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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

Parents
  • Former Community Member
    0 Former Community Member
    All


    Thank you, some great advice. I also managed to speak to the company that will be inspecting on behalf of BC on Friday and now am happy I have a solution. Not using a pipe, I have a lot of existing galvanised pipes, all redundant, in my garden already. I don't want any confusion. The company are content with marker tape, concrete slabs and sand. However. In looking into this installation, I now have concerns about some existing external wiring and would appreciate your views.


    My garden is a long narrow garden with lighting provided by aluminium lamp posts. These are connected in two circuits. The lighting to the front is fed by the house consumer unit in 1.5mm SWA protected by a 6A MCB in turn protected by the consumer unit 63A/30mA RCD. The rear in a similar manner to a CU in the rear garage (this is a third outbuilding and not one under previous discussion, with exported TNCS for which the installation was signed off by in 2013). My concern is that the earthing of all of these lights relies upon exported TNCS from the CU (s). This is via a 1.5mm core plus armour in the SWA. Is this sufficient?. The lights are fairly old and I believe designed to be earthed ( I do need to check this). Each one is bolted down to concrete in the ground. 


    Any thoughts on this appreciated.
Reply
  • Former Community Member
    0 Former Community Member
    All


    Thank you, some great advice. I also managed to speak to the company that will be inspecting on behalf of BC on Friday and now am happy I have a solution. Not using a pipe, I have a lot of existing galvanised pipes, all redundant, in my garden already. I don't want any confusion. The company are content with marker tape, concrete slabs and sand. However. In looking into this installation, I now have concerns about some existing external wiring and would appreciate your views.


    My garden is a long narrow garden with lighting provided by aluminium lamp posts. These are connected in two circuits. The lighting to the front is fed by the house consumer unit in 1.5mm SWA protected by a 6A MCB in turn protected by the consumer unit 63A/30mA RCD. The rear in a similar manner to a CU in the rear garage (this is a third outbuilding and not one under previous discussion, with exported TNCS for which the installation was signed off by in 2013). My concern is that the earthing of all of these lights relies upon exported TNCS from the CU (s). This is via a 1.5mm core plus armour in the SWA. Is this sufficient?. The lights are fairly old and I believe designed to be earthed ( I do need to check this). Each one is bolted down to concrete in the ground. 


    Any thoughts on this appreciated.
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