Please Help ! Ring fault finding

[Joe Hyde]

Practicing for my 2395 C&G on a friends house
tester KT63 6 month old
he has 3 ring finals for sockets in his house, reason he asked me if I would test his house is that his RCD keep tripping out overnight ( once a week )
1st Ring final Circuit is fine
Circuit 2 has given me some results I don't understand, I wondered if anyone could shed any light
Firstly may I say RCD Test Trips at 1/2 in both directions, *1 and *5 are both under 40ms. Unless MCB for circuit 2 is Off , then RCD passes all tests !
( Changed RCD for a new one and same results)

Results so Far for circuit 2
Continuity
L-L 0.89 Ohms
N-N 0.89 Ohms
cpc-cpc 1.23 Ohms

also tested cpc to Earth bar and got continuity of 0.9 Ohms

another off the cuff test showed continuity between Both L of the ring to another Ring circuit he has ( Circuit 3 ) his upstairs sockets reading was 228 Ohms
No continuity between N of circuit 2 and Neutral Bar.

I split the N on the ring and tested Long Lead each N back to the CU
One way was 1.01 Ohms the other was 900 Ohms

Fig 8 testing I did not get round to doing yet as his wife came home and wanted the electric back on !!!

I managed to do a quick IR test before wife came home ( lots of neons so I did LN to cpc ) everything unplugged on the circuit and I got a reading of 0.08 M Ohms !!!

Any Ideas would be most welcome ,

Thank you

 

[bartkusal]

Practicing for my 2395 C&G on a friends house
tester KT63 6 month old
he has 3 ring finals for sockets in his house, reason he asked me if I would test his house is that his RCD keep tripping out overnight ( once a week ) Most probably has to do something with of peak economy 7 heating system
1st Ring final Circuit is fine
Circuit 2 has given me some results I don't understand, I wondered if anyone could shed any light
Firstly may I say RCD Test Trips at 1/2 in both directions, ( it shouldnt trip, I have a feeling you have acumulative earth leakage on that same heating system,with existing leakage and you introdusing 15ma, you going over the limit of that RCD) *1 and *5 are both under 40ms. Unless MCB for circuit 2 is Off , then RCD passes all tests !
( Changed RCD for a new one and same results)

Results so Far for circuit 2
Continuity
L-L 0.89 Ohms
N-N 0.89 Ohms
cpc-cpc 1.23 Ohms

also tested cpc to Earth bar and got continuity of 0.9 Ohms

another off the cuff test showed continuity between Both L of the ring to another Ring circuit he has ( Circuit 3 ) his upstairs sockets reading was 228 Ohms
No continuity between N of circuit 2 and Neutral Bar.

I split the N on the ring and tested Long Lead each N back to the CU
One way was 1.01 Ohms the other was 900 Ohms

Fig 8 testing I did not get round to doing yet as his wife came home and wanted the electric back on !!!

I managed to do a quick IR test before wife came home ( lots of neons so I did LN to cpc ) everything unplugged on the circuit and I got a reading of 0.08 M Ohms !!!(obviously no good, investigate with proper testing)

Any Ideas would be most welcome ,

Thank you

My bet is on, L to E or N to E short on economy 7 heating circuit.
Best regards: Al

 

[MDJ]

.

 

[Clive P]

Hi,

On initial reading of your post I am thinking you have an interconnection between Ring 2 & 3. If my calculations are right you have a ring of 120mtrs. If you have continuity back to the Earth Bar from the Cpc's of Circuit 2 then this needs investigation, also with the IR results you have on Circuit 2; was this with the appliances isolated just on circuit 2 , or Circuit 2 & 3 ? The readings you obtained on the the RCD are satisfactory except for the X 1/2, but you say this tests OK with circuit 2 switched off, more cause for concern.
I would certainly be looking at isolating Rings 2 & 3 and carrying out further tests to determine what you have there, hope this all makes sense,

Regards.

 

[Joe Hyde]

Hi,

On initial reading of your post I am thinking you have an interconnection between Ring 2 & 3. If my calculations are right you have a ring of 120mtrs. If you have continuity back to the Earth Bar from the Cpc's of Circuit 2 then this needs investigation, also with the IR results you have on Circuit 2; was this with the appliances isolated just on circuit 2 , or Circuit 2 & 3 ? The readings you obtained on the the RCD are satisfactory except for the X 1/2, but you say this tests OK with circuit 2 switched off, more cause for concern.
I would certainly be looking at isolating Rings 2 & 3 and carrying out further tests to determine what you have there, hope this all makes sense,

Regards.

All makes sense , thanks ! IR only had circuit 2 isolated, ( but I thought the LN to Cpc test would negate plugged in items ) ? I am only learning so please correct me if im wrong !
The house has had many alterations and extensions , I guess these have not been done correctly !
Isolation of circuit 2 on its own does De-energise all identified sockets on this ring ( Kitchen Socket ring ) I have not started testing on Circuit 3 yet ( Upstairs sockets including extension added a few years back ) I would have thought a full interconnection would leave circuit 2 energised when off if circuit 3 was still on ? )

Thanks alos to the other reply I had however there is no economy 7 Heating system installed.
I am agreeing about an earth leakage somewhere, I have inspected all socket outlets & junction boxes on the ring and all correctly wired.

Mainly worried about the IR of the kitchen sockets as they are all metal front plates ! ( Hopefully this has been caused by something plugged in on an unfound socket maybe in the upstairs extension )

Thanks for helping
Joe

 

[Clive P]

Hi,

My thoughts as to the cross connection was coming from the Cpc to Earth Bar reading (although this could possibly be a connection to Earth from the ring to Water or Gas pipework ) and the spurious connection between the two rings. Like I say further testing will no doubt sort this out.

Regards.