Insulating under upstairs floor, advice about cables please

Discussion in 'Electrics UK' started by pjo123, 27 Mar 2020.

  1. pjo123

    pjo123

    Joined:
    16 Jul 2006
    Messages:
    116
    Thanks Received:
    1
    Location:
    Norfolk
    Country:
    United Kingdom
    Hi all.

    Kitchen ceiling has a sheet of plasterboard as it's ceiling, the bedroom upstairs gets both smells noise and cold from the kitchen.

    The wiring is all rooted through top (or near top) of joists.

    I intend to put 4" insulation on the plasterboard, which will under the wiring. But some of the wiring will be resting on the top of the insulation.

    My only concerns are both the cooker (6mm I think, might be 10mm) and the immersion heater (2.5mm,, on a 16amp breaker).

    The cables run across the top of the joists, above the insulation but at some point will go through the 4" (100 mm) insulation. In other words 4" of these cables will have installation on them. Haven't taken up the floor where the cooker wire is yet, but I imagine it will be similar to the immersion heater.

    Pic of immersion cables attached (megaflow tank with two immersion heaters on it, only one used)

    is this safe or should I put the 4" of cables in some conduit?

    thanks

    p1.JPG
     
  2. Sponsored Links
  3. pjo123

    pjo123

    Joined:
    16 Jul 2006
    Messages:
    116
    Thanks Received:
    1
    Location:
    Norfolk
    Country:
    United Kingdom
    The cooker wire has a 40 amp fuse on it.

    Looking at http://www.cable-ratings.co.uk/

    It seems to say my 2.5mm for the immersion when in insulation is 18.5A or 17.5A (not sure why there's 2 columns?) so that having an 16amp breaker, I presume is fine.

    My cooker wire is 6mm and not 10mm, it's only rated at 32A or 29A, hence I presume this going through 4" of insulation might be a problem? Or is this talking about a long run being in insulation (presuming there's a difference)?

    Many thanks
     
    Last edited: 27 Mar 2020
  4. winston1

    winston1

    Joined:
    11 Jan 2010
    Messages:
    7,342
    Thanks Received:
    572
    Location:
    London
    Country:
    United Kingdom
    Your cooker will never take 40a as the rings cycle on and off independently.
     
    • Thanks Thanks x 1
  5. oldbutnotdead

    oldbutnotdead

    Joined:
    11 Jan 2013
    Messages:
    4,776
    Thanks Received:
    1,007
    Location:
    Durham
    Country:
    United Kingdom
    You'll struggle getting an airtight seal with insulation boards, you'll get better performance (especially for sound transmission) with rockwool.

    If you were contemplating renewing the kitchen ceiling a vapour control layer (polythene) would help a lot with reducing air passage (& thus smells)

    Cables through insulation- there's a handy link here https://www.tlc-direct.co.uk/Book/4.3.6.htm.
    Short version- if one side of the cable is clipped direct (to wall or timber) or in free air then you're fine.
     
    • Thanks Thanks x 1
  6. pjo123

    pjo123

    Joined:
    16 Jul 2006
    Messages:
    116
    Thanks Received:
    1
    Location:
    Norfolk
    Country:
    United Kingdom
  7. oldbutnotdead

    oldbutnotdead

    Joined:
    11 Jan 2013
    Messages:
    4,776
    Thanks Received:
    1,007
    Location:
    Durham
    Country:
    United Kingdom
    • Thanks Thanks x 1
  8. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
  9. Sponsored Links
Loading...

Share This Page