High R1 R2 reading

[EddieB]

Guys, was changing a consumer unit today in a 1970s house, twin and earth for the power seemed to be the old 7036 with a 1mm earth, maybe 1.5 but it didn't look it and it was solid which suprised me as i would have expected stranded as the live and neutral were.Anyway when i did the R1 reading it was 2.2 ohms live and Neutral were .65 respectivley. I expected to get a high R1 reading as there were only 2 rings the Kitchen and the rest of the house, the kitchen was a later addition so no problems, but 2.2 ohms seems high. I traced out every leg and found no issues but the readings between sockets were reasonable but added together came to 2.2 ohms. Has anybody else had issues like this, this is the first time I've had it in excess of 1 ohm

 

[Guest123]

What were the r1, r2 and rn values???

 

[EddieB]

Hi Lenny
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[EddieB]

Hi Lenny I quoted the R1in the previous mail value i meant of course the R2 value that was 2.2 ohms. To begin again the readings were R1 was .65 Rn was .65 and R2 was 2.2

 

[Guest123]

Ok I get you now.

For a 2.5/1.5mm T+E if the value of r1 was 0.65, the r2 value would 1.67 x that = 1.08.

For a 2.5.1.0mm T+E the value of r2 would be 0.65 x 2.5 = 1.62.



Your value is higher than this so maybe there's a bad connection at a socket outlet or maybe the probe connections were a bit slack at the time of test, could be any number of reasons.

Be worth a quick check of the outlets on that circuit for soundness/corrosion.

 

[EddieB]

Hi Lenny re-tested and went through the sockets again now reads 1.90ohms, the cpc conductor is a very soft copper that was a favourite for a while with the cable manufactures back in the day, didn't last long due to the fact that you could tighten right through the conducto, a bit like the alluminium they introduced at the same time, I wonder if the resitiivity of that particular copper was different to the resitivity of the copper we use today. Straw clutching time methinks