Live earth fault??

[Kyle_Trainee]

So was testing a house today (new build)
When I came to testing on of the ring finals in the house, when testing insulation resistance the live and earth legs on the ring are clear but live to the earth on cpc’s on the cooker circuit, other ring, downstairs lights and heating its bang down I’m thinking something to do with damp walls? But every time Other circuit tested out fine on IR

 

[timhoward]

How far down is ‘bang down’?

 

[timhoward]

2nd question, did you try any other pair of conductors on the same cables and were they ‘bang down’ too?

 

[Kyle_Trainee]

How far down is ‘bang down’?

How far down is ‘bang down’?

Basically 0 M ohm

 

[timhoward]

Basically 0 M ohm

Ah. So if that low did you also try a normal continuity test? And as above what about other conductor pairs (if tested)

 

[Kyle_Trainee]

2nd question, did you try any other pair of conductors on the same cables and were they ‘bang

All other combinations seemed fine just the lives on the ring that was really poor , all other results were decent numbers so I’m unsure weather the walls are actually damp

 

[Kyle_Trainee]

Ah. So if that low did you also try a normal continuity test? And as above what about other conductor pairs (if tested)

I’ve not tried continuity yet, going to try that tomorrow it got late so I left it

could you give an example of the conductor pairs you’ve asked about just to see if I’ve done that or not

 

[timhoward]

What I meant was if for say the cooker circuit you did:
L to N and got >999mohms
N to E and got >999mohms
And L to E gave 0mohms

then you can be pretty sure there’s a dead short somewhere as
1) any dampness would not cause zero anyway
2) any dampness would be unlikely to affect just one core

So I would then use the (low resistance) continuity function to measure more accurately what the resistance is between L and E. That can then give you some idea where the fault is.

As there’s a rfc affected, if you take both ends out of CU and measure L to E on continuity at the sockets the resistance should drop as you get nearer the fault and the fault will be between the two lowest readings.

It interesting that so many circuits are apparently affected. Forgive the silly question but are you testing in the top of the breakers and are the breakers all off?

 

[pc1966]

Even if damp it should be over 0.5M or it is seriously wrong somewhere (exposed conductor in wet plaster style of "seriously wrong").

 

[ruston]

Even if damp it should be over 0.5M or it is seriously wrong somewhere (exposed conductor in wet plaster style of "seriously wrong").

Or his gaffer might of been at it if he is training him

 

[Kyle_Trainee]

What I meant was if for say the cooker circuit you did:
L to N and got >999mohms
N to E and got >999mohms
And L to E gave 0mohms

then you can be pretty sure there’s a dead short somewhere as
1) any dampness would not cause zero anyway
2) any dampness would be unlikely to affect just one core

So I would then use the (low resistance) continuity function to measure more accurately what the resistance is between L and E. That can then give you some idea where the fault is.

As there’s a rfc affected, if you take both ends out of CU and measure L to E on continuity at the sockets the resistance should drop as you get nearer the fault and the fault will be between the two lowest readings.

It interesting that so many circuits are apparently affected. Forgive the silly question but are you testing in the top of the breakers and are the breakers all off?

For the cooker circuit all tests are clear including L-E the only one that’s down is L on the sockets the other cps I was disconnecting the cpcs one at a time from earth bar
For example
Clip on L from sockets circuit then clipping onto cpc for cooker that’s down

 

[Kyle_Trainee]

What I meant was if for say the cooker circuit you did:
L to N and got >999mohms
N to E and got >999mohms
And L to E gave 0mohms

then you can be pretty sure there’s a dead short somewhere as
1) any dampness would not cause zero anyway
2) any dampness would be unlikely to affect just one core

So I would then use the (low resistance) continuity function to measure more accurately what the resistance is between L and E. That can then give you some idea where the fault is.

As there’s a rfc affected, if you take both ends out of CU and measure L to E on continuity at the sockets the resistance should drop as you get nearer the fault and the fault will be between the two lowest readings.

It interesting that so many circuits are apparently affected. Forgive the silly question but are you testing in the top of the breakers and are the breakers all off?

All breakers off just in the top individually testing them to earth

 

[Pete999]

Basically 0 M ohm

So was testing a house today (new build)
When I came to testing on of the ring finals in the house, when testing insulation resistance the live and earth legs on the ring are clear but live to the earth on cpc’s on the cooker circuit, other ring, downstairs lights and heating its bang down I’m thinking something to do with damp walls? But every time Other circuit tested out fine on IR

Are all the conductors under test dissed from the CU INCLUDING THE MAIN EARTH During testing?

 

[pc1966]

For the cooker circuit all tests are clear including L-E the only one that’s down is L on the sockets the other cps I was disconnecting the cpcs one at a time from earth bar
For example
Clip on L from sockets circuit then clipping onto cpc for cooker that’s down

Normally you IR test with all CPC connected to the MET so a fault from, say, L to some wet brickwork will appear. Only then would you remove the CPC for that circuit to try and find out if the fault is L-CPC or L-Earth somewhere.

I see @Pete999 just posted about that!

 

[Kyle_Trainee]

Normally you IR test with all CPC connected to the MET so a fault from, say, L to some wet brickwork will appear. Only then would you remove the CPC for that circuit to try and find out if the fault is L-CPC or L-Earth somewhere.

I see @Pete999 just posted about that!

They was all connected to start with then I started disconnecting some then still testing via the MET to see which cpcs were bringing it down