Non-footy help (advice) needed...

Discussion in 'Bulletin Board' started by Tekkytyke, Dec 17, 2024 at 1:23 PM.

  1. Tek

    Tekkytyke Well-Known Member

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    Hi all.

    Long time no speak! Any sparkies on the board can clarify something for me...

    Winter has arrived here in sunny!? Italy with snow now on the mountains, meaning our heat pump has finally sprung into action for our underfloor heating. Regardless of supply source -Solar when it is sunny -or grid it pulls around 3.3kW when running. Given, being rural, we only have 6kW grid supply (Solar panels output 7200W DC) 10kW battery backup our board has 10A RCD for lighting (way too much since it is all LED or low voltage now) and 16A RCD for the sockets.

    This which means when the heating is on with fridges freezers etc. and we try to turn on the oven or microwave, dishwasher etc. the damn thing trips for it exceeds the 16A RCD capacity. Our workaround is to time the heating to operate during for non cooking, washing times but that is not always easy.

    When earlier this year the solar/ heat pump was fitted the supply cable to the distribution board from the meter was upgraded to 10mm but when I suggested to an electrician that we could replace the 10A lighting RCD with 5A (given we would only ever run about 1A) and put a 25A RCD to replace the 16A one he told me that the cables would not handle that and anything above 16A could cause them to melt. therefore a separate circuit would need to be installed for the heat pump. Now if my memory serves me correctly most UK houses ring have either 3.5mm or 4 mm cabling handling much more than the 25A I am asking for. He tells me things are different in Italy although I thought the law of physics was pretty much universal. Our house was restored (practically rebuilt) with new wiring in 2010.

    Am I missing something, or is he trying to bump up the price? Swapping out a couple of RCDs is not a long job (about 30 minutes I reckon) but adding a dedicated supply cable cable is a lot more involved (and expensive!!)
     
    Tekkytyke, Dec 17, 2024 at 1:23 PM
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  2. Gimson&theBarnsleys

    Gimson&theBarnsleys Well-Known Member

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    I thought UK ring mains were 2.5 mm squared.
     
    Gimson&theBarnsleys, Dec 17, 2024 at 2:06 PM
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  3. WG Red

    WG Red Well-Known Member

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    They are
     
    WG Red, Dec 17, 2024 at 2:16 PM
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  4. Deafening Silence

    Deafening Silence Well-Known Member

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    If the cable is 2.5mm and wired as a radial circuit, dependent on the installation method and cable type it may take 25A.

    Not sure if you can make it out properly in the picture, but if the cable flat twin and earth and is clipped direct with no thermal insulation then it will take 27A and still comply with the IET wiring regs.
     

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    Deafening Silence, Dec 17, 2024 at 3:20 PM
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  5. Deafening Silence

    Deafening Silence Well-Known Member

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    You can also get a 20A RCD if it meets the requirements for more than 16A but less than 20.
     
    Deafening Silence, Dec 17, 2024 at 3:23 PM
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