SWA underground - using cable protection tiles

Discussion in 'Electricians' Talk' started by THexplodinghead, Jan 13, 2022.

  1. THexplodinghead

    THexplodinghead New Member

    I have dug a trench for SWA cable to a garden office. The trench is along my drive but in places I cant get the digger through the ground to more than a depth of 300-400mm (the ground is either brick or concrete). Can I therefore use the cable protection tiles for the areas where the trench is not deep enough to meet the 600mm regs? (I will also use the flexible tape asan additional marker)

    Would this be accpetable for an electrician to sign off the works?

    Thanks
     
  2. Hans_25

    Hans_25 Screwfix Select

    May be you should ask the electrician who will be signing off the work...personally I don't see it as a big issue. Not sure there is a reg that says it has to be 600mm. 300mm-400mm should be fine.

    Hopefully one of the resident Sparks will chime in.
     
  3. elecstick

    elecstick Member

    It wouldn't bother me because the cable would be protected by an RCD. Cable protection tiles dont achieve much, because they look like bricks to anyone digging a hole. Where as yellow plastic marker tape is very good and hard to ignore. Have you considered putting the cable in a duct and data/phone cabling
     
  4. THexplodinghead

    THexplodinghead New Member

    I have some 50mm plastic ducting for network cables - but I figured it wouldnt add much protection for the SWA. My understanding is the regs show a 600mm depth with sand around and 100-150mm above the elect warning tape. my problem is I cant get to 600mm for approx 5m or a 10m run. As I want to get the installation certified and to be safe - I need to know what is legitimately acceptable
     
  5. sparko69

    sparko69 Screwfix Select

    Ducting won't protect swa but it would alert someone who hit the ducting while digging that they should stop digging and therefore the swa would remain undamaged.
    The 50mm ducting would be a good idea .
     
  6. Bazza-spark

    Bazza-spark Screwfix Select

    It's unlikely SWA would be RCD protected at source.
     
  7. spinlondon

    spinlondon Screwfix Select

    I’m trying to fathom how he knows the cable will be RCD protected as well?
    As far as I’m aware, it’s only on agricultural premises where there is a specific depth for underground cables.
     
  8. elecstick

    elecstick Member

    It would be if I was doing the job
     
  9. spinlondon

    spinlondon Screwfix Select

    It wouldn’t be if I were doing the job.
    1, it’s not required.
    2, it would cause problems if there were any other RCDs further down the line.
    3, it would to my mind not complete with the requirement to minimise inconvenience in the event of a fault.
    4 it would hinder maintenance and repair.
     
  10. Sparkielev

    Sparkielev Screwfix Select

    What is the cable supplying?
     
  11. spinlondon

    spinlondon Screwfix Select

    A garden office.
     
    Sparkielev likes this.
  12. Bazza-spark

    Bazza-spark Screwfix Select

    Agreed.
     
  13. Sparkielev

    Sparkielev Screwfix Select

    Yeah thanks been a long ****** day
     
  14. THexplodinghead

    THexplodinghead New Member

    Thanks for the comments - but the main question is about whether the cable in the trench has enough physical protection for an electrician to be ok with and to certify?
    As you can probably tell, I'm not an electrician but I can dig holes and get the cables in place. I will wont be doing the connection work myself and will find a qualified elec to connect the main consumer box and the garden office (small consumer box). thks
     
  15. Bazza-spark

    Bazza-spark Screwfix Select

    You need to find him now, before you start work, so he can advise and observe as the job progresses. He won't sign off otherwise.
     
    Hans_25 likes this.
  16. elecstick

    elecstick Member

    From IET - ELECTRICAL INSTALLATIONS OUTDOORS: A SUPPLY TO A DETACHED OUTBUILDIN
    ■ An RCBO in the dwelling’s consumer unit for the garage supply, or
    ■ An RCCB in the dwelling’s consumer unit, or
    ■ Selecting a device that includes RCD protection a the main switch for the small two-way
    consumer unit in the garage, or
    ■ Protecting the socket-outlet circuit in the garage with an RCBO, or
    ■ Providing an SRCD (a socket-outlet incorporating RCD protection) for the
    socket-outlet in the garage
     
  17. nigel willson

    nigel willson Screwfix Select

    Why would you protect a n swa with an RCD, it goes the other end if designed correctly
     
    BiancoTheGiraffe and Sparkielev like this.
  18. elecstick

    elecstick Member

    You are incorrect, see post #16
     
  19. Bazza-spark

    Bazza-spark Screwfix Select

    Sorry. You are incorrect. With an SWA cable feeding an outbuilding, the RCD goes in the outbuilding not at the house CU.
     
    Hans_25 likes this.
  20. elecstick

    elecstick Member

    Don't apologise, what makes you more knowledgeable than the IET? my post #16 is a direct quote from the IET.
     

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