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Advice on whether cable is suitable for outdoor hot tub socket

Discussion in 'Electrics UK' started by uptown47, 4 Aug 2021.

  1. uptown47

    uptown47

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    Hi there,

    (Basically my question is - can I use the outdoor socket I've run in using 2.5mm SWA for a Lay-Z spa hot tub which uses 2,060W for the heater and 600W for the jets - so probably best calling it 3KW - the details of the installation are below).

    We are currently getting an extension built and decided to put in an outdoor socket (for mowing the lawn etc).

    I have a (currently not yet terminated) 2.5mm SWA cable running from the cupboard with my consumer unit out to the back garden. The full run of cable is around 10m.

    The cable is buried underground (I'm not an electrician but I did ask advice about the regs so I have buried it 500mm in PVC reinforced conduit (I know that's not necessarily needed but I wanted to do the belts and braces thing) and put "Caution" tape above it.

    The cable enters the house and travels under the (soon to be poured) screed in ducting (see photo below) to the cupboard with the consumer unit in.

    My wife has asked if we can re-purpose the socket for a Lay-Z spa hot tub that uses (not more than) 3KW.

    My questions are as follows:

    1) Do you think the 2.5mm will be suitable for running a hot tub - I've read that it should really be 4mm but that would be a LOT of work at this stage to change it?

    2) We're having water-based underfloor heating in the extension and I've read that the temperature affects the current carrying capacity of cables. Will this have a large effect as the insulation and pipes will be either side of the ducting?

    3) I'm going to put the socket on its own circuit breaker - which is protected by an RCD - I was going to use a Type B 10A CB? Do you think this is suitable or would you advise a different type/rating?

    4) I'm going to use an RCD outdoor socket (and the lay-z spa has it's own internal RCD protection too) but I've read that it's not good practise to take out the "house earth" into the garden? And that it's best to install another earth spike in the garden and connect the outdoor socket to that? Do you know if that's the case or not?


    Below is a photo of the ducting going to the cupboard with the consumer unit

    IMG_20210803_202316.jpg
     

    Attached Files:

  2. Sureitsoff?

    Sureitsoff?

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    do you really mean 10a breaker?? is that conduit liable to fill with water and then bring the water into the house under the screed?
     
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  4. uptown47

    uptown47

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    Thanks for getting back to me. I did mean 10A breaker but wasn't sure what size to put in? I was thinking of protecting the 2.5mm SWA cable etc? Do you think 16A? (Or another size). It's on it's own circuit breaker and is only feeding that single outdoor socket.

    Good thinking about the conduit but it should be fine. The cable in the garden is a lot lower than the conduit. The cable goes through two walls (outside block wall and then the timber extension kit) before it gets into the conduit. There is a drop immediately on the outside of the extension kit and then another drop after the outside block wall. Saying all that though it might fill with screed when they pour that and then "set"?? I'm not sure about that as I've not seen the "pouring screed" so don't know how viscous it is and whether it would run into the pipe to fill it? I'll ask the guy who's doing the project about it and see what he says.

    Do you think (based on all that) that the 2.5mm will be okay for the hot tub?

    Thanks for all your help :)
     
  5. winston1

    winston1

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    This is all notifiable work. Did you notify Building Control before you started?

    1. 2.5 cable is OK for a single 13 amp socket.

    2. Probably OK as even 2.5 cable is more than enough for a single 13 amp socket.

    3. 10 amps at 240 volts is 2.4kW. What do you think will happen when you load it with a 3kW load?

    4. You don’t need an RCD socket as the circuit is already RCD protected in your CU and the Lazy Spa has one as well. Whether you need as earth spike or not depends on your type of supply. Your sparks will advise.
     
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  7. uptown47

    uptown47

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    I've got a sparky coming to do the work in the extension so I'll get him to do the connections as part of that work and check it all. I'll buy a 16A breaker for him to fit.

    Thanks for your help. :)
     
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