Identifying csa of t&e

[zap]

Greetings.
I tested an rfc and recorded the following results:
r1 = 0.62
rN = 0.89
r2 = 1.45
The difference in r1 and rN indicate loose connections so I checked all the sockets (bar one) on the ring which revealed two loose connections.
The rfc now tests as follows:
r1 = 0.58
rN = 0.59
r2 = 1.45
The measurements indicate a 80 metre circuit of 2.5mm^2 csa.
I've checked every socket in the dwelling except one which feeds a waterbed and is inaccessible. So I told the customer that I have some homework to do before I can issue certification.
BUT, I hadn't realised that it could be 2.5/1 t&e in which case the measurement of 1.45 (remaining constant) is correct.
I don't have a micrometer to measure the cpc so how do I confirm the cable conductor's csa? ... and if it's 1mm^2 cpc is that okay?

The wiring is about 25 - 30 years old.

 

[R G]

what you could try is connect L to E on one side of the ring and leave the other open at the board, check the R1 R2 readings at the sockets nearest then move further along until you notice any major jump , if its a gradual increase on all then o/k ,

 

[Octopus]

those readings look like 2.5mm/1.0mm dating from late 70's to early 80's

 

[shanky887614]

what you could try is connect L to E on one side of the ring and leave the other open at the board, check the R1 R2 readings at the sockets nearest then move further along until you notice any major jump , if its a gradual increase on all then o/k ,

to make this quicker, wire a plug with a bit of flex from it going to connector strip.

this makes it quick to a quick check without removing fronts (very useful if there if there is a dead short somewhere)

or if you have a multimeter etc with non gs38 leads just shove them in the socket

 

[zap]

Thanks, R G,
The route the cable takes is not obvious but I sort of did what you're suggesting with expected results.
If the cpc is 1mm^2 is it acceptable (i.e. compliant with BS767)?

 

[shanky887614]

Thanks, R G,
The route the cable takes is not obvious but I sort of did what you're suggesting with expected results.
If the cpc is 1mm^2 is it acceptable (i.e. compliant with BS767)?

as long as earthloop is acceptable at furthest point its fine

 

[R G]

I would compare a bit of new cable with the old , for the earth wire size , if you have test leads to a plug then you won't need to remove the socket fronts ...

If you have done this then as shanky says if Zs is good at end of circuit then its o/k

 

[zap]

those readings look like 2.5mm/1.0mm dating from late 70's to early 80's

Thanks Murdock, that's what I suspect. But is it satisfactory?

 

[zap]

I would compare a bit of new cable with the old , for the earth wire size , if you have test leads to a socket then you won't need to remove the socket fronts ...

Thanks again R G,
I started to doubt myself and stopped thinking clearly.

Is it satisfactory to have a 1mm cpc on a rfc protected by a 32A type b breaker?

 

[R G]

Thanks again R G,
I started to doubt myself and stopped thinking clearly.

Is it satisfactory to have a 1mm cpc on a rfc protected by a 32A type b breaker?

No problem if Zs is good and RCD protected whats the problem

 

[zap]

Thanks shanky, this appears to have answered my question.

I've lost the 'thanks' button. Can anyone elucidate?

 

[Octopus]

Thanks Murdock, that's what I suspect. But is it satisfactory?

What were your test results?

 

[shanky887614]

Thanks shanky, this appears to have answered my question.

I've lost the 'thanks' button. Can anyone elucidate?

can you click on like/thanks on the posts?

it shows people who the long standing members are that help people out

 

[zap]

can you click on like/thanks on the posts?

it shows people who the long standing members are that help people out

Apparently, yes, and thanks again.

 

[zap]

What were your test results?

Preliminary result was too high i.e. 1.45 Ohms. But two loose connections have been rectified since so I'm returning to retest and this time I expect satisfactory results.

Thanks again for helping me understand.