On Wednesday, 17 July 2019 01:43:15 UTC+1, John Rumm wrote:
On 16/07/2019 23:05, Mathew Newton wrote:

Measuring the L-L and N-N resistance on a ring circuit is giving me
0.7 and 1.1 ohms respectively. Does this point towards a poor/loose
neutral connection in the back of a socket somewhere?

Quite possibly, or something else not quite right.

If so, is there
a good way to locate where through testing as opposed to removing
each socket for direct inspection?

You could go for a "binary chop" type approach. Disconnect the ends of
the ring at the CU, and short L & N & E of one end together. Now using a
plug as a test point, plug it in somewhere on the circuit near to where
you think the middle might be. [...]

Well John, it looks like it really was 'something else not quite right'! .....

I was all set to tackle this at the weekend and disconnected the ends of the ring. Measuring the L-L and N-N resistances again I found them both to be 1.1 ohms with the E-E at 1.5 ohms. Factoring in the 0.4 ohms test lead resistance gives me 0.7 ohms and 1.1 ohms respectively.

I see that copper cable is 7.41 mohms/m for 2.5mm2 and 12.1 mohms/m for the 1.5mm" CPC so with my measurements that suggests my circuit is ~90-95m long which sounds feasible for a 45m2 house footprint, a dozen or so sockets over two floors and 2.4m ceiling drops.

My conclusion is that I'd screwed up the original measurements somehow - perhaps measuring the L-L resistance of another ring or already taking off the test lead resistance; either way it seems like user error and that I don't have a problem afterall. I can't help but feel a bit disappointed as I was looking forward to finding and fixing the 'fault'!

Thanks anyway John for the suggestion and I'll bear it in mind should I ever have to do this again.