Voltage measured when breaker is off

[Iron Balls McGinty]

Hi ther

I'm fitting a new IKEA kitchen for my father and have insta Ed a new cooker switch. When testing with cooker breaker off I was sill seeing 9.6v on my multimeter. As I individually switched other breakers off I saw the voltage decrease witheach breaker till i switched off the main breaker and got 0 volts. The sockets beaker next to the cooker breaker was responsible for about 7 volts of the 9.6v. This seems strange and wrong to me - can anyone offer some advise on this?

 

[Iron Balls McGinty]

Apologies for all the typos above but it is murder trying to type when you can't see what your typing. Must be my tablet/browser settings as all I can see when typing is constant requests for push notifications! Anyway if my question is understood then any advise will be gratefully received

 

[littlespark]

First of all, what were you measuring between? L-N, L-E?

Also, your multimeter, if it’s just a hobby type, it won’t have the required accuracy that our professional test equipment has.
9 volts over 240 is probably a normal margin of error.

 

[Iron Balls McGinty]

I was measuring between L-N using a fluke clamp meter type (I don't know the model as I've left it up there). It's true RMS and is a good one

 

[Marvo]

The tester you're using has a very high imput impedance which makes it very sensitive. The 9.6 volts you're seeing is a voltage that's being capacitively coupled into the disconnected circuit by other live circuits that are in close proximity to it. It's commonly referred to as a ghost voltage or phantom voltage or stray voltage.

Some tester manufacturers sell an 'add-on' device for their testers that lowers the input impedance and therefore eliminates ghost voltages from being displayed. Some tester have a 'low impedance' mode or 'Lo-Z' mode built into them which does the same thing.

Bottom line is you're actually using the wrong type of tester to prove a circuit is dead. I think it's GS38 in the UK that outlines suitable test equipment...maybe one of the UK members will confirm.

 

[Iron Balls McGinty]

Littlespark and Marvo many thanks for your kind advise. I have heard of phantom voltage readings but I was worried that this was a sign of a faulty breaker hence I came here for expert advise. I'm reassured so cheers

I'll do a wee tounge test between L-N tomorrow just to prove the phantom voltage!

Only joking!

Cheers!