What should the voltage be across the mains switch when off?

Hi

In my (new) consumer unit, there are 3V across the Neutral bar and the earth bar, when the mains is off. There is also 53V across the mains switch from L to N when it's off and 44V between the line supply and line out. Is this normal when the mains switch is off? Isn't N and Earth connected together at some point therefore should be 0 volts difference?

Could this explain why my LED bulbs never switch off but only go dim when switched off via a wall switch?

See pics for actual readings - does anyone know what the readings should be in a good installation?

Thanks in advance...

Wouldn't test anything 'mains' with a LOMYUM.

Please don't take this the wrong way but, you know when you want to stop loose bits of paper flying around and you need a paperweight?

use of he LOMYUM for that!....it is not the right tool for the job, seriously,

one wrong move and the family get an hour out with the Vicar and then a party that you aren't invited to

that meter is more suited to DIY hobby/battery powered stuff. Full mains is nasty and can hurt quite a lot

just saying 

Your meter is a high impedance device designed for testing electronic circuits. This means it will pick up and display capacitively coupled voltages;  - that's what you are seeing across your main switch.  All totally meaningless .  No indication of any fault there.

If you have problems with leds glowing when off this will be local to that circuit and also probably harmless.

(I love Kerching's subtle hint that you are putting yourself in harms way.  -  Do be careful!)

Xerxel said:

Hi

In my (new) consumer unit, there are 3V across the Neutral bar and the earth bar, when the mains is off. There is also 53V across the mains switch from L to N when it's off and 44V between the line supply and line out. Is this normal when the mains switch is off? Isn't N and Earth connected together at some point therefore should be 0 volts difference?

Could this explain why my LED bulbs never switch off but only go dim when switched off via a wall switch?

See pics for actual readings - does anyone know what the readings should be in a good installation?

Thanks in advance...

Click to expand...

If it is a new installation or consumer unit and the LED problems date from that installation these are questions better addressed to whoever installed and certified it.   

Likely you are seeing induced / capacitively coupled voltages in the CU and the (probably cheap) LEDs  and there are several ways of minimising the effects of that.  Not really DIY though so generally I'd carefully close the CU and leave it alone yourself 

Geoff1946 said:

I love Kerching's subtle hint that you are putting yourself in harms way.  -  Do be careful!)

Click to expand...

It has been said that, at times, I can sometimes come across as subtle  as a In a shop doorway

personally I don't see where folk get this idea from, but, hey ho

I have a similar tester to that one on the bench  , no idea where it came from TBH ,  checked it against my annually recalibrated Megger  , showing a 15Volt   higher on the mains scale .    Doesn't look so bad in the 9  -- 12V  areas.  

Didn't we have a good thread on LEDs glowing  when off ?   

Xerxel said:

Hi

In my (new) consumer unit, there are 3V across the Neutral bar and the earth bar, when the mains is off. There is also 53V across the mains switch from L to N when it's off and 44V between the line supply and line out. Is this normal when the mains switch is off? Isn't N and Earth connected together at some point therefore should be 0 volts difference?

Could this explain why my LED bulbs never switch off but only go dim when switched off via a wall switch?

See pics for actual readings - does anyone know what the readings should be in a good installation?

Thanks in advance...

Click to expand...

If you have concerns about this "(new)" consumer unit, I would be addressing them to the electrician who installed, tested, certified, (and notified for Part-P if located in appropriate parts of UK), the work.  The electrical certificate will state the earthing arrangements, typically page 2 of the standard BS7671 model forms. If its a TT installation there will be a significant difference between Neutral & Earth compared to a TNCS.  You may also want to ask about the significant lack of sufficient RCD's to comply with wiring regulation 314.  If you are attempting to measure mains voltages you will do better with an approved voltage tester. The electrician who installed & tested the installation should have one and if they come back may be able to show you what the real potential differences are between the points you are trying to test and help resolve your LED problems at the same time.

Doc H.

LED lamps glowing faintly when off is not unusual, it's caused by induced voltages in the cables.

You will need to fit a snubber on the light switch wire.