Earth continuity

[happysteve]

Any supplementary bonding in place? That would do it. (Parallel paths, as other have said.)

 

[polo1]

Is there a central heating supply fed from the RFC? If so, try disconnecting the cpc at the fused connection unit and retest.

 

[rattlehead85]

Firstly you'll be lucky to ever reach the exact line-c.p.c. ratio on rings especially in big houses with lots of sockets. Usually these sort if readings would be caused by parallel earth paths such as bonding or conduit wiring containment earthed back at source or throughout the circuit.
As you say you have no conduit i would definitely put it done more to an earth bond or sups through heating system or bathroom.
The fact you have equal line and neutral readings suggests that this is more likely the case. Your main concerns really should be to ensure your circuit Zs readings comply, you have adequate fault and additional protection in place and your IR readings are of an acceptable value. Most sparks who do testing these days fudge ring continuity readings coz they can't be assed to go fault finding when a problem does show itself especially when it happens in occupied properties full of gear and inaccessible outlets behind furniture etc etc. Poor really!

 

[nicsin02]

If the circuits are disconnected from db and there's nothing plugged in what could the parallel paths be?

 

[rattlehead85]

Well think about it for a minute....do you have anything on the ring running through the bathroom i.e spur for heater, towel rail, fan without over run, shower pump..... all which may have sup bonding connected especially if an installation to previous 16th norm.
Or you could have the good ol' "useless cross bonding" under a boiler run back into a spur next to it. These would all cause unexpected low cpc end-end continuity results below the value of your L & N readings.

 

[nicsin02]

Well think about it for a minute....do you have anything on the ring running through the bathroom i.e spur for heater, towel rail, fan without over run, shower pump..... all which may have sup bonding connected especially if an installation to previous 16th norm.
Or you could have the good ol' "useless cross bonding" under a boiler run back into a spur next to it. These would all cause unexpected low cpc end-end continuity results below the value of your L & N readings.

there is none of the above, this is a brand new house and the circuit is just a ring circuit with nothing added, no cross bonds,

 

[richy3333]

Then it must be non BASEC. approved cable?

 

[Guest77]

Really. 2 conductors of the same size having matching poor terminations to give identical readings...... so say both incorrect, based purely on the fact that cpc end to end is lower than expected value. Lottery odds that one. Obviously parallel earth paths.

Yes really, if the readings were done at the board with all conductors disconnected at the time of testing which is perfectly possible then how would parallel paths come into it? if he tested around the ring with conductors still connected in the board then yes I agree very very likely parallel paths, there is more ways to kill a pig than just stabbing it.

 

[polo1]

Yes really, if the readings were done at the board with all conductors disconnected at the time of testing which is perfectly possible then how would parallel paths come into it? if he tested around the ring with conductors still connected in the board then yes I agree very very likely parallel paths, there is more ways to kill a pig than just stabbing it.

See my earlier post. If the heating is a gas boiler and fed from the RFC, and the gas supply is bonded, this may be the parallel path?

 

[telectrix]

See my earlier post. If the heating is a gas boiler and fed from the RFC, and the gas supply is bonded, this may be the parallel path?

even so, it c an't provide a parallel path if the RFC conductors are all dissed from the CU.

 

[nicsin02]

even so, it c an't provide a parallel path if the RFC conductors are all dissed from the CU.

It's definitely not connected to heating or that just a simple ring circuit, could it be cheap cable? Or I noticed the earths were twisted fully at each socket??

 

[Midwest]

Hi there this is been happening in a few houses now I've been testing and im
a little confused, when testing my ring continuity my earth hasn't been the standard 1.67x bigger than live and neutral when using twin and earth 2.5 cable, what causes this? ...........today my neural and lives were 0.8ohms but my earth was only 0.6ohms which is well short ....

Are you sure that the L-L & N-N are correct. A figure of 0.8ohms (2.5mm) suggest a cable length of over 100m? Whereas 0.6ohms (1.5mm) suggest a cable length of 50m. Just a thought.

 

[telectrix]

possibvly not nulled meter and leads for the L-L and N-N??????

 

[nicsin02]

The leads get zero' before every test I do, it's possible the L and N could be wrong but I thought it would be unlikely for both to have the exact same slack resistance?? Out of curiousity what is the formula for calculating length of run? Cheers

 

[Midwest]

Out of curiousity what is the formula for calculating length of run? Cheers

Errr.....cough, got mine out of a book. 100m of cable, is quite a large RFC? Can you assess you RFC length and then compare to your test results?