Two faults on the ring?

[Addlight]

I'd appreciate any suggestions on this one. Went to job that was "socket not working" and quickly found loose neutral - owner had installed new faceplate.

Fixed the neutral problem, however, when testing I got a very high ELZ reading at that socket - this must have been an existing problem, as CPC connection on socket was fine.

I got the very high ELZ reading at one other socket.

Started to check all sockets on ring and found a number with loose terminations. Fixed all these, and replaced a couple of sockets, but higher ELZ at the two sockets remained.

Checked at board doing dead tests and we see the lose of continuity in CPC there.

So it sounds like a CPC break or partial break between sockets - but to get a bad reading on two sockets there would have to be two separate CPC breaks? So we can't split the ring into two 20A radials - need to find the breaks.

Before we start lifting flloor boards I wondered if I'm missing something obvious here - something that someone out there can point out? I'm hoping for a Doh! moment....

 

[stef]

Does the 'figure of eight' sounds familiar? Do the connections in the db (isolate first!!!) and then
go from socket to socket. Be prpared that somebody might have hammered a nail through a cable.

 

[Addlight]

Thanks Stef - I understand figure-8 on ring, but can't see how it applies to the fault symptoms we're getting here.

I'd already isolated the db and done dead tests on the ring from there. The line and neutral are both good. Test cpc-cpc and get no continuity

If the cpc ring was interconnected with a fault, and only the two sockets showing fault were on that part of loop that might explain it.... Although the two sockets showing a fault reading a some ways away from each other ....

 

[bugsy]

Have you tried testing from the terminals on the socket? somtimes the sockets contacts get dirty and give high readings

 

[Addlight]

Thanks Bugsy - yes, we had the faceplates off those two fault sockets, and tested on the conductors - issue remains.

As I said in my original post, one break would be okay. If we couldn't find and locate it we'd have the option of splitting the ring.

What bothers me here is there appears to be two breaks, but some distance apart, as one of the faulty socket is in the kitchen, and another in a bedroom. (The rings are front and back here.)

Planning to talk it over with owner - discuss options before going back in.

I think I'll need to completely break the ring down to see if there's just one segment with the two faults. We've found plenty of faults already - installation needs a good seeing to generally.

 

[bobby101]

i think your best bet is like you said to totally disconnect the ring from the board and disconnect all face plates then do a continuity test to each part of the of the ring to verify all legs.
very time consuming but it will give you the reqired test information but by the sound of it there may a joint box under the floor spuring some other equipment so be prepared for that too good luck

 

[Des 56]

Have you tried testing from the terminals on the socket? somtimes the sockets contacts get dirty and give high readings

A good point as far as high readings are concernd and I agree with that, however,there is no continuity of the cpc s,and a loop path is there for all sockets, so maybe another problem here I suspect
I would go for a jb or some other joint being the culprit

With the sockets being far apart,I think I would split the ring at those positions, to get an idea of the run of the circuit and go from there

It doesn't seem to me to be a quick eureka moment will surface ,so if the problem doesn't surface at the accessories,at least you will have an idea of what boards you are better off lifting by knowing the routing

We all know these jobs,lots of going around in circles and the customer wondering what he's paying you for

 

[bobby101]

yes possibly more than one joint box with loose cpc connections nightmare

 

[Addlight]

I think Des has hit the nail on the head - hopefully not the same nail Stef's referring to...

Yup, customer is getting a bit 'concerned'.

Sounds like patience and step-by-step approach is the only way forward - shame about the Eureka moment!

 

[bobby101]

quick tip if you havent already thought of it isolate the ring circuit then energise the board then check the existing installation to see if i all circits are live at accesories that will quickly determine if the ring spurs anything
this is a quick way of determining the installation

 

[reefagrim]

did you do a continuity test and did you then break the test down to between the sockets themselves. if its a existing ring which you may find it was what colour ot type of wires was it white or grey i mean the old grey cable . as your aware when you do a continuity test r1 to r2 you get a nice reading do the maths you get a calc'd zs but when you do r1 to r1 and r2 to r2 the r2 reading for a 2.5 cable is 1.67 times greater due to the resistance 2.5/1.5 =1.67 but what if the reading is greater than 1.67 then are you sure its a 1.5 earth older cables had a 1mm cpc there fore would give you a higher reading in your part p book on page 38 their is a explaination and ten if i am right in thinking this is why the Zs reading high you have to also cal'c the adiabatic to assertain that the earth cable can actually take the fault current under and during a fault if not replace it ... i hope this helps

 

[SirKit Breaker]

Some really good advice given, so i wont complicate matters. If it were me, i would start at the beginning. Disconnect the ring, then see what is still working, by doing this you know exactly what is on the circuit you are having trouble with.
Then do the ring continuity tests, insulation resistance test etc as per GN3, this will highlight what is wrong, and at which outlets, and will also confirm ring continuity (or not), will show up any interconnections, spurs and spurs on spurs. Once you have got your head around exactly what the faults are, you can then put temporary cables between dodgy outlets, and isolate the area of the fault. After this though, you are into detective work, but you can make an educated guess at where the floor needs to come up etc. Good luck.

Cheers............Howard