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Earthing alternatives

  1. Nov 4, 2004 #1
    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?
     
    Last edited: Nov 4, 2004
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  3. Nov 4, 2004 #2

    NoTime

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    No! Absolutely No! It would not work.
     
  4. Nov 4, 2004 #3

    Cliff_J

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    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
     
  5. Nov 5, 2004 #4

    Gokul43201

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    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 !
     
  6. Nov 5, 2004 #5

    Cliff_J

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

    Cliff
     
  7. Nov 5, 2004 #6
    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.
    ...
     
    Last edited by a moderator: Nov 5, 2004
  8. Nov 5, 2004 #7

    Averagesupernova

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    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.
     
  9. Nov 5, 2004 #8
    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 learnt 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 realised 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.
     
  10. Nov 5, 2004 #9

    Averagesupernova

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    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.
     
  11. Nov 6, 2004 #10
    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?
     
  12. Nov 7, 2004 #11

    Gokul43201

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    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 :biggrin: !
     
  13. Nov 7, 2004 #12
    by the way how much amperes (min) across your heart does it take for you to die?
     
  14. Nov 7, 2004 #13

    brewnog

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  15. Nov 8, 2004 #14
    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.
     
  16. Nov 8, 2004 #15

    Averagesupernova

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    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.
     
  17. Nov 8, 2004 #16

    Cliff_J

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    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
     
  18. Nov 9, 2004 #17
    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. :smile:
     
    Last edited by a moderator: Nov 9, 2004
  19. Nov 9, 2004 #18

    brewnog

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    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!)
     
  20. Nov 9, 2004 #19

    Cliff_J

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    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....:smile:

    Thanks for the info!
    Cliff
     
  21. Nov 9, 2004 #20
    thanx for pointing that out to me Averagesupernova because that was exactly what i was assuming.
     
  22. Nov 9, 2004 #21

    Averagesupernova

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    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.
     
  23. Nov 10, 2004 #22
    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.
     
  24. Nov 10, 2004 #23

    NoTime

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    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.
     
  25. Nov 11, 2004 #24
    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?
     
  26. Nov 11, 2004 #25

    NoTime

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    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.
     
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