Earthing to stop 'live' computer case

[Crossy]

Pop the lid off the heater (breaker off of course) you should see a terminal marked 'Earth' or 'E' or have the earth symbol ⏚, there will probably also be a label stating "This appliance must be earthed".

With luck it will have a wire on it that goes somewhere sensible, if it doesn't buy a second rod and connect it to that terminal.

You won't feel a tingle from the un-earthed shower, until it kills you.

With luck your Safe-T-Cut will save you from death (set it to the lowest setting that will stay on, never set it to 'direct'). But remember that the parameters chosen internationally for these safety devices are for healthy adults, the weak, elderly or young have a lower tolerance for shock and could still be killed

[lopburi3]

As said all water heaters sold in the last decade or more will have stickers on outside in Thai that they must be earthed (too many were not and built in RCD failed - I had one of them that did). You do have the added Safe-T-Cut upstream so should be protected better than most homes but a simple wire outside to ground rod for both the shower and computer would be a wise action as as mentioned nothing is 100% so the more protection the better.

Your original posts showed a US plug adapter that would not fit that Schuko plug so we believed you actually had a two wire computer (which as I mentioned had never seen here but apparently are common upcountry). You could buy a socket to accept that plug and run the ground wire from there to ground stick if you prefer. This is an example of one that I use (complete with dirt - Thai do not clean near electrics).

[Rorri]

Your computer is NOT earthed. Most power outlets, in Thailand are not earthed, including those that are a 3 pin socket.

[Rorri]

I had the same problem before and the suggested fix was a (quality) UPS. Not only grounds everything plugged into it but gives you that extra bit of time to save/shut down stuff during the all-to-frequent power outages. Heavy little sucker but better than getting shocked all the time (while sitting in my chair, barefoot on recently washed tile flooring) !

Um, a UPS does not ground "everything" if the UPS itself is not "grounded"/earthed. The reason a UPS can stop these small shocks is that the output could be isolated from the input, this removes the connection to earth that is connected to the neutral(grounded) line at various points from the power station to your home.

[makecoldplayhistory]

I had the same problem before and the suggested fix was a (quality) UPS. Not only grounds everything plugged into it but gives you that extra bit of time to save/shut down stuff during the all-to-frequent power outages. Heavy little sucker but better than getting shocked all the time (while sitting in my chair, barefoot on recently washed tile flooring) !

Um, a UPS does not ground "everything" if the UPS itself is not "grounded"/earthed. The reason a UPS can stop these small shocks is that the output could be isolated from the input, this removes the connection to earth that is connected to the neutral(grounded) line at various points from the power station to your home.

So even if it does it differently, would a UPS stop the shocks?

[Tywais]

all computer power supplies are switch mode.

the older ones have a slightly live case unless your condo has an earth.

Most condos do not have an earth and it is expensive to provide an earth.

the newer power supplies do not have a slightly live case.

Being a SMPS supply or linear power supply has no bearing on the case being hot. It is all to do with the incoming EMI/RF filter in the PS. It has a network of inductors and capacitors. Two capacitors, one connected from high side AC to the ground pin and in turn to the case and another one connected from the neutral side to the ground pin and case. This makes an AC 1:1 voltage divider putting the case at 110VAC above ground. The caps have low values though and as such their impedance is high limiting the current to ground to a few hundred microamps at most. So it doesn't take much of a ground to remove that tingle.

I had a friend on the 10th floor of a condo who asked me to take a look. The only option was a wire to the case and then to the rail on the balcony sanded down a spot to expose the metal. Not ideal but it made his girl friend and him happy not to get zapped every time she used the computer.

My first encounter with this issue was over 30 years ago when working on a student's research instrumentation setup and getting a buzz whenever touching it. He had removed the ground pin of an old tektronik oscilloscope to 'float' the ground of the scope. Dug out the schematic of the scope (linear power supply) and found the front end EMI filter and the LC filter cap divider.

[Rorri]

You can make a better earth by digging in garden a ditch, getting a few concrete blocks or pouring wet concrete into it. Then use 1-2 meter copper rod to connect to the concrete and cover the ditch. This way is used in dry places like desert to make an earth. In a condo a few small concrete blocks and a copper wire to those in balcony will get rid off the shocks but it is not a proper earth but better than nothing.

WARNING, unless I miss-understood the comment, this is DANGEROUS, an earth needs to be conductive, last time I checked, concrete isn't, well ok technically, highly resistive. An earth rod needs to go into low resistance earth, this sometimes means keeping it moist. One method, like that in Australia is to use the water pipe, this copper, going to the meter, makes an excellent earth.

[Rorri]

It is quite common sometimes you can get a little shock touching your car but you say your computer uses internal 1kw that is 1,000 watts. I made sure all stuff in my home that uses high enough watts is earthed, if your computer has a 3 pinn socket hole it is there for an earth, also make sure your showers are earthed if you have electric water heaters in there.

So much miss-information. Watts is a measurement of volt and current. In a DC circuit (easier to explain than AC) it is Volts x Current. So a HIGH Watts can be high volts x low current, high volts high current, high current x low volts or high current x high volts. The tingling people feel is caused by voltage, current AND the fact it is an AC source, the voltage and current can vary depending on your bodies conductivity and the conductivity of the floor you are standing on.

[Crossy]

So even if it does it differently, would a UPS stop the shocks?

Maybe yes, maybe no. the correct fix is a ground (and it's cheaper than a UPS).

WARNING, unless I miss-understood the comment, this is DANGEROUS, an earth needs to be conductive, last time I checked, concrete isn't, well ok technically, highly resistive.

Actually you should Google "Ufer Ground" sometimes called concrete encased electrode, it actually makes a very good ground and is now a requirement on new builds in the US. That doesn't mean to say what was being proposed is safe!

[Rorri]

I had the same problem before and the suggested fix was a (quality) UPS. Not only grounds everything plugged into it but gives you that extra bit of time to save/shut down stuff during the all-to-frequent power outages. Heavy little sucker but better than getting shocked all the time (while sitting in my chair, barefoot on recently washed tile flooring) !

Um, a UPS does not ground "everything" if the UPS itself is not "grounded"/earthed. The reason a UPS can stop these small shocks is that the output could be isolated from the input, this removes the connection to earth that is connected to the neutral(grounded) line at various points from the power station to your home.

So even if it does it differently, would a UPS stop the shocks?

It might stop the shocks, however, from a safety point of view you really need to earth the chassis of the PC, this can be done by many methods already mentioned, get an earth rod installed, close to you septic tanks, or any other area where the ground is moist. As a side issues, your other appliances, eg washing machine, should also be earthed.

[lopburi3]

One method, like that in Australia is to use the water pipe, this copper, going to the meter, makes an excellent earth.

But this is Thailand and I have yet to see a copper water pipe from a water meter.

[Rorri]

So even if it does it differently, would a UPS stop the shocks?

Maybe yes, maybe no. the correct fix is a ground (and it's cheaper than a UPS).

WARNING, unless I miss-understood the comment, this is DANGEROUS, an earth needs to be conductive, last time I checked, concrete isn't, well ok technically, highly resistive.

Actually you should Google "Ufer Ground" sometimes called concrete encased electrode, it actually makes a very good ground and is now a requirement on new builds in the US. That doesn't mean to say what was being proposed is safe!

Even with Ufer there are conditions to be met and many installations still tie the rebar to an earth rod, you still need some moisture or a conductive soil...simple electrical theory.

[Crossy]

Even with Ufer there are conditions to be met and many installations still tie the rebar to an earth rod, you still need some moisture or a conductive soil...simple electrical theory.

No argument here, I only mentioned Ufer as there are many, even those in the industry, who have never heard of the technique.

Our home was never designed as Ufer, but it turns out that our roof steel is a better ground than our rod, both are tied together at the distribution board.

[hhiser]

If you notice there are only 2 wires and not a third wire (ground/earth). This is why you are getting a shock. You could ground the plug the computer is plug into, the entire house, or just unplug everything before you touch any metal parts.

[makecoldplayhistory]

...or just unplug everything before you touch any metal parts.

like the keyboard?!?

[lopburi3]

If you notice there are only 2 wires and not a third wire (ground/earth). This is why you are getting a shock. You could ground the plug the computer is plug into, the entire house, or just unplug everything before you touch any metal parts.

Actually there are three wires - the L and N to the two prongs and the Ground to the metal strips on sides and the hole.

[Timwin]

WARNING, unless I miss-understood the comment, this is DANGEROUS, an earth needs to be conductive, last time I checked, concrete isn't, well ok technically, highly resistive. An earth rod needs to go into low resistance earth, this sometimes means keeping it moist. One method, like that in Australia is to use the water pipe, this copper, going to the meter, makes an excellent earth.

No, it is not dangerous. In dry conditions Ufer grounding is the way to do it and Thailand is part of the year dry. The concrete itself acts as a sink for electricity. Obviously you do not know enough about grounding.

"Concrete is naturally basic (has high pH). Ufer observed this means that it had a ready supply of ions and so provides a better electrical ground than almost any type of soil."

Edited November 13, 2013 by Timwin

[Crossy]

WARNING, unless I miss-understood the comment, this is DANGEROUS, an earth needs to be conductive, last time I checked, concrete isn't, well ok technically, highly resistive. An earth rod needs to go into low resistance earth, this sometimes means keeping it moist. One method, like that in Australia is to use the water pipe, this copper, going to the meter, makes an excellent earth.

No, it is not dangerous. In dry conditions Ufer grounding is the way to do it and Thailand is part of the year dry. The concrete itself acts as a sink for electricity. Obviously you do not know enough about grounding.

"Concrete is naturally basic (has high pH). Ufer observed this means that it had a ready supply of ions and so provides a better electrical ground than almost any type of soil."

Gentlemen!

There is no argument that an Ufer is a good ground, it's just what was described would not be an Ufer meeting the NEC, the concrete needs re-bar and a horizontal copper electrode in order to meet that code.

Also Ufer's are not recognised by the Thai codes for domestic, they specify a 1.4m copper or copper clad earth rod, no alternatives.

Enough now!

[Timwin]

There is no argument that an Ufer is a good ground, it's just what was described would not be an Ufer meeting the NEC, the concrete needs re-bar and a horizontal copper electrode in order to meet that code.

Also Ufer's are not recognised by the Thai codes for domestic, they specify a 1.4m copper or copper clad earth rod, no alternatives.

Enough now!

With that plugin one is never going to "meet the code" The question is what kind of grounding is possible if in a condo there are no ways to connect to proper grounding. I'd say with few small concrete blocks in balcony you at least get rid off the shocks and provide a lower impedance pathway to a sink, when compared to yourself! It is the same with cars and planes, there are no real grounding to earth.

[bankruatsteve]

"Ground" is relative zero potential. It doesn't have to be the dirt. It does need to be a large enough conductive sink to be effective.

[Crossy]

With that plugin one is never going to "meet the code" The question is what kind of grounding is possible if in a condo there are no ways to connect to proper grounding. I'd say with few small concrete blocks in balcony you at least get rid off the shocks and provide a lower impedance pathway to a sink, when compared to yourself! It is the same with cars and planes, there are no real grounding to earth.

Condo grounding comes up quite often here. You really need to get to the structural steel for the Ufer effect to be significant. The steel is often connected to the local transformer star point too which will give a very good earth.

Potential solutions in order of preference:-

1. Galvanised water pipe
2. Structural steel
3. Balcony railing

There was a discussion of a similar idea to your concrete blocks in the form of a 'flowerpot ground'. I did actually do some measurements from my 10th floor condo, unfortunately I can't find the thread now, it was a long time ago. The flowerpot was actually good enough to kill the shock from a PC, just, but an aluminium plate sat under the pot was much better (copper would be even better). It does have to rank as the absolute last resort.

[Eagleizer]

I had the same problem before and the suggested fix was a (quality) UPS. Not only grounds everything plugged into it but gives you that extra bit of time to save/shut down stuff during the all-to-frequent power outages. Heavy little sucker but better than getting shocked all the time (while sitting in my chair, barefoot on recently washed tile flooring) !

Um, a UPS does not ground "everything" if the UPS itself is not "grounded"/earthed. The reason a UPS can stop these small shocks is that the output could be isolated from the input, this removes the connection to earth that is connected to the neutral(grounded) line at various points from the power station to your home.

Exactly! I have a 6 months old 1500VA UPS, and I still get electric

shocks if I put my feet outside the plasick mat..