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Discuss Welfare Cabins connection. in the Electrical Wiring, Theories and Regulations area at ElectrciansForums.co.uk.

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  1. IL1970
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    IL1970 Guest

    Im trying to get some clarification on the correct methods of connecting up the welfare cabin area of a construction site.

    Although technically not classed as a construction site in most cases (they tend to be separate from the actual working area) you more often than not find materials, scaffolding etc stored around these areas which would lead me to believe that an armored cable (SWA) should be used as the distribution cables.

    Is there any reason why hardwiring SWA into site canteens, offices, stores containers, drying rooms etc(as in transportable cabins) is a problem? Obviously a plug and socket is not an option with SWA cable.
     
  2. supasparxs
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    supasparxs Electrician's Arms

    Location:
    Leigh, Lancashire
  3. IL1970
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    IL1970 Guest

    Generally the way I do it. Have heard people talk about the fact that a transportable building must be connected via plug and socket but unless i missed an update to 717 that says something along the lines of 'for example by plug and socket'

    If a plug and socket has to be used in some cases I would assume MDU mounted sockets and cabin mounted appliance inlets with SY cable between would be the prefered method? (with 30mA rcd protection)
     
  4. supasparxs
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    supasparxs Electrician's Arms

    Location:
    Leigh, Lancashire
    It states

    "717.1 Scope
    The particular requirements of this section are applicable to mobile or transportable units.

    For the purpose of this section, the term 'unit' is intended to mean a vehicle and/or mobile or transportable structure in which all or part of an electrical installation is contained, which is provided with a temporary supply by means or, for example, a plug and socket outlet"

    In some cases yes plugs and sockets are used, however in my experience in most cases they are not.

    I'm not sure why this is, possibly it is cheaper to have the supply cables to these site cabins to be disposable.

    As a site 3 phase 10 KVA transformers tend to be supplied with 3 core X 4mm SWA.
    The site offices also being supplied using 3 core X 4mm SWA.
    It makes sense for a site delivery of SWA, Transformers and an MDU.
    Using commando Plugs and sockets the different lengths of cables would push the costs up

    (admittedly the installation time would be reduced)
     
  5. vernam616
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    vernam616 Regular EF Member

    Location:
    North
    I used to install these setups on a daily basis

    We wired everything in armoured, which went to a rotary isolator on the side, then from that into the internal db

    Dont forget to provide your own means of earth, i.e a rod
     
  6. derek preece
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    derek preece Guest

    I may be mistaken but I thought if the supply was TN-S then an earth rod wasn't required.
     
  7. danzor
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    danzor Trusted Advisor

    Location:
    London
    :17::17:
     
  8. IL1970
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    IL1970 Guest

    Ive tended to use B40 MCBs and 6mm 3c swa. Some of these new 'eco' units can pull a fair bit especially the canteens. As for rods, its normally just one adj the generator as its a TN-S system.

    Plugs and leads are soooooooooooo expensive I just priced one jobfor 5 cabins on sy leads and the cost of 5 leads, plugs, sockets and appliance inlets is almost £1000!!!!!
     
  9. supasparxs
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    supasparxs Electrician's Arms

    Location:
    Leigh, Lancashire
    That is why SWA is used

    the cost of a gland pack and a SWA cable is alot less then SY cable, plugs and sockets.

    in addition the movement of machines and materials around the site, the cables could be damaged.
    I think you will find a SWA cable is more resilient than a SY cable.
    Also if the cable thieves realise that all they have to do is unplug the cable from the Cabin and MDU, then it's easier for them to steal the cable.
     
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  10. mogga
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    mogga Just me Electrician's Arms

    SWA even to a plug,socket on the cabin as swa would be glanded and earthed at one end

    various methods are used SWA straight in the bottom of cabin connected inside
    plug and socket outside
    isolator outside and c.u. inside
    4x4 box outside through to c.u. inside
    BLAKEY MDUs as the dogs plenty room ect
    As for cables likley to be damaged 3 scaffolding boards 1 either side 1 covering may help reduce damage or duct across road,pass ways and of course leave a drawstring in as no doubt there will be additional cabins added later
    Some sites prefer plug,sockets as they can then add units and take them apart as required
    Some cabin manufacturers,hire companys dont like damageie Holes in their cabins
     
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  11. needasparks
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    needasparks Electrician's Arms

    Location:
    Essex
    Have not got the book in front of me but i think site cabins are recommended to have a 3 monthy inspection also.
     
  12. mogga
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    mogga Just me Electrician's Arms

    the "Cabin" may fall under the hire agreement but the supply to it and any transformers ect is 3 monthly OR if moved this is a MAXIMUN recomended but if YOU as the person doing the test feel it may be damaged ect then a more frequent test may be applicable depends what the contract says as well
     
  13. needasparks
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    needasparks Electrician's Arms

    Location:
    Essex
    Thought it was something like that. I knew it was a short time between inspecting but could not remember.
     
  14. IL1970
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    IL1970 Guest

    you cant put a plug on an swa cable though as it is not a flexible cable?

    "a connector which is integral with, or intended to be attached to, the flexible cable or cord"
     
  15. IL1970
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    IL1970 Guest

    we test cabin supply setups every 3 months, internal cabin circuits tend to be 12month depending on the hire company. TBH though I dont think many test them until they return to the yard as the testing cost 'should' be down to the hirerer
     
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