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Safe to have power cables running through wall insulation?

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  1. #1
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    Default Safe to have power cables running through wall insulation?

    Hi again all,

    Forgot to mention in my earlier post:

    We removed some cosmetic cladding from the outside of a wall and were able to view inside the wall (ie behind the plasterboard). We noticed that the power cable running through the wall to the powerpoints is surrounded by the insulation in the wall. The cable is run inside conduit in the wall, but I was under teh impression that you couldnt surround power cables in walls with insulation?

    Please explain lol

    Ciao,

    Adam.

  2. #2
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    Tell us a bit more, which one of the following applies?
    insulation.jpg

  3. #3
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    It would be number 4 - completely surrounded with insulation inside wiring enclosure.

    And its the flat wire type.

  4. #4
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    Well that changes things somewhat. Your normal power circuit cable has a rating of 25A if it is just twin and not enclosed in anything usually a CB of 20A is installed for protection. Now with full insulation and enclosed in conduit it now derates the cable to 14 A so for full protection of the cable to allow heat to dissipate you will need a 14 A breaker but they don't make them so you will be forced to go to 10A.
    Armed with this information I think you should see your local electrician.

    There is one thing he can do and that is to pull the conduit out which will increase the cable rating to 16A still short of the normal 20A but with 4 power circuits this should be no problem. This should only be a problem on the outside walls as no one in their right mind would put insulation in the internal walls I hope. One thing you could do before he comes is isolate all the power circuits then switch on one breaker at a time and see which power points are energized as it might be just a case of derating one of the power circuits something you could live with.

    That is the problem with insulation with the house wired according to the rules at the time then someone comes along and pumps insulation into cavities and the cables have the potential to overheat

  5. #5
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    Thanks Bros. Im sure I can save some time with the sparky armed with that info. It is an external wall and its the glasswool batt type insulation. What about if we just removed the insulation from around the cable so there was about 100mm space either side? Or does it need to come out of the conduit to keep cool?

    There is 2 double power points on the line and then it goes straight into the mains box.

  6. #6
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    Is there insulation inside the conduit as well? if you removed the insulation from around the conduit that has the cable inside the cable rating would come up to 23 A for partially surrounded with insulation or even 28 A .

    I believe it is time for an electrician to actually look at the installation. What about the ceiling you better check that out as well, if it is a 70's house and wrap over roof might be a case of lifting a few sheets. if you have down lights and insulation was indiscriminately put in there, look and see if it surrounds down-lights or down-light transformers if they are low voltage.
    The aim is to allow air to circulate around the cable.

  7. #7
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    No theres no insulation inside the conduit, I meant does the cable need to come out of the conduit to be cool enough? And I know theres no insulation in the ceiling. I believe it was just this one external cosmetic wall that was replaced with a metal stud wall and corro cladding.

  8. #8
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    No just rip the insulation out from around 100mm either side of the conduit and your cable rating will come up to 23A more than enough

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