interconnections on ring how to carry on

[domn]

at a job today i tested the ring to make sure we can extend it phase .31 neutral .34 and earth .24 r1 plus r2 at ..13 so that checks out ive checked for interconnections and think its going to be at jboxes under the floor (it's a bit of a diy house )
whats the way forward as customer doesn't want floors lifting etc can i just note on cert that the readings are not what they should be but still safe etc
i also found a bit of 1mm connected into the back of the cooker switch cpc snipped off ran to a metal cooker hood pushed through a drilled hole and quite frayed not the best

 

[GLENNSPARK]

so you`v got an r1 of .31...an rn of.34 and an r2 of .24?...well, theres something wrong then there straightaway...

 

[VoltzElectrical]

really? Why?

 

[domn]

i know that its wrong ive checked the ring for interconnections and it looks like its been done in jboxes under the floor the customer doesn't want the floor lifted to find (sorry just read what i posted i ment that the r1 r2 test confirmed the readings from the end to end test) really just asking about recording and carrying on

 

[onfire25]

With an r1/rn of .31/.32 i would be looking for a r2 of around .51?!.......something not quite right there

 

[SPARTYKUS]

Yes but it usually a high r2 thats a problem.

Ok its not the expected reading, there's some form of parallel path thing going on, you didn't install it, the reading(s) are BETTER than could be hoped for. Whats der problem

 

[domn]

i know its better than expected i was just a bit unsure if i would have to make a note on it because its not what was expected if you know what i mean

 

[GLENNSPARK]

Yes but it usually a high r2 thats a problem.

Ok its not the expected reading, there's some form of parallel path thing going on, you didn't install it, the reading(s) are BETTER than could be hoped for. Whats der problem

the problem is....theres a high resistance on both r1 and rn.....

 

[dagrat]

Not necessarily, the R2 resistance is usually higher granted, however this is an existing installation and there are probably other parallel earth paths. If the R2 was higher than x 1.67 then further investigation would be required

 

[SPARTYKUS]

Good point glennspark !!

Hmmm....

 

[Billynm]

And we havn't even mentioned the 1mm in the back of the cooker switch yet !!!

 

[GLENNSPARK]

i know its better than expected i was just a bit unsure if i would have to make a note on it because its not what was expected if you know what i mean

r2 is not necessarily `better than expected` at all.....it may be the correct value....
r1 and rn however...

 

[rodney12]

way forward - change to a 16A or 20A mcb

 

[domn]

r2 is not necessarily `better than expected` at all.....it may be the correct value....
r1 and rn however...

but as r1 and rn are about the same this points to the readings being ok and i ring on a 3 bed semi also looks about right no loose connections etc in sockets or at board. not finished job as we will be back in the morning when i will do all the tests at each socket

 

[i=p/u]

Look ok to me, 1mm within cooker , I would want to change

 

[GLENNSPARK]

but as r1 and rn are about the same this points to the readings being ok and i ring on a 3 bed semi also looks about right no loose connections etc in sockets or at board. not finished job as we will be back in the morning when i will do all the tests at each socket

does it?..

 

[domn]

does it?..

yes i think it does to get a high reading on both which from loose bad connections that read about the same would be some bad luck don't you think

im open to suggestions though whats your thinking being them being high not the cpc being lower

 

[GLENNSPARK]

its either bad joints....
are there any singles in here?...any conny work?....

 

[GLENNSPARK]

it may be that a section of the `ring` is without a CPC...and the CPC from the sections that have it have been jointed someware...to create the illusion of a CPC throughout the whole of the ring...so...
an R1 R2 at every point served should verefy this.....

 

[domn]

it may be that a section of the `ring` is without a CPC...and the CPC from the sections that have it have been jointed someware...to create the illusion of a CPC throughout the whole of the ring...so...
an R1 R2 at every point served should verefy this.....

no its all twin t+e (what i can see ) ill be doing the r1r2 at all points tomorrow i was just starting this when the lad showed me the 1mm so i got rid of that first .
if im right on the lower cpc do i need to put this on cert ?

 

[GLENNSPARK]

no its all twin t+e (what i can see ) ill be doing the r1r2 at all points tomorrow i was just starting this when the lad showed me the 1mm so i got rid of that first .
if im right on the lower cpc do i need to put this on cert ?

what you doin here?...an EICR?...if so then just make sure it meets disconnection times....
you`v got 2 choices
you get an R1 R2 (recommended here) on every point of the ring....or you go with the end to end resistances obtained and get your points on a Zs...all of em...that would be the easier way....
summats not rite though....
if it meets disconnection times then go with it....
how old`s the install (estimated)?...
any signs of alterations/additions?
RCD`d?
just be on the lookout for stuff won`t you...as if this is giving back the values you have described then there may be other `nastys/anomalies` lurkin....

 

[dagrat]

Both the R1 and Rn readings equate to just under 50m in length and the R1+ R2 is appropriate to these readings. It's the R2 reading that is lower than expected, but this is very common on existing installations. Unless I'm missing something

 

[SPARTYKUS]

Here's an idea- discon. all the other cpc's and check r2 again?

Its almost as if there's a section of the ring with a 10mm bond to a pipe & another bond to the same pipe from another point in the ring

 

[Guest55]

its threads like these that remind me why i favour radials these days.
lifes too short to waste it on endless continuity tests lol.
;-)

 

[Badged01]

Sounds like old wiring in a property that has been subject to DIYing. On the face of it the Live and Neutral seem OK but do an R1/R2 to confirm as Glen says that you have a continous earth path. If you do have an earth path Id be tempted to open up each socket and look at the wiring configuration ---time consuming I know. You've got a parallel earth path in there somewhere reducing the value. If there arent any obvious additional wires then it may be as Sparty says, you have a path somewhere junctioned off the CPC thats lowering the resistance. Be interesting to know if you eventually track down the root cause to the CPC or something on the live/neutral!!

And Biff your right ....... a lot of continuity testing & checking eating up valuable time!!

 

[dagrat]

I think the of has already carried out a R1+R2 test and it concurs with the end to end readings. Really can't see the problem

 

[SPARTYKUS]

Should bring out a new bit in regs, every socket radial with a dedicated run of 6mm