R1+R2 unusual reading

solavie · Nov 4, 2012

I was asked to add 3 extra sockets to a bedroom. It is a one ring supplying upstairs and downstairs with no RCD. Kitchen has a different ring.

When doing R1+R2 with cross joining Live & cpc at cu, I get a reading of 0.23 ohm upstairs and it keeps rising to 1.01 ohm downstairs.

Same problem with R1+Rn, I get 0.16 to 0.89 ohm

I measure r1 as .28, rn as 0.26 and r2 as 0.40

Insulation resistance is >299 on all .

Ze is 0.24 ohm on TNS

Planning to put an RCBO on the circuit.

Advise appreciated.

Amp David · Nov 4, 2012

All upstairs is 0.23?

Downstairs could be a series of spur off spurs or a second ring tagged onto the upstairs ring

derek preece · Nov 4, 2012

Have you definately identified each leg of the ring final and cross connected them correctly, if they are gradually rising from socket to socket as you go around the ring then it may be that you haven't, or it could be spurs as mentioned already?

malcolmsanford · Nov 4, 2012

As David says, also are the sockets where your testing old/cheap ?

Engineer54 · Nov 4, 2012

Not that it would make that much of a difference, but it was once common practice, where a single ring circuit covered both up and downstairs, to wire the upstairs sockets as a ring and spur of the upstairs sockets to the downstairs sockets. Saved a hell of a lot of cable. ...lol!!! The clue being 3 X cables at the upstairs socket positions. Alternatively the downstairs sockets could have been spurred off the ring cable via JB's....

solavie · Nov 4, 2012

Yes, I have Definitely cross the wires as I could see the grey PVC cable coming into the CU. I will be going back there and will try the wires differently.

There is only one 2 wires going up from consumer unit. There is also a ring for kitchen and a ring for garage where the cu is situated. There is an extension on the ground floor (conservatory where I got the highest R1+R2.

The sockets are old and the wires has been crossed together before going into the sockets. Still that is quite a big difference. I have removed quite a few sockets and tighten the wires on some I had a few good turns.

i changing the wires round does not help, I guess it will be a job of disconnecting all the sockets to try to identify if there is any crossed circuit.

Cheers