Voltage present in wall?

[sivoodoo]

Hi all,

Just been to look at a job where the elv lighting in the kitchen sometimes trips the mcb, put my voltstick to the interior wall near were the lighting controls are and it shows voltage present in a 2 sq meter area on the wall, the other side of the wall shows the same

Any ideas what could cause this, I asked about problems with damp, the customer said she had problems years ago but it had been sorted?

Could damp be still trapped in the wall?

Not done any tests yet.

Any advice would be helpful,
Thanks
Si.

 

[4x4 mark]

i would think you are more likely to be picking up a cable in the wall, try a proper tester one probe on the wall and the other to the nearest earth terminal and i doubt you will get any voltage.

 

[sivoodoo]

Cheers, but its strange that the area of detection is so large.

 

[4x4 mark]

i did have a similar case a woman complaning that she was getting a shock off a wall in her new house that i had just wired. turns out she was right the wall was live and it happened because when the joiner was fixing the tank stand down in the loft the tip of a nail went into a cable live to earth and tripped the breaker, so later on he reset it and went on his merry way. the fault occured because the earth core had blow apart and the live was still in contact with the now un-protected side of the switch wire which made the back box live and the still damp wall

 

[sivoodoo]

mmmm.... thanks, so when testing can i use a multmeter, I just set my tester to volts ac then stick one probe into the wall and the other to say a screw on the face plate of a light switch (if its earthed of course) to get a reading?
thanks, still saving up for a propper tester the multimeter im using is this, it has probes too.
Uni-Trend Group Limited

 

[animal]

mmmm.... thanks, so when testing can i use a multmeter, I just set my tester to volts ac then stick one probe into the wall and the other to say a screw on the face plate of a light switch (if its earthed of course) to get a reading?
thanks, still saving up for a propper tester the multimeter im using is this, it has probes too.
Uni-Trend Group Limited

i think its more likely you are picking up the field from a cable in the wall
The correct way to test this is to do an insulation resistance test at 500v on all the cables that are in the wall ,if they are "clear" then it will just be stray voltage you are detecting

 

[BEN5637]

Have had this too.transpired that a wall light had been removed and the feed had just been cut and not disconnected. caused intermittent tripping as well took a while to find but once disconnected no more probs. just a thought

 

[sivoodoo]

Thanks for your comments, acording to the customer it may well be the case with an old cable burried in the wall, when they had low voltage lights put in.
I shall try and find it, wil be a nightmare its a 5 story victorian building thats been split into bedsits in the past and now back to a family home, its messy, I advised a complete rewire but in the current climate - no chance!

 

[WarrenG]

Very common to find live stay old cable left in walls, under floor boards etc. Either left by the DIYer or so called sparks cutting corners. Dangerous and annoying!

I would isolate a circuit one at a time and test again each time for voltage and see which circuit it is supplying it. Then I would investigate that circuit further to try and find where its connected into.