HappyHippyDad

-
Esteemed
Arms
Supporter
I rather foolishly booked in a fault finding job in a 2 hour slot thinking I could solve it quickly, I couldn't!

It has me confused, although I haven't let myself slow down yet and focus so you guys may point out something obvious.

It is an intermittent tripping MCB on a 32A ring ciruit (sometimes the RCD trips) on a dual RCD board. It trips a number of times each day. This has been going on for perhaps a week. Over the last 2 days 5 sockets have actually stopped working completely even with the power on. The ring feeds the whole house.

r1 = 0.14 Mohm (140,000 ohms)
r2 = 28K ohms (28,000 ohms)
rn = 0.7 ohms

With all sockets connected and the ring split in the CU I get :

Leg 1 = L/N - E 0.01Mohms
Leg 2 = I didn't write down the results but they were >1Mohm.

When I split the ring at one socket the IR results were all >1Mohm when tested in the CU, I didn't test at the split socket.

I think I'm getting confused because of the 5 non working sockets. If a ring is broken (as this is) all sockets should still work. Am I right in thinking there HAS to be 2 faults either side of those non working sockets (assuming they are not all spurred from the same socket) or am I missing something?

Usually, in order to find the break I would split the ring. Reconnect the leg that has continuity with the relevant leg in the CU liven them up and eliminate the working ones, but if there are 2 breaks this wont work, i don't think!

Update... the customer has literally just rang saying he removed a socket and just plastered in the cables a while ago and when he bangs that part of the wall it trips! However, this would be just one fault and would still not stop 5 sockets from working!! o_O :disappointed::anguished::tired:
 
Last edited:
Update....

I returned this morning at 8am. It turns out the customer hadn't hidden a socket in the wall, they had removed a TV wall bracket and plastered over. I cut a hole in the wall (stud wall) where the bracket had been and found this..

Above socket.jpg close up.jpg

I fixed the above which cleared the poor IR results and got the 5 non working sockets working, I then started fault finding the broken ring. I'd already quizzed the customer a number of times about any thing they'd done or anything out of the ordinary. 30 mins into the fault finding they remembered they'd had a spark off a redundant fused spur. I opened it up and found a disconnected line and cpc. Connected them up and the ring tested as intact.

Then.... I tested the RCD (as at the beginning it was not tripping when tested which I thought may be due to the fault(s) as this sometimes stops the RCD from working) with all outgoing terminals disconnected (thanks again DS). It was faulty. I put a new one in, all tested fine!

3 major faults! Bloody ell, never had that before. I am now having a half day off so I can sit contentedly with a superior grin on my face whilst sipping my coffee and telling you all about it ?:D
 
Result. There's nothing better than using skill and strategy to solve a problem that started out so obtuse that it was difficult even to describe to begin with.
 
Best EV Chargers by Electrical2Go! The official electric vehicle charger supplier.

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

Advert

YOUR Unread Posts

Daily, weekly or monthly email

Thread starter

HappyHippyDad

Esteemed
Arms
Supporter
-
Joined
Location
Gloucestershire
If you're a qualified, trainee, or retired electrician - Which country is it that your work will be / is / was aimed at?
United Kingdom
What type of forum member are you?
Practising Electrician (Qualified - Domestic or Commercial etc)

Thread Information

Title
This fault has me confused!
Prefix
N/A
Forum
UK Electrical Forum
Start date
Last reply date
Replies
23
Unsolved
--

Advert

Thread statistics

Created
HappyHippyDad,
Last reply from
Gary latto,
Replies
23
Views
2,726

Advert

Back
Top