Obtaining R2 value on RFC

[Zdb]

If for whatever reason you can't do an R1+R2 test on a ring final circuit (unable to identify opposite legs). There's also an option on the paperwork for the R2 value...

Am I correct in thinking that you do an end to end test on the CPC's which would give you r2, then just divide it by 4 to give you R2?

 

[Ian1981]

If for whatever reason you can't do an R1+R2 test on a ring final circuit (unable to identify opposite legs). There's also an option on the paperwork for the R2 value...

Am I correct in thinking that you do an end to end test on the CPC's which would give you r2, then just divide it by 4 to give you R2?

Yes but what about your continuity tests end to ends on the ring final?
If it's periodic testing then just take the zs at each socket.
If it's initial verification then continuity needs to be established/verified so R1+R2 shouldn't be an issue.

 

[Pete999]

no because you will not have cross connected and tested the RFC correctly, why the difficulty in identifying the RFC legs?

 

[Zdb]

It's just a minor works (socket replacement).

 

[Ian1981]

It's just a minor works (socket replacement).

Just test zs and just to ease your mind do continuity check at the socket your replacing end to end of conductors, unless it's a spur.

 

[Zdb]

I did continuity of L, N & E at the D.B. I just didn't want to leave a box blank.

 

[Ian1981]

I did continuity of L, N & E at the D.B. I just didn't want to leave a box blank.

So how come you can do R1+R2 if you've already done end to end readings on the live and cpc especially?

 

[Zdb]

Yeah you're right I'm being stupid again aren't I

 

[Ian1981]

Yeah you're right I'm being stupid again aren't I

Haha long week?

 

[Zdb]

It's not even over yet lol

 

[westward10]

Not till the fat person squeals.

 

[Ian1981]

Edit But yeah doing end to end on live and cpcs added and divide by 4 should give you total value of R1+R2 as you have 2 middles which can be considered the end of the circuit if it was a radial and 2 conductors in parallel

 

[Zdb]

Thanks for the replies.

Always appreciated

 

[davesparks]

Following on from the above question consider a situation where you can't readily disconnect the cpc at any point to test it, or doing so is rendered largely pointless by the installation method.

I'm thinking of a circuit wired in SWA, MICC or steel conduit/trunking.

 

[Ian1981]

Thanks for the replies.

Always appreciated

Your total R2 resistance you mentioned earlier would be your end to end continuity of the cpcs you'd have measured

 

[Pete999]

Your total R2 resistance you mentioned earlier would be your end to end continuity of the cpcs you'd have measured

If it was a Radial circuit

 

[Pete999]

Your total R2 resistance you mentioned earlier would be your end to end continuity of the cpcs you'd have measured

If it was a Radial circuit sorry don't know what happened there posted twice

 

[Ian1981]

Following on from the above question consider a situation where you can't readily disconnect the cpc at any point to test it, or doing so is rendered largely pointless by the installation method.

I'm thinking of a circuit wired in SWA, MICC or steel conduit/trunking.

Yes R1+R2 really only works in an all insulated wiring system I guess.
Method 2 is usually used for conduit systems

 

[Ian1981]

Is it now a ring final pete?

 

[Pete999]

Is it now a ring final pete?

So R1 =r1 and R2=r2, R1+R2 =r1+r2 ? is that what you are saying Ian, and cross connecting is out of the window?

 

[Zdb]

So on a RFC I would divide the end to end of the CPCs by 4 to get R2?

 

[Ian1981]

So R1 =r1 and R2=r2, R1+R2 =r1+r2 ? is that what you are saying Ian, and cross connecting is out of the window?

No I meant you posted twice mentioning a radial so I said now is it a ring?
Just jesting pete

 

[Pete999]

No I meant you posted twice mentioning a radial so I said now is it a ring?
Just jesting pete

Sorry Ian had a hard day, ran out of vino, visitors all afternoon we didn't want, then JWs arrived trying to preach to me.

 

[davesparks]

So on a RFC I would divide the end to end of the CPCs by 4 to get R2?

why do you think it is, can you back it up with a bit of science or is it guesswork?
With questions like this you'll understand it better if you logically think through and work out the answer first, then ask the forum to confirm it or otherwise

 

[Ian1981]

So on a RFC I would divide the end to end of the CPCs by 4 to get R2?

Remember we have a divider of 4 because we have in effect to mid points furthest points and 2 cables /conductors in parallel

 

[Octopus]

Why even bother with a cert for an accessory change?

Zs test , note value on invoice.

Tin hat and 3d glasses on

 

[Deleted member 93172]

When we do ring main testing and find that all the earths are twisted together in the consumer unit, usually with no sleeving, and you can't identify the pairs going out of the board. We remove and disconnect a socket and split all cables, define the cables coming in and going out, you can then carry out the proper testing procedures on the ring at the this point.