SWA to shed

Discussion in 'Electricians' Talk' started by Tot1984, Jan 17, 2021.

  1. Tot1984

    Tot1984 New Member

    I am planning to run a SWA from a spur to a consumer unit in a shed. The ring main the spur is coming off is a separate ring main in the extension and is located in the garage joined to the house. Before I wire it all up, I am a little confused on what I need as I would like to be able to isolate the power running down to the shed via a switch. I was thinking a 4mm t&e spurred off my socket running to a 45a switch, then a 4mm t&e running to a junction box outside and the 4mm SWA running from that down to the consumer unit in the shed. Would that be right?
     
  2. rogerk101

    rogerk101 Screwfix Select

    What do you think your power requirements will be in the shed? Don't just think of what you need now ... think of what you might need in the future.
    Like a shortsighted idiot I ran a 2.5mm2 SWA to my garage which was fine when it was a garage. I then converted the garage to a granny flat in which I installed a 12kW instant water heater, and I ended up running a 25mm2 SWA to it. More work, more expense, more hassle. It's obviously worthwhile, but I would have saved myself a big ball ache had I done the job properly in the first place.
     
  3. Tot1984

    Tot1984 New Member

    I only want to run a TV and a few plugs for charging appliances. Nothing major but I am stuck what isolator switch to install. 45amp?
     
  4. rogerk101

    rogerk101 Screwfix Select

    The maximum you can spur off a ring final is 13A, and this should be done via a switched fused spur fitted with a 13A fuse.
    If that really is the configuration you want and the load you plan on running, then you probably don't even need 4mm2 SWA. You don't say how long the run needs to be, but if it's 10m or even 20m, a 2.5mm2 SWA would be good enough for the loads you plan on running.
    You would need to terminate the SWA correctly on both sides, which you won't be able to do in a switched fuse spur enclosure, so you'll need another junction box on the house side.
    If you install a shed mini consumer unit then buy one that accepts SWA termination.
    All this assumes your house CU contains an RCD and the ring that you're tapping into is protected by that RCD.
     
  5. Tot1984

    Tot1984 New Member

    O
    i am running it 12 metres, so I only need a 13AMP switch? Yes the ring main its spurring off is RCD protected. Do I use 4mm t&e from existing socket to switch and junction box or 2.5mm?

    Thanks in advance
     
  6. rogerk101

    rogerk101 Screwfix Select

    For 13A and only 12m, you can use 2.5mm2 all the way ... twin and earth to the SWA junction box, and SWA to the shed's consumer unit, assuming you get a CU that can terminate SWA; otherwise you'll need another SWA terminating junction box, and then T&E after that.
     
  7. Lectrician

    Lectrician Screwfix Select

    Personally I would bring the 2.5mm SWA right into the garage and terminate it with an SWA gland into a metal clad switched fused spur. Use a galvanised conduit coupler if you’re worried about space in the box, but most will be fine. Run 2.5mm T&E from a socket on the ring to the fused spur. The fused spur doesn’t need to be adjacent to the socket, put it where convenient for the SWA.
     
  8. Tot1984

    Tot1984 New Member

    How would I tidy up entrance through the wall if I brought the SWA straight in through to the fused spur?
     
  9. Bazza

    Bazza Screwfix Select

    One of these. SWA cable comes up the wall, gland screws in to the bottom. Leave inner sheath long and it will feed through the wall to the FCU without the need for any joints.
    B5BE1A13-2DB3-4F76-B981-EFC1E7D4231F.jpeg
     
  10. Banallsheds

    Banallsheds Well-Known Member

    You don't need a consumer unit in the shed. You can wire your sockets direct. You shed light via a switched FCU with a 5 amp fuse.
     
  11. Lectrician

    Lectrician Screwfix Select

    A hole at a decent angle into the ground?
     
  12. Bazza

    Bazza Screwfix Select

    Here’s one I prepared earlier.
    22DA4D26-811A-4940-A5E2-2752F23A1D9B.jpeg
     
    rogerk101 likes this.
  13. sparky Si-Fi

    sparky Si-Fi Screwfix Select

    Yup as above, just to add, I hate it when folk try and squeeze 5A choc blocks in them plus shed loads of silicone there not really designed for that IMO
     
    Last edited: Jan 18, 2021

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