Help needed please - voltage on dead cable.

[danlightbulb]

Hi all,

I cut the 10mm cable that leads from CU to cooker ages ago, and rerouted to a new shower. All works fine.

Now ive come to do my kitchen and I am detecting a voltage of 40V between earth and live in the old cooker switch, which I was planning to just blank off.

Live - neutral is 0V, but earth to both live and neutral is giving me a 40V reading. The cable is definately cut and well out of the way. Now i'm not detecting 240 V, which I suppose is a good thing! But where is this stray 40V coming from, cos the earths were cut as well! It should just be a dead length of cable!



UPDATE 17:12, my multimeter reads 40V on the 200V AC setting, but nothing on the 700V AC setting, which is what I use to measure the 240V mains.

 

[breezer]

probably its induction

 

[Steve]

probably its induction

ie. nothing to worry about.

 

[baldelectrician]

when did you last change the multimeter batteries?

They tend to do this when the batteries are on the way out.

 

[sijaysee]

i've just posted an almost identical question and then saw your post!
i am getting 40 volts on a cooker cable when the mcb is switched off.

 

[breezer]

well why don't you follow the advice?

 

[danlightbulb]

Batteries are ok I believe.

So other live cables up in my ceiling are causing an induced voltage. So if I was to touch this cable there would be no current source and the voltage would immediatly dissipate? Correct?

Anyway just to be safe I wrapped the ends of the cable in insulation tape before filling in the box.

 

[breezer]

not quite right.

an induced voltage such as you have has little current so if you touched it the voltage colapes and so no current flows.

but you have done the best thing.

incidentaly a transformer works by induced voltage

 

[Maxxy]

Lick the ends of the cables.

Not really im kidding.



Disclaimer: For those who didnt realise it was a joke

ITS A JOKE.

Please dont lick cables. They dont taste nice.

 

[JohnD]

A light bulb will usually drain all the voltage away, and will not even light up. CFLs will sometimes flicker (I suppose they must be rectifying the AC and charging up a capacitor until it reaches striking voltage, or something).

 

[simon_d]

probably its induction

ie. nothing to worry about.

actually, on 600V and above, after making dead, you should earth conductors to prevent inducatance causing a shock.

 

[Maxxy]

I was megger testing cable runs of around 80 meters. Kept getting little belts off the previous ones as i went onto the next lol. Due to its length it had kept some charge, like a capacitor

 

[ricicle]

Mineral insulated is a favourite for retaining capacitive charge after insulation resisitance test