Locating fault in a house full of craft junk?

[ericmark]

The house has two ring finals, the original and second one which was added latter, both from different consumer units and different RCD's the original wiring also included an immersion heater, that is now a radial, plus one socket on the cooker.

House has been empty for 18 months and my wife has been busy rearranging rooms, the result is the room over the garage where the two CU's are is crammed full of junk, (she would not call it junk) so the closest sockets to the consumer unit are not accessible.

She was using the kettle in kitchen when the ring final failed, also builder outside doing pointing, and cables run from new thorough the cavity wall, so when cavity wall insulation was put in, I insisted that section of garage wall was missed.

It would seem the RCD tripped, it has done this on and off for years, it tripped once in last 18 months and since not in house lost contains of one freezer.

Normal procedure, switch off all MCB's switch RCD back on, then switch on the MCB's again, however the old ring final did not power up, all but one of the original sockets were dead. My thoughts were likely two faults, one likely been there for years, tested ring and neutrals and earth still show as being a ring.

The one socket still working turns out to be a spur, the consumer unit looks A1 like the day it was installed all wires pass the tug test for poor connection, swapped the MCB just in case so not that and not found in any socket where an original spur has been taken.

House built around 1980 so then people did fit the old round junction boxes under floor boards, but don't recall every seeing one.

So trying to think of ways to locate where the problem is. All accessible sockets removed and checked, already moved loads of furniture to access the one socket still working, only to find it is a spur. At least sure the MCB is OK. Considering methods to find out route, next job is find the low ohm meter. Thinking measuring ohms earth to neutral should show order sockets connected, but any ideas welcome. Other than get a new wife who does not fill house with craft junk.

 

[PrenticeBoyofDerry]

I like the new wife idea.

 

[PrenticeBoyofDerry]

If you know the layout of the circuit. I would split ring at board and test as a radial, ideally find highest continuity reading at socket outlets, then split there again and work back towards board, hopefully given only one leg to concentrate on.

 

[bernardgreen]

I like the new wife idea

As long as she removes the junk that wife one collected.....

On a serious note. Driving a high DC current round the ring final Neutral and using a millivolt meter to measure voltage Neutral to Earth ( Earth linked to one side of the DC current source as a reference ) or using a flying lead from one side of the DC current source as the reference will enable you to locate where on the ring the sockets are. Sockets with the same N to reference voltage will be spurs.

I have used a 5 amp constant current source for this using 12 volt car battery as the power source.

 

[securespark]

So you have neutral and earth continuity round the ring but no continuity on the line?

If, as you suspect, you have a long-standing break in L continuity, with another happening recently, that means you should have two healthy legs leaving the board, there's nothing for it but to trace that break.

You need to tell wife number 1 to clear the stuff so you have access to wiring, otherwise you will be without power for a long time!

I presume the kettle socket is sound?

 

[securespark]

also builder outside doing pointing

 

[JohnW2]

Normal procedure, switch off all MCB's switch RCD back on, then switch on the MCB's again, however the old ring final did not power up, all but one of the original sockets were dead. .... The one socket still working turns out to be a spur ....

Interesting!

Are you certain that it's a spur off the 'dead' ring? If so, that seems very odd, since one would then expect at least one of the ring sockets (the 'spurred' one) to be working. For both legs of the ring to become disconnected from a socket but for at least one of them to remain connected to a spur cable would seem very improbable. Similarly, if the spur originated from a JB, it would seem very improbable that a JB could remain powered when all of the sockets on the ring were dead!

.... tested ring and neutrals and earth still show as being a ring.

Are you saying the L, N and CPC all show end-to-end continuity at the CU? If that is the case, it would seem almost inconceivable that at least the first and/or last sockets on the ring would not be working. Off the top of my head, the only possible explanation I can think of is that, after leaving the CU, both legs of the ring hit JBs before any sockets AND that both those JBs had somehow become disconnected from the sockets AND a connection between the two JBs had arisen - but that would surely be 'beyond belief'?!

I look forward to hearing how the investigation evolves!

Kind Regards, John

 

[securespark]

expect at least one of the ring sockets (the 'spurred' one) to be working. For both legs of the ring to become disconnected from a socket but for at least one of them to remain connected to a spur cable would seem very improbable. Similarly, if the spur originated from a JB, it would seem very improbable that a JB could remain powered when all of the sockets on the ring were dead!

The spur comes from the board?

 

[securespark]

As I see it, there could have been an historic break in the ring.

Now another one has occurred so cutting off the line.

The spur is live as it is fed from the ring's breaker.

There are still two live ring legs leaving the board.

ERIC - if you are saying the spur is the only socket on that circuit that is live, then both breaks must be at the sockets where the legs going back to the board terminate.

Could one of the first sockets be in the garage?

 

[JohnW2]

The spur comes from the board?

I thought of thatpossibility, but since eric says that he has changed the MCB, he would surely have noticed if there were three cables connected to it?

Kind Regards, John

 

[securespark]

He hasn't said there wasn't three connected.....

Hold on - ERIC?? Are there three conductors at the board??

 

[securespark]

I haven't heard back yet...

 

[JohnW2]

ERIC - if you are saying the spur is the only socket on that circuit that is live, then both breaks must be at the sockets where the legs going back to the board terminate.

As I said, that would require that both first and last sockets were disconnected, but with ring continuity still through them (very unlikely) and, as I've just said, it also seems very unlikley that eric will have changed the MCB without noticing a spur originating from there.

Kind Regards, John

 

[securespark]

As I said, that would require that both first and last sockets were disconnected, but with ring continuity still through them (very unlikely)

Can you explain this for me, bearing in mind I am a bear of very little brain...

 

[JohnW2]

He hasn't said there wasn't three connected.....

He hasn't - but he's no fool, so would surely have realised the possible significance of finding three cables there.

However, as I keep saying what is more difficult to understand is how there can be two (assuming just two!) live cables leaving the MCB, with continuity all around the ring (which is what we appear to have been told), but with absolutely no ring sockets live. Doesn't one has to postulate not just two faults, but umpteen faults for that to be the case?

Kind Regards, John