8.5 kw shower

Discussion in 'Electricians' Talk' started by ouch, Sep 16, 2007.

  1. ouch

    ouch New Member

    Advice needed please.
    The shower which has just died is an 8 kw Triton T80 which I want to replace with a 8.5 model.
    My plumber is unsure about the electrics side of things and wants to make sure that the new one is OK for the current electrical supply, fair enough.
    I have checked the electric wiring as far as I can and it is as follows from shower to pull switch from pull swirch to circular junction box in the loft, it is grey sheafed wiring as per that used for the cooker (10mm ??)
    From the junction box presumably to the consumer unit it is white sheafed and smaller (6mm??).
    From my amateur description does this appear OK? Does a shower 0.5 kw stronger really make that much difference ?
    The old shower / wiring was in place at least 9 years without setting the place alight, that was left to my neighbour !!!!!
    Thanks in anticipation.
  2. Rabbit Rabbit

    Rabbit Rabbit New Member

    If, and I must emphasise the IF, all is described (10mm then 6mm t/e) then that is all OK.
  3. andyspark

    andyspark Active Member

    You'll wish you hadn't asked.

    Anyway here we go;

    What size breaker/fuse is protecting the circuit at the moment. If its 32A you'll be ok (this is in the real world though).

    Unfortunately I sense Ib<In<Iz rearing its head and if it does you are in trouble.
  4. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Well, [10mm???] is a guess. And [6mm???] is a guess.

    I guess it would be better to KNOW.



    Mr. HandyAndy - really
  5. Rabbit Rabbit

    Rabbit Rabbit New Member

    True Handy (hence my IF) if it's 1.5 or 2.5 t/e then forget the whole idea.

    I assumed it was not either as it has been running an 8kW shower and the fire would have already happended had it been lesser than 6 mm t/e!
  6. ouch

    ouch New Member

    Fair comment, but getting an electrician in for such a check appears difficult to say the least.
    Judging by what I can work out those sizes are correct ie the 10mm is cooker cable and the white cable is identicle to the 6mm sold in BQ.
    Just to say that I am not a risk DIY'er and will gladly pay for this job, I just want to know what shower to look for, if it is a 7.5 or 8 kw so be it, but SHE would like a 'better' one probably 'cos her mates got one (you no doubt get the picture !!).
  7. ouch

    ouch New Member

    Ib<In<Iz and t/e sound like another couple of Curbishleys signings. I give in what are they ?
  8. andyspark

    andyspark Active Member

    Handy
    I am not guessing.
    A 8.5 kW shower installed with 6mm and protected by a 32A breaker WILL be ok (providing Zs is correct)

    8500W/240V = 35.4A (240 is the measured voltage)

    BUT whether it satisfies BS7671 is another thing.
  9. andyspark

    andyspark Active Member

    ouch

    Ib = design current
    which should be less than
    In = protective device rating
    which should be less than
    Iz = current rating of cable

    In this instance your design current is 35.4 which isn't less than your fuse/breaker which is 32.

    But don't worry about it
    All is well
  10. andyspark

    andyspark Active Member

    t/e is easy

    Twin and Earth. The type of cable in your installation
  11. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Handy
    I am not guessing.
    A 8.5 kW shower installed with 6mm and protected by a
    32A breaker WILL be ok (providing Zs is correct)

    8500W/240V = 35.4A (240 is the measured voltage)

    BUT whether it satisfies BS7671 is another thing.




    Not you andyspark. The 6mm and 10mm 'guess was from the OP ouch.

    Would I be correct to say that if the cooker was in 6mm and the shower was the same as that, with the cable from the JB being 4mm, it might still work for yreas without problem ?

    A closer look at the cable sheathing might reveal the size printed or raise-stamped on it.



    Mr. HandyAndy - really
  12. zeespark

    zeespark Member

    I would be tempted to rip all the cable out for the following reasons:

    OP said that there is a round junction box - More connections equate to a potential hot point in the circuit and cause fires.

    Second with all the differing theories about the cable size I would just remove the circuit and install 10mm for the run.
  13. JP.

    JP. Screwfix Select

    ouch

    Ib = design current
    which should be less than
    In = protective device rating
    which should be less than
    Iz = current rating of cable

    The above is what is needed in the forum for us Diy'ers..
    If I read that in a book a second thought would not be given..however portrayed as above a second thought would be given and all absorbed.

    And no i'm not taking the **** Andyspark.
  14. ban-all-sheds

    ban-all-sheds New Member

    ouch - get your electrician to install a 45A/10mm² circuit, and fit a 10.5kW shower.
  15. Rabbit Rabbit

    Rabbit Rabbit New Member

    Blimey OP only asked a simple question he does not want to bring Battersea Power Station to its' knees (it's an old expression and yes I know Battersea Power station isn't any more).

    I think OP knows what he knows - that is the cable is NOT 2.5 t/e.

    If the cpc is single standed then it's 6.00 mm csa if the cpc is standed then it's 10.00 mm csa.

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