopefully this will be an easy one for the hive mind, and I've tried the 'Search' but to no avail:

I manage an old industrial complex built in 1960. During the EICR testing most of the fixed wiring circuits have failed the insulation tests, with readings of less than 1Mohm. These cables are all MICC and have been untouched since installation. To replace all these cables would be an epic task and these works would need to be done in the next three months to satisfy the handover of the premises to the landlord.

Is there a method to test these 'legacy' cables other than to test to current standards (500v)? Istr mention of testing such cables at 50v but I can't find where I saw this. Is there a method to implement mitigation measures instead of replacing all the cables, or spending many hours isolating sections to fault find?

As you may be able to tell, I'm no electrician and every contractor I've approached has insisted that the entire building needs to be recabled, which isn't currently viable.

Thanks.

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    I'm not desparately familiar with MICC and appropriate values and wouldn't venture an opinion in your particular case, but if suspecting low values are due to moisture I might think about finding a test device that will allow you to measure Dielectric Absorption Ratio and Polarisation Index... these are fancy names for a prolonged insulation resistance test and watching how the resistance varies over a prolonged test (DAR = 60s, PI = 10min) and using the knowledge that if the issue is moisture in the cables rather than a resistive fault the IR should drop over time. Conversely if it is stable at an unacceptably low IR there's a real, resistive fault somewhere.

    It sounds fancy but it can be a case of having a stopwatch, a calculator and a multifunction tester that reads out continuously rather than stopping the test as soon as it's happy with the answer.

    (You can do cleverer things, particularly if you can plot the IR during the test and re-test every year, so you can compare plots over time, but that's the general idea)

    PS - Sorry just re-read your OP in which you say you're not an electrician, but this might help someone

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  • 0

    I'm not desparately familiar with MICC and appropriate values and wouldn't venture an opinion in your particular case, but if suspecting low values are due to moisture I might think about finding a test device that will allow you to measure Dielectric Absorption Ratio and Polarisation Index... these are fancy names for a prolonged insulation resistance test and watching how the resistance varies over a prolonged test (DAR = 60s, PI = 10min) and using the knowledge that if the issue is moisture in the cables rather than a resistive fault the IR should drop over time. Conversely if it is stable at an unacceptably low IR there's a real, resistive fault somewhere.

    It sounds fancy but it can be a case of having a stopwatch, a calculator and a multifunction tester that reads out continuously rather than stopping the test as soon as it's happy with the answer.

    (You can do cleverer things, particularly if you can plot the IR during the test and re-test every year, so you can compare plots over time, but that's the general idea)

    PS - Sorry just re-read your OP in which you say you're not an electrician, but this might help someone

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