Try and figure this one out!!!

[youngspark]

Im at the fuse board and there is a fault with one of the lighting circuits. Cut a long story short when the Live is in the breaker the neutral becomes live aswell.
So I presume its a short circuit, I isolate the power and test continuity between Live a Neutral (My tester is calibrated and I tested on a known source before hand) but there is no continuity between the two!!??
Has anyone.... I mean anyone!!! Got an explanation for this?

 

[LlandrilloSpark]

What voltage is between them?, isolate every other circuit on the board and then test, Neutrals are meant to be "live" by the way

 

[JulianC]

So, you have the line in the breaker and juiced up. Is the neutral dangling in fresh air when you measure the voltage, or in the neutral bar. Are any lights switched on?

 

[snowhead]

RCCB? neutral link from the breaker to neutral bar fallen out?

 

[youngspark]

The voltage is 240v between the Neutral and Earth, I isolated all of the circuits in the board and then tested it and still the same result

 

[LlandrilloSpark]

Should be 0v between Neutral & Earth!, you have a polarity issue my friend

 

[youngspark]

Yes the line in the breaker is livened up, the neutral is dangling in fresh air when I tested it. I don't no if the lights were on or off

 

[Sintra]

Why are you performing a test like that anyway.

 

[JulianC]

Check all the lights are off then measure again...


edit: But Sintra has a good point!

 

[nickblake]

sounds to me like you have lost your neutral if you have removed the neutral from the board then you will get 230volts on the neutral between the earth and neutral , not a very clever thing to do as you could electricute yourself if you touch it, to test it properly do an r1r2 test to ensure you have good continuity on the circuits then do an r2rn to ensure you have neutral continuity

 

[telectrix]

so the N is dangling and there are 1 or more lights switched on. as the circuit is open circuit at the n END, then you will have 0 volt drop across the load, therefore you will get the line voltage on the N.

 

[youngspark]

I was shocked as well (not literally) and that's what I thought about the polarity but it still doesn't explain why there is no continuity between the Line and Neutral conductors?

 

[Octopus]

What were you doing prior to the test/fault?

 

[nickblake]

if all the lamps are low energy you may not get a direct continuity reading due to the electronics in the lamp, depends on the electronics of the lamp , i am asuming the light switches have been switched on

 

[JulianC]

You're reading 240v through a lamp which, if it's say a 60W filament lamp will have a resistance approaching 1k ohm - too high for your continuity tester.

 

[telectrix]

a filament lamp will read around 80 ohms cold. still too high for some continuity testers.

 

[youngspark]

sounds to me like you have lost your neutral if you have removed the neutral from the board then you will get 230volts on the neutral between the earth and neutral , not a very clever thing to do as you could electricute yourself if you touch it, to test it properly do an r1r2 test to ensure you have good continuity on the circuits then do an r2rn to ensure you have neutral continuity

So even when I remove a neutral from a different circuit in the fuseboard and test between Earth and that neutral the voltage will still be 230v?

 

[youngspark]

so the N is dangling and there are 1 or more lights switched on. as the circuit is open circuit at the n END, then you will have 0 volt drop across the load, therefore you will get the line voltage on the N.

Really helpful cheers telectrix, so if there is no load on the circuit (all of the lights are off) will there be any voltage at the neutral?

 

[nickblake]

So even when I remove a neutral from a different circuit in the fuseboard and test between Earth and that neutral the voltage will still be 230v?

yes think about it like the lads have said you may not get continuity readings if the light switch is switched on breaker on , lamp in the holder then the 230 volt will run through the circuit back to the neutral bar hence making the circuit , if you disconnect the neutral then it stays positivly charged so you will have 230 volts on the neutral , like i said in my post you need to check the circuits continuity by using the r1r2 , r2 rn formual this will confirm polarity and continuity of the cpc , live and neural conductors

 

[nickblake]

sorry mis read your post , dont go removing neutrals from other circuits with the power on you could end zapping your self if all your switches are off then you shouldnt get 230 volt on the neutral thats if you have the correct neutral or if you have a shared neutral you could end up with 230 volts , you could also get a lower voltage reading due to induced voltage