how to find earth leakage in light circuits

[Zehroni]

an electrician replaced the CU in my house but he connected and below what he said and done;
"Lights circuit has an earth leakage which can't be located. So was connected in mcb without RCD protection"
I believe one of the wires that is going from one light ross to another is faulty and need to be replaced.
how to find this wire and where do I start?

 

[terryplumb]

Didn't the electrician even try to find the location of the earth leakage ?

 

[Zehroni]

no he did not. all he said " further investigation is needed

 

[Murdochcat]

Further investigation is what is required. Rather than Earth leakage it’s probably a damaged cable giving very low insulation resistance

Has he given you an EIC with his test results ?

 

[Zehroni]

he recommended to rewire the light circuit which I believe is an over kill. all I need to do is to find that piece of wire and replace it whether is the main feed (from ross to ross) or from switch to ross. but I need to know where to start. I have a multi meter

 

[Zehroni]

do you mean this one "DOMESTIC ELECTRICAL INSTALLATION CERTIFICATE"

 

[Murdochcat]

he recommended to rewire the light circuit which I believe is an over kill. all I need to do is to find that piece of wire and replace it whether is the main feed (from ross to ross) or from switch to ross. but I need to know where to start. I have a multi meter

You need competence and test kit that does insulation resistance for staters

What about the certificate ?

 

[Murdochcat]

do you mean this one "DOMESTIC ELECTRICAL INSTALLATION CERTIFICATE"

Ignore the word domestic, so yes

Do you have it ?

 

[Zehroni]

yes i do, here it is

 

[Murdochcat]

Interesting.

No Zs for the lighting circuit. Why not ?

Also LIM for the cooker - why?

Could you post a photo of the CU ?

 

[Harry Bloomfield]

an electrician replaced the CU in my house but he connected and below what he said and done;
"Lights circuit has an earth leakage which can't be located. So was connected in mcb without RCD protection"
I believe one of the wires that is going from one light ross to another is faulty and need to be replaced.
how to find this wire and where do I start?

Domestic lighting circuits, are normally wired as what is called a radial circuit. Which means the wiring goes from the source, at your consumer unit, then works its way around all of the lights on that circuit. Unless the fault has a very low resistance, what is needed, is an insulation tester, which applies an high voltage across the wiring, to simulate the mains voltage.

Usually, the process of finding such a fault on a radial circuit, involves disconnecting the radial circuit, at certain points, followed by retesting to see whether the fault remains or not, so you can decide whether the fault is in the near section or far section, beyond where you have disconnected. The quick way, is to guess where the middle of the radial circuit is, break and test each half - Logically half'ing, then quartering, and so on, until you have got the fault cornered, to a small section of cable.

 

[pcaouolte]

That EIC is dated 2020. Has this been a problem for 3 years?

 

[Zehroni]

no it has not but, I wonder why the the light circuits on mcb

 

[EFLImpudence]

In view of that picture of the consumer unit, (a bit different than the description and certificate) I would hazard a guess that you might have what we call a borrowed neutral on the stair landing light circuit.

If I am correct, this will indeed require some rewiring of one of the lighting circuits.

 

[Zehroni]

In view of that picture of the consumer unit, (a bit different than the description and certificate) I would hazard a guess that you might have what we call a borrowed neutral on the stair landing light circuit.

If I am correct, this will indeed require some rewiring of one of the lighting circuits.

many thanks will start with those lights and see what I can find