Lots of sockets on spurs

[spur-man]

My house has a solid ground floor, and when I was replacing some unswitched sockets with switched ones downstairs, I noticed that they were all wired as spurs, with the cable dropping down conduit buried in the walls. When I lifted some floorboards upstairs I found that the sockets up there are on a proper ring (well, all the ones I checked were), and then single runs of cable are teed off from junction boxes or the sockets to go downstairs.

Does that describe it understandably? Shame I can't post a diagram.

Anyway - is this OK? Or should they all be on a proper ring? It's 2.5mm cable throughout, so just not quite enough, in theory, for a spur to a double socket, although in practice of course the chances of me running 2 x 13A appliances off one of the sockets is smaller than a small thing that's very small. But I imagine the regulations would say that if it can be done it must be safe....

The problem is that there isn't room in the conduit that's there for two pieces of 2.5mm cable. I haven't tried, but there is probably room for 4mm, which could safely carry the theoretical 26A, if that method of supplying the sockets is OK. Also if I removed the outer sheath from some 2.5mm I could probably get the individual wires down them to make a ring.

Another factor to think about is how long the ring would then be - it's only a typical 3-bed 1950s suburban semi, but if the ring went up and down the walls several times could it get a bit too long?

Dunno what's best - simplest thing would be to replace the drops with 4mm - I really don't want to have to rip the walls apart to put in bigger conduit.

Any advice?

 

[supersparks]

My house has a solid ground floor, and when I was replacing some unswitched sockets with switched ones downstairs, I noticed that they were all wired as spurs, with the cable dropping down conduit buried in the walls. When I lifted some floorboards upstairs I found that the sockets up there are on a proper ring (well, all the ones I checked were), and then single runs of cable are teed off from junction boxes or the sockets to go downstairs.

Does that describe it understandably? Shame I can't post a diagram.

Anyway - is this OK? Or should they all be on a proper ring? It's 2.5mm cable throughout, so just not quite enough, in theory, for a spur to a double socket, although in practice of course the chances of me running 2 x 13A appliances off one of the sockets is smaller than a small thing that's very small. But I imagine the regulations would say that if it can be done it must be safe....

The problem is that there isn't room in the conduit that's there for two pieces of 2.5mm cable. I haven't tried, but there is probably room for 4mm, which could safely carry the theoretical 26A, if that method of supplying the sockets is OK. Also if I removed the outer sheath from some 2.5mm I could probably get the individual wires down them to make a ring.

Another factor to think about is how long the ring would then be - it's only a typical 3-bed 1950s suburban semi, but if the ring went up and down the walls several times could it get a bit too long?

Dunno what's best - simplest thing would be to replace the drops with 4mm - I really don't want to have to rip the walls apart to put in bigger conduit.

Any advice?

its been done because there wasent room in he conduit, its fine, nothing wrong with it, just very unflexable (you cant have more spurs than you have sockets on the ring)

 

[spur-man]

Thanks for that.

OK to leave the 2.5mm in, or should I replace it with 4mm?

I was thinking as well about splitting the upstairs/downstairs rings, but that would mean downstairs was all spurs.

What does "you cant have more spurs than you have sockets on the ring" mean?

I havent gone round and counted, but I think I've got more sockets downstairs than up. If I had 2 rings then what?

 

[breezer]

What does "you cant have more spurs than you have sockets on the ring" mean?

as it says.

For example ten sockets on a ring means you can have 10 spurs (or less)
but you can not have 11 spurs.(or more)

 

[supersparks]

>OK to leave the 2.5mm in, or should I replace it with 4mm?
keep the 2.5 nothin wrong with it
and i would keep em the same, unless you plan to totaly rewire the sockets, also if you re wire you will still have a problem unless you chop out the plaster and run new cables ad cover them in capping or put bigger conduit in

BR

 

[spur-man]

as it says.

For example ten sockets on a ring means you can have 10 spurs (or less)
but you can not have 11 spurs.(or more)

Sorry - was just being a bit thick - wanted to make sure it really did mean what it said, 'cos
a) I've already got more than that (7 sockets upstairs, and 8 downstairs)
b) It doesn't really make sense to me - it seems as though I could fix (a) by adding another socket upstairs. One on the landing would be useful for hoovering, I suppose. But why that makes my existing wiring any better or safer is a mystery.

Still - good that it's OK to have all these spurs fed by single lengths of 2.5mm - I was a bit worried by that.

I'd better not go ahead with my plan to split the two rings, cos then I'd have a ring that was physically upstairs, but with no sockets on it and 8 spurs.

 

[ban-all-sheds]

If it were me, and there was room, I'd be tempted to replace those bits of 2.5mm with 4mm.

It's all very well you knowing what's there, but when you move out, and someone plugs 2 3KW fan heaters into one of those double sockets, I'm not sure the current carrying capacity of 2.5mm in conduit which is buried in the wall would be enough. I think (haven't got time to check right now) that cable in that circumstance is rated at 18A, so 26A would be almost a 50% overload.

Have a go - if you use lubricant, and have a helper dress the cable as it goes into the conduit to make sure it doesn't kink or twist, do you think you could pull it through using the old cable?

 

[spur-man]

It's worth a try.

What about making 2 rings? Do you know why I can't have more spurs than sockets?

 

[breezer]

It's worth a try.

What about making 2 rings? Do you know why I can't have more spurs than sockets?

because of the capacity of the cable.

have two rings, two is always better than one.

 

[spur-man]

I'm very sorry but I'm even more confused - not on how to do things, but why. Some people say that you can't have more spurs than sockets. Not having more than 1 socket on 1 spur I can understand, but not this.

And then if I make a second ring, which people say I should, I would have a ring with no sockets and all spurs!

Ive sent some drawings to the admin of the forum, which will I hope will be here soon and will show what I have and why I'm confused, so if everybody who has been kind enough to help me so far could check back in a couple of days when they appear in the message I would be eternally grateful

Fig 1 shows what I have now with 7 sockets on a ring, and 8 spurs, which is not OK? The exact details of which spurs are from sockets and which are from junction boxes are not accurate, but it's the type of setup I have.

Fig 2 shows how I could fix the problem of 7 sockets and 8 spurs, but I don't see how it makes any difference to the spurs?

Fig 3 shows what would happen if I made a separate "ring" - no sockets and all spurs. But if the new ring had 8 sockets instead of the 8 junction boxes that would be OK? If it would, this is where I get really puzzled, because if nothing was in those sockets directly on the ring, it must still be OK, so it would be OK if I left the sockets under the floorboards and if I did that then what is the difference with junction boxes?

DIAGRAMS:

Ring layouts 1
Ring layouts 2
Ring layouts 3

 

[Scoby_Beasley]

Each socket on a ring can have a spur, (single or twin). Me, myself , I, if I was ripping up boards to look would add a ring, if for one socket, splice in, makes life easier

 

[spur-man]

Thanks to all who've replied, and thanks to the forum administrator for posting the diagrams I sent. I'm sorry I kept on, but I always like to understand the whys of something, rather than just accepting what I'm told. But this time I'll have to accept it, because I still don't understand it.

I can't see why, in terms of the current flowing at any point in the ring, or down any given spur, this //www.diynot.com/img/forum/spur-man2.gif is any different to this //www.diynot.com/img/forum/spur-man1.gif, i.e. why No 2 is OK because it has one more socket on the ring than No 1.

Also I don't understand why Breezer and Scoby are saying "yes, have a second ring", when that second one couldn't have any sockets on it. It would be a loop of cable with nothing but spurs. It would have no sockets at all directly on the ring. From what everyone is saying, that's not allowed, you can only have the same number of spurs as sockets.
Which leads me to the completely nonsensical conclusion that if I did what is shown here //www.diynot.com/img/forum/spur-man3.gif, but where that shows junction boxes I had sockets, that would be OK. If I never, ever used those sockets, nothing would change, but they would be doing exactly what the junction boxes would do.

So I'll retire hurt - if I don't make a separate ring for downstairs I'll add another upstairs socket to the ring to balance the numbers.

If I do have a new ring, I'll use cheapo unswitched single gang sockets (95p ea at screwfix) as "junction boxes" and leave them under the floorboards upstairs. I'll try not to fret about how daft it all seems.

 

[breezer]

what scoby and i are saying is to take the sockets off from upstairs and put them on their own ring downstairs.

that way if ever you want to add a socket, you don't spur it you make it into part of the ring

 

[spur-man]

I can't have a ring downstairs as the house has a solid concrete floor. Sorry, but ripping up the quarry tiles in the kitchen and the parquet in the hall and lounge in order to channel in some cables is NOT an option...

Apart from the kitchen which has a circuit down one side which runs in the wall, the only way I can have any sockets downstairs is to have them on spurs that drop down the walls in buried conduit.

Hence my problem - more sockets downstairs than up; not all sockets downstairs are spurred off upstairs ones, some come from junction boxes; spur cables are 2.5mm, which is a bit marginal for 2 x 13A sockets; could probably replace the spurs with 4mm; could less probably turn it into a ring by using single core cables down & back up the conduit.

 

[supersparks]

I can't have a ring downstairs as the house has a solid concrete floor. Sorry, but ripping up the quarry tiles in the kitchen and the parquet in the hall and lounge in order to channel in some cables is NOT an option...

Apart from the kitchen which has a circuit down one side which runs in the wall, the only way I can have any sockets downstairs is to have them on spurs that drop down the walls in buried conduit.

Hence my problem - more sockets downstairs than up; not all sockets downstairs are spurred off upstairs ones, some come from junction boxes; spur cables are 2.5mm, which is a bit marginal for 2 x 13A sockets; could probably replace the spurs with 4mm; could less probably turn it into a ring by using single core cables down & back up the conduit.

The problem with 4mm is that its gunna b a b^tch to get into the terminals with two other 2.5mms. and only add the extra socket if you want to, your unlikely to use all the sockets on spurs for heavy equip. another thing you could do is split the ring and have two 20amp radials thsi way the cable at 24amps and the breaker at 20.......no problems with overloading and no disruption


AR