Spur off a spur.

[kp7722]

Hi all,

I was changing some sockets over the weekend and noticed that one double socket which was already a spur, had another spur coming off to another double socket. Now I know this is wrong even though it's been this way for the last 20+ years, and can be corrected by putting an FCU before the first double socket. However, this will require making a mess in our newly plastered and decorated lounge which is a minor inconvenience compared to telling the missus about making a mess in our newly plastered and decorated lounge. So as far as I can tell I have one solution; drop the second spur and put a blanking plate on (or even leave the double socket on, just not wired for aesthetics).

I was just wondered whether if anybody knows if you can get an fused double socket (even if one half is a socket and one half is the fuse)? I can't seem to fine one but for me this would solve all my problems.

Cheers,
Paul.

 

[Spark123]

I can't think of anyone who makes a half socket half FCU unit anymore, infact I have only ever seen one on here which was an ancient one.
You could of course use a dual backbox with a single socket and a FCU in it.

 

[Chri5]

Buy a double (2 x single fittings) back box and replace the 1st spur with 1 x socket and 1 x f/spur to keep the (new) single and old double within the 13a limit.

A double fitting back box is about 20-25mm larger than the double socket back box, so you will need to chop a bit of wall, brick and plaster. A dremel makes a decent tool for cutting that shouldn't cause too much mess to the decorated wall.

 

[kp7722]

Cheers all, that's a great help. Dremel eh? Any excuse to get a new tool in the armoury...

Paul.

 

[kp7722]

I forgot to ask...if the first spur was 4mm T&E, not 2.5mm then it would be fine without any changes, wouldn't it? At no point would I be able to overload the cable. I'm presuming it's 2.5mm but I will check some time this week.

Just curious.

 

[PrenticeBoyofDerry]

Really the cable feeding a spur, should be the same as the rest of the circuit.
When installing a FCU the cable between the socket being spurred from, to supply the FCU, should again be the same as the original circuit.
The cable between the FCU and your additional spurred sockets, should be rated higher than the fuse in the FCU (normally 13Amp for standard socket-outlets). So you can get away with using 1.5mm cable, as this will carry 13Amps, providing it is not run through thermal insulation or grouped with other cables.
If the circuit was 2.5mm and the cable supplying the spur was 4.00mm,
as you stated it would not be unsafe, just not the ideal way to do it

 

[sparkwright]

You could get a 'grid' arrangement to replace the first socket.

This would consist of a double sized plate, with three modules.

One module will be a 13 amp in-line fuse.

The other two modules would be blanks.

20 amp switches, neons etc are also available to fit in the module holes.

or

Since you want minimal disruption to the wall, leave the double box in the wall, and fit a single box next to it. Re-route the supply cable into the single box. You may have to extend the cable. This will provide the supply to the FCU. Then you need a load cable to the double socket, which will supply the second double socket.

You can chain-drill round the outline of the new box. Use a 5.5 or 6 mm drill bit. Go in a few millimetres deeper than the depth of the box. Then gently cut through the holes with a bolster.

So you don't have an unsightly gap between the faceplates, leave a gap of one inch exactly between the centres of the fixing lug holes. If your faceplates are larger than standard size, work out the size of the gap you require.

or

Perhaps you can fit the FCU in another room somewhere, so it still does the required job.

 

[sparkwright]

Is the circuit a ring circuit wired mainly in 2.5 mm?

or

Is it a 30 amp radial circuit wired mainly in 4 mm?

 

[ban-all-sheds]

Since you want minimal disruption to the wall, leave the double box in the wall, and fit a single box next to it ... You can chain-drill round the outline of the new box. Use a 5.5 or 6 mm drill bit. Go in a few millimetres deeper than the depth of the box. Then gently cut through the holes with a bolster.

Maybe I'm missing something, but that sounds like more disruption to the wall than making the existing hole a bit wider, not less....

So you don't have an unsightly gap between the faceplates, leave a gap of one inch exactly between the centres of the fixing lug holes.

kp7722 - get 2 of these:



and 4 of these:



to connect the boxes together and guarantee alignment.

 

[sparkwright]

Since you want minimal disruption to the wall, leave the double box in the wall, and fit a single box next to it ... You can chain-drill round the outline of the new box. Use a 5.5 or 6 mm drill bit. Go in a few millimetres deeper than the depth of the box. Then gently cut through the holes with a bolster.

Maybe I'm missing something, but that sounds like more disruption to the wall than making the existing hole a bit wider, not less....

So you don't have an unsightly gap between the faceplates, leave a gap of one inch exactly between the centres of the fixing lug holes.

kp7722 - get 2 of these:



and 4 of these:



to connect the boxes together and guarantee alignment.

My logic was removing the old box could cause more damage than adding a single box next to it.

Though the couplers would ensure alignment it would mean filling the gap in the plaster between the boxes.

 

[kp7722]

I will have to check when I take the face plates off again. I just presumed that it was all 2.5mm in a ring circuit but I may be wrong.

I presume 2.5mm would indicate a ring, and 4mm would indicate a radial?

I like the idea of the grid arrangement (although that would only give me one more socket than just using a blanking plate). Where do I get these from - I haven't seen these on the Screwfix website?

ban-all-sheds, that's a great idea getting them to line up. Unfortunately the previous owners obviously didn't care and the two sockets are BADLY lined up (to be hidden behind TV stand). I do have about an inch gap between the two sockets though which I may be able to chisel out without much disruption as it's a little messy - perhaps just filler (I hope!). I could then use the dual back box.

Thanks to all for your advice. It's greatly appreciated.

 

[holmslaw]

..

 

[sparkwright]

2.5 mm cable can be used in a radial circuit, but the overcurrent protection would have to be 20 amp maximum.

 

[ban-all-sheds]

Its a stupid idea, it will not get them lined up.

Why not?