Ring not a ring

[bandejapaisa]

Electrician is putting in some new circuits, he pointed out that my existing ring circuit is not a ring, and is in fact radial - so I understand what this means (i think), but how would one go about finding where the connection to the ring is broken?

On another note regarding rings, why can't you spur off a spur? Is it to do with overloading the cable as ring cables are smaller?

 

[winston1]

Electrician is putting in some new circuits, he pointed out that my existing ring circuit is not a ring, and is in fact radial - so I understand what this means (i think), but how would one go about finding where the connection to the ring is broken?

On another note regarding rings, why can't you spur off a spur? Is it to do with overloading the cable as ring cables are smaller?

It is most likely broken at a socket, you'll have to check each one. Are all 3, L, N, and E broken? If so it was probably never a ring anyway.


Rings and spurs are wired in 2.5mm cable. A ring has 2 paths back to the fuse or MCB whereas a spur only has one between itself and the ring so the total load is limited.

 

[bandejapaisa]

Yes, I think I remember him saying all 3 were broken.

Well it has 2 cables for that circuit leaving the consumer unit, so does that mean it must have been a ring at some point?

How could this happen? Do I need to be that concerned? He's wired the new kitchen and bathroom sockets on new circuits.

I have about 8 sockets on the old circuit, half of them never used - the ones in use run a TV setup (temporarily), computer, hoover and any mobiles charging etc.

I'm currently crawling around under the floor mapping out the cables - feel like i'm doing this the hard way. Although maybe I'll find something interesting down here, other than spiders and dust.

 

[Taylortwocities]

What value MCB is on that circuit? If it is 32amp then, under fault or over load conditions, it will allow too much current to go over those cables and the cables could overheat=fire etc….

I would want to find out where the break is and fix it, there may be bare wires dangling, somewhere.,

If the MCB is 32amp then the quick and dirty way is to change it to 20amp , but I'd still want to know where the break lis.

 

[AndyPRK]

As said if its a 32a MCB then it's a problem.
I'd be concerned when under the floor as there could be a bare live cable.

The easy way is to disconnect one live cable from the MCB.
You should then find some sockets work and some don't.

Near where the sockets stop working is the break.

As all conductors are open circuit it doesn't sound like a loose connection or easy fix. Therefore fitting a 20a MCB sounds like a practical solution for you.

 

[SimonH2]

Well it has 2 cables for that circuit leaving the consumer unit, so does that mean it must have been a ring at some point?

No, it could have always been two radial circuits.
But as said, the size of the supply fuse or MCB is key.

As said, if it's a 32A MCB then it "should" have been a ring*. If it was 20A (or possibly 25A) then it's likely that both were always radials.

* At work I took some wiring out of our server room when I rebuilt it and sorted out the electrics. There were 4x FCU ("fused spurs") and 2 cables leaving the board with a 32A MCB. I found that the 4 FCUs were a radial and one of the cables supplied an FCU for the alarm.
We were running a steady "not much shy of 30A" through that radial - and the cable was "fairly warm"
All installed by a qualified sparky

 

[EFLImpudence]

There were 4x FCU ("fused spurs") and 2 cables leaving the board with a 32A MCB. I found that the 4 FCUs were a radial and one of the cables supplied an FCU for the alarm.

Could you please reword that?

I am confused.

 

[bandejapaisa]

What value MCB is on that circuit? If it is 32amp then, under fault or over load conditions, it will allow too much current to go over those cables and the cables could overheat=fire etc….

I would want to find out where the break is and fix it, there may be bare wires dangling, somewhere.,

If the MCB is 32amp then the quick and dirty way is to change it to 20amp , but I'd still want to know where the break lis.

It was a 32 MCB when the electrician found it, now I remember him saying something similar and for safety he swapped it onto 16amp.

I've already mapped out a lot of the sockets after being under the floors - it aint so bad, I've got about 3 foot height down there (old edwardian house).

I'm gonna find the break...!

Thanks for the help.

 

[bandejapaisa]

The easy way is to disconnect one live cable from the MCB.
You should then find some sockets work and some don't.

Near where the sockets stop working is the break.
.

Good idea, thanks.

What I've mapped of the current wiring so far already looks a bit ropey, whoever did it .... I've already found 2 spurred sockets already on a spur.

 

[SimonH2]

There were 4x FCU ("fused spurs") and 2 cables leaving the board with a 32A MCB. I found that the 4 FCUs were a radial and one of the cables supplied an FCU for the alarm.

Could you please reword that?

I am confused.

There were 4 FCUs.
There were two 2.5mm T&Es leaving a B32 in the board.
Logical expectation - either an RFC or 2x radials with 2 FCUs on each.

What I found was one radial with 4x FCUs on it, and we were pulling around 30A between them. The other T&E fed the alarm panel.

 

[EFLImpudence]

Ah. Thank you.

 

[DaftPunk]

Rings and spurs are wired in 2.5mm cable. A ring has 2 paths back to the fuse or MCB whereas a spur only has one between itself and the ring so the total load is limited.

Wrong again whinny boy. When are you going to stop making a fool of your self on here?

 

[ericmark]

There are odd times when having split a ring into two radials that the limits are then exceeded with volt drop and loop impedance but in the main two 20A radials instead of a single 32A ring final is no worse than the ring and can be better.

You say the electrician fitted a 16A MCB likely as all he had and clearly makes it safer.

Also one would like to know were broken in case that means there are loose wires. However all three broken would look more like an alteration than simply a wire popped out of a terminal.

With assess to consumer unit or once twin MCB's have been fitted by energising just one leg at a time you should be able to work out which sockets are on each branch an electrician using a loop impedance meter can even work out quite quickly which socket is at the end of the branch so he can quickly say the break is between this socket and this socket.

Without a loop impedance meter harder to work out which socket is end of line what we are looking at is the increase in volt drop as we get near the end of that radial.

A simple plug in energy meter and a good fixed load say a kettle would do the same job as the electricians loop impedance meter. Simply note voltage with kettle off and with kettle on and record the difference for each socket. The socket with greatest difference is the one at end of line. However not quite so easy if both radials are powered together but should be able to isolate at least one of the end of line sockets.

Once you know area to break then its down to looking for likely scenario. Any added door way? Or other work which could have caused the break. And clearly inspect end socket.

You may of course have more than one end socket any spurs from the radial will also be an end socket.

Next door is also a likely help. Have they got any sockets which you haven't and are they some where that would not be possible in your house for example you don't have the wall it's mounted on.

Kitchen fitters were in the past rather poor in their treatment of electrics. When they fitted a kitchen instead of doing a proper job of moving sockets they would fit the new sockets on work tops etc and run loose cables to old sockets hidden behind the units.

In my house the builder clearly expected the fridge to be positioned next to the door and provided a high socket clearly to supply fridge sockets like this can get in the way not unknown for kitchen fitters to remove them.

If you think that the break is not causing a danger then using two MCB's one for each leg it is unlikely you will ever have a problem. I have swapped many a 32A MCB for 20A without it ever tripping.

In the main where some one has mistaken an old 7/0.036 cable of a 32A radial for 7/0.029 of an old ring and have tried to extend the ring with modern 2.5mm² but it was never a ring to start with.

Which of course is a point to consider it may be there were two 4mm² radials from the same 32A MCB it may have never been a ring to start with. We all tend to jump into the conclusion it's a broken ring because it had a 32A MCB but with 4mm² cable one can use that size MCB for a radial.

With 2.5mm², 4mm², 6mm² plus 3/0.036, 7/0.029 and 7/0.036 cables unless printed on the cables it can be very hard to identify which you are looking at. Specially since the sheave also changes size so the imperial always looks bigger than the metric equivalent. Likely the best option is to assume all is 2.5mm² as that is the smallest.

I wish you luck as often it is down to luck finding what has happened. I remember doing a second fix on a house and finding the ring incomplete and I found a socket box with tails ready for socket to be fitted behind the plaster board where the plaster had failed to put a hole in plaster. This was back in the 1990's when we were more lax about testing at it would have been easy for this to have been missed. Hence why good to look at next door if living on an estate of similar houses.

 

[ban-all-sheds]

Err....

At work I took some wiring out of our server room when I rebuilt it and sorted out the electrics. I'm not a professional spark... Just a keen amateur.

Are you and you employer familiar with your duties and responsibilities in the Electricity At Work Regulations, and with the terms & conditions in the tenancy agreement and all the insurances?

 

[ban-all-sheds]

Rings and spurs are wired in 2.5mm cable. A ring has 2 paths back to the fuse or MCB whereas a spur only has one between itself and the ring so the total load is limited.

Wrong again whinny boy. When are you going to stop making a fool of your self on here?

Can you be more specific on what you think is wrong?