Main Earth Bonding (two supplies)

[chris day]

Large house with x2 power supplies/ service heads.

first supply 3 phase TN-S located in a pig of a place and is furthest away from the gas and water entry points and meter positions.

Second supply is a single phase TN-S located only a few meters away from the water and gas entry points to the building.

currently there is no bonding to these pipes, question is would it be wrong to use the single phase supply's MET position to main bond the water and gas?

 

[Nigel]

I would say yes it is wrong. Certainly if the single phase supply will not be being used at all.

 

[telectrix]

can you establish (wander lead) if the 3 phase and the single phase METs are equipotential, i.e. a suitable low resistance between them. otherwise, an earth fault on the 3 phase installation would not cause a rise in potential of the extraneous metal.

 

[westward10]

You need to connect the two main earth terminals together.

 

[Deleted account]

What kind of house is this that needs 4 phases?

Is the single phase on one meter and the 3 phase on another.

Last time I cam across a setup like this was in a hotel b& b.
The 3 phase was the original supply to whole property.
The single phase was an illegal supply suposedly fitted by a western power employee for cash in hand. It had a head, meter and CU.
I only found out when I was about to call western power regarding the tails coming out the head showed evidence of overheating (burning).

The hotel owner had put most of the hotels supply on this free single phase meter. Thus overloading it.

 

[PEG]

I reckon,the first thing to find out,is the origin of both supplies. They may even arrive from separate sources,and the joining of MET's could cause some complications.
Have you long-leaded from the SP to the three others?

 

[westward10]

If the DNO were involved they would do one of two things, disconnect one supply or insist the earthing systems are physically connected together.

 

[PEG]

A pal of mine,has a place at Stockton Heath,which has an original underground TP+N from the roadside,TNS,to the main house,and the large garage/workshop,at the rear,has an overhead supply,with it's separate metering.
Over the years,the garage has become an extension of the property,with it's supply catering for some of the extension,and all outside lighting,etc.

Both supplies from the same DNO,and although in the past,there have been visits,regarding separate issues with both supplies,there has been no insistence,on either connection of earths,or disconnection.

 

[westward10]

Do the circuits cross over in any way.

 

[PEG]

Hi,yes,physically,and at varying distances,they do.

They do not enter any enclosure or junction box,together,but are present in the same rooms,voids and garden.

The most, any agent of the DNO has said - to my knowledge - is "....as long as any spark is aware...crack on..."

This is not the only example,of such a situation,and i myself,have left information at the incomers,to assist and prevent.

If numpties get involved....all bets are off