Sorry for this but my boiler recently had her annual service all was well except they said I don't have any bonding in place except I think I do the gas main is bonded in the meter cupboard and the radiators and hot and cold water feeds are all bonded in the bathroom upstairs. All pipework is copper throughout the plumbing never been altered in 40 years except for a new boiler oh and removal of the water tanks. So can I be confident the bonding upstairs is good enough?
You cannot verify the earthing method just by visual inspection of the supply cable. There is a fair chance that your external supply cables have been repaired by inserting a length of 3 core wavecon cable making the earthing TN-C-S (PME). You need to ask your DNO what earthing arrangement you have? If you live in the UKPN area they have declared that where they have supplied and earth from an incoming cable the supply is TN-C-S (PME). Only premises with their own transformer on the premises are likely to be TN-S. If the DNO cannot confirm the earthing method the advice is to consider the earthing system to be PME so Table 54.8 for the CSA of the bonding conductor applies.
So why are you saying the regulation does not apply to external gas meters. It's an “or” not a “shall”.
544.1.2 The main protective bonding connection to any extraneous-conductive-part such as gas, water or other metallic pipework or service shall be made as near as practicable to the point of entry of that part into the premises. Where there is a meter, isolation point or union, 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.
Which regulation are you talking about?
As I said the 600mm. only applies to internal meters - normally the gas.
or at the point of entry to the building if the meter is external.
Either way - bonding on the outlet (consumer's) side of the meter is incorrect electrically as (for internal meters) the extraneous-conductive-part (if it is an ext-c-p) is the supply side pipe where it enters the premises.
I live in a Scottish and southern area I don't know if they would tell me but Il ask them in due course I think that when they replaced a link box near hear I saw they had added an ea rth rod laid horizontaly in the dirt but il still ask as its not always easy to tell as you say
The honest answer is that regs. written by different groups of people do not always join up well, and whoever writes electrical guidance for plumbers does not bother to check what is in BS7671 and if it has changed in the last 50 years. It has.
Add the complication that the latest gas installation advice is that there should be an insulating joint or insulating insert (so called “IJ” or “II”) in the gas pipe between the street main and the meter if the electrical supply is PME, presumably to disrupt diverted currents leaving the building by an ever shrinking metallic network of gas pipes.
see here for an article about it and section 5,2 here
Now personally I have never seen this done in the wild, but if anyone at all actually did follow that guidance it would totally undo much of the benefits of any bonding to the incoming main anyway.
Mike
John Peckham:
You cannot verify the earthing method just by visual inspection of the supply cable. There is a fair chance that your external supply cables have been repaired by inserting a length of 3 core wavecon cable making the earthing TN-C-S (PME).
I am so tempted to ask SSE to tell me my earthing arrangement. If they have good records, they will tell me that I know fine well 'cos I saw them “PME” the cable under the side lawn. No wavecon anywhere between me and the tranny across the road!
Geoff
You bond the gas and water installation pipes not the service pipes see Regulation 411.3.1.2. In fact you are not allowed to bond a gas service pipe without the consent of the National Grid for the reason Mike above has said. The gas supply may have an insulated insert either a ceramic one from years gone by or a plastic one in modern times. I have a picture of a gas control valve with a plastic insert somewhere I will see if I can find it and post on here. My house has been surveyed by gas and water suppliers to have my service pipes replaced. I will see if they if they renew the gas control valve if they install one with a plastic insert.
Chris
At least you know that you have a PME supply.
Kelly
If you have seen an electrode laying next to the joint in the ground that is almost certainly a PME supply. The DNOs should/maybe lay an earth electrode next to a joint in a 3 phase cable on a PME service.
John Peckham:
Kelly
If you have seen an electrode laying next to the joint in the ground that is almost certainly a PME supply. The DNOs should/maybe lay an earth electrode next to a joint in a 3 phase cable on a PME service.
John unfortunately in the SSEN area (at least the old Wessex division ( where Kelly is)), an earth rod was often added connected to the lead sheath.
John Peckham:
Geoff
You bond the gas and water installation pipes not the service pipes see Regulation 411.3.1.2. In fact you are not allowed to bond a gas service pipe without the consent of the National Grid for the reason Mike above has said. The gas supply may have an insulated insert either a ceramic one from years gone by or a plastic one in modern times. I have a picture of a gas control valve with a plastic insert somewhere I will see if I can find it and post on here. My house has been surveyed by gas and water suppliers to have my service pipes replaced. I will see if they if they renew the gas control valve if they install one with a plastic insert.
411.3.1.2 says extraneous-conductive-parts must be main bonded, then says:
Metallic pipes entering the building having an insulating section at their point of entry need not be connected to the protective equipotential bonding.
It depends how close to the point of entry, but if any of the service pipe before an insulated section is accessible then it should be bonded.
Whatever the gas regulations state:
If the supply has an insulated insert then you are not bonding the service pipe which is the ext-c-p and the consumer's side is not an ext-c-p.
If the supply does not have an insulated section and you bond the consumer's side then you are bonding the service pipe - so should connect the bonding conductor to the service pipe.
We're about to take you to the IET registration website. Don't worry though, you'll be sent straight back to the community after completing the registration.
Continue to the IET registration site
