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Jimbo8

Voltage on earth ar cu when earth disconnected from earth bar and mcb on

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Jimbo8

Hi everyone I'm after some advice I've just noticed that my earth had voltage on when I disconnected from earth bar in cu when mcb was on could any one shed a bit of light on this thanks it is on ring mains and light ccts 

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binky

what sort of voltage?

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Jimbo8

Any thing between  118v and 33v 

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Jimbo8
6 minutes ago, binky said:

what sort of voltage?

33v to 118v

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Rob.

Firstly, it is extremely dangerous to be disconnecting a circuits CPC with it still energized.

 

Are you measuring with a digital multi meter by any chance?

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Geoff1946

Probably just capacitive coupling from the live conductor.  Why? Are you experiencing RCD trips or something?

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Jimbo8
5 minutes ago, Rob. said:

Firstly, it is extremely dangerous to be disconnecting a circuits CPC with it still energized.

 

Are you measuring with a digital multi meter by any chance?

Hi pal I do realise it not the thing to do I am aware of the dangers but I was alone in the house and I was just seeing if anyone else had come around this thank you

6 minutes ago, Geoff1946 said:

Probably just capacitive coupling from the live conductor.  Why? Are you experiencing RCD trips or something?

No rcd trips.

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Rob.

As said, most probably capacitive coupling. 

 

Even more likely if you're using a digital meter. 

 

Was there a reason you were doing this? Sheer curiosity or, finding a fault?

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Jimbo8
Just now, Rob. said:

As said, most probably capacitive coupling. 

 

Even more likely if you're using a digital meter. 

 

Was there a reason you were doing this? Sheer curiosity or, finding a fault?

Yes pal fluke tester also megger multimeter and metrel multimeter all it was I had put the earth in wrong terminal so was moving it over when I noticed a little spark on earth when they was disconnected from each other ie was a ring main but when there together it's no longer there just never come across this before has I've never disconnected earths while a cct has been energised  before 

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Rob.

If you got an actual spark, this is suggesting a more sinister fault. 

 

A floating capacitive voltage, shouldn't have enough energy to produce a visible spark. 

 

All other circuit testing ok? 

 

TNCS earthing by any chance?

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Murdoch

Voltages such as you describe are more likely to be "phantom" and are only "there" because the CPC isn't connected to the earth bar. As for the "spark" - may suggest earth leakage.

 

Best get a spark with an earth clamp meter to investigate, to put your mind at ease.

 

PS. As others have said its not a wise idea to disconnect the CPC when the circuit is live.

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Jimbo8
49 minutes ago, Murdoch said:

Voltages such as you describe are more likely to be "phantom" and are only "there" because the CPC isn't connected to the earth bar. As for the "spark" - may suggest earth leakage.

 

Best get a spark with an earth clamp meter to investigate, to put your mind at ease.

 

PS. As others have said its not a wise idea to disconnect the CPC when the circuit is live.

I am a electrician a clamp meter would only tell me the loading 

59 minutes ago, Rob. said:

If you got an actual spark, this is suggesting a more sinister fault. 

 

A floating capacitive voltage, shouldn't have enough energy to produce a visible spark. 

 

All other circuit testing ok? 

 

TNCS earthing by any chance?

I believe it is a tncs rob but u do not get a shock off the voltage that's being produced by the earth 

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Jimbo8
1 hour ago, Murdoch said:

Voltages such as you describe are more likely to be "phantom" and are only "there" because the CPC isn't connected to the earth bar. As for the "spark" - may suggest earth leakage.

 

Best get a spark with an earth clamp meter to investigate, to put your mind at ease.

 

PS. As others have said its not a wise idea to disconnect the CPC when the circuit is live.

Hi Murdoch just in twenty plus years of doing this and have never seen it before I wonder how many sparks have never noticed this with the earths I understand what ur both saying and not to disconnect earths while mcb is on but how would we ever know this is happening  if I never did do it 

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Sharpend

You might want to invest in one of these? 

https://www.google.co.uk/search?

 

you can get as said induced/capacitive  voltage however these don’t usually produce a spark? I’d test the earth leakage then the  circuit fully individually as a start. 

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Risteard

I think you need retraining about safe working practices.

 

An incredibly dangerous and stupid thing to have done.

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Jimbo8
2 hours ago, Sharpend said:

You might want to invest in one of these? 

https://www.google.co.uk/search?

 

you can get as said induced/capacitive  voltage however these don’t usually produce a spark? I’d test the earth leakage then the  circuit fully individually as a start. 

Hi there I tested circuit fully insallation  resistance  999 and continuity all ok earth loop 0.81 and rcd all ok 

40 minutes ago, Risteard said:

I think you need retraining about safe working practices.

 

An incredibly dangerous and stupid thing to have done.

Thanks for ur advise mate but just to let you it would only be dangerous if someone else was in the house just to let you know I was alone 

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Murdoch
4 hours ago, Jimbo8 said:

I am a electrician a clamp meter would only tell me the loading 

 

 

If you read my post again it says earth clamp meter ............... maybe I should have written earth leakage clamp meter.......

 

If you do fault finding, they are an expensive but extremely useful item to have 

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Risteard
3 hours ago, Jimbo8 said:

Thanks for ur advise mate but just to let you it would only be dangerous if someone else was in the house just to let you know I was alone 

It's dangerous regardless. You put yourself in harm's way by doing it.

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Jimbo8
3 hours ago, Risteard said:

It's dangerous regardless. You put yourself in harm's way by doing it.

Have u ever checked the earths dont have voltage on pal guess not so maybe ur leaving people at harm 

5 hours ago, Murdoch said:

 

If you read my post again it says earth clamp meter ............... maybe I should have written earth leakage clamp meter.......

 

If you do fault finding, they are an expensive but extremely useful item to have 

Cheers murdoch I'm rewiring house now just never seen this before but like we all know we never disconnect earths when its powered up just a one off and couldn't believe what I was seeing really appreciate  you taking time to chat with me thankyou 

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Risteard
1 hour ago, Jimbo8 said:

Have u ever checked the earths dont have voltage on pal guess not so maybe ur leaving people at harm

How exactly is disconnecting them from the Earth bar a good test for anything? And voltage is a potential difference so can only ever be between more than one point.

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Jimbo8
13 minutes ago, Risteard said:

How exactly is disconnecting them from the Earth bar a good test for anything? And voltage is a potential difference so can only ever be between more than 

It's not a test I'm asking you a question never mind why not move onto someone else if you cant answer the question all the best thanks 

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Sharpend

Let’s stop right there shall we? jimbo you have asked a question that has been answered, it has also been suggested that you’re actions are dangerous, you for some unknown reason now want to turn the good advice into something bad as if you’ve been insulted or attacked? 

We all have to learn and if it’s something you don’t understand that’s fine but to insult those that are trying to educate you then that’s not right. 

 

If there is something else about this that you don’t understand then please ask, otherwise try to understand the advice you’ve been given. 

 

Getting defensive serves no purpose other than to prevent people gaining assistance when needed. 

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kerching

I would have thought an Electrician would know what an Earth Clamp meter is...maybe it's just me

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Doc Hudson
15 hours ago, Jimbo8 said:

Hi everyone I'm after some advice I've just noticed that my earth had voltage on when I disconnected from earth bar in cu when mcb was on could any one shed a bit of light on this thanks it is on ring mains and light ccts 

 

Some appliances can have natural earth leakage, on occasions relatively high protective conductor currents, (hence section 7.5 of On-Site-Guide). Some appliances can produce earth currents due to faults or deterioration over time. Or an accessory wired incorrectly between live and earth can all produce earth currents / voltages that would not trip and RCD under normal conditions. Unless a full evaluation of exactly what is still connected to a circuit has been made, it is risky attempting to disconnect any conductors of a live circuit. Hence the Legislation against live working. Don't forget 30ma @ 230 is just under 7watts. so a 5watt LED lamp wired between Live & Earth may not trip an RCD, but would put a significant voltage onto the CPC!

 

on a very simplistic level consider one of these DIY type socket testers https://www.toolstation.com/socket-tester/p82826?searchstr=socket tester  If you disconnect the CPC on a live circuit with one of these still plugged in, depending upon the make of tester it is not uncommon to measure 100+ Volts ac between a disconnected earth and real earth.  

 

Doc H.

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Jimbo8
6 hours ago, Doc Hudson said:

 

Some appliances can have natural earth leakage, on occasions relatively high protective conductor currents, (hence section 7.5 of On-Site-Guide). Some appliances can produce earth currents due to faults or deterioration over time. Or an accessory wired incorrectly between live and earth can all produce earth currents / voltages that would not trip and RCD under normal conditions. Unless a full evaluation of exactly what is still connected to a circuit has been made, it is risky attempting to disconnect any conductors of a live circuit. Hence the Legislation against live working. Don't forget 30ma @ 230 is just under 7watts. so a 5watt LED lamp wired between Live & Earth may not trip an RCD, but would put a significant voltage onto the CPC!

 

on a very simplistic level consider one of these DIY type socket testers https://www.toolstation.com/socket-tester/p82826?searchstr=socket tester  If you disconnect the CPC on a live circuit with one of these still plugged in, depending upon the make of tester it is not uncommon to measure 100+ Volts ac between a disconnected earth and real earth.  

 

Doc H.

Thankyou doc really appreciate  advise pal 

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