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Self-builders!

Chris Pearson
I am due to do some more installation work on my self-builder chum's house next month.


He is going to have two BS1363 double sockets in the floor of his drawing room. God knows why! There is wet under-floor heating.


He asked me this week whether it was OK to wire them as spurs off the ring, so the first thing to do was work out the installation method. He has laid some 20 mm flexible plastic conduit into the insulation under the pipes. I reckon RM A is probably the best fit taking a conservative approach, but we may need to de-rate for the ambient temperature.


The loading on the sockets is never likely to be significant, but clearly there is a risk that it may exceed 13 A on a double socket.


I have an inherent dislike of spurs, although in this instance, there is a case for them.


I have suggested the following options:


1) unfused spurs to single sockets

2) fused spurs to double sockets

3) fused spurs to BS 546 sockets (could have 2 A sockets on the lighting circuit)

4) use 4 mm² cable for that section of the ring.


Now he has got all confused!


Wouldn't it have been better if he had asked the design questions before he did anything? ?


There, rant over, and I am feeling better now. ?
  • 0
    Full compliance will be assured if the spurs are 4mm Chris, no skin off your nose! BTW what is wrong with spurs, they are simply ring-attached radials by another name? Perhaps you hadn't thought of that?
  • 0
    If you are going to do radial, do radial.


    A 4 mm² spur might not fit if taken off at a socket (2 x 2.5) + 4 > 8.


    I did suggest radial earlier on, but he wants rings 'cos he has always had rings, and his family has always had rings ... In fact, they suit the layout reasonably well.
  • 0
    A 4 mm² spur might not fit if taken off at a socket (2 x 2.5) + 4 > 8.

    Nothing says you have to take all the conductors directly into the socket terminals - if they won't fit you can always (US style) take a selection into a floating terminal in the back-box and then have just a fly-lead to the socket itself.

      - Andy.

  • 0
    AJJewsbury:
    A 4 mm² spur might not fit if taken off at a socket (2 x 2.5) + 4 > 8.

    Nothing says you have to take all the conductors directly into the socket terminals - if they won't fit you can always (US style) take a selection into a floating terminal in the back-box and then have just a fly-lead to the socket itself.


    Yuk!


    Or just use a better quality socket with 12 mm² terminals, but Sir prefers Screwfix's cheapest.


  • 0
    In view of the potential ambient temperature, the simplest approach would seem to be an unfused spur from a ring final circuit, but in 4mm cable rather than the more common 2.5mm cable.

    Alternatively a dedicated 20 amp radial circuit, again 4mm rather than 2.5mm due to high ambient temperatures.


    Whilst the total loading is probably modest, one should allow for heavy loading if needs change.


    I can not recommend the use of 2 amp BS 546 sockets on ANY common type of  modern installation. They were designed back in the days of very small, twin twisted, single insulated lamp flex and are much too small to neatly accept 3 core, 0.75mm, insulated and sheathed flex as used today.


    The 5 amp and 15 amp sockets are fine for modern installations when something other than a 13 amp socket is required.
  • 0
    If his thinking is that he is going to have a desk for working at, then trying to plug a PC and monitor into 2A or 5A sockets is going to be a right pain.


    What's wrong with a 13A FCU at the origin of the spur, and as many 13A sockets as is needed at the floor box?
  • 0
    Simon Barker:

    If his thinking is that he is going to have a desk for working at, then trying to plug a PC and monitor into 2A or 5A sockets is going to be a right pain.


    What's wrong with a 13A FCU at the origin of the spur, and as many 13A sockets as is needed at the floor box?




    That would do the job, but is perhaps a little restrictive if say a space heater, a kettle and a laser printer are to be used.

     


  • 0
    Well I`d question does he really really need a floor socket.

    If he can not be dissuaded  then like said will 4mm be required, then does it need/can it be protected or placed deep enough.

    Rings can be a good idea. Radials can too. Both have advantages and disadvantages.

    Us older ones are probably quite ringy the younger ones less so. There is no yes or no as to which is best as a blanket statement. it depends.

    Even a ringer like me will admit that if they were only invented today I`d think twice or thrice about them, but I was brung up on em and can see the benefits.
  • 0
    ebee:

    Well I`d question does he really really need a floor socket.


    That's not for us to say, but to my mind, it is very odd. It is a newly retired couple's house. Downstairs, there will be a kitchen with ample room for day-to-day eating; a dining room; and the drawing room. I dare say that the latter two will only be used when they have company, say Christmas and Easter. If you withdraw after dinner, you'd be supping brandy and making polite conversation. (Though to be really authentic, the ladies would withdraw, and God knows what sort of conversation they would have.)


    He wants them for things like table lamps and a wireless, but why would you be reading or listening to the wireless, or both in the drawing room? He can do that in the "library" upstairs. (That's having floor sockets as well.) ?


  • 0
    Simon Barker:

    If his thinking is that he is going to have a desk for working at, then trying to plug a PC and monitor into 2A or 5A sockets is going to be a right pain.


    What's wrong with a 13A FCU at the origin of the spur, and as many 13A sockets as is needed at the floor box?


    Desk, assuming that there will be one, will be in the library. I quite agree - an FCU at the origin of a spur is a good idea. Clutters up the wall though!


    Some of the kitchen sockets will be in the window recesses (think stone cottage or a castle). You try working out the safe zones for that! ?


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