Supplies bonding...

I thought services were to bonded as close to the point where they enter the premises. So if you have a gas meter outside then it is bonded at the meter for convenience of inspection.

 

The BS7671 works on the proviso that each bonding point will be individually bonded.
There is no mention of it in the BS7671 regs because you are expected to run individual equipotential bonding.

In the guidance notes from the IET they do accept the ability to share the main equipotential bonding but if done this way it must be continuous and there is where the confusion lies because the BS7671 does not allow you to share an equipotential CPC.

If you follow the BS7671 to the word then you bond it individually but if you accept the guidance note to share one equipotential bonding method then it must be continuous as per the guide notes and this is deemed acceptable as it serves the same purpose and need of individual bonding. Why? because if connection to one of the bonding points was to fail it does not disconnect all the other bonding points sharing the CPC.

Common sense really.

http://electrical.theiet.org/wiring-matters/43/bonding.cfm?type=pdf

 

Looking at the regs. I don't think it does if it is plastic under the ground. I think the gas people do it because it is their custom to do so.
The old gas meter position will still be attached by copper pipe to the new gas meter position and the old meter position is earthed by 6mm cable to the earthing point next to the CU and so if this cable remains in place I don't see much of a problem.
It is 6mm instead of 10mm and is a lot more than 600 mm from the new meter.
Anyway I waiting for a phone call from an electrician working for Balfour Beatty who are upgrading the gas mains.
I have managed to get the gas pipework done through my brick porch and into the house to the existing pipework which does not look to bad , if you are fan of pipework that is.
The next task is to get the electrician to route his earth cable through an existing hole in the house wall and to follow the existing porch wiring route through the lounge to the CU under the stairs.
This is 10 or 11 meters. So fingers crossed!

 

There is no must about it although prudent.

 

Yes "Prudent" which makes for strongly advised to keep it continuous based on the fact in the future it may become disconnected and go unnoticed.

 

Just an update on this. My gas meter has now been moved to its new position. I am still waiting for the bonding to be done.
Using a Kewtech 107 tester, as I am just a householder not an electrician, which has a rudimentary earth loop tester built in, all the sockets in the house results in the orange "check" light coming on instead of all green as previously.
This means an earth loop impedance of over 1.8 ohms on all sockets so presumably Ze has increased as nothing has changed in the internal electrical system of the house.
As it has not illuminated " red" for "urgent check do I need to worry? Might the earth loop impedance be reduced when the bonding is moved to within 600mm from the gas meter?
Or could the old lead gas pipe, which has now been replaced by plastic, have been providing an additional earth in addition to the TNCS one?
The house is a middle terrace of five and I have checked with two of the neighbours who I know well and the socket tester shows green in one of each of their sockets.
They all have had their metal gas pipes replaced with yellow plastic.
Any advice would be much appreciated.

 

Following on from the above I have asked my next door neighbour to check a couple of her sockets and they both showed " orange".
Her gas meter was moved at teatime last night and this is when the problem started.
Her gas meter is not yet bonded at all. So it seems to be a gas matter that will have to be rectified by the gas installers when they get round to it.

 

You might be waiting a long time for the gas board to reconnect bonding; my meter was moved outside from cupboard under the stairs, they reused the existing metal pipes but left the earth bond in the original position. I phoned em but they would not return to connect earth bond to its proper position (where pipe enters building); I ended up doing it myself !

As for the Ze being increased I cannot see how disconnecting the gas bonding would make any difference on a TNCS system. Ze does fluctuate but for a TNCS should be ever no greater than about 0.35 ohms. If your socket circuit Zs is now high since the meter change (looks like it is if over 1.8) then somethings amiss and potentially dangerous. I would call the DNO about this !, dont leave it to the gas board !

 

Thanks very much. Just to clarify. So I have already checked that the Loop tester is not faulty as one immediate neighbours' sockets show green but ours and our other immediate neighbours' snow orange which indicates over 1.8 ohms.
I will ring North West Electricity (our DNO) on Monday.
I am not sure but I think our electric cable .which presumably dates from the late 1930's comes up our front garden on the boundary. It might even be a shared cable with next door.
The mole that the gas used to get the new plastic gas pipe in came from next door.
I know that this is all purely speculation but if the cable to the house or a junction box under the gardens or pavement have been damaged by the gas people either digging or using a mole could this have caused the problem?

 

Before calling them, I suggest you use a proper, calibrated EFLI tester, remove all other earths and bonds and test exactly what the Ze is at the origin.

THEN you can contact NWE with a real issue. Those "quick check" things are all right for a quick check, but you need proper data before calling out the cavalry.

 

I am not competent to do that so I will have to get an electrician in .

 

I was very lucky to get my electrician in this morning. as he had an hour to spare.
He said the Earth Loop Impedance was potentially dangerous and I should ring the DNO urgently.
The DNO came this afternoon and their reading of Ze was 5 ohms.
It is a TNS system and as you will know the upper limit is 0.8 ohms.
Our electric main is looped in from the terraced house next door which with my simple tester appeared to be in a similar position to ours.
Unfortunately my neighbour was not in or unavailable and he could not check her system.
So as the ELI was less than 20 ohms he downgraded our main fuse from 100 amps to 80 amps and temporarily put a 100ms ( I think) RCD between the cut out and meter
pending investigating what if anything has gone wrong next door before going into the cable and junction boxes in the street.
I feel a lot happier about it now.
Thank you to everybody who helped on here. It is much appreciated.

 

Glad you have progress on this. Let us know how it goes when the DNO returns!

 

I will do indeed.

 

Hi all, just has my gas installation passed by a local GS registered engineer. He was completely happy with a 10mm earth from the incoming earth (before the CU) bonded to the copper from the meter. A run of about three meters.

 

No reason for him not to be happy with that, it's the standard way of doing things.