House installation - induced voltage

[bk1]

Recently I moved in into a new-built house. When installing the lights (chandeliers, etc.) I noticed that on some lights there is voltage in the cable, even if the light switch is turned off. Later I discovered that this problem happens only in the lights with two or more switches. Because I measured up to 120V AC in the cable (between L and zero wire) when the switches were off, I called the my electrician who said that this is due to induced voltage. We actualy proffed this when we temporary changed the wall cable with a cable that ran inside the room and there was under 3 V of induction (because the wires were far apart). Electrician said that this is not a problem, but I am still concerned because 110V when lights are off is quite a lot in my opinion. What do you guys think?

 

[chrish_1977]

It's only a problem if your going to start playing around with the cabling, your electrician is correct and nothing to worry about

 

[telectrix]

try measuring the induced voltage with an analogue meter.

 

[snowhead]

And try connecting a load, eg lamp, to the cable with induced voltage and neutral or earth and see what happens to the voltage with a meter connected.

There's a simpler test but I can't publicise it..

 

[GStueyXR]

It's a long time since i done my electrical theory........ BUT, voltage is induced when a large current flows, so isolate everything in the house barring the affected circuit and see if the voltage still exists.... Personally i would be inclined to believe your electrician is talking a lot of crap!

It is a lot more likely that a cable has been slightly caught by a screw giving a high resistance fault or the switch is not breaking the contact properly.....

 

[Brightspark2]

It is induced voltage, its just showing up on your digital meter. It isnt like 120v as you may think its a sort of phantom voltage. Sounds in your situation like its down to the 3 core and earth cable used on the 2 way switching.

Have a search on here about it theres lots of threads and information.

But also when changing a light fitting you should be isolating it at the consumer unit not just switching the light switch off as there can still be live wires in there even with the light switch off.

 

[GStueyXR]

It is induced voltage

Voltage does not induce voltage...... Only current induces voltage (or magnetism) so how can you possibly make such a statement?

 

[Knobhead]

Just have a look where the OP is from............

 

[telectrix]

so why ain't he over here? most of his countrymen already are.

 

[snowhead]

so why ain't he over here? most of his countrymen already are.

He's on holiday,,

 

[Silly Sausage]

so why ain't he over here? most of his countrymen already are.

He probably already knows what a dump it is over here, and he's saving himself the time and money by not coming.