Earthing/Grounding Alternatives

[exequor]

Earthing/Grounding alternatives

Ok, in my house there are 220V outlets with 3 pins (earth, live and neutral). the Earth wire is sent to a metal pipe outside which was pounded into the ground. i was thinking of alternative ways to get setup the earthing system. i know that if the Earth wire was disconnected from the metal pipe there would be no where for the excess charge to go hence it would go back into appliances and so on and probably hurt someone.

what i am thinking of is other ways of getting rid of the excess charge like placing the ground wire in a sealed container containing water. Would the container with water work as good as the metal pipe in the Earth's surface?

 

[NoTime]

No! Absolutely No! It would not work.

 

[Cliff_J]

Yikes! Step away from the tools! You have HOT HOT Neutral and no Earth ground on a 3-plug 240V outlet. That is why 4-plugs are used today, so there is an Earth ground available at the outlet.

If you have mistyped and put 220V where you meant 120V this isn't as bad. But you need to have an acceptable path for grounding things and that is why electrical code exists. If a fire were to happen and the home was found to be wired to not comply with code, insurance hassles are likely to be next and so on.

Cliff

 

[Gokul43201]

Cliff, I think cipher is not in the US...probably Europe or Asia, where standard household single-phase supply is about 220-230V.

cipher, I can't see how a can of water serves as ground (earth). You need a conducting reservoir whose potential does not change when you add charge to it...sort of like a giant capacitor.

And what's wrong with the existing system ? Just leave it be !

 

[Cliff_J]

Please excuse my American-centrentic viewpoint if this is true. But the water is still a bad idea.

Cliff

 

[GENIERE]

In fact the neutral – ground bond is made (with some minor variations) in the main breaker panel. From that point the bond is earthed via a single conductor. Earthing has nothing to do with protecting someone from getting an electrical shock; it is there to maintain the internal power distribution system at reasonably low potentials occasioned by a lightning strike. Some countries, France I believe, do not reference their power grid to Earth, and others make the connection via intentional high resistance. Each method has advantages. Internal to the residence, the safety ground may not be connected to the neutral conductor at any point except the main breaker panel. In the US, the safety ground must be run in the same cable or conduit as the current carrying conductors because during a fault condition the coupling of the magnetic fields lowers the impedance of the safety ground. This trips the breaker quicker due to higher current flow. The safety ground never carries current except in some fault conditions. You might say it is there to blow the circuit breaker. You can have a generator, producing residential voltage, in an airplane and use the power safely without system being “earthed” which could be quite a stretch.

[edit] Oh- and altering your earthing system is a serious violation of your countries electrical code and would probably nullify your fire insurance.
...

 

[Averagesupernova]

Although this has nothing to do with the OP's question I want to point something out to Cliff. In a 3 wire 240 volt circuit in the U.S., the 3rd wire IS in fact a ground and NOT a neutral. 4 wire 240 volt outlets are the norm now when the 3rd wire needs to carry current. They no longer allow you to share the ground and neutral on clothes dryers and such as they have in the past. However, if you want to install an outlet in your home to run an electric heater for instance (experience with this within the last year) that runs STRICTLY on 240 volts and NO part of it on 120 volts like would happen in a clothes dryer, you are allowed a 3 wire circuit and 3 prong outlet. No current except during a fault will ever flow on that 3rd wire.

 

[exequor]

i love the responses to this thread but first i must get something straight. i am not trying to alter my grounding system in my house i was just thinking of alternative ways of doing it. i live in the caribbean so houses get a 2 phase 240 volt connection while some business places have a 3 phase connection (this one has 4 wires).

i learned something new, i always thought that the ground was just responsible for getting rid of the excess current that the appliances and so on don't use, but it is now that i understand that it is necessary for other things. i guess the reason i thought so was because i sometimes do crazy things like one time i plugged in an aplifier with only the live and neutral wires and left the Earth wire out. i realized that it still worked but was shocking a bit, i guessed that it was shocking because it was not getting rid of the excess electricity, i believe that it was from this that i got the impression that Earth was for getting rid of the excess electricity.

hey Gokul43201 is 230 - 240 volts single phase or 2 phase because i think that it is 2 phase.

 

[Averagesupernova]

cipher, the voltage does not determine the number of phases. There really is no such thing as '2 phase'. Some people will have you believe that it is 2 phase. In the U.S. the transformer is center tapped with the center being the 'neutral'. It is in the center so it is referred to as this. Each leg off of the transformer is 120 volts in reference to the center, which is grounded to Earth and the voltage between the 2 legs is 240 volts. The legs are 180 degrees out of phase relative to the neutral. But ONLY one phase on a pair of wires is hooked to the transformer or transformers. I say transformerS because sometimes 2 are hooked in parallel. 3 phase requires the 3 phases to come ALL THE WAY from the power plant. The way the transformers are configured will determine what the voltage is between each of the 3 legs and ground or 'neutral' and any leg.

Delta connected transformers use one transformers center tap as the neutral. Then each end of this transformer has legs that are 180 degrees out of phase relative to the center tap. The last leg is considered the 'wild' leg and on 240 volt 3 phase its voltage will be around 165 volts (I think) in reference to the neutral where the other 2 legs are regular 120 volts. But beween any 2 legs the voltage is 240 volts.

Wye connected transformers have a common point that all 3 transformers are connected to and this is the neutral. The voltage between the neutral and any leg will be 120 volts. The voltage between any two legs is 208 volts. You won't get 240 volts (to run a water heater for instance) out of a 3 phase wye configuration.

 

[exequor]

thanx for the indept explanation Averagesupernova, it was really informative and it cleared some of my perceptions on electricity.

hey guys i understand why Earth is not just to get rid of the excess electricity, i was wondering is it because of its lower potential (charge flows from higher potential to lower potential if i remember correctly) that causes someone to die if they touch hightension wires and the ground at the same time. correct me if am wrong but i think that it is possible for someone to hang from hightension wires and not electrocuted once they are not touching the ground right?

 

[Gokul43201]

hey guys i understand why Earth is not just to get rid of the excess electricity, i was wondering is it because of its lower potential (charge flows from higher potential to lower potential if i remember correctly) that causes someone to die if they touch hightension wires and the ground at the same time. correct me if am wrong but i think that it is possible for someone to hang from hightension wires and not electrocuted once they are not touching the ground right?

Yes, that's about right.

Mostly, it's the current passing through your body (across your heart) that kills you. If you hang (off both hands) from a power line, the current won't pass through your body, because the power line itself provides a lower resistance path among the two alternatives (actually, a very tiny fraction does pass through you).

If your foot touches the ground while you do this, you are providing a short to ground, and all the current passes through your body...vaporizing it !

 

[exequor]

by the way how much amperes (min) across your heart does it take for you to die?

 

[brewnog]

As little as 70 milliamps, but electric chairs seem to supply somewhere in the region of 5 to 20 amps, according to the following link:

http://hypertextbook.com/facts/AprilDunetz.shtml

 

[exequor]

its interesting that such little current could kill someone, especially from the fact that many people survive coming into contact with electricity. i guess the main reason for that is that the current didn't go across their heart.

 

[Averagesupernova]

Unless they had an ammeter hooked up to them they have no idea how much or little current actually passed through them. Well, within reason anyway. Think of it this way. Just because you come in contact with a wire hooked to a 20 amp circuit does not mean that your body is passing 20 amps. I suspect you are assuming that it does? Check ohms law to see why.

 

[Cliff_J]

Although this has nothing to do with the OP's question I want to point something out to Cliff. In a 3 wire 240 volt circuit in the U.S., the 3rd wire IS in fact a ground and NOT a neutral. 4 wire 240 volt outlets are the norm now when the 3rd wire needs to carry current. They no longer allow you to share the ground and neutral on clothes dryers and such as they have in the past. However, if you want to install an outlet in your home to run an electric heater for instance (experience with this within the last year) that runs STRICTLY on 240 volts and NO part of it on 120 volts like would happen in a clothes dryer, you are allowed a 3 wire circuit and 3 prong outlet. No current except during a fault will ever flow on that 3rd wire.

Thanks for the info, but fundamentally if the wire is allowed to pass current like the clothes dryer is allowed to, isn't that wire more technically functioning as a neutral? I sure wouldn't want to have it connected to the metal chassis...

But then again my own house (and my neighbor is a general contractor and swears code fully allows it) is wired with 3-way circuits using 14/2 wire where the black and white are the two legs and the bare copper is the neutral. No red wire and not even the courtesey piece of black tape on the white wire. And I wonder why it took a lot of looking and odd faces about the 'red wire' when I tried to get some 14/3 at the home center...

Cliff

 

[GENIERE]

I have only a limited knowledge of the US electrical code but perused the manual for work related reasons (electrical safety). I believe until the late 1980’s (residences only) it was permitted to ground certain appliances by connecting the chassis to the neutral conductor. I think this applied only to the electric range and laundry machines, and only 240vac versions. I questioned this and was told that empirical evidence determined few accidents occurred. This is no longer permissible, the NEC requires newly constructed residences to provide electrical outlets (240vac) having 4 wires, groundING conductor, neutral or groundED conductor, and 2 other conductors. The last two will measure 120vac to the grounding conductor or to the neutral conductor; they will measure 240vac to each other. Often this 240vac circuit is referred to as “two phase” but that is not correct, as another poster stated. If your residence has the old 3-wire 240vac appliance outlet, you are grandfathered and may use the neutral as chassis ground. If you have 4 -wire outlets, you must ground the appliance via the green or non-insulated grounding conductor.

So Cliff J, your neighbor was at one time correct, but is now incorrect. Hopefully he subcontracts the electrical work.

 

[brewnog]

Nope, I think they almost certainly had an ammeter hooked up when they were doing the experiments on electric chairs...

(although I only found the link and cannot vouch for its accuracy!)

 

[Cliff_J]

He actually does most of his business in remodeling, no new construction thus far. Things are very different in the south, here they force contractors to pay for all assesments, utility installation, and what not on properties so an individual cannot really purchase a lot and find a builder to construct a home anyways. Its a very 'vertical' system and is in sharp contrast to what happens in the midwest where the city handles the infrastructure and anyone can purchase a plot of land.

I have yet to see what is the bare minimum for the code here but when I add the 240V outlets for an electric water heater and air compressor/welder I plan on using 4-wire. I'm even considering opening the walls to run 3conductor for the 3-ways and adding a 4-way switch so I can have a switch at the bottom of my stairs (and sleep a little better knowing no current is flowing on the bare copper and the switches are grounded).

I'm sure empirical evidence could be accumulated to argue the point but it seems odd when both devices are near water sources and have items containing water used on/in them. At least we know better now...

Thanks for the info!
Cliff

 

[exequor]

thanx for pointing that out to me Averagesupernova because that was exactly what i was assuming.

 

[Averagesupernova]

Brewnog: I am certain that they would have had ammeters hooked with the electric chair example. I was referring to ciphers comment about accidental shock victims who came into direct contact. Not likely an ammeter to view.

Cliff: Some people confuse or accidentally refer to the ground and neutral interchangably. Bottom line is, NO CURRENT EXCEPT FAULT CURRENT IS ALLOWED TO FLOW ON THE BARE WIRE. At one time there were exceptions in ranges and clothes dryers. Possibly more. This is no longer the case and as far as I know has NEVER been the case in mobile homes. However, as I stated earlier a true 240 volt only appliance with no current flowing on the neutral only requires a 3 wire feed consisting of 2 hots and a GROUND and not a neutral. Your water heater, welder, possibly compressor only will require 3 wires. There is nothing to stop you from installing 4 wire outlets and running your stuff off of them but I think it would be a hassle. Here is what I would do. Run all 4 wire cable and install the appropriate outlets that match the device you are running. Just don't use the extra wire. If you later change, just put in a new receptacle and the wire is there ready to use. As for the water heater, or anything else that doesn't come with a cord, don't plug it in. If you want to disconnect it, install a disconnect switch next to it. The work I did in the last year we installed 2 electric heaters in a garage that hung from the ceiling. 240 volts, 30 amp circuit, 2 wire with ground. We also installed a 50 amp outlet for a welder, compressor, pressure washer or whatever. We ran a 4 wire cable for that one but installed the standard 3 prong 50 amp outlet.

 

[sheldon]

The ground and neutral are the same electrical point, meaning they are all tied together. The reason for a ground is safety. If there is a short the ground can become an alternative path for current. The reason there is a ground rod or Earth ground on an electrical system is because there is a difference in potential from neutral to ground, since the ground and neutral are the same electrical point the casing of something verses the ground your standing on could electrocute you. Without this ground rod the system would be considered to be floating in reference to earth. There are floating systems like battery banks etc. that need to be isolated from ground and have ground fault detection if such grounding should occur. In this case though it is mainly for safety.

 

[NoTime]

AFAIK, in the US, localities are not required to adopt the NEC.
In practice there could be additional requirements.
Or they may not require that all provisions be followed.
Or they may specify an older version of the NEC.
It is (or at least certainly was) worthwhile to check the local requirements.

 

[exequor]

The ground and neutral are the same electrical point, meaning they are all tied together. The reason for a ground is safety. If there is a short the ground can become an alternative path for current. The reason there is a ground rod or Earth ground on an electrical system is because there is a difference in potential from neutral to ground, since the ground and neutral are the same electrical point the casing of something verses the ground your standing on could electrocute you.

I thought you said that were at the same electical point, maybe i misunderstood but could you clarify what you mean by they are at the same electrical point but at different potentials. Is current always flowing through the ground wire from what you explained?

 

[NoTime]

I thought you said that were at the same electical point, maybe i misunderstood but could you clarify what you mean by they are at the same electrical point but at different potentials. Is current always flowing through the ground wire from what you explained?

It might make more sense to say "physical point" rather than electrical point, since this is how the system is now required to be constructed.
This is done to eliminate (reduce) what are known as ground loop currents.
Ground loops are not necessarily a health problem but they can raise havoc with electronic equipment and or cause corrosion.

Normally, if everything is working properly there will be no current in the ground (earth) wire/rod at a residence.
Things don't always work properly.
Lightning strikes and falling tree branches are big offenders here.

 

[Averagesupernova]

Cipher, I suspect you do some research into basic electrical principles and laws. Not to try to brush you off, because it seems you have a genuine interest in electricity and are are pleasant poster here on P.F.


Sheldon, you aren't making sense. You say that neutral and ground are at the same electrical point and then you go on to say they are not at the same potential. The neutral and 3rd prong ground wire are tied together at the service entrance. They are for all practical purposes the same potential and the same 'electrical point'. Whatever that means. In an isolated system where there are NO ground rods and there is a short in an appliance causing the case to touch a hot wire you would NOT get a shock by touching the case of the appliance. There is no path for the current to go so the person touching the case won't get a shock. But in the system we do have, touching the hot wire will cause a current to go through your body, into the ground, and back out of the ground at the ground rod completing the circuit. No ground rod, no completed circuit, no shock. However, a completely isolated system is difficult if not impossible to achieve. There are always leakage currents.

 

[sheldon]

They are the same physical or electrical point. Thats why you must ground it to earth, if you don't there would be a difference in potential to earth, but because it is grounded the difference no longer exists. If something should happen to the Earth ground be carefull. I know you think of neutral as neutral but if you aren't grounded to Earth there will be voltage measured with a meter from neutral to "earth ground", which become all the same potential once you use the grounding rod. So since neutral and the ground wires are tied together at the box they are the same in referance to earthground and yes the casing of something could become leathal without the grounding rod on the system. besides messing up some electronics from harmonics. I realize I didn't explain when I was talking about circuit ground and Earth ground, apology. http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/info/earth/earth.htm

Cipher, I suspect you do some research into basic electrical principles and laws. Not to try to brush you off, because it seems you have a genuine interest in electricity and are are pleasant poster here on P.F.


Sheldon, you aren't making sense. You say that neutral and ground are at the same electrical point and then you go on to say they are not at the same potential. The neutral and 3rd prong ground wire are tied together at the service entrance. They are for all practical purposes the same potential and the same 'electrical point'. Whatever that means. In an isolated system where there are NO ground rods and there is a short in an appliance causing the case to touch a hot wire you would NOT get a shock by touching the case of the appliance. There is no path for the current to go so the person touching the case won't get a shock. But in the system we do have, touching the hot wire will cause a current to go through your body, into the ground, and back out of the ground at the ground rod completing the circuit. No ground rod, no completed circuit, no shock. However, a completely isolated system is difficult if not impossible to achieve. There are always leakage currents.

 

[Averagesupernova]

So by your logic hooking 10 car batteries in series and touching one of the end posts will result in a shock even if the whole battery bank is isolated from the earth. Think about this.

 

[GENIERE]

Sheldon - Averagesupernova is correct, time to learn, not argue.

 

[sheldon]

OK Averagesupernova is correct on his example, and not to argue, I just would like to ask a question then. When you have a hot wire and the system is not grounded to earth, do you have voltage between the hot and Earth ground?

 

[GENIERE]

OK Averagesupernova is correct on his example, and not to argue, I just would like to ask a question then. When you have a hot wire and the system is not grounded to earth, do you have voltage between the hot and Earth ground?

Simple question, but not a simple answer. E fields exist between the Earth and the electrical wiring in the home. When you close a light switch, the electrons in the wire are set in motion and produce an electro-magnetic field exactly in the same manner, as does a radio station when it generates an EM field in the antenna. There also exists the natural electro static field between the Earth’s surface and any point in the atmosphere. If memory serves, there may be several hundred volts difference in potential measurable between your head and feet when standing upright in a pasture.

When measuring these potentials, the results will vary depending on how you make the measurement. If you wish to measure the natural static E-field, you will need to use a DC volt meter with an extremely high input resistance, the lower the input resistance, the lower the reading. Of course all depends on the atmospheric conditions at the time of measurement. Avoid doing this if there’s an anvil shaped cloud overhead.

Your question really concerns the EM fields generated by the household wiring. Again, the result will depend on the measurement. Let's assume you have two 10 foot ground rod buried in the ground separated by 5 feet and make a resistance measurement. The resistance will vary considerably dependant primarily on the moisture content of the Earth. One could expect readings of tens of ohms per foot to megohms per foot. Generally speaking, the Earth is a poor conductor. If you measure the potential difference between one of the conductors in the home to a ground rod and the home wiring is not referenced (connected) to the Earth, what do you measure? The 60Hz radiated EM field will produce a potential difference between the wiring and the Earth. When you connect the voltmeter between the wiring and the Earth, the internal impedance of the meter will be in parallel to the impedance of the Earth and the radiated field. In other words the impedance of the meter greatly influences the measurement. With a 20,000 ohms per volt AC meter, I’d guess 20 –70vac. With a 1000 ohms per voltmeter, I’d guess only a few volts.

What about the safety aspect in a non-earth referenced system when a person is touching the “hot” black wire of an extension cord and standing on the ground with bare feet? How much current will pass through a person’s hand, through his feet to the Earth. In this scenario with a direct connection to the hot wire, the radiated field can be ignored due to its high impedance. It’s simply a guess, but the impedance of the Earth, body impedance, and the capacitive and inductive impedance of the entire system would limit the current. This would likely be on the order of micro amps, possibly milliamps and not noticed by the individual. In hospital OR’s and in other intentionally non-earth referenced systems (gas stations?), I believe the total impedance must be maintained above one (1)megohm. The above scenario is “safer” then the Earth referenced system, wherein only the impedance of the Earth and the person’s body would limit current flow. In ideal conditions that current could be quite high, perhaps several amperes with household voltages and capable of causing death.

Why do we use the less safe Earth referenced power distribution system? IMHO the hundreds of thousands of miles of high voltage conductors from the Utility electrical generators to the home are coupled to the Earth via the total inductance and capacitance of the system. The total impedance of the system would be quite low and comparable to a direct wire connection. I believe the non-earth referenced system would require the utilities to also run an additional common conductor (“Y versus Delta configuration) besides the three phases thus adding to the expense and decreasing reliability. If the load was completely balanced, no current would flow in the additional conductor but one could not expect the load to be always balanced.

 

[sheldon]

Is that a yes?

 

[chroot]

sheldon,

If the electrical system is isolated from the earth, it may or may not have a potential with respect to it. If it had a large potential, it would not last long, since ions in the air would carry away the difference in charge. If the wiring is truly isolated from the earth, no significant current will ever flow between it and the Earth -- but it and the Earth can be at wildly different potentials.

- Warren

 

[sheldon]

sheldon,

If the electrical system is isolated from the earth, it may or may not have a potential with respect to it. If it had a large potential, it would not last long, since ions in the air would carry away the difference in charge. If the wiring is truly isolated from the earth, no significant current will ever flow between it and the Earth -- but it and the Earth can be at wildly different potentials.

- Warren

Ok then my case is true that you can be shocked or electricuted in a system that is not Earth grounded via the neutral? after all its the center tap of the xformer right?

 

[GENIERE]

By definition the neutral is the grounded conductor, but I understand your intent so I won’t bicker.

There must be a complete circuit path for current flow. In your scenario, can you describe the current path?

 

[sheldon]

well in this case you become the path for current to travel from the neutral to the earth, if the system is grounded to Earth via grounding rod the current will take the path of least resistance through the ground wire instead of your body.

By definition the neutral is the grounded conductor, but I understand your intent so I won’t bicker.

There must be a complete circuit path for current flow. In your scenario, can you describe the current path?

 

[GENIERE]

Ok then my case is true that you can be shocked or electricuted in a system that is not Earth grounded via the neutral?

Not correct.

after all its the center tap of the xformer right?

Correct.

well in this case you become the path for current to travel from the neutral to the earth…

OK, current flows from the neutral, through you, to the Earth, to where? The current path is not complete. So far we have an open circuit.

...

 

[sheldon]

If you have a difference in potential and create a path the charges will try and equal through the conductor. Think of the neutral as hot and the Earth as neutral. Ok well I am starting to get discouraged, I just don't want anybody to get hurt thinking that in a system that is not Earth grounded nothing will happen to them if they accidently touch the neutral and are holding onto a water pipe (earth ground). If you choose to do so heading my warning then at least I tryed the best I could to explain.

Not correct.
Correct.

OK, current flows from the neutral, through you, to the Earth, to where? The current path is not complete. So far we have an open circuit.

...

 

[Averagesupernova]

Sheldon. You are assuming that the neutral when not connected to the Earth is a shock hazard. Correct? Assuming that no other part of that particular system (secondary circuit of the transformer) has leakage to ground it is NOT a shock hazard. It is no more of a shock hazard than a bunch of wire suspended by insulators stretching between a number of poles. If it were the case that current would leave the neutral and go into the ground then someone would be paying for it in the electric bill. In order to qualify as current electricity and not a static buildup there needs to be a path from the source, through the victim, and back to the source. In an isolated system no such path exists. Part of the path exists when you touch the neutral. But until the path is completed by means of current flowing back out of the ground and into another tap on the secondary of the transformer no complete circuit is established and no shock will ocurr. The only possibility of a shock is from static buildup and that is VERY unlikely due to fact that there is enough leakage in the system (even through slightly humid air around metal conductors) to keep a charge from building up.

BTW, anyone who grabs onto something electrical and does not understand in their own mind what is going on and are just simply taking someone elses word for it is a candidate for natural selection.