Earthing related questions

I was reading this article at:

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I have a couple of questions regarding this. I'll ask my question after quoting the portion my question is related to.

  1. "A further earth wire leads off to the water service and, in the case of more modern homes now, a separate earth stake driven into the ground."

Why does a earth wire lead off to the water service? What has water service got to do with earth wire? Also, what exactly is meant by water service here? Could someone please help me in visualizing? Is it like they expose the earth wire to stored water?

  1. "Taking the case where no earth stake exists, if the main neutral conductor coming into the house is interrupted (and often can be for a variety of reasons) then the only return path for electrical continuity is the earthing system, down through the water service, out into the street and back up through EVERYBODY'S water service / earth system."

How does the earth wire act as the return path. Let us take a room heater for example. The live wire would be connected to one end of the heating element and the neutral wire would be connected to the other end of the element. The earth wire would perhaps be connected to any metal in the body of the heater to ensure that in case the live wire comes in touch with the body of the heater, it doesn't induce an electric shock to the user who happens to touch the body. So, the earth wire is not connected to the heating element at all.

So, if the neutral wire is broken, there is absolutely no return path. How does the earth wire become the return path in this case?

  1. "How do I know a water service is live? Standard procedure (for those who follow rules and procedures - idiots don't) is to first connect, by way of proper earth clamp, an insulated earth wire of standard 4 mm size to the water service as it emerges from the water main. This cable is then run out to the meter box for connection to the neutral link."

What is "water main"? Where exactly is the earth wire connected at the water service's end?

A final question about this Usenet group. Is this the right place to ask these questions? Why posting is no longer allowed in sci.electronics?

Reply to
Disc Magnet
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Modern waterworks nowadays uses lots of plastic tubing. So dont think that you will get a reliable earth contact that way. However, connecting anything metallic(heating, concrete skeleton metal, any metal in the bathroom, your (metal)watertubes, etc , to a reliable grounding rod , is fine. Just dont rely on the water service as a provider for ground. Also check at the entry point of the wiring entering your house, in our country (Netherlands) there is a reliable ground connection supplied by the electricity company.

Reply to
Sjouke Burry

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Water supply generally uses metal pipe.. which is in the ground deep and makes for a good conductor, since it is coming in contact with a lot of ground.. The water main is just the main pipe that enters your home in some secure place where it's protected from cold weather to prevent freezing.. Being underground x number of feet, protects it from this problem..

If for some reason you lose the noodle from the pole and you have a ground problem with one of your appliances, You can have issues.!

Reply to

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The important point is right in the beginning of the article

Take a look at

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and especially about the TN-C-S picture. In addition for the three phases L1, L2 and L3, there is also a combined Protective Earth/Neutral (PEN) wire from the transformer to the house. At the main distribution panel (or whatever you call it in different countries), the PEN is split into Protective Earth (PE) and Neutral (N) wires, which are kept separate inside the house.

In normal situations only the N conductor will carry some current but no current will flow in the PE conductor and all PE terminals in the house will be at the same potential (the potential of the PEN to PE/N split point). An isolation fault in a load device will drive a very large current into the PE conductor and then into the PEN conductor and finally blow the fuse in the corresponding live line.

Now assuming that every load device is working OK, but the loads on the phases are unequal, so some current is flowing from the house to the transformer through the PEN wire. Assuming the PEN wire is broken, the potential of all the in house PE and N conductors will float to some potential between the phases, depending of the size of the loads. In a single phase system, the PE and N conductors will float to the full line voltage. If there are truly grounded objects, such as water/gass pipes and someone touches it and the case of an equipment is floating, up to the full mains voltage would be across the person.

To avoid this, a separate grounding electrode is used at each house.

Notice that in the TN-C-S picture, the N star point of the transformer is connected to a grounding electrode at the transformer (as well as to the PEN line to the consumer).

When the PEN line between the transformer and consumer is broken, but both the transformer as well as the consumer earthing electrodes are intact, a current will flow through the earth to the transformer neutral point, thus the PE and N wires inside the house do not float freely at high and dangerous levels, but will remain in safe levels for humans (but not necessary for equipment).

Connecting the PEN to PE/N split point to the water system serves two purposes, as long as metallic pipes are used, the pipes will function as additional ground electrodes but it also functions as equipotential bonding

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In practice, the grounding resistance can be quite high (several ohms) in a dry sandy environment, the potential can still float to dangerous levels.

By connecting all the in house PE and N wires, the incoming PEN wire, the water, gas, central heating pipes as well as antenna frame earth as well as the actual grounding electrode into a common bar, everything within the house will float at similar potentials, thus there is not a serious risk of touching the water pipe and an earthed device, even when both the PEN wire and the grounding electrode are broken or the grounding resistance is high.

Reply to
Paul Keinanen

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