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Shed Supply From Ring Main

PG
A small (7ftx5ft) shed is to be located at the rear of a house. There will be a 2ft gap between the shed and the rear of the house.
The shed is to be used as a utility room, initially, with a tumble drier and freezer It will also have a frost protection heater and lighting.  If we allow a bit of power for future or garden tool use then there could be a max demand of about 18A. There are no other services planned (no water, gas or drainage). The 230V supply is TN-C-S
The house has a lightly loaded RFC on the inside wall by the shed and the proposal is to break into the RFC and loop the RFC through the shed. The RFC is supplied from a Consumer Unit that is located near the front of the house..
Not exactly a standard arrangement, probably wouldn’t even consider it if the shed was a few more yards down the garden but I haven’t managed to locate a statement in the Wiring Regs that precludes this approach. I wouldn’t have thought twice about extending an RFC through a conservatory.
 I wondered if the Forum thought that 465.1 (Emergency Switching) could come into force, say for isolating the shed in the case of a fire but I suppose that the shed isn’t too different from another room?

  • 0
    Regs wise quite OK;  but one thing-  how permanent is the shed ? Some are like a battleship, others more flimsy.

    If there is a credible risk  that the shed may be removed again,it might be better as a spur or two that could also be more rapidly be isolated if the shed  roof leaked or something.


    Given the proposed loading you may sometimes want more than 13A, but the provision of 2 spurs or doing the full ring loop is almost the same, but  once the loop is hooked out it is harder to undo, and if it has to be done in a hurry, it may lead to a broken ring.

    Another  (but highly non standard) approach, and one that may therefore have a few folk sucking their teeth, could be a 4mm unfused spur from the 2.5mm ring- again the loading on the rest of the ring is the same as if you had extended the ring, but the outdoors  can be isolated more readily if there is a problem.

    M.
  • 0
    Now, why would anyone used to us here suck their teeth Mike, this is probably the best approach from the standpoint one may want to remove it later. I would certainly not fit a switch either, the freezer may otherwise be switched off, and no one notices. In fact, perhaps a switch with a neon might be best? A fault would then become more obvious, I assume the ring has an RCD/RCBO of 30 mA.?
  • 0
    2.5 mm SWA out of the back of a socket into a small consumer unit in the shed with a 16 amp MCB in it to feed a 2.5mm radial circuit within the shed for sockets and a switched 3 amp fused connection unit to supply the shed lights.


    Done and dusted.
  • 0
    Sounds like a formidable trip hazard might be created. How will the cable get from the house to the shed?
  • Former Community Member
    0 Former Community Member
    Sparkingchip:

    2.5 mm SWA out of the back of a socket into a small consumer unit in the shed with a 16 amp MCB in it to feed a 2.5mm radial circuit within the shed for sockets and a switched 3 amp fused connection unit to supply the shed lights.


    Done and dusted.


    Hi Andy, how do you connect an SWA out of the back of a domestic socket and it be available for future inspection?


  • 0
    Weirdbeard:
    Sparkingchip:

    2.5 mm SWA out of the back of a socket into a small consumer unit in the shed with a 16 amp MCB in it to feed a 2.5mm radial circuit within the shed for sockets and a switched 3 amp fused connection unit to supply the shed lights.


    Done and dusted.


    Hi Andy, how do you connect an SWA out of the back of a domestic socket and it be available for future inspection?




    Might have to be wired through a box on the external wall as getting a gland into the back of the socket will be a challenge, though not impossible.


  • 0
    Chris Pearson:

    Sounds like a formidable trip hazard might be created. How will the cable get from the house to the shed?




    Under a slab?


  • 0
    Cables (2 x 2.5 T&E) out of the back of the indoor twin 35mm deep socket box, through the wall, into a plastic conduit box and 25mm pvc conduit dropped 18" underground to shed position.
  • 0
    In this particular case the spur from the socket ring into the shed could be less than 3 metres, so it seems acceptable to put the overload device within the shed.
  • 0
    PG:

    Cables (2 x 2.5 T&E) out of the back of the indoor twin 35mm deep socket box, through the wall, into a plastic conduit box and 25mm pvc conduit dropped 18" underground to shed position.


    Concerning the socket box: is the intention to joint one leg of the ring in there, or go back to the previous socket in the ring?


    Is PVC conduit suitable for use as an underground duct? How will water be excluded?


    I do not have any problem whatsoever electrically with extending the ring, and Mike's upside-down lollipop is just as good; but what troubles me a little is whether there will be adequate protection from external influences.


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