ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades US EARTHING SYSTEMS

Over here in Ireland bonding to a water pipe to ground an installation is absolutely illegal as there is a strong possibility of the watermains being made of plastic resulting in a pretty poor grounding arrangement.This has been the situation since the 1960s. Even where a water service enters the house as a copper pipe the main feeding it might be plastic.

semiflexible plastic pipes are increasingly being used in internal plumbing here too further complicating bonding requirments as it is still necessary to bond the metal parts of the plumbing to ground and obviously to ensure that the plumbing doesn't carry a current in the event of something energising the pipework (e.g. a faulty immersion heater) With plastic pipes there is a possibility that the path of least resistance may be via the tap/shower and the person touching it if bonding is not carried out properly.
Particuarly considering that Irish houses use a plastic tank in the attic as a head tank for the hot and cold water systems other than the kitchen. So you could have a completely electrically isolated body of water in the attic feeding the bathrooms!!! If the water heater had a ground leak to the water system the only path to ground might be via the shower if grounding / bonding is not correctly carried out.

Local grounding's always done through an earthrod, these come as a large concrete block the top of which is suitable for blending into paving slabs/bricks.

If anyone's interested in seeing all of the permissable connections in domestic LV situations click on this PDF http://www.esb.ie/main/downloads/energy_home/National_code_of_practice_3rd_Edition.pdf

ESB network's code of practice.

also Pictures of irish service entrances, main fusing arrangements, metering arrangements, etc etc..

It even has pics of how to wire up a non-metered service for a payphone & associated lamp & on street CCTV cameras


[This message has been edited by djk (edited 09-02-2003).]

Let me add a comment about North American practices {and typically worldwide} that may be apparent. [I hope I haven’t overlooked someone already detailing this here.] “Bonding/grounding” of interior metal water and gas piping serves two ends. To an increasing degree, it’s use as a grounding electrode where an insufficient length of it has direct soil contact, is becoming less common with the increase in non-metallic piping, both underground and above ground.

Nowadays, the primary reason for “bonding/grounding” is to limit potential difference between metal piping and other conductive objects in and around buildings. Continuity is also conducive to rapid clearing of overcurrent-protective devices (breakers/fuses.)




[This message has been edited by Bjarney (edited 09-02-2003).]

Outlawed 01/01/01, but I installed such a system myself (or at least extended it) some time ago.
Original wiring was like this: 10A Edison base MCB (awfully old no-blow type, was stuck in the "on" position). Feeder to kitchen 2 black cloth covered wires in plaster. At wall sconce NYIF cable tapped off to receptacle, 1.5mm2 red wire in conduit from water line somewhere near the sink or maybe the toilet tank on the other side of the wall to the receptacle. From this point cables with ground fed the 1500W 5l HW boiler and another receptacle. I rerouted the wiring, but the grounding remained the same until we replaced the feeder. And we installed a 30mA RCD and new breakers right at the beginning. Old apartments were usually like that. All outlets apart from 1 or 2 in the kitchen ungrounded, these few bonded to the water pipe. If there was an infrared heater in the bathroom it was probably grounded as well. And even though it's illegal I think hardly anyone bothered changing old wiring. Even where water risers in apartment buildings are replaced with plastic the grounding usually remains that way, i.e. the ground isn't a ground any more but just a useless wire.

Since it seems that in some countries at one time the earth rod was the only means for hopefully opening a fuse in case of a fault, I am wondering how any electrician could be so optimistic.

This is a question I have for US electricians also, since so many still assume that the connection to earth provides this safety. One would think that everyone learned V=IR and could understand that a rod/earth impedance of, say 50 ohms would allow only 2+ amps at 120 V or 4.8 amps at 240 V. How can that blow a fuse or trip a circuit breaker?

Does anyone on this forum understand the thinking involved?

Karl

That's an interesting document from the ESB in Ireland. It suggests that all new services are PME (TN-C-S). Is that right Dave?

The grounding in Austria sounds as though it was very haphazard in the past. (Maybe that's why they chose red for ground: It might actually be energized to 220V by a fault! )

Karl,
I think the issue of grounding/earthing in general is an area which is grossly misunderstood, both by the layman and by some electricians.

It goes hand-in-hand with another problem that we've discussed at ECN in the past: The belief that electricity always tries to return to ground. It doesn't.

If people would abandon that misguided concept and accept that current will simply try to flow in a complete circuit back to its source, then they would see that the earth can just be a big conductor in a part of that circuit.

Paul,
Yes, that is what I try to get across: the fault current is seeking to complete the circuit to the transformer (following voltage gradients). I have referred to the belief that the earth is an electrical sponge as the picture some people have, perhaps because they see lighning strikes disappearing into the earth, but even here there is a circuit being completed between earth and atmosphere.

But what I am still mystified about is how V=IR has escaped the attention of so many electricians and also engineers.

Karl

Paul,

Yup is the standard even on old installations, except in absolutely exceptional circumstances.

The ETCI (ElectroTechnical Council of Ireland) and ESB are pretty strict on neutralising requirements contractors have no flexibility or options the ESB specify after a pre-connection site survey how it will be done and the bond is sealed.

[This message has been edited by djk (edited 09-03-2003).]

Karl,
The use of Ohms law is made with the UK requirement that the earth electrode resistance multiplied by the nominal operating current of the RCD should not exceed 50V for normal installations and 25V for special locations like farms and construction sites.

I find the ESB's use of that term quite amusing. Maybe it's because we apply the term neutralizing in electronics to a totally different concept.

For whatever reason, some people seem to believe that ground connections work differently and don't obey the same laws of physics as the rest of the circuit. It's as if they think that driving a rod into the ground at any point makes an automatic zero-ohm link to any other ground rod.

Lyle mentioned the 50V requirement for RCD-trip x ground impedance here. When the voltage-operated ELCB was installed here, it was also a design requirement that the breaker must trip with 50V across its operating coil. In many cases, the ELCB tripped at considerably less than that.


[This message has been edited by pauluk (edited 09-04-2003).]

The ESB just like words ending in "ise"

Neutralise
Energise
De-Energise

so then you can sound really complicated and talk about the neutralisation and energisation of the 0.23 kV 80Ampere supply, which was previously de-energised, that occured at 12:02:39.

that way you charge four times the price


[This message has been edited by djk (edited 09-04-2003).]