Issue with r2 reading on ring final circuit due to parallel paths

[Tom256]

Did you test any of the wiring at the first fix stage?

 

[Des 56]

Just read the thread, left wondering what is the problem ?

 

[brianmoooore]

Is there any requirement for the cpc of a RFC to be a 'ring' at all? A RFC in metal conduit, with the conduit being used as the cpc. A RFC in plastic conduit, with a single cpc (of adequate cross section) serving things other than sockets in the conduit system, with spurs to the individual sockets.

 

[Geo9073]

Just read the thread, left wondering what is the problem ?

My end to end readings for r2 are lower than the r1 end to end readings. (r1- 0.39 and r2 - 0.17) As it’s been wired in twin and earth my r2 should 1.67x bigger (r2 - 0.65). This is due to the parallel paths of steel conduit fixed on to metal caddy straps and metal stud frames. Usually you would disconnect the fly leads from the back boxes so you can get an accurate r2 reading. But due to flats being signed off and finished I’m restricted on doing that, so I’m wondering if the low r2 reading (0.17) is acceptable to write down. This will also give a much lower R1+R2 reading as a result.

 

[Tom256]

Is there any requirement for the cpc of a RFC to be a 'ring' at all? A RFC in metal conduit, with the conduit being used as the cpc. A RFC in plastic conduit, with a single cpc (of adequate cross section) serving things other than sockets in the conduit system, with spurs to the individual sockets.

No requirement to confirm on a ring.
I had a situation on a recent EICR to which I made a nore in the report that read:

'As such the r1 / rn readings of the circuit must be made at the origin of the circuit as defined by the point of supply - Regulation 643.2.1 (ii) only requires continuity of live conductors on a ring final circuit to be confirmed'

We all know that one test does not a satisfactory result make.
That this is an E.I.C. as such I would have considered asking about the testing after first fix and if this installation was energised before the required testing was completed.

 

[westward10]

I would say no as the r2 you are recording is not correct. There is a possibility r2 is open circuit but the parallel paths are masking this.

 

[Tom256]

Did you test any of the wiring at the first fix stage?

Not saying this is the case here yet something seen often is the cabling / installation is not being inspected and tested during the course of the installation. Regulation 641.1

The person named on the EIC as the inspector should not be waiting until after 2nd fix to start testing as such there should be test results from these cables on this ring after 1st fix.
Was the installation powered up before testing?
Have the cables been subjected to a 500 volt insulation test? Is this insulation test [always] possible after 2nd fix without removing outlets [as requested not to do here]?

EDIT: Typo's

 

[paul-bristol]

you are asking about a compleation certificate so will need to disconnect all the fly leads and leave the fronts off to test, if it were an PIR i would just not there are parrelle earth paths but the readings were satisfactory but for a compleation thats no an option you must confirm it is correct.

 

[Pretty Mouth]

Is there any requirement for the cpc of a RFC to be a 'ring' at all? A RFC in metal conduit, with the conduit being used as the cpc. A RFC in plastic conduit, with a single cpc (of adequate cross section) serving things other than sockets in the conduit system, with spurs to the individual sockets.

Often, but not always:

543.2.9
Except where the circuit protective conductor is formed by a metal covering or enclosure containing
all of the conductors of the ring, the circuit protective conductor of every ring final circuit shall also be run in the
form of a ring having both ends connected to the earthing terminal at the origin of the circuit.