Cooker Socket showing 3 volts when off

[Maggie]

Hi there, wondering if anyone can give me some advice please.

In my kitchen I have a cooker switch with a plug socket which I believe is on a dedicated circuit. If I test it with a Voltage Tester it read all correct as it should. Now if I turn off the Mcb on the CU which is labeled "Cooker" it still shows a Voltage of 3.

On the CU there is another mcb which is labeled "Sockets" which is powering the washing, dishwasher, hob, and hood on a plate with 4 switches and 4 fuses altogether and also a separate switch with a fuse powering the fridge.

If I turn this off there is no Voltage to the Cooker Switch/Socket.

I want to know if this is normal or not please?

I have attached some photos if that helps at all.

Thank you in advance

 

[Lucien Nunes]

That's probably capacitive coupling from the appliance gridswitch feed cable to the cooker cable, if the two run side-by-side for some distance. When a conductor is completely isolated, as would be the line core of the cooker cable when both the MCB and the isolator are switched off, it can take up any potential induced on it by fields from other cables. What exact voltage you read depends on the input resistance of the meter or tester. If that is very high (i.e. it does not load down the conductor under test) then you can get quite high readings, up to 100V or more in some cases, on supposedly disconnected wiring. That voltage collapses as soon as even the tiniest load is applied, because it is actually a very high-impedance current source, leading to the common term 'ghost voltage.'

What is the model of tester you are using there? It would be interesting to know the input resistance. Many testers have a deliberately low input resistance to avoid registering ghost voltages but some do not, nor do multimeters which deliberately have as high an input resistance as possible.

 

[Maggie]

What is the model of tester you are using there? It would be interesting to know the input resistance. Many testers have a deliberately low input resistance to avoid registering ghost voltages but some do not, nor do multimeters which deliberately have as high an input resistance as possible.

TIS 851 Voltage & Continuity Tester - Self Proving

Here's the link for you if that helps....

TIS 851 Voltage & Continuity Tester - Self Proving | Toolstation

With LCD and LED display this is an exclusive voltage and continuity tester, with built in proving test that conforms fully to BSEN 61243-3:2010 and HSE GS38 12B. Features additional built in two pole phase rotation test. Will not trip any RCD when testing between live and earth. Digital LCD...

www.toolstation.com

 

[Marvo]

The accuracy of that test instrument at such a low voltage is going to be awful. It says 3 volts but it might only be 1.5 or 2 volts. I can't imagine why they thought it was a good idea to even display or register voltages that low. Personally I would consider anything below 12 volts as dead unless the input resistance of the instument you're using is less than 1 M ohms.

I'd be interested to see what voltage other guys would consider to be a 'dead' circuit though or whether there's any guidance in the UK regs.

 

[Maggie]

The accuracy of that test instrument at such a low voltage is going to be awful. It says 3 volts but it might only be 1.5 or 2 volts. I can't imagine why they thought it was a good idea to even display or register voltages that low. Personally I would consider anything below 12 volts as dead unless the input resistance of the instument you're using is less than 1 M ohms.

I'd be interested to see what voltage other guys would consider to be a 'dead' circuit though or whether there's any guidance in the UK regs.

So would you say it's all good and safe?