Ring Extension

[GrantF]

I have a 'new build' house and would like to add a couple of double sockets, into the loft.
I have a single socket on the upper landing which I can access and which is part of the 'upstairs sockets' ring main, to I could easily add a single spur, but I would rather have a couple of double sockets

Now, given that I have only access to this socket, without ripping into all the new plasterboard everywhere else. Can I extend this ring circuit from here, as illustrated in my diagram, or have I got this wrong

 

[mapj1]

Your idea is absolutely fine, just make sure the cable is the right rating (probably 2.5mm), and all screwed joins are easily accessed, (or any that are not accessible should be crimped) and that the new cables are run in the permitted zones or protected (see figures in 'for reference section')

Actually that diagram is almost nice enough to be used as a 'for reference' itself (if the wire colours were red/black & green yellow)..

One other thing, on that note, if you are mixing old and new colours (red/black and blue/brown) then there needs to be a label at the consumer unit to say so.
cheers M.

 

[GrantF]

Your idea is absolutely fine, just make sure the cable is the right rating (probably 2.5mm)

Is the 25m of 2.5mm T+E (Black,Red+bare copper) the right stuff, to extend the brown\red and copper? Seems to make sense.

all screwed joins are easily accessed, (or any that are not accessible should be crimped) and that the new cables are run in the permitted zones or protected (see figures in 'for reference section')

I was planning to connect use crimped connectors to extend the run vertically from the right hand connector, and just run a length of T+E from the 'donor' socket, up behind the plasterboard into the loft floor area

Actually that diagram is almost nice enough to be used as a 'for reference' itself (if the wire colours were red/black & green yellow)..

One other thing, on that note, if you are mixing old and new colours (red/black and blue/brown) then there needs to be a label at the consumer unit to say so.
cheers M.

The colours are brown\blue\copper but dont transfer too well, so I will update and repost.

One other thing, on that note, if you are mixing old and new colours (red/black and blue/brown) then there needs to be a label at the consumer unit to say so

Is there a particular\specific label I should add?

 

[Damocles]

2.5mm is almost certainly fine. If the existing wire is anything thicker then you should use the same. I

t is possible that your existing circuit has reached the maximum permissable length for a ring. Then you might consider using a thicker cable so that it could be longer. Except that for this to work you would need to replace some of the existing cable too.

If it is a normal size house and this is a ring only for upstairs then you are probably ok.

cables are supposed to be double insulated, so even crimped connections should be in some sort of enclosure. If the connection was accesible from the existing socket box then all to the good.

 

[ban-all-sheds]

Is the 25m of 2.5mm T+E (Black,Red+bare copper) the right stuff, to extend the brown\red and copper? Seems to make sense.

Like Damocles my eyebrows went up a bit at the mention of needing 25m extra just to get a couple of sockets into the loft. According to the OSG the max length for a 2.5/1.5 ring on a 32A Type B is 84m, so you should be OK though. But if you need +25m for a couple of sockets in the loft, how big is your house?

I was planning to connect use crimped connectors to extend the run vertically from the right hand connector, and just run a length of T+E from the 'donor' socket, up behind the plasterboard into the loft floor area

Or you could replace the existing single socket on the landing with two singles side-by-side in a dual accessory box:

Would be cheaper than buying a ratchet crimper if this is the only time you'll use it....

Is there a particular\specific label I should add?

Yup. You can buy them from wholesalers, and specialist label suppliers like Seton, but they aren't cheap.

Or feel free to save this one:

and shrink to fit whatever label stock you have for your printer.

PS - heatshrink tubing is OK to cover crimped joins.

 

[GrantF]

Is the 25m of 2.5mm T+E (Black,Red+bare copper) the right stuff, to extend the brown\red and copper? Seems to make sense.

Like Damocles my eyebrows went up a bit at the mention of needing 25m extra just to get a couple of sockets into the loft. According to the OSG the max length for a 2.5/1.5 ring on a 32A Type B is 84m, so you should be OK though. But if you need +25m for a couple of sockets in the loft, how big is your house?

LOL, I was actually referring to the amount of cable I bought, as it comes in 10M or 25M, and I guesstimated it would be well over that.
The loft is just over 8M from one side to the other, and 2.5 from the socket to where the cable will enter the loft area vertically from the socket, so I make that 21M to get up and across to both ends and back down to the socket?

 

[Damocles]

Well the non-technical way would be to figure out where the existing cable goes and roughly how long it is. The tech way would be to isolate the ring cables at the CU and measure the loop resistance. This would tell you how long it is from the resistance/m of copper cable. But you need an ohm meter reading to .1 ohm or better, really .01 ohm.

How much power do you really need in the attick? It might be simpler just to fit a FCU and have a spur.

 

[GrantF]

Well the non-technical way would be to figure out where the existing cable goes and roughly how long it is. The tech way would be to isolate the ring cables at the CU and measure the loop resistance. This would tell you how long it is from the resistance/m of copper cable. But you need an ohm meter reading to .1 ohm or better, really .01 ohm.

How much power do you really need in the attick? It might be simpler just to fit a FCU and have a spur.

Thanks for the replies so far guys.

Well I would like to put in power to both ends of the attic, as I want to put in an mains powered 'aerial booster\splitter' at one end, and perhaps another device at the other, though I dont know what yet., and I thought this was the simplest way.
Im open to suggestions, but the limiting factor is that I can only run the power from this socket. If I use a FCU, am i not limited to one supplying one socket?

 

[ban-all-sheds]

No - the whole point of an FCU is that it limits the current you can draw to 13A, thus preventing you from overloading the spur cable, which you could do with multiple sockets. So if you use an FCU, aka a fused spur, you can have as may sockets as you like on it. If you take a non-fused spur off the ring it can only have 1 socket.

An aerial booster will require negligible current, so a spur limited to 13A will not be a restriction, and will be a lot easier to do.

 

[felix]

It all comes down to what you might want up there in the future.

If you've got one of those truss construction roofs which make loft conversion impossible then a fused spur is a lot easier. This will give you adequate power for your aerial booster and a socket at each end for the day you need to use a soldering iron or electric drill.

If any kind of loft conversion is even remotely possible then I would go for the ring because you can extend it with ease.

 

[ban-all-sheds]

Even with a non-trussed roof a loft conversion involves major work, structural alterations, Building Control etc, and a bit of electrics at the same time would be neither here nor there. You might well want a loft conversion on a separate circuit anyway (or even its own sub-main if you put a shower in).

I'd say do a spur now, and if ever you convert the loft, then at that point you can do whatever is appropriate. Also, if you do convert, then a spur is much easier to remove whilst the roof is being torn apart than a ring extension....

 

[GrantF]

Felix
So far Im not proposing to ever use the loft for anything other than storage, which is why it is being floored after the wiring is going in,

OK, new picture, , Is this the correct approach for wiring from the FCU to the sockets or should a use a junction box to split off both directions, as the cable will enter the loft in the middle point so this would make for less cable running?

One more consideration is that I want to add an external security light just below roof level, so should the power be drawn from this extension or from the main upstairs lighting circuit?

 

[plugwash]

you should be able to get two cables in the output terminals of a FCU with no problems.

 

[GrantF]

....and am I also ok to run a security light from the cable after the 2nd new socket?

 

[mapj1]

Allow me to pour water on troubled oil... and arrange options in a 'preference' order, depending on the length of wire in the existing ring main
(as suggested by others a grand round loop length of 84m for a 'normal' wiring arrangement, but we are assuming a 'B32' type circuit breaker and no RCD, for hot-wire fuses or other types of breaker the maximum permissible length changes - see guide in 'for reference' section for the gory details)

1) If the ring after being extended as per option 1 will not exceed 80 metres, then simply extend it. This option gives you the simplest method, and would allow larger loads in the loft if ever required.

2) If it is only just over the limit, then why not extend the ring to the first socket in the loft then add the second as a simple spur from it. The length of the spur is not then part of the loop length...

3) If you are already right at the maximum ring main length
Then add the sockets as a fused spur as has been suggested.

(though unless you have one super ring, this is rare in a modern house.)

BUT, Whatever you do for the sockets, your security light will certainly be best on its own fused spur, just so when it dies, you don't have to turn off the indoor house lights to change the bulb.

regards Mike P-J