Ring/Radial Help

[matt80]

Hi everyone.

I have a few questions about the way my house is wired up (I must confess to being a real novice at DIY, so apologies in advance!).

I have an old-style fuse box with four main fuses, each one serving as follows:

1. Power shower/immersion heater.
2. Living room/hall sockets
3. Upstairs/kitchen sockets
4. Lighting (both upstairs and downstairs).

I have an electric cooker, which doesn't appear to be served separately. How bad is this? I believe it is on the same supply as the upstairs/kitchen sockets.

However, the main reason for my post is this: How do I know how my sockets are wired up? I took the faceplate off the ones in the living room and the hall and all I see is a single wire coming into the box, each of which splits into a red/green+yellow/black smaller wires. I was expecting to see more than one wire, or do I need to remove the *entire* bracket to see this - including the backplate?

Thanks for your help.

Matt

 

[HandyJon]

I have an electric cooker, which doesn't appear to be served separately. How bad is this? I believe it is on the same supply as the upstairs/kitchen sockets.

Is it a electric hob and oven or just an oven. An electric oven can be run of a 13A plug. An electric hob needs a it's own heavy duty cable from the CU (or in your case the fuse box).

However, the main reason for my post is this: How do I know how my sockets are wired up? I took the faceplate off the ones in the living room and the hall and all I see is a single wire coming into the box, each of which splits into a red/green+yellow/black smaller wires.

Does sound like you've got a radial wiring system especially if you've got an old style fuse box.

 

[matt80]

Is it a electric hob and oven or just an oven. An electric oven can be run of a 13A plug. An electric hob needs a it's own heavy duty cable from the CU (or in your case the fuse box).

Its an electrive oven with a gas hob and an extrator fan/light. I guess I'm ok then!

Does sound like you've got a radial wiring system especially if you've got an old style fuse box.

How can I tell for sure? There must be a way of telling whether its ring or radial?

If it is radial, then why is there only one big black wire coming to the socket? Surely there should be another one going off to the next socket on the main "radial" wire?

Thanks very much for your reply.

 

[HandyJon]

How can I tell for sure? There must be a way of telling whether its ring or radial?

Pulling out the wires from the wall and following them back to the fuse!

If it is radial, then why is there only one big black wire coming to the socket? Surely there should be another one going off to the next socket on the main "radial" wire?

A radial usually means your sockets are wired up in a star configuration where all the sockets are on seperate wires, all of them leading back to the fuse box. A ring circuit has a wire coming into the socket and
one going out to the next until it gets back to the Consumer Unit. A cable in a radial might have more than one socket on it, but there is no guarantee that that is the case.

An alternative explanation is that the sockets you've looked at are spurs from a ring main, but it would be unusuall for all your hall and living room sockets to be spurs. Yet another posibility is that you have a ring main and that each socket is a spur of the ring wired off a junction box hidden in the wall, very unlikely though.

 

[Damocles]

Umm. First, can you tell how thick the cable is coming into the socket? I mean the copper wires, not the insulation. A ring normally uses 2.5mm^2 cable. Though if this is an old installation the actual conductor might be made of several strands rather than being solid like a modern one.

Second, are you quite sure the fuses do what you have described? Have you checked each socket with one fuse pulled to make sure it is powered from where you think?

With two 32A fuses available I would expect one was dedicated to the cooker and one to the sockets.

Have you checked the sockets elsewhere to see if they are all alike? a ring should have two cables coming in. Some sockets might be spurs, which would have one socket with just one cable, and another with three cables where the spur starts. Or there might be junction boxes under the floor where some spurs start.

If you feel happy to look inside the fusebox, you can see how many wires of what size start from each fuse.

It is possible that there might be an actual ring upstairs with spurs coming off to all the downstairs sockets.

This talk of brackets and back plates... I have a picture in my mind of really quite old surface mount sockets which have a bakerlite plate behind them. The face plate comes off leaving the socket screwed to the wall and the cable connections visible. Next the socket comes off, leaving the plate with wires coming through. Behind this I would expect just wall and a hole, but who knows.

 

[ban-all-sheds]

How can I tell for sure? There must be a way of telling whether its ring or radial?

Pulling out the wires from the wall and following them back to the fuse!

Err--- how about just looking at the CU - if there is only 1 wire coming out of the fuse, it must be a radial. 2 wires doesn't mean it must be a ring though - could be 2 radials. You'd then have to disconnect both the cables at a socket and test to see which one(s) are live. If both, it's a ring, if only one, it's a radial.

A radial usually means your sockets are wired up in a star configuration where all the sockets are on seperate wires, all of them leading back to the fuse box.

I think it usually means circuits like these...

An alternative explanation is that the sockets you've looked at are spurs from a ring main, but it would be unusuall for all your hall and living room sockets to be spurs.

Not if the ground floor is solid - then all the downstairs sockets could easily be spurs dropped down the walls from a ring main cable running under the upstairs floorboards....

 

[Damocles]

This single black wire. Not made of rubber is it? Modern pvc cables are usually either grey or white. Rubber was frequently black. And again, at least 40 years old. Old enough to be a serious problem if it has started falling apart. Also, I think radial circuits would be more likely on an old installation.

Just how old-style is this old style fuse box? Is it bakerlite with push in plastic topped fuses, or really old all ceramic ones?