Earthing issue

[granada42]

Hello

We had an electricians report on our electrics last week. He suggested replacing the consumer unit to a more up to date one and running an earthing cable from under the stairs all the way to the other side of the house where the stopcock is. The stopcock comes in near the lounge and is a blue plastic pipe. I also had to get Central Networks (EoN) out to look at a high ZE reading.
The guy from EoN suggested just drilling through to the kitchen which is the other side of where the electrics are and earthing to an old metal stopcock (unused) then cross bonding the copper pipes which are nearby.

Not sure who to believe here, surely earthing to a plastic pipe wouldn't do much?

Obviously I'll be getting a third opinion on this but in the meantime any suggestions?

Cheers.

 

[GaryMo]

544.1.2 The main equipotential bonding connection to any gas, water or other service shall be made as near as practicable to the point of entry of that service into the premises. Where there is an insulating section or insert at that point, or there is a meter, the connection shall be made to the consumer's hard metal pipework and before any branch pipework. Where practicable the connection shall be made within 600 mm of the meter outlet union or at the point of entry to the building if the meter is external.

 

[sparkwright]

Is your electric supply overhead?

 

[GaryMo]

Is your electric supply overhead?

Surely the OP is talking of Protective Equipotential Bonding?

 

[sparkwright]

Yes, but he has also mentioned his high Ze and am concerned the main earth to the house MAY have been provided by the old water main that is disused.

 

[GaryMo]

I doubt the EoN guy would have suggested using an old water supply as an electrode.

542.2.4 A metallic pipe for gases or flammable liquids shall not be used as an earth electrode. The metallic pipe of a water utility supply shall not be used as an earth electrode. Other metallic water supply pipework shall not be used as an earth electrode unless precautions are taken against its removal and it has been considered for such a use.

 

[securespark]

The answer to this partly hinges on your supply type.

Do your supply cables come from overhead?

If not, is there a main earth connection to the supply cable or service head?

If the answer to the first question is yes and there is no earth connection to the service head, then you have a TT supply, similarly if the answer to the second question is no.

If your supply is TT, you cannot rely on a water pipe for an earth electrode.

You should have a rod installed, or ask Eon about a coversion to PME.

Plus you will need RCD protection.

 

[xr4x4]

can you have PME on overhead lines?

 

[RF Lighting]

It is possible, but depending on the age of the network, it is not always available.

Most of the overhead network round my area has been upgraded to PME, but there are still plenty of places where it hasn't.

 

[mfarrow]

Don't always assume TTs only come from overhead line supplies either.

My gran's street was always TT with overheads until 1999 when a housing developer built houses behind them (on land occupied partly by the overheads). Now they're TT with buried cables instead.

 

[granada42]

Thanks for the replies

The supply comes in via underground cable. Old TNS supply (what I gather from the elecrician's report)
The guy from EoN fixed the high Ze issue by re-newing the earth strap things (original had corroded) from where the thick cable enters the black box and fitting a white unit with earth wires coming out of it (sorry I'm not really sure what these are).
The EoN guy suggested that I upgrade the thin earth cable going to the gas supply cable to a thicker one and then have an earth cable going to the old stopcock (lead pipe in kitchen) instead of all round the house to the new stopcock (blue plastic inlet pipe) as suggested by the electrician who did the report.

Just a bit confused really now if the electrician is saying to earth to the stopcock of the new water supply (with the plastic pipe) and the guy from EoN is saying to simply run a cable through into the kitchen to the old water supply pipe.

Cheers

 

[sparkwright]

The new 10 mm earth cable wouldn't actually be connected to the plastic pipe. I imagine on the consumer's side of the new stop cock the pipework becomes copper throughout. If so, it is this copper (or steel) that needs earthing and as close to the new stop cock as possible.

Is the old stop cock still in service?

 

[mfarrow]

544.1.2 The main equipotential bonding connection to any gas, water or other service shall be made as near as practicable to the point of entry of that service into the premises... Where practicable the connection shall be made within 600 mm of the meter outlet union or at the point of entry to the building if the meter is external.

Is the answer, unless you consider the pipe coming into the kitchen as still forming part of the household services, in which case you need to bond to both.

 

[GaryMo]

Both may be extraneous-conductive-parts which are liable to introduce a potential so on that basis, both may require Protective Equipotential Conductors between them and the Main Earthing Terminal.

 

[granada42]

Cheers for the replies.

The old stop cock is not in service. I turned it on, it hissed for about 5 mins but there's no water there.

I'll post a couple of photos tomorrow sometime so that you can see exactly how things are at the moment.

Much appreciated