Ring Circuit with Spurs

[antonyr]

I've just moved house to discover that the front bedroom only has 1 single socket.

I was quite confident that I've been doing a proper job of DIY electrics in my previous house so installing some more sockets in the bedroom didn't seem much of a problem.
After investigating the wiring under the floorboards in the landing, I managed to indentify the upstairs ring circuit.

Bought some 30A Junction Boxes, Double Sockets & 2.5mm Cable & spurred off the main cable by using a JB. In the bedroom, ran some cable and added another JB which powers 2 seperate double sockets.

I thought using JBs was a safe & logical way to add sockets but have recently discovered from reading Collins DIY that you should only power 1 socket from a spur.

Why is it not OK to have multiple sockets from 1 JB? In theory it seems like there is the same load on the cables.

Also some of the wires in the landing don't seem to be sheathed but about 6 coloured wires joined at a terminal block (I think they are for the lighting circuit).

 

[Jim2287]

2.5mm2 cable is not capable of carrying 30amps of current.

Rings have two 2.5mm2 cables, which provides current from both sides of the ring, in theory, shares the load spreads, so 5mm2 cable is now carrying 30 amps

If you spur off with one length of 2.5mm2, and add multiple sockets, the current that could be flowing through that 2.5mm spur would be too much for the cable to carry, making it hot which then melts insulation causing shorts or worse, fire.
If you wish to have more than one socket on a spur, then the spur should have a Fused Spur connection unit, which will be fused at 13 amps, which will limit the current in the cable of the spur to 13 amps

If you are adding more sockets than practical to have on a 13amp fuse, then you may wish to extend the ring

 

[Adam_151]

You should have cut the ring cable, put a junction box on each cut end, joined a new cable to one, taken it around all the new sockets you needed and then come back and joined to the other junction box, thus extending the ring.

The reason why you should not have done what you have done has been explained by jim

 

[antonyr]

Thanks for your replies,

I think I understand now. I never really thought of the cables sharing the load. As it's AC current I should have known really.

I've still got the floorboards loose so it's no big deal changing the cabling scheme. Only real pain is trying to make the gaps bigger behind skirting board to accomodate the additional cables.

Ant

 

[ban-all-sheds]

I never really thought of the cables sharing the load. As it's AC current I should have known really.

That's completely irrelevant - it would work in exactly the same way with DC...

 

[antonyr]

Oh well, it's been a while since I studied electrics at school. I was under the assumption that AC was when the current goes forwards & backwards 50 times a second, whereas DC went forward in one direction (depending on whether it's the +ve or -ve cable)

Anyway, I've now changed the cables to the following:

cut ring circuit near hallway plug, ran cable from hallway plug to new Bed dbl skt, which then connects onto 2nd bed dbl skt, then back out of bedroom into a 30A JB connected the the other half of the original ring.

The reason why I liked using JBs was it seemed a lot more straightforward, and I find trying to connect 2 cables into the back of a socket really frustrating.

Still, at least I'm happy that I've done it properly now, as I intend to stay in this house for quite a while.

Whats your opinion on seeing people like myself, who shouldn't be officially touching circuits having a go themselves?

 

[RF Lighting]

Whats your opinion on seeing people like myself, who shouldn't be officially touching circuits having a go themselves?

Unless you are adamant you know what you are doing then dont. Electricity is far too easy to get wrong and it really does kill people. Even something as 'trivial' as a connection that is not properly tightened up could cause a loss of a protective conductor increasing the chance of an electrocution, or if it is a badly made connection on a circuit using some load (2kW is plenty) then this joint will get hot, burn, set fire...

You get the point

The one thing you have done is not be too proud to get advice to make sure you do the work properly.

 

[ban-all-sheds]

Oh well, it's been a while since I studied electrics at school. I was under the assumption that AC was when the current goes forwards & backwards 50 times a second, whereas DC went forward in one direction (depending on whether it's the +ve or -ve cable)

Yes, but with a ring circuit you have 2 cables, i.e. 2 lives, 2 neutrals (and 2 earths) going to each socket, so the current is split between the two cables in the ratio of their lengths. The fact that the current changes direction is irrelevant - whichever direction it is flowing, some will go along one cable, and some along the other.

Anyway, I've now changed the cables to the following:

cut ring circuit near hallway plug, ran cable from hallway plug to new Bed dbl skt, which then connects onto 2nd bed dbl skt, then back out of bedroom into a 30A JB connected the the other half of the original ring.

It would have been better to have replaced that cable, rather than extend it with a JB.

Is the JB accessible for inspection?

The reason why I liked using JBs was it seemed a lot more straightforward, and I find trying to connect 2 cables into the back of a socket really frustrating.

Don't understand that - all sockets on a ring final or radial (apart from the last one on a radial) will always have 2 cables going into them, unless you wire them as spurs off the main circuit cable using a JB for each one (which would be a dreadful thing to do).

Whats your opinion on seeing people like myself, who shouldn't be officially touching circuits having a go themselves?

There is no official restriction on you doing anything, up to and including a complete rewire, but you are required to notify some work to LABC in advance.

 

[antonyr]

Not long after writing about the AC/DC thing I realised my error.

The JB (Brown heavy duty) is under the floorboard on the 1st floor landing. Currently accessible now while they are not screwed down, and they won't be screwed down for a while.

Just out of interest, how many electricians actually

Also sent an email to Local Borough council asking if I need to inform them and they relied that you would need building regs for outside, bathroom, kitchen & garage electrics.

 

[RF Lighting]

Just out of interest, how many electricians actually

Actually what?

 

[JohnD]

Hardly any.

 

[securespark]

Well, you're both wrong. I do!

 

[RF Lighting]

Ahhh. The exception to prove the rule.

 

[antonyr]

What I mean't to say was...

How many electricians actually do a proper job of electrics?

Ant

Either way, I know my limits of what I really want to tackle. For example I'm due to get the house extended which I'm going to leave to an electrician.

I would have thought a JB connection would be just as weak as the connection at the back of a socket.

 

[Steve]

What I mean't to say was...

How many electricians actually do a proper job of electrics?

Thats like asking

"how many shopkeepers do a proper job of keeping a shop?"
"how many builders do a proper job of building?"
"how many police do a proper job of policing?"

There are rogues in every profession. An unlucky few people will get hit by them, most wont.

You tend to find reputable tradesmen drive a van. Rogues drive a Sierra or other old family car. Rogues give low prices (low quality work) and will do the job without seeing it first. Then they will hurry to do the job and do it in half the time it takes a pro.