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Self-builders!

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. ?
Parents
  • 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.
Reply
  • 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.
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