2.5mm Radial Doing All the Sockets

[nlbhoy]

I was called in to a recently finished house extension as the heating wasn't working, plus they needed
the alterations tested for building control.

There was a kitchen extension to the back of the house plus a 2 store extension to the side which was an office downstairs, plus 2 bedrooms and a bathroom upstairs.

The previous spark has done a runner.

When testing the board there were 2x 32a breakers, one being the kitchen and utility ring which is all fine,
when I've carried out test on what appeared to be the second ring I've found that this is actually a radial, one of the legs appeared to be doing nothing, while the other 2.5mm is supplying 25 double sockets, over 4 upstairs bedrooms, downstairs office, lounge and dining room.

This is obviously a substantial area, there isn't likely to be anything power hungry used in these sockets, as it's TV's, computers with the odd hairdryer and vacuum being used.

Would fitting a 20a mcb be acceptable? so a 2.5mm radial on 20a mcb.

I'm a little concerned about the size of the area this is covering.

I'm not sure if this has been like this before the previous electrician had added on to the existing circuits,
or if he's split the ring main in some way were only one leg is now doing pretty much the full house.

Any help/guidance on what best to do here would be great.

 

[Lucien Nunes]

I agree that 20A might not be adequate, but possibly more immediately worrying would be the leg that doesn't seem to be doing anything. It could well be an unfinished RFC with two live cable ends lying under the floor for a socket that was never installed, or a cable completely severed during interior fitout. I would not commit to any particular solution until I had found the dead end(s).

 

[nlbhoy]

I agree that 20A might not be adequate, but possibly more immediately worrying would be the leg that doesn't seem to be doing anything. It could well be an unfinished RFC with two live cable ends lying under the floor for a socket that was never installed, or a cable completely severed during interior fitout. I would not commit to any particular solution until I had found the dead end(s).

I have disconnected this from the DB and had a look to see if anything wasn't working, everything seems to be fine.

I'm back tomorrow so I can have a better look.

 

[Lucien Nunes]

That's my point. A sensible person would have installed an RFC, you have the right number of cables and the right MCB for an RFC, and everything works. The only thing missing is ring continuity...

 

[Flanders]

Have you done a as test on the circiut at its end point to make sure a 20amp Will disconect in time under fault conditions, I no the rcd should cover that but not ideal but as said you nead to make sure it's a radial and not a broken ring

 

[Pete999]

Had a few glasses of vino, so you have 2 32Amp CBs 1 of which covers a 32Amp RFC and the other supposedly covers a RadialFC wired in 2,5mm but with 2 x2.5s connected at the CB.

If that is the case the you have what could be a substantial problem, as someone else mentioned you may have 2x live end floating around somewhere, under the floor, in the ceiling void, buried behind some plaster board or plaster, does the owner know where he/she wanted any sockets but can't find them, maybe hidden behind a chair or cabinet somewhere.

Your best bet would be to start from scratch identifying cables as you go, it shouldn't be that hard to locate the break, the difficult part will be fixing it, go back to basics that's usually the best option, good luck, now where's me glass?

 

[ruston]

Just to add, as you are concerned, On a 20 amp protective device, historically the area is limited to 50m2.
Appendix 15

 

[Paul.M]

Unless I'm reading this wrong, he has 2 x 2.5mm at the CU that should be a RFC. One of them is feeding 25 sockets and the other leg (which has now been disconnected and rightfully so) can not be traced at this moment in time? So no live cable/s are hidden under floor boards/walls etc seen has he discounted the unknown leg.... Sounds safe atm but a bit of time is needed to locate and rectify, hopefully making this back into a RFC?????

 

[Flanders]

Unless I'm reading this wrong, he has 2 x 2.5mm at the CU that should be a RFC. One of them is feeding 25 sockets and the other leg (which has now been disconnected and rightfully so) can not be traced at this moment in time? So no live cable/s are hidden under floor boards/walls etc seen has he discounted the unknown leg.... Sounds safe atm but a bit of time is needed to locate and rectify, hopefully making this back into a RFC?????

He has disconnected 1 Leg at the board but if it's a broken ring there will be another end somewhere so still need to find it unless there is a socket with just one cable in it , but there still could be other joints , as said more investigation required to prove what is what

 

[Paul.M]

When testing the board there were 2x 32a breakers, one being the kitchen and utility ring which is all fine,

One RFC on a 32A mcb tested and noted.

when I've carried out test on what appeared to be the second ring I've found that this is actually a radial, one of the legs appeared to be doing nothing, while the other 2.5mm is supplying 25 double sockets, over 4 upstairs bedrooms, downstairs office, lounge and dining room.

Sounds like a broken RFC?

He then goes on to say:-

I have disconnected this from the DB and had a look to see if anything wasn't working, everything seems to be fine.

I'm back tomorrow so I can have a better look.

To me it sounds like one leg is feeding 25 sockets and the other leg has been disconnect at the CU so only the possibility of one live cable? Now he needs to find the last socket on the radial to locate the possibility of a disconnected live. Simple and quick fault find for the OP.

Take a Zs at every socket, make a note of each reading and at which socket. The highest reading should be the end (unless spurred off like a spider circuit....very possible?). Take a look at the highest 3 sockets and "bell them out". If that does not work, you have 25 sockets to bell out and find the missing cable...... Good luck

 

[mattg4321]

Or find the socket that the spreads have buried.

Any drawings available? Is there a socket not present that appears on the drawing? Possibly near the CU by your description.

 

[Adam W]

Would it cause too much disruption to run a new leg back to the board?

 

[Paul.M]

Would it cause too much disruption to run a new leg back to the board?

He has to find it first. Thats the fun part

 

[nlbhoy]

Would it cause too much disruption to run a new leg back to the board?

Hopefully it doesn't come to that as it would cause a lot of problems.

 

[nlbhoy]

One RFC on a 32A mcb tested and noted.



Sounds like a broken RFC?

He then goes on to say:-




To me it sounds like one leg is feeding 25 sockets and the other leg has been disconnect at the CU so only the possibility of one live cable? Now he needs to find the last socket on the radial to locate the possibility of a disconnected live. Simple and quick fault find for the OP.

Take a Zs at every socket, make a note of each reading and at which socket. The highest reading should be the end (unless spurred off like a spider circuit....very possible?). Take a look at the highest 3 sockets and "bell them out". If that does not work, you have 25 sockets to bell out and find the missing cable...... Good luck

Yeah, that's pretty much it.

I'll do a Zs at sockets and report back tomorrow.

There were a couple of walls taken down to open up for new extension, I'd imagine if there were sockets on any of these walls that the spark would have likely broken in to the RFC at tone of those points.