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a question about grounding

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samcheetah

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once i noticed that there was a potential difference of about 4 Volts between the neutral and ground of the socket in which i plug in the power cable of my computer. i checked the computer chassis with a tester screwdriver. the bulb of the tester lit up. somone suggested that u should ground the chassis yourself cause this may hurt the internal of the CPU. he told me to take a piece of metal, loop some wire on it, bury it in your garden and then take the wire to the chassis of the CPU. i did that. and u know what? when i checked the chassis with my tester the bulb did not lit.

now the bad ground is still there and the ground i made is also there (connected to the chassis). my question is that is it safe to keep both grounds connected to the system. which one should i take off.

and i havent noticed anything unusual happening. all of it works fine. no ground loops. no 50 Hz humming. before the CPU there is a stabilizer. sometimes its in boost mode and sometimes its in buck mode. nothing unusual there too. but still im quite concerned about it.
 

Russlk

New Member
The neutral wire is "daisy chained" from the distribution panel through many sockets, so it is likely that one of those sockets has corrosion or a loose connection, which is causing the 4 volt difference. Adding another ground did not solve that problem and you should find the problem because it could get worse and cause a fire.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
samcheetah said:
thanx Russlk.

the sockets are brand new but the wiring is quite old.

can i just connect the third prong to the self made earth and discard the grounding wire that is probably not functioning right
You don't have your location filled in, so I don't have a clue what country you are in!. Regulations differ widely, depending where you are.

I'm not an electrician (I'm a TV service engineer), but I have had a few dealings with this point in the UK.

Firstly, don't just 'loop a wire around a piece of metal buried in the garden', there are specific requirements in the UK (and presumably where you are as well). For it to pass an electrical check in the UK you need a specific thickness of wire, something like 6mm or 10mm (from what I can remember) connected to an approved 'ground spike'.

An alternative (in the UK) is for the Electricity company to provide you with a PME Earth - I'm not sure what this actually is (as I say, I'm not an electrician), but I think they provide you with an earthed neutral - of course they charge you for installing this!.

If you have a fault in your house wiring, you need to fix it - 'bodging' the symptoms is likely to leave a potentially dangerous fault waiting to get worse!.
 

samcheetah

New Member
i live in pakistan and nobody here seems to know any such regulations :lol:

that PME earth or any thing like that isnt available here either

If you have a fault in your house wiring, you need to fix it - 'bodging' the symptoms is likely to leave a potentially dangerous fault waiting to get worse!.
i understand. thats why i am really concerned about it. and i really will appreciate if someone has the solution to this problem
 

Nigel Goodwin

Super Moderator
Most Helpful Member
samcheetah said:
i live in pakistan and nobody here seems to know any such regulations :lol:
Do you have any regulations in Pakistan? :lol:

I'm afraid I know nothing about Pakistan (apart from roughly where it is), what is the mains voltage there?, and what type of mains sockets do you use?.

Presuming you use earthed three pin sockets?, obviously anything plugged in to the socket should be earthed through it. If it's not, it's either a fault in the house wiring (check if all sockets are like this, or just some), or a fault in the earth system for the house. Where is your earth system?, can you see a wire anywhere going out to earth?, I presume it would be near your fuse box and meter, as it is in the UK.
 

samcheetah

New Member
Do you have any regulations in Pakistan?
lolzzzz :lol: :lol:

the mains voltage is 240V and we usually use the two prong sockets. most people dont think about using the three prong sockets.

i have plugged it in a earthed socket. i dont know if there is a fault in the wiring or the earth system. i think both are faulty :lol: :lol:

yes almost all the sockets are like this

i dont know where the earth system is and i cant see any wire going to the earth. the fuse box is located inside the house alongwith the main switch. the meter is located with all the meters of the neighbouring houses beneath a staircase. the transformer and distribution box is located just in front of my house and i dont see any earth wire coming from there

but anyway can i use the self made earth :?: :?: :?:
 

Sebi

Active Member
Maybe nothing problem with wiring. The neutral is loaded, the earth unloaded, so this 4V always depend from current flow on neutral.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Sebi said:
Maybe nothing problem with wiring. The neutral is loaded, the earth unloaded, so this 4V always depend from current flow on neutral.
That was my thought as well, but he said the case of his computer tested live with a neon tester - so it's obviously not earthed.
 

nettron1000

New Member
Sebi wrote:
Maybe nothing problem with wiring. The neutral is loaded, the earth unloaded, so this 4V always depend from current flow on neutral.


That was my thought as well, but he said the case of his computer tested live with a neon tester - so it's obviously not earthed.
What puzzles me is why the neon tester is able to lite with an alleged voltage reading between neutral and ground of only 4 volts, am i missing something here ?

I dont know much about electrical standards/codes in Pakistan but i highly doubt that a peice of metal with a wire attached to it and buried in a garden would be an acceptable grouding means. Generally the best grounding system would be one which is connected to the street side of a copper water pipe and if this is not available then steel ground rods ( usually 4) have to be driven into the earth, these rods are about 1/2" in dia. and 6 feet long. A bare ground wire of a size determined by the amperage of your electrical service is then connected between these rods and then brought back and connected to the panel box grounding terminal block.

In residential panels the neutral buss is connected to ground via a grounding strap, if this strap is removed the neutral is considered to be "floating". Due to the fact that the neutral carries the un-balanced load between two live busses, the neutral can have a considerable voltage attached to it depending how much the live busses are unbalanced.

I use the term "floating" loosely, actually the neutral wire is the center-tap of a step down transformer supplied by the electrical company. Usually this center-tap ( or neutral ) is already earth grouded back at the street-side of the service. Again im not familiar with eletrical systems in Pakistan but to my knowledge this is the norm.
 

Sebi

Active Member
I'm sure, when the neon-tester lite on PC case, it is not grounded and the first two 4,7nF condenser work as capacitive divider so the measured voltage with DMM 120V AC if the input is 240V AC.
 

samcheetah

New Member
i suspect that the ground is the culprit because when i measure the difference between the live and neutral wires it gives 240V. and when i said that i tested the case with a tester it was before i used the self made ground. after i connected the self made ground to the chassis the tester didnt lit. so my question was that can i transfer the self made ground from the chassis and connect it to the third prong in the socket. i mean i will remove ground wire provided in the house and connect my ground.

i am looking for regulations here but still no luck. its sunday here so tomorrow ill ask the power company about this. until then u guys tell me is it ok to connect the self made ground like i said
 

Sebi

Active Member
Yes, there is no disadvantages to connect the self-made ground to third prong, and also good idea to remove the dead ground wire. In this case Your neighbours cannot use.
 
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