Spur Limits

[bobbandrew]

Hi all,
My house has limited electrical sockets and the previous owner seemed to just add what he wanted where he wanted and to hell with the consequences.
I know you cannot spur off a spur, and that it is usually best to extend the ring/radial circuit rather than add spurs. But I was wondering if there are any limits to the number of spurs you can have in close proximity.
Can you spur off of two ring sockets and use a junction box to spur off the wire connecting these sockets?
Can you have two or more junction boxes on the same ring wire?
Any help is appreciated as I need to figure out what to disconnect and what I can keep.

 

[Aragorn84]

Barring bad design, i dont think theres anything technically wrong with three spurs in close proximity like you describe.

You could spur off every outlet on a ring and it would still be fine afaik.

I'd imagine a junction box isnt seen as any different to a socket outlet, so you can spur from there too, although current regs say the junction boxes should either be accessible, or of a maintenance free type.

 

[dhutch]

You could spur off every outlet on a ring and it would still be fine afaik.

Which is in effect what I have in my house, council wired in the 80's, one ring main upstairs, with a spur from each socket down to a socket on the ground.

Presumably at present you have several spurs coming into the back of one socket, with no easy way of adding cable to make then into a ring?

##
In one student house when the boiler failed it transpired that the nearby socket had five cables going into it. Two twin and earths from the ringmain (one one for the whole house), one 2.5mm spuring into the 'utility room' (which looked origanal) , one 2.5mm in new colours spuring down to the oven (gas hob) and one peice of newish looking 1mm (old colours) which went direct into back of the boiler, no fused connection unit. Nice!

The plumber cut the 1mm short, wired it into a surface mounted fcu, and look flex from that into the new boiler. Passing a comment to the tune of 'god knows how anyone got that many wires into the back of one socket, but Im not planning to touch it'
##


Daniel

 

[bobbandrew]

Thanks for the replies
Yes I have just one ring circuit with various spurs and junction boxes, and am just deciding whether to split it up into a couple of rings.
The kitchen had me a bit worried with just one ring socket, a spur off it, and a third socket from a juction box somewhere between the kitchen ring and the bedroom above.

 

[JohnW2]

I know you cannot spur off a spur, and that it is usually best to extend the ring/radial circuit rather than add spurs. But I was wondering if there are any limits to the number of spurs you can have in close proximity.
Can you spur off of two ring sockets and use a junction box to spur off the wire connecting these sockets?
Can you have two or more junction boxes on the same ring wire?
Any help is appreciated as I need to figure out what to disconnect and what I can keep.

You can have as many sockets and JBs in a ring final circuit as you like and, as far as the regulations are concerned, you can have as many unfused spurs coming from those sockets and JBs as you like, provided only that each serves only one socket. There's not even any explicit prohibition in the regs of having more than one spur originating at the same socket or JB, although you'll be hard pressed to get four cables into a socket (and might violate the regs by going beyong the socket manufacturer's stated maximum number of cables). The IET's On-Site Guide (a 'companion' to the regs, but not part of the regs) recommends that the number of spurs should not exceed the number of sockets on the ring.

Orginating several spurs from the same, or very close, points on the ring, particularly if close to one end of a ring, could theoretically result in one 'leg' of the ring becoming overloaded. It is therefore not 'good design practice' and, as such, might fall foul of some of the 'catch all' clauses of the regs. However, when one is closer to the centre of the ring, that issue does not arise.

Hope that helps.

Kind Regards, John