Splitting and rejoining 16mm cable

Discussion in 'Electricians' Talk' started by MegaFatGray, Apr 30, 2017.

  1. MegaFatGray

    MegaFatGray New Member

    Hi all. I'm looking for some advice from qualified electricians. I want to reroute some 16mm cable that feeds the electric shower. It runs up from the consumer unit and straight into the ceiling. I want to drill a new hole in the ceiling (in a better place) for it. I can't access it at either end so I need to cut the cable and rejoin it. There's plenty of slack under the floorboard so my plan is make the cut there. So my question is what is the best way to do this? I was thinking of either using a suitably rated junction box mounted to the joist under the floorboard or crimping the two tails back together and covering in heatshrink.

    I've attached a picture of the cable. All I know is that it's 16mm wide. I don't know the conductor cross-sectional area or the current rating etc. It's a shower circuit though so it must be rated for a lot of current.

    What's the best, or most correct, method for doing this? Any links to items I would need to buy would be great.

    Thanks
     

    Attached Files:

  2. candoabitofmoststuff

    candoabitofmoststuff Screwfix Select

    I'm pretty sure that what you've said and I've quoted is a no-no, as the junction needs to be readily accessible, and "under the floorboards" it most definately aint!

    It might be permissable to join it if there is some kind of "maintenance free" connector you can use...

    But, speaking as a DIYer, the advice you're going to get from the experts here is DON'T do this yourself.

    You sure you aren't going to hit something, (pipe or cable), in the process?

    Good luck,

    Regards,

    Cando
     
  3. nigel willson

    nigel willson Screwfix Select

    1. Not a good idea putting joints in cables of this loading in my opinion. 2 as above needs to be maintenance free. This is not what we call a 16 mm2 cable, it's 6/10mm2 cable . It's the cross sectional area of the cable ,not the external dimensions of the cable. I would crimp and heat shrink it. Therefore not a diy job. Get a sparks to ave a look.
     
  4. fire

    fire Well-Known Member

    Most likely is a 10mm2 CSA, 32Amp = 6-10mm2, 40Amp =10-16mm2 etc and is dependant on the installation method of the cable. Take a look at the shower it is powering and see what power rating it is. Anything over 8.5Kw will need 10mm2.

    If the cable is chased into the wall and you cant get it out, you are best running an entire new length of cable in the place you want it.

    If it is in trunking then why cant you disconnect it from the consumer unit and pull it back out the trunking and move it. Provided cable is long enough.

    You need to provide more information.

    Prysmian cable of 10mm2 CSA spec and overall outside dimension is
    10mm2 / 4.0 mm2 CPC
    8.4mm x 16.8mm

    So you could well have a 10mm2, note this is an assumption based on the small amount of info you have already supplied. 10mm2 is pretty much the standard cable size used across the board for a shower rating 8.5kw upward and less than 10.5kw.

    A picture of your consumer unit, how the cable is run and so on would help.

    Simple answer is, No it is not a good idea to splice and re-join a cable under the floorboards this would require a large connection box which should not be hidden under the floorboards or in/behind walls.

    Moisture can get to the terminals and cause corrosion, terminal screws can come loose and because this is a high load 32Amps+ this can cause overheating at the connection joint which could well lead to a fire. If it is hidden bellow the flooring then no one would know what is going on before it is too late.
    The RCD protection may pickup on it but why risk it just because you wanted to move it from one spot to another.
     

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