1.5 or 2.5 for water heater

Discussion in 'Electrics UK' started by wv62, 3 May 2015.

  1. wv62

    wv62

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    I'm currently doing some work on our holiday chalet near Minehead and noticed that the Triton water heater is connected using 1.5mm T&E cable. It's a 3Kw unit which, if my maths is correct (assuming 230v) will draw 13A. I've checked the Triton web site and they say a minimum of 1.5. The cable runs in the wall (wood outer, Celotex insulation, MDF). Isn't that running very close to the max for 1.5mm? What would you lot use? My thoughts would be to rewire with 2.5mm.
     
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  3. JohnW2

    JohnW2

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    If the cable is totally surrounded by thermal insulation and does not touch the inner surface of the wall, then you are right, since the current-carrying-capacity of 1.5mm² cable would then only be 10A, hence inadequate. However, in all other situations it would be OK for at least 13A. What size MCB/fuse is protecting this cable?

    Kind Regards, John
     
  4. wv62

    wv62

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    Not sure. I'm at home at the moment. I'm hoping (work permitting) to get back down next week to finish off some other jobs. I'll check the MCB then.
     
  5. JohnW2

    JohnW2

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    Fair enough. It's not the most crucial question, anyway. The most crucial question is whether the cable is in contact with the inner face of the wall, or whether it is totally surrounded by thermal insulation. It's probably a 16A MCB.

    Kind Regards, John
     
  6. wv62

    wv62

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    It's not surrounded with insulation but is against the inner face of the wall.
     
  7. JohnW2

    JohnW2

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    In that case, it counts as Installation Method 102, with which 1.5mm² cable has a CCC of 16A - hence fine for your 13A water heater, provided it is protected by a 16A MCB.

    Kind Regards, John
     
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