Voltage Present on Earth Line

[johnduffell]

Im still surprised that there could be 240v on the earth line though.

I think that's your problem here, the misunderstanding of v=ir. Where for AC there r could actually be impedence.
If you have a 50kO resistor connected to line and the cpc, you will get a small current 5ma and nothing will go wrong
Disconnect the cpc and you will get 0v across the resistor due to no current flowing v=0mA*50kO therefore 240v to earth on either side, but very little shock. If you touch it a small current a few Mili Amps will flow and the voltage will be 150v or so and you'll feel a tingle.

 

[Octopus]

I think whats missing here is application of basic dead tests

"seeing" 75 v on the CPC could simply mean the CPC is not continuous back to the fuseboard.

 

[johnduffell]

I think whats missing here is application of basic dead tests

"seeing" 75 v on the CPC could simply mean the CPC is not continuous back to the fuseboard.

I think he knew that (as he disconnected it). I think the problem was he doesn't understand why and whether it's a problem in itself.
Although you reminded me that you could test between all conductors and get 0v but you should really dead test to any bonded or earthed metalwork in the area as well.

 

[w0z]

Thankyou. An explanation that makes sense! Appreciate the time you took to write that down. Am i right in thinking this could also be described as an impedance issue with the DVM?

It's certainly not a Dvm "issue", A Dvm has input impedance as does an analogue vm. By asking that question it appears that you still have no appreciation of what you're actually measuring, and I suppose by inference.. (I'm too polite to finish that sentence).. It is however a "you performed a dangerous/stupid test" issue

 

[w0z]

I think that's your problem here, the misunderstanding of v=ir. Where for AC there r could actually be impedence.
If you have a 50kO resistor connected to line and the cpc, you will get a small current 5ma and nothing will go wrong
Disconnect the cpc and you will get 0v across the resistor due to no current flowing v=0mA*50kO therefore 240v to earth on either side, but very little shock. If you touch it a small current a few Mili Amps will flow and the voltage will be 150v or so and you'll feel a tingle.

That depends which end of the resistor you touch...

 

[clanky]

It's certainly not a Dvm "issue", A Dvm has input impedance as does an analogue vm. By asking that question it appears that you still have no appreciation of what you're actually measuring, and I suppose by inference.. (I'm too polite to finish that sentence).. It is however a "you performed a dangerous/stupid test" issue

No, please go ahead and finish.

But i suspect it would be more for your benefit than mine.

 

[plugsandsparks]

Ok, this makes some sense. In my world the increasing use of cheap chinese SMPS's, especially in computer equipment, is definitely having an effect on inherent noise quality. That plus the use of crap zenor's (maybe the semi-conductors youre talking about?) as an after thought doesnt really address the initial problem in the first place. I could bemoan the loss of a good heavy linear PSU but then we all luv' a bargain dont we?

Im still surprised that there could be 240v on the earth line though. I guess everyday is a school day.

I guess the best way to convince you is to rent an oscilloscope , make sure the probe screen is properly earthed and measure the voltage of the disconnected earth with the probe. As the oscilloscope has a very high impedance, some 1Mohn plus, i will eat my hat if you dont see 240V or whatever volts you have at the time. The use of any other instruments like an AVO or DVM simply hides the true potential as it is competing for the volts with the installation hence, depending on the type of instrument and setting you can get any volts you want. Hence my previous comments.

 

[plugsandsparks]

Im working my way through this in order to understand the situation a bit better. Link may help others who are as ignorant as i

The principles of Protective Multiple Earthing (PME) - https://www.voltimum.co.uk/articles/principles-protective-multiple-earthing

This is a different situation as its referring to differences in reference points wrt neutral and earth and also it highlights how dangerous PME can be if you do actually loose the neutral. It is not relevant to what i have been saying as i am talking about normal electrical leakage to earth by appliances that collectively in a large installation can present nasty currents through the body if you grab the disconnected earth wire whilst being pretty well earthed yourself either by holding onto steelwork or even standing in a puddle,,,lol

 

[w0z]

No, please go ahead and finish.

But i suspect it would be more for your benefit than mine.

It wasn't for my benefit and I don't do schadenfreude.
There are three issues here, all which have been covered by other posters to this thread, you didn't safely isolate, you disconnected the earth and you don't appear to understand the difference between voltage and current. The top and bottom of it is you did what you did because you didn't understand what you were doing. We all have to learn so I'm happy that you have.
If you want me to be perfectly honest, (for your benefit not mine) it was your (as I interpreted it) dismissive and arrogant reply in post #28, which swayed me to post, but you've learnt from that too...

I suspect your washing machine (and dryer) is (are) probably OK; if a spark comes to test the sockets ask him/her if they have an earth leakage tester and to check them out; (there are other ways to check but I don't want to be responsible for any mishaps).

 

[clanky]

It wasn't for my benefit and I don't do schadenfreude.
There are three issues here, all which have been covered by other posters to this thread, you didn't safely isolate, you disconnected the earth and you don't appear to understand the difference between voltage and current. The top and bottom of it is you did what you did because you didn't understand what you were doing. We all have to learn so I'm happy that you have.
If you want me to be perfectly honest, (for your benefit not mine) it was your (as I interpreted it) dismissive and arrogant reply in post #28, which swayed me to post, but you've learnt from that too...

I suspect your washing machine (and dryer) is (are) probably OK; if a spark comes to test the sockets ask him/her if they have an earth leakage tester and to check them out; (there are other ways to check but I don't want to be responsible for any mishaps).

Hilarious. I seem to have attracted the attention of the self elected forum guardian. A heavy mantle to bear, im sure! Whilst your first post is an attempt to insult my intelligence, the second is so drenched in sanctimony, im actually almost impressed!

Your misinterpretation of the word ‘issue’ also indicates a propensity towards our cousins over the pond. Perhaps you’ve been watching too many action movies - hence your caped crusader complex. Good luck with that one.

As with everything though, this thread seems to reached the end of its usefulness. Ive gleaned enough information to take away and digest (and yes, correct my understanding of basic theory). I freely admit i fall into the conscious incompetent league but hey ho, onwards and upwards.


Many thanks to Plugsandsparks, johnduffel and Lucien for their help and guidance without resorting to gazing over their noses. Fully appreciate it guys!!!

TTFN
RC

PS this one for w0z – ‘I’LL BE BACK!!!!’

 

[w0z]

PS this one for w0z – ‘I’LL BE BACK!!!!’

 

[Pete999]

Ohhh Dear do I detect a case of bitter sweet in this post? Grow up guys, please

 

[w0z]

Apologies to the forum if I've posted inappropriately, I'll shall recalibrate my moral compass (or remove the magnets).

 

[Darkwood]

Let's not get personal please, it only pulls the thread off course and often leads to more heated and baiting comments and the lengthy task of staff to read through all the thread and tidy where needed, please read the forums rules and expectations in the empty post box before you write your post, it is how we expect members to conduct themselves.

 

[dmxtothemax]

QUOTE - [ the fault is with the washing machine and dryer. Both are now unplugged until i can find a reasonable explanation for their behaviour. ]
I think you will find some leakage is allowed.
And appliances with heating elements seem to be the worst.
You should check with the mnufacturer how much leakage they allow for that product.
Just because there is some leakage doesn't always indicate a fault.