Whats your opinion on using 4mm2 to spur off a ring main?

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Hi

I'm not too hot on the maths of electrics but I remember once being told that if I was spuring off a 32A ring main (albeit for an additional socket or FS) that I should always use 4mm2 cable as the load on the earth (or cpc to be technical) could potentially be higher than that on the cable in the ring main.

Whats the genreal opinion on this? I worked as a sparkys mate for a couple of years and the guys I worked with always just used to use 2.5mm2, although I've been told now this is within regs using 4mm2 is preferable.
 
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You can use 2.5 for a single socket or a F/S as you will only pull a max of 13A. but if you want a double socket the you should try and incorporate it in the ring but 4.0 is sufficient for one double socket
 
you can use 2.5mm² for a double as well..

the cable is rated at 27A clipped direct, and the socket itself is only rated at 13A total.. (not each outlet ) although you can draw 26A theoretically but that would damage the socket..

as said, it's preferable to incorporate spurs and such into the ring if you can..
 
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As with the main ring cable there is no need to use 4mm for a spur unless there are insulation or grouping factors involved that would reduce the capacity of 2.5mm below the 20A that regs require for ring cables.

You should not run more than one single socket, double socket or FCU from a non fused spur regardless of cable size because of the high potential for unbalancing the ring especially if it is later extended further.
 
i don't have a copy of the BS standard with me to peruse, and i'm not buying one just to read it....

I was just repeating what I've read on these very forums from other posters..

one of which had e-mail replys from several manufacturers stating that their double sockets are rated at 13A total but could withstand some 20 amps sustained..

also, the numerous instances where people don't advocate the use of washing machine and tumble dryer in the same double socket because it causes the socket to get hot and melt.. ( pictures provided from many submitters including RF.. )
 
the socket itself is only rated at 13A total.. (not each outlet )
I remember reading this years ago but no one believed me
Think it was in the old Mk book for the old 2747 sockets

before the new K2747
 

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