call out to ring main fault

[e-spark]

Called out to rental property i carried out an EICR on in March; this year to look at loss of power.
Narrowed it down to the down stairs ring main, done end to ends and ring in tact, insulation resistance failed, dropped every socket and inspected the wiring and socket fronts which 2 i had to replace.
Split the ring and worked on each leg and found it to be the return leg from the last socket; checked the EICR test results and it was over 200m ohm then; tenant swears there's been no DIY taken place but bar a rodent eating the cable or physical damage i.e a screw or nail im at a bit loss to how its gone from 200m ohm to failure.
Ended up downgrading the MCB to B16 and informing the LL the sockets need rewired asap as the leg on the B16 is on 2m ohm, genuinely think he thinks im trying to rob him!
anyone similar experiences?

 

[DPG]

Would 2M Ohm trip the RCD though?

PS, not being picky but use upper case M to avoid confusion, unless you do mean milliohms.

 

[Mike Johnson]

tenant swears there's been no DIY taken place

Dr House had it right "everybody lies"

 

[e-spark]

no that is the connected leg 2 M ohm, the disconnected leg at the CU and last socket has the complete failure on.

 

[DPG]

no that is the connected leg 2 M ohm, the disconnected leg at the CU and last socket has the complete failure on.

That seems odd then. If the ring last time was 200M, and now both legs are significantly lower. Two faults? Or 2 bits of DIY

 

[e-spark]

advised they get rewired and a SPD fitted for good measure.

 

[Pretty Mouth]

Called out to rental property i carried out an EICR on in March; this year to look at loss of power.
Narrowed it down to the down stairs ring main, done end to ends and ring in tact, insulation resistance failed, dropped every socket and inspected the wiring and socket fronts which 2 i had to replace.
Split the ring and worked on each leg and found it to be the return leg from the last socket; checked the EICR test results and it was over 200m ohm then; tenant swears there's been no DIY taken place but bar a rodent eating the cable or physical damage i.e a screw or nail im at a bit loss to how its gone from 200m ohm to failure.
Ended up downgrading the MCB to B16 and informing the LL the sockets need rewired asap as the leg on the B16 is on 2m ohm, genuinely think he thinks im trying to rob him!
anyone similar experiences?

Many times. A near-fault can sit there for years before it decides to become an actual fault.

An interesting example is one I visited a couple of weeks ago. The kitchen ring final was tripping, both the MCB and the RCD. Sometimes sporadically, sometimes every time the circuit was energised. The actual fault was due to 4 cables being forced into a 25mm steel backbox housing a FCU for the cooker hood. Eventually one of the line conductors had become damaged and was arcing to the top lug of the backbox.

Interesting because it hadn't been worked on for years, but also because at no point during my testing did I get a low IR reading L+N to E. With both MCB and RCD tripping with a noisy 'pop' on energising, you'd expect a dead short L to E, but I was getting >60M Ohms at 500V. Very strange.

BTW, 2 M ohm isn't that low, and is IME a common result for when equipment is still plugged in

 

[littlespark]

Socket face suddenly failed?

I had that a couple years ago at Xmas eve for a neighbour… individual legs between sockets were fine, but as I replaced the fronts, IR on L-E dropped like a stone.
Suspect splashed liquid as faulty socket was in kitchen.

WAGOed through joint, faulty socket as makeshift blank plate until wholesalers were open again to get a replacement.