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DIY domestic wiring to outbuildings

Former Community Member
Former Community Member
Hello, I am new to the forums and would like to introduce myself. In the past I have undertaken a lot of domestic wiring as a DIYer. Most of this predated the Part P requirements. However, in 2013 I undertook a fairly major wiring project at my home that included two new consumer units and half a dozen or so circuits. I did this under building control and they arranged inspection and testing. I secured a full set of certificates to underpin my work. I am about to go through the same process to add in two outbuildings to my set up. I have submitted a building notice and am awaiting to hear from Building Control re appointment of a firm to undertake inspection and testing.

Whilst I gather most DIY work scares many of you you, worth pointing out that whilst I am not any form of electrical Engineer, I do have (from many years ago) a HND in Mechanical and Production Engineering and a B Eng (Hons) in Engineering Technology. Both of these included a significant element of electrical technology and electronics. I have also worked in engineering (aerospace) for much of of my early career and still work in a STEM environment. Further,  intend to do a short course on the latest regulations and may also undertake a C&G course on testing and inspection to possibly get to a point where I can register with one of the governing bodies.

I have come to this forum as I am designing my changes and preparing for the first fix. i have been seeking guidance on the internet and from the regulations themselves. I find the regulations open to many interpretations and the advice on many forums to be wildly different. I really want to get this installation right and will have many questions, most requiring practical experience that I simply do not have. I believe this forum will be able to guide me in the right direction when I need it.


My first question relates to burial of SWA. I had a digger in last week to put in a series of trenches for cables. I intend to do all of the external wiring in SWA and in an ideal world would have buried it at 600mm. However, I have places in the garden where it is not possible to get that deep. For an example, under one lawn I have an underground structure that limits the trench depth to 300mm. What would be a appropriate method for installing SWA at this depth? Do I need to add something to prevent a spade/fork penetrating the cable, if so, what would you recommend? I also need to watch my budget here so looking for cost effective views if possible.


There will be further questions. Thank you.


regards

  • Former Community Member
    0 Former Community Member
    Why not just visit your local steel stockist and buy some large diameter galvanised pipe for the S.W.A. to run through if it is not buried sufficiently deeply to prevent future possible damage?


    They're called scaffold poles!


    Joking aside, I'd be wary of using a length of steel tube unless the exit points are above ground having formed 90 degree bends.


    Why? I've seen where the tube end has acted as a guillotine.


    Regards


    BOD


  • Former Community Member
    0 Former Community Member
    Hopefully the digger will come across the warning tape before they decide to operate the A.D.S. of the live S.W.A. cable by cutting it through. I normally erect warning notices on small posts or onto nearby buildings warning of a buried cable.


    This week's job is replacement of a SWA that had been buried 1000 mm deep in 125 mm DNO duct complete with warning tape....... You can hope as much as you like but if the 15 ton machine driver isn't careful, up it comes. The ADS only worked when the receiving end SWA gland broke out of the fibreglass enclosure and one of the cores splashed against the earthed backplate on its way out,,,,,,,,,,,,, The sending end DB now has a reasonable sized bow in the gland plate.............


    Regards


    BOD


  • Former Community Member
    0 Former Community Member

    perspicacious:

    The sending end DB now has a reasonable sized bow in the gland plate.............




     

    But does let the condensation drain out nicely- every cloud etc


    Regards


    OMS
  • Going to the extreme you could have one of these in your front garden 



    Google Earth Link
    https://earth.app.goo.gl/uADkJz

    #googleearth

  • perspicacious:
    Why not just visit your local steel stockist and buy some large diameter galvanised pipe for the S.W.A. to run through if it is not buried sufficiently deeply to prevent future possible damage?


    They're called scaffold poles!


    Joking aside, I'd be wary of using a length of steel tube unless the exit points are above ground having formed 90 degree bends.


    Why? I've seen where the tube end has acted as a guillotine.


    Regards


    BOD


     




    Yes scaffold poles can be included in the list of suitable pipes, but they are not exclusive.


    Z.

  • This is going a little crazy. There are HV cables outside my house, which it is true are red but still can be damaged by a digger. The cables for all the supplies are not very deep and similarly able to be dug up, particularly as they cross gardens, but it very rarely happens. SWA is fine buried without further protection, and steel pipes will need bonding and cost. If someone attacks with a spade the worst damage is a bit of a flash, and a repair. If a digger you may never know until the shed light doesn't work. Why the keeness to add protection which probably won't work? At 300 mm down you are at least 1 1/2 spade depths. You do not get there by accident!.
  • So Wolfie, it appears that underground cables may be cut into or otherwise damaged, by various idiots, so the only solution is to run the cables overhead, where at least they can be seen.


    Z.

  •  SWA is fine buried without further protection, and steel pipes will need bonding and cost. If someone attacks with a spade the worst damage is a bit of a flash, 




    Why will an underground metal pipe with the S.W.A. cable running through it  need bonding Dave?


    Z.


  • davezawadi:

    At 300 mm down you are at least 1 1/2 spade depths. You do not get there by accident!.




    That's a tiddly little spade! But I entirely agree - you do not get there by accident.


    Putting in fence posts is probably the biggest risk, but then you'd be a couple of feet deep.


  • davezawadi:

    This is going a little crazy. . . 




    I agree.Either direct bury it, or put it in a black plastic duct. Simple. 


    Regards,


    Alan.