Continuity between live conductors

[dokkan1080]

On my cu at home I have a continuity reading between my ring final circuit and a radial circuit of 114ohms between live conductors.

When I test continuity from each breaker.

Why would that be? Break down of cable

If I turn one off and leave the other on I don't get a voltage.

At what point would a voltage appear between them or would it trip the rcd?

I'm to lazy to unplug every thing and do an Insulation resistance test between the 2 cirxuits

 

[SparkyChick]

If you are testing for electrical separation, you must disconnect the neutrals of the circuit under test as well as isolating the line conductors. It's entirely possible you are reading the apparent resistance of a circuit that goes something like this....

line conductor on ring -> some load -> neutral conductor on ring -> neutral bar in consumer unit -> neutral of radial circuit -> some load -> line conductor on radial circuit

 

[dokkan1080]

If you are testing for electrical separation, you must disconnect the neutrals of the circuit under test as well as isolating the line conductors. It's entirely possible you are reading the apparent resistance of a circuit that goes something like this....

line conductor on ring -> some load -> neutral conductor on ring -> neutral bar in consumer unit -> neutral of radial circuit -> some load -> line conductor on radial circuit

Ah that makes sense. ?

I will try that in the morning.

so with Insulation Resistance Though you can test off the neutral bar and or earth bar and the breakers though right?

 

[Lucien Nunes]

Yes, but if you use the neutral bar you will test the neutral of all circuits at once, and the line of any circuits that have load connected (you should not apply insulation tests between line and neutral of loads). To test circuits individually you must disconnect their neutrals from the bar.

Agree with @SparkyChick that 114 ohms is probably the resistance of loads on the two circuits in series. It is not impossible, but very unlikely, for any cable fault to read in the hundreds of ohms. Copper touching copper is likely to be an ohm or less, while even burnt or wet insulation is likely to be tens or hundreds of kilohms.

 

[dokkan1080]

Yes, but if you use the neutral bar you will test the neutral of all circuits at once, and the line of any circuits that have load connected (you should not apply insulation tests between line and neutral of loads). To test circuits individually you must disconnect their neutrals from the bar.

Agree with @SparkyChick that 114 ohms is probably the resistance of loads on the two circuits in series. It is not impossible, but very unlikely, for any cable fault to read in the hundreds of ohms. Copper touching copper is likely to be an ohm or less, while even burnt or wet insulation is likely to be tens or hundreds of kilohms.

Thanks for the replies

I was just curious as all....before I brought the property the neutral in the main switch had burnt out.

And the board was replaced, what would cause that? Would the neutral cable have just become loose over the past 40 or 50 years or could the problem have been else where

It was an old wylex cartridge barkelite fuse board

 

[SparkyChick]

Sounds like a classic loose connection or possibly a bad neutral switch contact.