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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

    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

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    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

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    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

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    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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  16. sparksburnout
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    sparksburnout Electrician's Arms

    Location:
    Notts
    Could I just ask, if you don't mind - if you don't understand what sockets you can have on the end of what circuits, and how cables should or shouldn't be protected, how are you going to design it all and then cost it?
    I feel a bit sorry for the poor spark who gets called in to this one........
     
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  17. davesparks
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    davesparks Trusted Advisor

    Location:
    guildford
    Nah, any spark with an ounce of sense will be putting an 'awkward customer tax' on his price, or just walk away from it.
     
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  18. R.Voles
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    R.Voles EF Member

    Location:
    London
    man with no legs cartoon.jpg
     
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  19. R.Voles
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    R.Voles EF Member

    Location:
    London
    View attachment 37795
     
  20. R.Voles
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    R.Voles EF Member

    Location:
    London
    Thanks, SparksBurnout, I think you misunderstood the nature of my query - it's a LONG time since I was involved in the regulatory side of things and my queries were essentially legal (and an Olde Reg's forgetful misunderstanding of the nature of spurs, which SpinLondon sorted out tout sweet).

    All sorted now - and I hope whoever does the sparks side of this (tiny little) job will have a quick and easy run at it. If you live near Dalston, want a job? :)
     
  21. Vortigern
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    Vortigern Electrician's Arms

    Location:
    England
    Business Name:
    F.H. Electrical
    I suppose it is true "A little knowledge is dangerous" Good case in point.
     
  22. dksanders
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    dksanders Active EF Member

    As Davesparks said, also:

    If a fire in the garage could conceivably spread to the house, then the consumer unit in the garage has to be latest amendment compliant, i.e. either made of non flammable material (metal) or in a non flammable cabinet.

    I've seen some outhouse fires where even 8m was not enough to stop the flames let alone the heat, from damaging/catching the house.

    Unprotected cables should never be run at floor level, or even considered to be so.

    In a garage/workshop environment I fit metal accessories with 20mm plastic conduit taking the T&E up to the rafters where they are then clipped. The accessories and wiring have to be suitable for the environment and my view is that where you have workbenches, and tools, ladders, lawnmowers etc hanging from wall, the chances are high that something will smash into a socket or cable damaging them.

    Most electricians will get varying discounts for materials from their suppliers, which they may or may not (I do) pass partially or fully onto the client (to be competitive). So I would suggest your pricing the job is a pointless exercise.

    What you first described as an RCD at the house end you later described as a 'circuit breaker on the switch rather than a fuse'. I'm a little concerned you may be referring to MCBs as RCDs, or vice-versa are you sure you know the difference.

    If I arrived at a job and the customer told me what I had to buy, where I had to run cables, and how I had to do the job, I'd say thanks but no thanks and leave.

    If your going to ask an expert to provide you with a quote, using his knowledge (and with all due respect, you don't have the appropriate knowledge) and his experience, then I can't see any point in you going to the trouble and time to find all this out repeating what he's going to be doing.

    Unless of course you really intend to do it yourself, as you have stated a few times that you seem to think your 25 year out of date, inappropriate knowledge, qualifies you to specify what and how an up to date qualified electrician should do things.
     
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  23. davesparks
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    davesparks Trusted Advisor

    Location:
    guildford
    There is nothing in the regulations about the conceivability of the spread of a fire, nor do they stipulate non-flammable, they stipulate non-combustible. The requirement is plain and simple that a new CU installed today on domestic premises should be non - combustible or enclosed in a non-combustible enclosure, premises means everything within the boundary of the property, it does not matter how far away from the house an outbuilding is, the requirement is the same.

    An existing consumer unit does not have to be replaced purely on the grounds of being non-combustible to make an alteration to an existing circuit.
     
  24. Vortigern
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    Vortigern Electrician's Arms

    Location:
    England
    Business Name:
    F.H. Electrical
    Yes indeed fire is a consideration along with earthing requirements in such a situation none of which have mentioned until now. If the OP has little to no knowledge of these things his knowledge could do him a dis-service.
     
  25. sparksburnout
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    sparksburnout Electrician's Arms

    Location:
    Notts
    Well said dude, you have put into words what everyone else is thinking. The guy has gone into the sunset now, having raped and pillaged the forum for knowledge, to undertake the work on his Jack Jones. Fairly obvious really though, he even left us with a parting titter!
     
  26. dksanders
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    dksanders Active EF Member

    Hi Dave, Non-flammable/non-comubstable, I didn't bother to check the exact wording but aren't they the same thing?

    I quote here from the IET:
    421.1.201 Within domestic (household) premises, consumer units and similar switchgear assemblies shall comply with BS EN 61439-3 and shall:

    (i) have their enclosure manufactured from non-combustible material, or

    (ii) be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with Regulation 132.12.

    Consumer units in outbuildings or on the outside of a building

    Regulation 421.1.201 uses the term ‘premises’. The question could therefore arise: do the requirements of the regulation apply to a consumer unit or similar switchgear assembly within an outbuilding such as a garages or shed, or mounted on the outside or a building?

    Some dictionary definitions of ‘premises’ are ‘a house or building, together with its land and outbuildings’ and ‘the land and buildings owned by someone’.

    However, Regulation 421.1.201 was principally introduced to cover the interior of a household building and any garage or other outbuildings integral, attached, or in close proximity to that building.

    Doubt could exist about whether or not a particular outbuilding could reasonably be considered to be in ‘close proximity’ to the household building. A way of resolving this might be to make a judgement of the likelihood that fire originating inside the enclosure of a consumer unit or similar switchgear in the outbuilding might lead to the outbreak of fire in the household building or in any outbuilding integral or attached to it. Relevant factors to consider about such an outbuilding might include whether or not that building or its expected contents are highly combustible.

    Regulation 421.1.201 is not intended to apply to a consumer unit or similar switchgear assembly that is not within a building, such as a consumer unit mounted outdoors on the outside of a building.

    Personally I just fit metal CUs every time now but as the OP was stressing 'letter of the law' etc I included that for the avoidance of doubt.

    Thanks for the reply.
     
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    Last edited: Aug 12, 2017
  27. R.Voles
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    R.Voles EF Member

    Location:
    London
    What a thoroughly suspicious, critical and disagreeable bunch some of you are - many thanks again to those of you who offered sincere advice and help; SpinLondon, Telextrix. I'd considered posting for work in here, but now an electrician colleague of my plumber (family friend for 3 generations) will be popping in here for a site visit later in the week and I'm perfectly happy to pay him for a job well done.

    You might like to consider that people seeking advice in this forum are potential customers and treat them with the respect and friendly approach they deserve.

    Reg.
     
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