Sockets ring, Mains water leak, Rodents???

[alexmc123]

Perhaps someone can help?
Last week we were watching TV and the RCD for the downstairs ring clicked off. We clicked it back on and finished the program. Then afterwards it did it again whilst using the PC. So we decided to hit the sack.
Just before heading up we noticed some blistered gloss paint on a pillar in the living room. Investigation showed that the water main just before the stopcock (Typically) was leaking and beginning to spray. So I began disassembling the kitchen units for access and we called a plumber who came and sorted the leak. It was obvious that the leak had been going at a small rate for some time.
There were cables associated with the downstairs ring coming up of the floor here and there around the leak, but they seemed normal and undamaged.
We left it until the next day as it was now 2am!

Next day the downstairs ring RCD, a 32a one with the test button wouldn't stay on permamently, but would stay on for seemingly random lengths of time, from a few seconds to an hour, and irrespective of load upon it too!
It would click off within 3 seconds with nothing plugged in or loading it at all, to an hour with lots of stuff on, dishwashers going, kettles boiling etc?
I replaced the RCD for elimination purposes....... still exactly the same.

I spent some time trying to pin it down to an area, or an appliance or electrical device, but it seems totally random. I have thought I have heard the ocassional electrical 'pop' noise when switching the RCD on, but cannot honestly be sure about that one?

Two things have been mentioned to me, an intermittant neutral fault, and rodent damage.
It's difficult to get under the floor, so I cannot see if there have been any places in the wiring where water might ingress, or if the insulation has been gnawed, we did have a problem with mice though last year.

The problem seems to be limited completely to the downstairs socket ring, how might I go about testing for the fault?

Many thanks in advance.

Alex

 

[ricicle]

You will need a combination of a thorough examination and an insulation resistance test.

 

[alexmc123]

The thing is, it will be very difficult to get below the floor, so it would be helpful to try and pin down as accurately as is possible where the fault lays.

Would it be a sensible in that case to remove every socket on the downstairs ring, seperate the wiring to break it into shorter runs and do an insulation test on each segment?

 

[Chri5]

Breaking the circuit down after an overall ir test is sensible. I'd just disconnect wire and include the sockets in the ir test sequences.

 

[alexmc123]

The other problem is that we're trying to sell the house, have it under offer, so are in a bit of a position in trying to rectify the fault and not leave it behind, yet not get involved in any major works and expense! We are glad that the mains leak didn't occur very shortly after the new people moved in, as that would leave sour taste for them having just bought the house. Were we staying I wouldn't mind the extended work if it needed it.
In the short term we need to get it sorted, properly and safely.... but quickly and cheaply! I know those terms don't often go together very often!

The problem is the solid wood flooring laid last year throughout the ground floor! Were it still the old edwardian floorboards I have them up and be crawling about under the house before you know it!
I was thinking if it could be identified which run of cable has the problem, then I would replace it and channel in the cable behind the skirting perhaps? It would be an easier fix.

 

[Chri5]

Find the problem by splitting up the circuit and doing ir and wandering lead continuity testing.

If you can confine it to a run of cable between sockets you could split the circuit (minus the faulty cable) and have 2x 20 amp radials via changing the original mcb and adding in another for the 2nd cable / radial.

Routing cable behind skirt is a fail due to being outside cable safe zone.

You would also need to make sure the radials at 20 amp are able to cope with the existing loads.

 

[alexmc123]

Thanks for the info, it is all very helpful.
I have realised that I do have one area that I can possibly access the beneath floor space. Unfortunately it's a whole room away in the space under the stairs! I will have a look at it tonight to see if it's doable? I'm pretty slim so although it'll be mucky and horrible, I may be able to visually inspect all the cabling if I'm lucky!

 

[Chri5]

Might need a wet suit and scuba gear...

Seriously, get someone in to test it and confirm what the problem is, then if it's straight forward you can fix- or better still let them do it and ask for a condition report on the circuit as CYA for the purchasers legal.

 

[viewer]

Before diving into the underfloor-pulling up cables bit have a good visual and look inside the sockets and other "boxes" (fans, FCUs, lights etc). Also check inside any plugs which might have been exposed to the plumbing problems.Check fuses, connection points and holders because a wet area between fuse contacts or between socket cable connectors could have caused an initial short, but the effect would be to set down a conductive metal or carbon track on the surface
Your description of randomish trips and the flood is suggestive of a tracking fault. There is a high resistance short due to wet material. You may be able to see the culprit as there may be a blackish trace.
It could be a coincidence and rats have eaten the cable, but the two events and the symptoms suggest a direct link.
Best of luck.

 

[alexmc123]

There is a friendly electrician who lives very nearby. He's a good guy, but he's always very busy and works long hours, so I don't want to trouble him needlessly. He's tried to find a bit of time over the weekend but he often works it and has a family as well! He will come and test the insulation but I'd like to eliminate the simpler stuff first.

I'm well aware how grotty it's going to be under the floor! It's an Edwardian house so there's well over a hundred years of dust, earth, creepy crawlies and water down there!

I have checked about half the sockets so far, and they seem dry and normal. Another quarter are well way from the leak but I will check them anyway, the remaining quarter are behind appliances/cupboards etc. so will need a bit of work to get to.

 

[17thman]

you will may have a honeycombe wall between the access and the area you need to look into.

there could be a saturated junction box lying on the subloor. With a torch, directed through the honeycombe you might search for it.

If there is blistering on the plaster through a wall into another room, this leak has been ongoing for a while. Water has migrated up into the brickwork and plaster and could have dripped down from the plaster/brickwork into the knockouts and therefore into the internal areas of the terminal housings within the socket outlets. Try changing these.

Normal rules apply, make sure power is isolated.

 

[alexmc123]

An update:

The electrician came round last night.... good guy that he is!
We tested the circuit as a whole first, and then broke it at a socket, and chased the 'bad' section down and down, until we only had two outlets left with the 'bad' in the middle of it.

We ran out of time last night, but today I will replace all the sockets back except that 'bad section, and we'll test those two radial lines and hopefully confirm they are good.
That being the case it looks possible to run a new cable to replace the bad section under the floor. I could not gain access where I thought yesterday(under the stairs) as there simply wasn't room.

The bad section is under the floor of the kitchen, pretty close to the wet, and certainly within range of the plastic-hungry mice!

 

[alexmc123]

Well it turned out to be Rodent damage after all!

The ring turned out to not be very ring shaped in the end. In tracing back the known bad cable to see how it connected the only two remaining bad sockets, I discovered a section of it that ran in some trunking in the pantry, and then dived under the floor in the corner. And lo and behold, there was a 4 inch section with all the insulation nibbled off and a lock of blackening where it had been arcing!
The cable run still seemed very convoluted so a quick vist from my Friendly electrician and it got crimped and chocolate boxed and we're back to normal now with everything testing out okay!

So it would seem unrelated to the wet from the leak, as it was quite a way away and dry as a bone. But! Often these things seem to have some coincidence nonetheless? Perhaps the Mice backed away from the damp and suddenly felt hungry for a bit of plastic?

Anyway, job done now!

Thanks everyone for your help and advice!

 

[londonboy]

Thanks for posting the outcome.