90v instead of 0v

[solo2771]

Hi sorting out a couple of light fittings yesterday and found there were 2 live conductors a neutral and earth coming from inside. one of the lives was 240v and not switched at all, the other one was switching from 240v to 90v. chap didn't want his floorboards up so for now isolated the switched wire and set up a new switch on the live. any ideas where the 90 v could be coming from? and it is 90v to N too so don't think its an earth fault.
paul

 

[superd25]

Hi this is a hard one, what kind of switch is being used? thats the only thing i can think off.

 

[pushrod]

Just out of interest was there was 0V between neutral and earth? Was it a dimmer switch? Both fittings being controlled by one switch?

 

[pevvers]

Have you done an R1+R2 test on the circuit?

90V between neutral and earth sounds like a floating earth to me, and I will put a pint on it that you've got no earth continuity....

Let us know,

 

[Guest123]

Hi sorting out a couple of light fittings yesterday and found there were 2 live conductors a neutral and earth coming from inside. one of the lives was 240v and not switched at all, the other one was switching from 240v to 90v

Is it a combined emergency fitting you have there???

 

[solo2771]

Thanks all,
It's not combined emergency as it's domestic though same wireing setup ie perm live and switched live. N-cpc is 0v L-N 230v N-cpc 0v, not done r1+r2 as there is only switched wire from switch (presume JB in ceiling) I believe the reason its wired as is is switched supply for a light fitting and none switched for pir light circuit. I just can't think of any reason for the 90 V ever series wouldn't leave 90v i don't think. the only things I can think of are there is an alarm system on another circuit (wouldn,t have thought that would be 90v though) , also comes out of house next to another light feed (makes no difference if they are on or off though) Insulation resistance, can't test circuit properlly unless find JB's but as under floor buggered lol.
Can't think of anything else at moment unless the cables have been left coiled up under floor and its induced ? lol

 

[pevvers]

Do an R2 wander lead test then if you can. The only time you're gonna see something that isn't around 230V or 0V in domestic is if you've got a dimmer on it or no earth. If it's a top floor fitting, make sure someone hasn't decided to put in their own loft light.

My bet goes up now, I'll put two pints on it!!

one of the lives was 240v and not switched at all, the other one was switching from 240v to 90v.

Also, was it a normal filament lamp? If so, if it truly was switching to 90V you would expect the lamp to still have some brightness in it. If there's nothing, it's the earth.... 70-90V is a common floating voltage range for when there's no earth.