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cwdd

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Hi all,

I recently done an EICR on a property. It had a few repairs, one of which was no RCD protection on sockets which could be used outside.

Because I had carried out insulation resistance tests etc and knew everything was clear, I opted to just replace the main switch with an RCD main switch. There was only a lighting circuit, a socket circuit, electric shower and cooker circuit.

And because I had already tested it, I just went in and pulled the main fuse (there was no seal on the main fuse, the meter or the 2 Henley blocks which the consumer unit tails were joined with the tails leaving the meter).

I fitted the RCD and it wouldn’t even turn on so I started trying to investigate, I was getting 240v going into the meter and only 110v leaving it. I checked all continuity etc and everything was fine.

Eventually after I checked everything I just disconnected the tails from the out going side of the meter completely removing the installation and the meter was still showing 110v.

Client has had an engineer from the energy supplier in now (around 6 days later) and he has said everything is fine, 240v leaving the meter, however the RCD won’t turn on. (I’m currently on holiday so can’t go down to investigate) - the property is empty for now anyway.

Has anyone ever came across this before? I’m thinking the meter has damaged the RCD now so I’m going to order a new one for me getting home. But I’ve never seen 110v coming out of a meter then suddenly rectifying itself a few days later - it doesn’t seem plausible so I’m now doubting myself. Even though I checked L-N going in and it was 240 then 110v going out with everything disconnected.

Sorry for the long winded post but I tried to provide the most information and context.

Cheers.
 
That is a new one for me,
all I can suggest is when you get back, replace the rcd with the original DP isolator.

unplug everything from socket circuit
plug in a heater or other fixed load
energise board but only socket circuit

check voltages
L-N into meter
L-N out of meter
if they don't come out at 240 ish

check voltage from (L in to meter) to (L into board) should be near to zero
by checking voltage drop by same method through the incoming circuit on both L + N you should be able to narrow down where your other 130v is escaping to!!
 
Does sound like a job for a Fluke T110 or above
with its switchable load
-for more of a load than 200K (350K-MFT) Ohms-.
Drains 30mA short term to sort out phantoms ,
and other "Electronic" Wizardry .
 
An ordinary DP RCD doesn't need to see any particular voltage before you can close its contacts. Whatever supply was or wasn't coming out of the load side of the meter, the RCD should have mechanically reset as normal. If by 'wouldn't switch on' you mean it tripped immediately while you were pushing the toggle up, there was enough of a supply for it to do its job and there is probably a fault on one of the circuits. There is nothing the meter can sensibly do to damage the RCD or prevent it resetting.

If it is a smart meter fitted with internal motorised isolator, the 110V you were measuring may have been 'ghost' voltage at the load terminals while the isolator was open, triggered by you pulling and then replacing the company fuse. By the time the other chap turned up to test, the meter had closed its isolator and all seemed normal.

So that's my first guess - meter took offence to you pulling the company fuse and switched you off, but the RCD is a separate problem either faulty (if it won't reset even with the supply off) or caused by a duff circuit you've overlooked (if it won't reset with the supply on).
 

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