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M.I.C.C. in House. Why?

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Today I came upon some orange served M.I.C.C. cable running from the loft in a bungalow to a single metalclad socket. It may have been an immersion heater supply, but the copper cylinder has been removed. It appears to be quite big, perhaps 4.0mm2 or 6.0mm2.

 

I wondered just why it was installed in a domestic bungalow.

 

Apprentice training by an electrician father perhaps. Used as it was available. But the extra work terminating it would not warrant using spare cable from your works would it?

 

Bemused of Norfolk.?

 

 

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    So what causes the corrosion? We all know about copper roofs turning green, but why is Pyro so badly affected? I know that old churches can be a bit musty, but are they truly damp?

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    Chris Pearson: 
     

    So what causes the corrosion? We all know about copper roofs turning green, but why is Pyro so badly affected? I know that old churches can be a bit musty, but are they truly damp?

    Damp, and often lime in the old mortar…

       - Andy.

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    It was recommended many years ago that S.P.D.s be fitted where pyro may be damaged by high Voltages, caused by such as lightning strikes or inductive loads being switched off. I believe that they were called Voltage suppressors back then, but the memory fades. There were cases documented that showed damaged M.I.C.C. cables blown through by high Voltage surges.

     

    Having just looked into my old book on M.I. cables published by B.I.C.C. the devices were called “Surge Diverters”. A typical one was rated to protect cables up to 660 Volts. It could be connected across any coil taking up to 120 mA R.M.S.

     

    The steady leakage current was about 0.2 mA at 250 Volts, or 1.5mA at 440 Volts.

     

     

    The devices were to be disconnected before insulation resistance testing.

     

    Edit, add.

     

    My book says that Voltage breakdown can be a problem. Cables made to comply with B.S. 3207 (part 1)

    440 Volt cables were tested at 2kV R.M.S. and 660 Volt cables were tested at 3kV R.M.S.

     

    Surge Voltages of 12 kV were mentioned as having been recorded on 440 Volt circuits.

     

    Examples of usage in the book cite the Seven Bridge where M.I. cables were used extensively. The London Post Office Tower had 21 miles of M.I. cable installed in it.

     

     

     

    Z.

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