Adding spur to power attic...

[andru]

I've little practical experience in electrics beyond wiring plugs and lightswitches, but am in the middle of converting my attic and want to install some plugs up there.
There's no way I can expand the ring from the second floor as the wires all lie behind plaster, and I simply don't have the time, money, or expertise to dismantle my house. However, I can manage taking a spur from a plug in a room below - but will this limit me to one double socket?
The wiring for the electric shower runs into the attic, is there any way I could take a spur from this that will allow more plugs?

I'm not going to be running any demanding equipment (mostly under 5a), I just need more than 2 sockets.

Any suggestions?

 

[Adam_151]

Spur from shower cable is not allowed

Unfused spur from socket can only feed one socket, its possible that you would be able to have more with either a fcu or thicker cable (4?, 6?), you'll have to wait for comment from someone else as I don't know whether those options are allowed, even though they seem to make logical sense to me. Of course you would have to make sure that the socket you want to take the spur from is not already a spur itself.


Is it possible to put in an extra circuit from the cu?

 

[andru]

Hi adam, thanks for the quick reply

The socket I'd be taking it from isn't a spur, as far as I can tell. I can't take a new circuit from the cu, as it's all the way downstairs and I can't tear the house to bits to bring a new circuit upstairs. I stupidly forgot to note the thickness of the cable I've bought, but I know for certain it's far thicker than is required.

Is there no way whatsoever I can take power from the shower? I was hoping I could go this method, as it's by far the easiest.

If only I could afford to call in someone more qualified than me

 

[breezer]

There is NO WAY you should connect to the shower cable. The reason being that to connect to it you must use the same size cable then how you going to get that into a socket, answer you cant just do not even think about it, it is dangerous and can cause a fire. end of story

A suggestion

the nearest socket in the room below, you could always run two cables to it, and then put the loft socket on the ring (providing the total floor space is not now more than 100m square)

you could run the two twin and earth cables up to the loft in trunking.

 

[andru]

Oh well, guess I'll have to do things the hard way then!

As I'm still not totally clued up about all this stuff, could someone explain to me the benefits of having two cables? Couldn't I just use one thats double the thickness?

Also, I just went and had a proper look at my archaic CU. There is one 30a fuse (for the shower, I'm guessing), four 15a and one 5a. The 5a, however, is inserted upside down and not all the way in (because it's upside down). Does this mean the lighting circuits are running on a 15a fuse? If so, does it need to be sorted, or is it ok?

 

[breezer]

havent a clue what size fuse the lights are on, sorry but i am nit there, you are.

Take the fuse out and turn it the right way up, you will then find it will go "all the way in"

you can not use a cable twice as thick,

1) it will cost more £££££
2) it will still be a spur
3) by using 2 cables you can extend the ring that all sockets are on.

have a look in the sticky for reference section. for more detailed info

 

[andru]

Thanks breezer.

I'd be interested in hearing a technical description of why I can't tap into the circuit for the shower. I'm happy to accept that I can't, and certainly won't, but I'd be interested in finding out exactly why. Is it purely to do with the size of the cable? Would it be too much current for a normal socket?
The more I can learn before I start hacking my house to pieces the better

 

[JordanBlack]

It's somthing to do with the power in the cable if you feed a socker which has less amp, then if the plus over heats then the rcd wont pick it up as the cable running to the shower is still more than the socket, and then the socket may catch fire.

I'm not an Electrian but i think that's one of the reasons

 

[breezer]

It's somthing to do with the power in the cable if you feed a socker which has less amp, then if the plus over heats then the rcd wont pick it up as the cable running to the shower is still more than the socket, and then the socket may catch fire.

I'm not an Electrian but i think that's one of the reasons

sorry to say, but that is a load of not truth, although you said it with best intent

 

[Damocles]

Sounds a bit odd, this. be prepared to start again on all the advice you have had so far.

It is quite important which fuse is running what. Normally, a ring will be a 30A fuse or 32A mcb.

A shower would normally expect to have its own protective device, and rated more than 32A. The circuit should be designed to just supply the power needed by the shower, which is very likely to be its full power all the time. This is why you can not add on another socket, which might theoretically add another 15-20A to the load on that circuit.

But you have only got one 30A fuse? Sure there are not some more somewhere? Would also expect another for a cooker point.

15A would suggest a number of radial circuits. Possibly supplying sockets. If the 30A fuse is really the shower and nothing else, then the 15A pretty well must be for sockets? If the 15A are supplying sockets then it is is very unlikely you have a ring. Instead they may be 2.5mm^2 cable looping from one to the next ot the next. If so, you can add more without having to complete a ring.

Bear in mind that such a radial can only deliver 15A. This should not be a problem, but if you have a choice, do not extend a cicuit which has more than average load already.

Please check exactly which fuse supplies what. It has been known for someone to just tag a shower onto a ring, which is probably even worse than tagging a socket onto a shower.

 

[securespark]

There may well be a seperate box for shower.

If you insist on only wiring one cable to the loft, there is one way you can have all the outlets you want.

Wire the loft from the "load" terminals of a 13A fused spur. This way, you cannot possibly draw more than 13A total load. And if you use a neon spur, you will know when the indicator goes out that the fuse has popped.

 

[Damocles]

Or more likely, the bulb has failed

 

[andru]

Thanks for all the replies so far guys Nice to see people so willing to help!

I've checked my CU - the 5a fuse is indeed for the lighting circuit, godknows why it was upside down but it was in just enough to work, so I've turned that the right way up.
I pulled the 30a, and the shower light went off, so that's certainly powering the shower. I'm guessing the remaining 4 15a fuses are 2 pairs for radials - one for each floor?

So, if it is a radial circuit, how do I go about extending it? If it helps, I'm perfectly happy to sacrifice a socket in the room below, as it's in a pointless place anyway.

 

[toasty]

Why don't you spur off the ring on the floor below, us a fused spur unit (perhaps switched if you like the idea of isolating the loft)

Then run as many sockets as you like from the fused spur in the loft.

As long as you use a 13Amp fused spur you'll have plenty of power for low current appliances and no danger of overloading the cable.

Also, and this wouldn't achieve much, but you could even use 1.5mm cable ofter the fused spur which is slightly cheaper and easier to work with. (as long as the run of cable isn't massive then voltage drop won't be a problem)

That's what I'd do if I were you .

Hope this helps.

 

[andru]

Thanks toasty, that sounds like a good idea to me. Is 1.5mm the same as lighting cable? Also, would I have the fuse/switch before the length of cable going to the attic or after?
Just out of curiosity - how dangerous is what I'm doing at the moment: Running a 13a extension lead from the plug downstairs up into the attic, to power a few low current appliances.

Edit: I just remembered to mention that while the appliances are low current, a couple of them use transformers and draw a lot of power - will this have an impact on how I need to wire the attic?

I thought I'd take a picture of my CU for anyone who might be interested. Sorry for the shoddy quality, but I had to sandwhich myself between a fridge and a wall while crouching under a worktop just to take it!