Can you calculate ring final conductors if you have a measured R1 + R2?

[bcwright]

Hello there everyone, I've dead tested some ring mains on a job recently but unfortunately I didn't do my measured end to ends. The circuits only have two spurs on each.

I have my R1 + R2's, it was wired in 4mm T and E so the earth is obviously 1.5mm.

For example, if one circuit measured 0.33 ohms, is there a calculation to work out r1, rn and r2.

Many thanks in advance.

 

[Paul.M]

Cringing when doing this but.... thread approved. Be nice to him, it's almost Xmas.

 

[Octopus]

Hum... be nice.

How can you dead test a RFC and NOT do the end to end readings?

EDIT: Its not as if the end to end isn't important!

 

[Paul.M]

Only did half the tests on one circuit and trying to work out the rest of the RFC's?????? May be???? Possibly????

 

[happysteve]

Being kind...

If - and this is a big if - you have:

- all the readings (R1+R2) from all sockets on the RFC (not just the highest) and
- knowledge of the lengths and cross sectional area of cable between all sockets (and back to the DB)

... then you can, for most circumstances, be pretty confident of r1 and r2, and will be able to confirm from your calculations whether the ring is continuous or not. (unless there are two faults that cause equal and opposite effects).

However, knowing R1+R2, there is no way on earth you can give a value for rn. And if the neutral is not continuous, this is a dangerous fault.

 

[Guest77]

Hello there everyone, I've dead tested some ring mains on a job recently but unfortunately I didn't do my measured end to ends. The circuits only have two spurs on each.

I have my R1 + R2's, it was wired in 4mm T and E so the earth is obviously 1.5mm.

For example, if one circuit measured 0.33 ohms, is there a calculation to work out r1, rn and r2.

Many thanks in advance.

Word of advice, ask a mod to close this thread.

 

[Paul.M]

Word of advice, ask a mod to close this thread.

I'm in the shadows

 

[Andy78]

Hello there everyone, I've dead tested some ring mains on a job recently but unfortunately I didn't do my measured end to ends. The circuits only have two spurs on each.

I have my R1 + R2's, it was wired in 4mm T and E so the earth is obviously 1.5mm.

For example, if one circuit measured 0.33 ohms, is there a calculation to work out r1, rn and r2.

Many thanks in advance.

What's fortune got to do with it ? Apart from ... unfortunately you'll have to return to the job and do it properly.

 

[Paul.M]

@ the OP. Go back and carry out the full test procedures.

I'm closing this thread now. Any questions please PM the Staff or myself directly.