Ring Main Tripping RCD, Line to Earth reads 0

[JimmyB1988]

Hi All,

Will post an introduction on the new members forum but need to blurt out my question while its still in my head.

Me and Mrs JimmyB1988 have moved into our first house, it has a split consumer unit, half on RCD half not, my sockets were on the half without an RCD. One breaker does all the sockets including the Kitchen. So I moved the sockets breaker over to the RCD side, moved the neutrals too over to the RCD neutral bar. But it keeps tripping the RCD, all works fine on non protected side, i insulation resistance tested the circuit and reads 0Mohms between line + neutral, neutral + earth, line + earth? Confused?

Can anyone think of anything obvious?

Thanks Guys/Girls

 

[uksparks]

Sorry can you just clarify the readings as not 100% sure about what you have written.

Line to Neutral =
Line to Earth =
Neutral to earth =

Also can you provide

r1 =
rn=
r2 =

 

[jimjimjim]

Unplug stuff

 

[Clive P]

Hi,
Firstly I see your qualifications are in Engineering, although you may have electrical experience.
You need to double check the cables you have moved across are definitely the Line Neutral & EARTH for that circuit.
Secondly , unplug everything from the Ring Main to check whether it may be an appliance fault.
Finally, If you are using an IR tester it may show a dead short, but can be higher due to the resolution of the meter.

This should get you started anyway.

Regards.

 

[Megavolt]

Just see it now. Boiler, tv ect now not working for some strange reason. 1000 of them

 

[JimmyB1988]

Hi,

Line - Neutral 0.00 Mohms
Line - Earth 0.00 Mohms
Neutral - Earth 0.00 Mohms

I have unplugged everything in every room, and the boiler is on a spur from the ring which i've knocked off. Cooker is on the ring, but i knocked that off too. (As I type I realize the extractor is on the ring too so i will try again with that disconnected)

I switched off the main switch at the c/u, I disconnected the ends of the ring from the breaker and neutral and earth bar.

R1+R2 is 0.32 ohms

 

[Plonker 3]

Them IR readings are a dead short, looks like someone had a fault and changed it non RCD protected to stop it tripping, or you haven't actually disconnected the cables from the DB.

 

[JimmyB1988]

Yep I'm a maintenance guy, so i have a bit of knowledge about electrics and access to meters etc from work. But i'm no domestic electrician.

 

[JimmyB1988]

I thought they read as a dead short, but if they did it wouldn't it trip the MCB when on the non RCD side?

 

[Plonker 3]

Not if the earth path is faulty or has a higher resistance than the neutral.

Have you disconnected EVERYTHING?

 

[Silly Sausage]

Them IR readings are a dead short, looks like someone had a fault and changed it non RCD protected to stop it tripping, or you haven't actually disconnected the cables from the DB.

Re think that Dilb!

 

[Octopus]

Yep I'm a maintenance guy, so i have a bit of knowledge about electrics and access to meters etc from work. But i'm no domestic electrician.

Why do people write this? the theory and practice of electrics doesn't differ much between commercial and domestic, especially when it comes to this stuff!

 

[Plonker 3]

Re think that Dilb!

Well you knew what I meant

 

[Marvo]

When you did the IR test what test voltage did you have your tester set to? If there's still something connected such as an electronic ballast or TV amplifier if might give you low IR readings due the test voltage exceeding the clamping voltage of the built-in surge arrestors.

 

[Silly Sausage]

Well you knew what I meant

Hahaha...we don't want to send the innocent up the wrong garden path now...

 

[HandySparks]

You need to repeat the tests on a low ohms range to get a proper picture of the state of this circuit.

Edit: 0.00Mohms could be as much as 5k ohms.

 

[Plonker 3]

Hahaha...we don't want to send the innocent up the wrong garden path now...

I thought we could, until the thread got moved into the DIY board

 

[Silly Sausage]

No it hasn't, I can't post there.

 

[Marvo]

The opening post had good concise info and there's obviously a good degree of competence so I've left the thread in the General forum.

 

[Plonker 3]

Strange, I thought the mods were bored, as just about every other thread today has been moved lol