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Discuss Some advice please, regarding wiring inside garden shed workshop? in the Electrical Forum area at ElectrciansForums.co.uk.

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  1. R.Voles
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    R.Voles EF Member

    Location:
    London
    Some professional advice greatly appreciated here for design and costing purposes - two simple questions.

    Background: We've just replaced a 25 year old wooden shed - good service but sagging a little from age and too small for our needs - with a larger one from Beast Sheds Ltd. (Recommended!).

    The old shed was wired properly with an armoured cable spur from the house; a separate feed through an RCD switch box at the main house circuit board running about 8 metres out in the garden to a small 2-way (5A for lights and 13A) switch/junction box with RCDs inside the shed. I intend having the old junction box refitted in the new shed - it has had little use and is in good condition.

    I know regs have changed since 1992... so before I get a sparks in, my questions are:

    1) Since the junction box is effectively just on a fused spur (albeit with RCD protection at both ends) and not a ring, my understanding is that I am allowed only one twin 3-pin 13A socket from the junction box (by the door). Is that correct - or can I have a second twin 3-pin 13A socket over the workbench as we had before?
    I can make do with extension cables if only one twin 3-pin 13A socket is allowed.

    2) In the old shed, all the wiring was simply surface mounted on the wooden studs using cable clips over 1.5mm twin core & earth to the strip lights and 2.5mm to the sockets. Is it still OK to have exposed wiring like this or does it now require to be in plastic trunking?
    (If so are there any specs/regs for the trunking type?)

    Thanks hugely for a quick reply here.
    (Anyone here in the Dalston or Shoreditch area? ;) )

    Best,
    Reg
     
  2. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    Best advice is to find a local spark through recommendation .....
     
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  3. spinlondon
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    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    There are basically two types of circuit.
    Ring Final and Radial.
    Either circuit can have as many sockets or connection points as you wish.
    The fuse or MCB is rated to protect the cables, if you plug too many things onto a circuit, the fuse/MCB will trip protecting the cables.
    A ring is effectively two cables in parallel, whereas a Radial is just a single cable.
    The fuse/MCB for a ring can have a higher rating than that of a radial wired in the same cable as a ring, because the two cables combined can carry a greater load than the single cable used in a radial.
    It is spurs from rings that are limited to one single or double socket, as the cable used for the spur would have a lower rating than that of the combined rating of the two cables used in the ring.
    The same would apply with a radial, if a smaller cable were to be used for the spur.

    You should not have two RCDs in line on a circuit, unless the first RCD is time delayed.
     
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  4. R.Voles
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    R.Voles EF Member

    Location:
    London


    =====================


    Many thanks for the clarification, Spin London.

    OK - that answers least one question. It does appear that the original 2 x twin socket setup in the shed was correct.

    Can you tell me whether surface wiring in the shed is still acceptable or if it requires trunking? This will help me design the layout of the lights, sockets and wiring to minimise routing and cost.

    Regarding the two RCDs. It appears the Hager fuse box at the start of this radial circuit at the main board in the house has a circuit breaker on the switch rather than a fuse. The junction fuse box in the shed splitting the feed into 5A and a 13A is also fitted with RCB trips for safety instead of fuses (sorry, photos would be easier!). Is this what you mean by not having two RCDs?

    Many thanks again for a detailed answer.

    Reg.
     
  5. R.Voles
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    R.Voles EF Member

    Location:
    London

    Don't worry, Murdoch - I'm just trying to sort out costs and design before I get a sparks in. Your job is safe - especially if you live near Dalston ;)
     
  6. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

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    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    if the cable runs in the shed/outhouse/whatever may be subject to mechanical damage, then fitting appropriate containment ( e.g. trunking or conduit ) is required. if not, then T/E can be surface mount.
    the idea of not having RCD protection in the house is that a fault in the shed will trip in the house. if you have 2 RCDs ( house and shed ), then it's either or both will trip. this is not unsafe, just inconvenient, and possible that some of the house circuits may be lost. this would be bad if it were freezer circuits, or the telly when her indoors is watching Constipation Street.
     
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  7. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    How can you sort out "costs" on an internet forum?
     
  8. R.Voles
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    R.Voles EF Member

    Location:
    London
    Because I can design the layout economically, cost all the parts, get a rough idea of the materials and time involved for a pro - I worked as theatre technician many, many years ago which involved a fair bit of onstage wiring so I know what I'm doing, but I'm sticking by the letter of the law where installation is concerned. I know this is a trivial job, but I'd prefer it if you helped me like your colleagues here, rather than carping, Mr M?
     
  9. R.Voles
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    R.Voles EF Member

    Location:
    London
    ===================

    Thanks, Telectrix - v. useful! No - nowhere in the shed is the exposed t/e cable likely to be subject to disturbance or damage, but on your advice I can cost runs across the ceiling and down rather than at floor level to ensure that is the case.

    Yes - I think any fault on the RCD in the shed would trip in the shed for sure and *might* trip in the house - but it is a completely separate feed from the main bus that wouldn't affect any other of the house circuits. If I caused her indoors to lose a minute of telly, I'd be *living* in the shed...!

    Thanks again, best,
    Reg.
     
  10. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

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    i think murdoch's post was considering that we don't know exactly what you want fitting, what cable and how much of it, and whether or not other improvements are required to the installation, such only becoming apparent at a site visit with some basic inspection and testing involved.
     
  11. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

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    I'd be *living* in the shed...!

    been there, done that, got the splinters.
     
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  12. R.Voles
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    R.Voles EF Member

    Location:
    London
    Fair dos - but I do know enough to spec all that stuff up and advise a professional sparks accordingly, complete with wiring diagram and plan :) Thirty years ago I was wiring pantomimes for stage explosives and other onstage portable effects....
     
  13. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

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    you must have got summat right then, as you;re still here 30 years on. :D
     
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  14. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    Hum ................. best you get your screwfix catalogue out then. In my experience customers don't have a clue how long these jobs take...........
     
  15. davesparks
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    davesparks Trusted Advisor

    Location:
    guildford

    Amongst many other jobs I also work in theatre and fireworks, I do those jobs you mentioned and can tell you that it bears no relevance to electrical installation work.

    In fact I make a fair amount of money putting right the incorrect work of theatre technicians who think they know what they are doing.
     
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