Open neutral advice please

[Dray]

Hi all.
I'm having an Issue with a family members board.
They have had either the breaker for a ring or the RCD trip on numerous occasions, and I have already replaced a socket where the neutrals connections were burned out on said ring.
So I went to run a few tests to see if I could find the problem. I don't have much experience in the way of testing or fault finding as there has always been someone else on site that does that, but I need to pull my finger out and crack on with getting to grips with it.
I started by finding out what was running off that ring....20 double sockets...two under floor heating systems and the heating/hot water for the house. three of those double sockets were single point spurs, and then spurred off the heating...two lighting points.
I ran an end to end at the DB and got a reading for live and earth but nothing on neutral ( so open neutral.....somewhere??) I have removed every socket and switched fuse spur that is on that circuit and all looks good, no screws through the insulation...nothing. so I know something about connecting only one side of the ring back into the breaker (making safe the other ends) and then testing at each socket around the house....but this is where I am a bit lost. I need a clarification as to what I am looking for and maybe a bit of why. I left the installation with the ring ends removed from the board and a temp supply from a working ring to feed the heating and hot water, but I want to nail this one asap thanks in advance people ....Dray

 

[chris gray]

In essence you create s radial

 

[Octopus]

You need to find the 2 points between which there is no continuity ..... that should be relatively easy ....

 

[Richard Burns]

Switch off the supply, disconnect the cables for the ring from the board, test for dead.
Try and determine your best estimate of the likely run of cable around the accessories.
Connect a wander lead to one of the neutral legs, connect the other end of the wander lead through your low resistance ohmmeter and then on to the neutral terminal of a socket adaptor, test continuity from what you would expect the first socket in the ring would be and if you get a low reading then continue outward from that socket to the further sockets until you get no continuity. At that point the disconnected neutral is either at that socket or the run of cable back to the previous socket.
You can also test round the ring the other way with the other neutral leg to confirm the disconnection.
Then start physical investigation coupled with continuity testing to determine the exact point of the fault.
Obviously FCUs and so on will limit your instant testing but they can generally be ignored until the likely fault area is known.

 

[Dray]

Thank you Mr Burns

 

[gazdkw82]

Wonder lead from one if the neutrals

 

[Deleted member 9648]

A broken rn would possibly explain why you had burnt out neutrals on a socket as the current in the neutral would be increased relative to the line. However it is unlikely that a broken rn alone will cause mcb or rcd tripping, thorough insulation resistance testing is required.