Slightly high r2

[Wattsy]

Hi all,

Altering a ring in an old house rewired about 6 years ago. Got the lounge ceiling down so replaced all the ring and used maintenance free JBs. Connected all the ends together and done end to end tests etc today before i replace the ceiling and got the following results:

r1 = 0.59ohms

rn = 0.59ohms

r2 = 1.17ohms

I was expecting r2 = 0.98ohms

I've had a quick look and cant see anything obvious could be a JB under another section of floor i suppose.

What would be the limits for what would be deemed acceptable and should it be recorded on the MWC under the limitations on the insp and test section even though theres no section for r1, rn and r2?

Sorry its long winded

 

[Theorysparky]

did you test r2 before you started alterations ?

I take it you have not replaced all the ring ??

so you cant confirm that the earth has not been repaired or knicked ??

ir test shows it ok ????

poor connection to the rear of a socket ????

 

[kme]

Also possible that some of the existing cable is 2.5/1.0 rather than 2.5/1.5

KME

 

[Wattsy]

Centre section of the ring had been removed by a previous "electrician" because of a damaged cable in the wall i believe, spliting the ring in two! Wires were just terminated in two of the sockets!

So i wasn't able to r2 test.

No i havent replaced it all theres a lot thats inaccessable under upstairs floor.

Insulation resistance L+N to E was 125Mohms theres a booster in the loft.

I did think about there being 2.5/1mm t&e in there somewhere.

If i check all my connections etc and its all fine would those reading be acceptable as i dont think the customer will want all the carpet up and floor boards lifted in their bedrooms and like i said there is no space on the MWC for r1 rn r2?

 

[Theorysparky]

it is what it is record the fact it is a bit high

what zs did you get at your furthest socket ?????

 

[Wattsy]

I haven't done the Zs tests yet just joined the cables together to make sure i've got cont before putting the ceiling up and hiding the JBs. All the walls need plastering yet.

Done R1 + R2 though which was 0.39ohms. which is what i would have been expecting if r2 reading was correct in relation to r1 ie 1.67 times higher

r1 0.59 x 1.67 = r2 0.98ohms

r1 0.59 + r2 0.98 / 4 = 0.39ohms

but my r2 measurement was 1.17ohms

Strange

 

[sparkytim]

Not enough to worry about mate

Things are never THAT perfect in the real world, if you wan't to check and tighten up every CPC connection you MAY improve it, or maybe its a 1mm CPC.

 

[ianmacd]

Agreed. Just record them as listed above. As long as you are within limits for Zs and you have ring continuity then there is no real issue.

If it had been a completly new circuit I would be more concerned but on an existing circuit these things happen in the real world.

 

[batty]

Should not have problems on a six year old circuit and certainly should not have any 1.0mm cpc.

 

[Wattsy]

Thanks for you help guys.

Just guessing that the cu is about 6 years old but the house is almost 200 years old so its been chopped and changed around quite a bit.

 

[tom1]

got results here of a ring with both 1mm and 1.5 mm cpc

L 0.39

N 0.4

E 0.77

 

[Wattsy]

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