Grounding Issue For Cpu

[tuffy]

Help!

The house I live in has the older style 2 prong plug recepticals and with out the 3rd grounding plug.

When I touch the CPU case I constantly feel a small current. This happens anytime that i touch the end of a usb cable coonnected to the CPU as well.

I tried putting the case on a wooden block and this helps somewhat but does not fix the problem.

I am afraid I am going to fry this system if i continue on like this.

Any ideas how to correctly fix this problem?

[johng]

Take a look here.

http://homepages.enterprise.net/crossy/wiring/earthing.html

[Crossy]

Take a look here.

http://homepages.enterprise.net/crossy/wiring/earthing.html

Also http://homepages.enterprise.net/crossy/wiring/2pin.html

Please take time to read http://www.crossy.co.uk/wiring where many of the common problems are addressed

[paulfr]

This is not as big a problem as you might think.

Nearly all computers in Thailand in private homes have this problem and no one dies or is injured.

I recommend ( I am an Electronics Engineer w 30 yrs experience) making sure all power cords go to the same power strip even if you need extension cables to do it.

The wooden isolation block is good, keep it.

The problem stems from the internal power filters. So unless you change it/them, you will be with the problem forever.

Do not go attaching ground wires here and there as you then create ground loops for current to flow and can actually damage your system.

Relax and do the above and you'll be okay.

And remember, This Is Thailand.

[Rice_King]

...making sure all power cords go to the same power strip even if you need extension cables to do it.

The problem stems from the internal power filters. So unless you change it/them, you will be with the problem forever.

Paul: Could you expand on these two points? Why should all power cords go to one power strip? Couldn't this overload it? Also, I am not familiar with the term "power filters." What are their purpose and where are they located?

This issue is of keen interest and, as you may surmise, I have little knowledge of what constitutes proper wiring. This thread and the links herein are very informative.

[Crossy]

This is not as big a problem as you might think.

Nearly all computers in Thailand in private homes have this problem and no one dies or is injured.

I recommend ( I am an Electronics Engineer w 30 yrs experience) making sure all power cords go to the same power strip even if you need extension cables to do it.

The wooden isolation block is good, keep it.

The problem stems from the internal power filters. So unless you change it/them, you will be with the problem forever.

Do not go attaching ground wires here and there as you then create ground loops for current to flow and can actually damage your system.

Connecting to a single plug board and a single earth point is the CORRECT way to go.

Whilst leaving the grounds floating is unlikely to kill a normal person, give someone a weak heart and damp feet and you have a whole different story, and, of course, if you do get a line-ground fault that little 'tickle' you feel will turn into a full blooded whallop!!

Paulfr is quite correct, it is leakage throught the mains inlet filters that causes the problem, but those filters are there for a reason and without a ground they don't operate correctly, ungrounded the casework floats at about 110V.

I'm not sure how the wood block can help, maybe paul can enlighten us

And yes, I'm a qualfied electronics engineer with around 30 years of experience, just in case someone asks

[joka]

Ok, sorry, i did not read the article, but i have had a ground wire to my computer case and running out the window to a earthing rod in the ground. the electrician who installed my hot water heater did the same thing to that appliance (separate ground wire and rod). Is this safety?

[Crossy]

Ok, sorry, i did not read the article, but i have had a ground wire to my computer case and running out the window to a earthing rod in the ground. the electrician who installed my hot water heater did the same thing to that appliance (separate ground wire and rod). Is this safety?

Should really be a single earth rod for the entire building , but what you have is 1000000 times better than nothing

I hope you have an RCCB / RCD / GFI / Safe-T-Cut as well.

[solo siam]

Buy a decent (brand name) PSU for your PC and you shouldn't have this problem, Every computer I have with a cheap (free with the case) PSU gives me a shock, whilst the aftermarket PSU's are fine.

[paulfr]

Buy a decent (brand name) PSU for your PC and you shouldn't have this problem, Every computer I have with a cheap (free with the case) PSU gives me a shock, whilst the aftermarket PSU's are fine.

This is probably your best solution.

Will run you maybe 2000THB but well worth it.

Cheers

[Totster]

I just got some wire and an some metal rodding (bout 3ft i think).... knocked the metal rod all the way into the ground, fixed the wire to it.. then attached the other end to the earth loop on the back of the PC.. works fine.

totster

[Crossy]

Buy a decent (brand name) PSU for your PC and you shouldn't have this problem, Every computer I have with a cheap (free with the case) PSU gives me a shock, whilst the aftermarket PSU's are fine.

This is probably your best solution.

Will run you maybe 2000THB but well worth it.

Cheers

NO, NO, NO!!! The BEST, in fact the ONLY solution is a ground rod, period!!

Paulfr, as an engineer you ought to know better than this.

Besides, a few metres of green wire and a rod (from HomePro) will cost considerably less than 2000Baht.

Two simple rules, not all encompassing but nearly so:-

1. If it has a 3 pin plug, it almost certainly needs a ground.

2. If it has exposed metalwork, it almost certainly needs a ground.

If you ground something and it doesn't need it, 100% of the time, no problem. If you don't ground something and it does need it, 99.99% of the time, no problem, 0.01% of the time, someone dies. I just hope it's not your kids (or someone elses kids) in the 0.01% group.

[paulfr]

Buy a decent (brand name) PSU for your PC and you shouldn't have this problem, Every computer I have with a cheap (free with the case) PSU gives me a shock, whilst the aftermarket PSU's are fine.

This is probably your best solution.

Will run you maybe 2000THB but well worth it.

Cheers

NO, NO, NO!!! The BEST, in fact the ONLY solution is a ground rod, period!!

Paulfr, as an engineer you ought to know better than this.

Besides, a few metres of green wire and a rod (from HomePro) will cost considerably less than 2000Baht.

Two simple rules, not all encompassing but nearly so:-

1. If it has a 3 pin plug, it almost certainly needs a ground.

2. If it has exposed metalwork, it almost certainly needs a ground.

If you ground something and it doesn't need it, 100% of the time, no problem. If you don't ground something and it does need it, 99.99% of the time, no problem, 0.01% of the time, someone dies. I just hope it's not your kids (or someone elses kids) in the 0.01% group.

Sorry Crossy but most of what you say here is patently false.

I am not going to go round and round on this subject again here.

So I will just say this .... if you drive a stake into the ground outside your house/apt and connect a wire from the CPU metal case to it and the shock goes away, ..... great, fine, do it.

But for me, I'd just buy/invest in a good power supply unit that does not leak.

For kicks though ..... Crossy, you know that all current flows in a loop. There has to be a return current. This is perhaps the most fundamental rule of electronics. So if the wire to the stake has current in it, where does it go and how does it get back to the source/CPU ?

Edited June 6, 2006 by paulfr

[Crossy]

For kicks though ..... Crossy, you know that all current flows in a loop. There has to be a return current. This is perhaps the most fundamental rule of electronics. So if the wire to the stake has current in it, where does it go and how does it get back to the source/CPU ?

Well Paul, it's like this:-

The neutral of the mains is grounded at the substation (and at other locations as well if you have a MEN [Multiple Earthed Neutral] system), this is why you get a shock if you grab the live. If the supply was truly floating you could hold the either wire (on its own) and not get a shock (as often demonstrated by our Machines and Control lecturer Mr Bentley as our lab had a floating 3-phase supply).

So, the mains filter provides a capacitive divider between live and neutral with the centre point connected to the chassis. The result is approximately 110V above neutral = 110V above ground (roughly) at the chassis.

So, when you ground the centre point of the filter (the casework) a small current flows down the ground wire into the earth via the stake and through the earth itself back to the grounding point at the substation thereby completing the loop.

QED.

BTW, let's agree to differ on the grounding issue, don't want to start a flame war here

[tuffy]

Buy a decent (brand name) PSU for your PC and you shouldn't have this problem, Every computer I have with a cheap (free with the case) PSU gives me a shock, whilst the aftermarket PSU's are fine.

I purchaced this PSU while i was still in the states and it was a pretty good unit at the time. Is there a way to test it to see that is the problem or not?

[Tywais]

Regardless of a different PSU there other components that have three wire requirements such as your monitor and it won't help there. A ground connection is the way to go. I have attached a picture of my internal ground for my computer room. Because I rent the house I have no control over doing a full MEMs wiring of it. However there was a small hole placed in the floor of my computer room where they sprayed for termites.

I drove a copper stack (1.5M) into this hole (after putting some water in it first, don't have access to the proper chemicals). Attached a 12AWG wire to it and to a 2 prong to 3 prong converter where the other end of the ground connects to. I have "true" three wire power strips and it is connected to this outlet. The case and all supporting equipment are now grounded. This supplies a good bleed path for the PSU input RF/EMI filter. If you search the forums you can find a post I made showing pictures of the standard input filters for PC power supplies and actually for most equipment (3-wire electronics) and the AC voltage divider effect it has.

Seems several of us here with over thirty years experience as electrical/electronic engineers. I didn't jump into the fray because it seemed a bit of information overload already.

Edited June 6, 2006 by tywais

[Crossy]

Regardless of a different PSU there other components that have three wire requirements such as your monitor and it won't help there. A ground connection is the way to go. I have attached a picture of my internal ground for my computer room. Because I rent the house I have no control over doing a full MEMs wiring of it. However there was a small hole placed in the floor of my computer room where they sprayed for termites.

I drove a copper stack (1.5M) into this hole (after putting some water in it first, don't have access to the proper chemicals). Attached a 12AWG wire to it and to a 2 prong to 3 prong converter where the other end of the ground connects to. I have "true" three wire power strips and it is connected to this outlet. The case and all supporting equipment are now grounded.

ABSOLUTELY PERFECT Tywais :)

Cheap and neat.

BTW, can we filch your photo to put on the website?? Which can, of course, be found at http://www.crossy.co.uk/wiring

Edited June 6, 2006 by Crossy

[elkangorito]

Buy a decent (brand name) PSU for your PC and you shouldn't have this problem, Every computer I have with a cheap (free with the case) PSU gives me a shock, whilst the aftermarket PSU's are fine.

This is probably your best solution.

Will run you maybe 2000THB but well worth it.

Cheers

NO, NO, NO!!! The BEST, in fact the ONLY solution is a ground rod, period!!

Paulfr, as an engineer you ought to know better than this.

Besides, a few metres of green wire and a rod (from HomePro) will cost considerably less than 2000Baht.

Two simple rules, not all encompassing but nearly so:-

1. If it has a 3 pin plug, it almost certainly needs a ground.

2. If it has exposed metalwork, it almost certainly needs a ground.

If you ground something and it doesn't need it, 100% of the time, no problem. If you don't ground something and it does need it, 99.99% of the time, no problem, 0.01% of the time, someone dies. I just hope it's not your kids (or someone elses kids) in the 0.01% group.

Sorry Crossy but most of what you say here is patently false.

I am not going to go round and round on this subject again here.

So I will just say this .... if you drive a stake into the ground outside your house/apt and connect a wire from the CPU metal case to it and the shock goes away, ..... great, fine, do it.

But for me, I'd just buy/invest in a good power supply unit that does not leak.

For kicks though ..... Crossy, you know that all current flows in a loop. There has to be a return current. This is perhaps the most fundamental rule of electronics. So if the wire to the stake has current in it, where does it go and how does it get back to the source/CPU ?

Dear paulfr,

You obviously know about Kirchoffs Law & some simple chemistry/physics, so can you please explain how PSU's that may have 'capacitive coupling' (to chassis earth) do not leak? Also, EXACTLY WHAT are the specifications of the 'leakage free' PSU's that you prescribe? What 'standards' do they meet? You also might like to provide some info about the 3rd order harmonics spewed from 'switch mode power supplies' & how they can affect other equipment. How about quoting some 'Standards' to substantiate your claims for 'earths are not required'?

On a slightly different note & to support Crossy's claims, current will always flow from a lower potential to a higher potential (electron flow not conventional flow) & as such, the 'world' is a great source of free electrons. Consequently & since all things are not perfect insulators, devices are always leaky but not as dangerous as leaky things like the metal chassis of Personal Computers. This is how & why currents flow to & from EARTH. As Crossy said, a wet hand or a weak heart & you can kiss your bum goodbye.

There is only one solution in this situation...USE A SINGLE EARTH SYSTEM. This does not mean belting a metal rod into the earth & then believeing that your worries are over. What if the metal rod corrodes badly after a couple of years because it is the wrong metal? What if the connection to the metal rod becomes corroded due to an incorrect connection? What if you install multiple earths & then wonder why you get zapped when walking on the ground near the multiple earths?

These questions have been answered in MANY countries by thousands of ELECTRICAL ENGINEERS (not electronics engineers). The answer has been to install a Multiple Earthed Neutral system (MEN system). Although YOU believe that this is not necessary, many Electrical Supply Authorities will dispute you.

At the end of the day & if your computer chassis gives you 'shocks', it is because that your electrical system is not earthed safely & correctly. This earthing can only be done by an electrically qualified person. To dispute this information will mean the possible cost of human life...UNNECESSARILY.

Should you have any questions, I'm sure that Crossy &/or myself will be more than happy to answer.

By the way, you MAY decide to learn something about the 'electrical' world from a 'power' point of view by visiting http://www.crossy.co.uk/wiring/ & reading carefully...if you value your life.

[Tywais]

ABSOLUTELY PERFECT Tywais :)

Cheap and neat.

BTW, can we filch your photo to put on the website?? Which can, of course, be found at http://www.crossy.co.uk/wiring

No problems. I just took it a few minutes ago with my phone camera to pop it up here quickly. If you want a better quality one I'll use my digital camera.

[Crossy]

ABSOLUTELY PERFECT Tywais :)

Cheap and neat.

BTW, can we filch your photo to put on the website?? Which can, of course, be found at http://www.crossy.co.uk/wiring

No problems. I just took it a few minutes ago with my phone camera to pop it up here quickly. If you want a better quality one I'll use my digital camera.

Well, if it's not too much trouble, but don't put yourself out. Why not resize to about 800x600 and post it in the domestic wiring thread, I'll pick it up from there.

Cheers muchly.

[Prasert]

The office I rent has ungrounded outlets. I invested some money in grounded outlets, which I put on the wall. The earth from every outlet is interconnected and finally goes to a single line into the ground (steel bar, several meters into the ground).

A set of wires (2.5 square mm) come from the original power supply, go to an automatic stabilizer and finally to the grounded outlets.

UPSes are connected to these grounded outlets and the equipment is connected to the UPSes. All computer cables used are 3-wire.

I never got a shock from any equipment.

Note: the stabilizer is only because of the poor government power supply here. The voltage goes from 160V to 230V and varies throughout the day.

At this moment a friend of mine is building his own house. I managed to talk him into running 3 wires to every outlet in the house. It will cost some extra money, but will save his equipment (and more important: himself). And (of course) a single wire into the earth........

[tjo o tjim]

OK, it's pretty easy for desktop PCs to make things work fine with grounding, but what the heck can I do with my laptops that have two-pin DC power connectors to the laptop that continue to shock me (only when plugged in of course)? The power supplies are plastic cases, so they don't actualy continue the ground wire internally.

[Crossy]

OK, it's pretty easy for desktop PCs to make things work fine with grounding, but what the heck can I do with my laptops that have two-pin DC power connectors to the laptop that continue to shock me (only when plugged in of course)? The power supplies are plastic cases, so they don't actualy continue the ground wire internally.

What are you touching to get the shock? There should be no issue with laptops as they do not have a metal case and normally don't require grounding. They usually have smaller PSUs than desktops and can get away with simpler mains filters.

Are you sure it's not an issue with either static, or maybe a peripheral that requires a ground and doesn't have one?

[Tywais]

OK, it's pretty easy for desktop PCs to make things work fine with grounding, but what the heck can I do with my laptops that have two-pin DC power connectors to the laptop that continue to shock me (only when plugged in of course)? The power supplies are plastic cases, so they don't actualy continue the ground wire internally.

Do you have any other equipment plugged into the laptop that is also connected to the mains such as a video monitor? I have seen some power bricks that are 'leaky', that is not well isolated internally. I have one or two here (power bricks) that are only two pronged but can give a tingle when touching the power connector ground pin. I assume it doesn't do it under battery operation under the same conditions?

[tuffy]

OK, it's pretty easy for desktop PCs to make things work fine with grounding, but what the heck can I do with my laptops that have two-pin DC power connectors to the laptop that continue to shock me (only when plugged in of course)? The power supplies are plastic cases, so they don't actualy continue the ground wire internally.

Do you have any other equipment plugged into the laptop that is also connected to the mains such as a video monitor? I have seen some power bricks that are 'leaky', that is not well isolated internally. I have one or two here (power bricks) that are only two pronged but can give a tingle when touching the power connector ground pin. I assume it doesn't do it under battery operation under the same conditions?

my laptop does the same when plugged into the same powerstrip as my cpu. I noticed it today when I touched the metal slot for the pcmcia card. I didn't notice it before when it was plugged in by itself leading me to believe that I am getting feedback from the cpu/monitor or there is something squirrly with this certain wall receptical. I like that 3rd wire earth ground shown in the picture by Tywais but as I am in a rental house the owner might not be too happy with me drilling holes and running wire about. I have a feeling if you could ground a decent power strip in this manner you wouldn't get that feedback with your laptop anymore.

[gharknes]

be very very carefull with unearthed mains appliances in Thailand, I have had several incidents with my own stuff, my mains tester glows on nearly every thing I touch it on, I have had several small shocks that where limited because I was not earthed very well........very different story if I had been earthed, you wouldn't be reading this......240 mains is lethal in most cases if you are well earthed, it makes me very very nervous not having that 3rd connection to appliance chassis or metal work.

[solo siam]

What about double insulated audio equipment? is that safe? Because on some equipment there is no way to earth it (two core cable).

[Crossy]

What about double insulated audio equipment? is that safe? Because on some equipment there is no way to earth it (two core cable).

It SHOULD be OK (like your laptop) as this equipment is designed to operate without an earth.

BUT, I have received tickles off my VCR / DVD player which are supposedly double insulated.

[elkangorito]

The difference between 'earthing an appliance' & 'an appliance that is earthed by the MEN system' is distinct.

1. The MEN system attaches the consumers Main Neutral to the consumers Main Earth within the Main Distribution Board (main breaker box). This arrangement will virtually eliminate a floating voltage on the neutral conductor & therefore may assist in reducing the problems of DC appliances giving shocks (the AC power supplied to the DC power supply will be of the correct voltage).

2. Earthing a single appliance may effectively eliminate dangerous voltages upon metal casings but it will NOT have any effect on a floating neutral voltage.

A floating neutral voltage can cause strange things to happen to equipment as well as reducing the life of the same equipment.

Furthermore, an MEN system can help to reduce (slightly) the strange effects upon equipment, created by harmonics (switch mode power supplies, electronic inverters etc).

None of the problems experienced by Thaivisa posters are experienced by people in Australia (& other MEN countries). The reason? Australia uses an MEN system. The equipment used by Australians is the same as that of other countries.

This is the ONLY difference...the MEN system is not installed into Thai households.

For further info, see http://www.crossy.co.uk/wiring/ & read carefully.

Edited June 8, 2006 by elkangorito

[tjo o tjim]

For the laptop problem, I always assumed it was a floating neutral. I forget the BS designation for the "ungrounded wye" configuration, but it seems pretty common in Thailand. (If there is a N-G/PE-E bond, it is small wire at the transformer.)

The other distinct possibility is that equipment operating below 50V is allowed to shock you.

The only solution I can think of is to ground the internal chassis by using a monitor set-screw connected to a ground wire. Not so pretty, and some risk to screwing up the internal signal reference.

(I get shocked off case screws when it sits on my lap, metallic latch release buttons, any metal on the ports, and occassionally peripherals. Two different makes, three different models, all with two-pin power connectors.)