Help - Problems with R2 CPC readings on Ring Main

[Stu Too]

Hi.

Just tested a home, which has three ring mains. All are 2.5mm rings with CPCs of 1.5

Both Ring 1 and Ring 2 gave normal figures for R1 and R2 however, ring 3 has a very low reading for r2 cpc.

Ring 3.

Step 1 - r1 0.56 , rn 0.61 and r2 of 0.40

Step 3 - I Checked all the sockets and had readings of betwen 0.25 and 0.28

I was expecting around 1.00 for r2 on Step 1. which would have made the readings in 3 around 0.40 (ish).

I have checked the 8 sockets that coem off it and cannot see any issues. Any thoughts on why I am getting this low reading at the CU when running continuity between E1 and E2 and when running the E1 to L2 and E2 to L1 I am getting what I should expect, based on the low cpc. so at least that matches up!!

Any help appreciated!

Thanks

 

[Darkwood]

Sometimes readings of this nature can be found due to parallel earth paths thus reduce resistance readings, say you taken a boiler supply of the ring and the boiler has its supplimentary bonding as well as the water and gas been bonded at origin, this is just an example but shows the many paths the earth may return to the board thus reduced r2 reading, as long as you have ring continuity and no other reading abnormalities then i wouldnt scratch your head too long.

Hope this helps.

 

[Stu Too]

Darkwood - You are THE man (well for today anyway!)

No longer scratching my head. Forgot the spur that was running the boiler - which is connected to the main bonding probably not more than a metre or two away from it!

Thanks for that.

 

[Amp David]

I had an extension that was added onto the ring, but they had connected all the earths into the back of the socket together.

So when testing out, the r2 reading was only being read as the original house ring.