Head Scratcher Time.

[telectrix]

this is baffling.
situation is an existing rfc that has had a minor repair. a socket had been removed and the live cables left in back box and tiled over. cables were pulled back above ceiling and jointed.

prior to reconnectio in a new CU tests were done on the circuit.

now here's the baffling bit:

r1 = 0.28
rN =0.28
r2 = 0.47

fine so far, expected R1+R2 = (0.28 + 0.47) /4 = 0.1875

measured R1+R2 = 0.17 . perfeck.

then, here's the rub....

Rn + R2 = open circuit, tested at 2 points on the ring.

both R1 + R2 and Rn + R2 measured with the respective ends cross connected @ CU.

it's as if the N's are continuous but loose in the sockets but sockets were working fine before.

tester plug lead checked as OK by plugging in a socket on another circuit and live readings were normal.

as i said, a head scratcher.

 

[Pete999]

this is baffling.
situation is an existing rfc that has had a minor repair. a socket had been removed and the live cables left in back box and tiled over. cables were pulled back above ceiling and jointed.

prior to reconnectio in a new CU tests were done on the circuit.

now here's the baffling bit:

r1 = 0.28
rN =0.28
r2 = 0.47

fine so far, expected R1+R2 = (0.28 + 0.47) /4 = 0.1875

measured R1+R2 = 0.17 . perfeck.

then, here's the rub....

Rn + R2 = open circuit, tested at 2 points on the ring.

both R1 + R2 and Rn + R2 measured with the respective ends cross connected @ CU.

it's as if the N's are continuous but loose in the sockets but sockets were working fine before.

tester plug lead checked as OK by plugging in a socket on another circuit and live readings were normal.

as i said, a head scratcher.

Can you get access to the joint you mentioned?

 

[ImpededLoop]

Figure of eight ring? The "ring" nearest the cu is sound, the rn in the other part of the figure of eight is incomplete. Try measuring r1, rn, r2 from behind the sockets where you're getting odd results.

 

[Richard Burns]

You only have to have neutrals twisted together and then put loosely in the terminal for the connection to be somewhat variable, I would usually expect high resistance rather than open circuit though, especially as the sockets were working.
However any small movement of cables such as when they were brought out of the wall may have affected nearby sockets.

 

[telectrix]

You only have to have neutrals twisted together and then put loosely in the terminal for the connection to be somewhat variable, I would usually expect high resistance rather than open circuit though, especially as the sockets were working.
However any small movement of cables such as when they were brought out of the wall may have affected nearby sockets.

thought of that, so just for a laugh, tried Rn+R2 with a 500V IR test. came back with 500Meg.

 

[ImpededLoop]

Did you test by using the plugtop lead on your tester? Could be plugtop and socket don't quite make contact as well as whatever appliance is normally plugged in there. Have you tested from the back of the offending sockets?

 

[telectrix]

this was a problem that another member had me look at. time was limited as it was 4.00pm yesterday and after sorting out the fault on another job ( see new Ring circuit tripping RCD thread), was gasping for a beer and 25 miles back home.

 

[Richard Burns]

Either the customer went round unscrewing sockets whilst the CU was being put in place or the cables have been mixed up and you are measuring the neutrals with the cpc of another circuit.

 

[telectrix]

Can you get access to the joint you mentioned?

can do pete, but that's the next thing for Simon to check. i was only there to give him a second opinion and some pointersas to how to proceed. end of the day, we don't usually test N-E continuity. it's just someting he picked up on when trying to get his head round testing.

 

[ruston]

I go with Richard on this one , loose connection in the back of a socket .
In the test from back of the sockets camp.

 

[telectrix]

that's what i have told Simon to do. seems like the N connection is not being seen by plug in . strange though it's same at original (1980's ) sockets and also at new added ones.

 

[ruston]

And 80's wiring had loads of twisted connections.

 

[telectrix]

Either the customer went round unscrewing sockets whilst the CU was being put in place or the cables have been mixed up and you are measuring the neutrals with the cpc of another circuit.

no customer. flat is empty, undergoing refurb. apart from the o/c Rn+R2. all other dead tests are perfect.

 

[telectrix]

And 80's wiring had loads of twisted connections.

yes. 7/029 cables. usually twisted in terminals.

 

[Midwest]

You wanna be careful Tel, some members might suggest (not me) that your out of your depth, and should get someone in who knows what they're doing

I just say that 'cos it just shows, none of us are connoisseurs of the lecky art, and how useful this forum is.