Some of it is here //www.diynot.com/wiki/electrics:main_equipotential_bonding
mains gas pipe bonding,?
- Thread starter joesoap1
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I think you are right, this is guidance. Quoting from Guidance Note 8:
'Extraneous-conductive-parts may be, and often are, connected to the MET individually, as shown in Figure 5.4. However, it is permitted to connect them collectively or in groups where the main equipotential bonding conductor is looped from one extraneous-conductive-part to another. Where bonding is undertaken in this way, the main equipotential bonding conductor should remain unbroken at intermediate points, as shown in Figure 5.5, thus maintaining continuity to other extraneous-conductive- parts should one be disconnected for whatever reason.'
An earth connection prevents a metal part from becoming live under fault conditions, by ensuring that the supply is disconnected by protection devices. The main bonding ensures that the touch voltage generated by an earth fault between an exposed conductive part (e.g. casing of boiler) and, for instance, an adjacent water pipe that is introducing an external earth potential (extraneous conductive part) is minimised.
See description here: http://electrical.theiet.org/wiring-matters/22/bonding.cfm?type=pdf
Hi bengasman, much appreciated advice. If I didn,t have a cut out hatch, under Fitted carpet, there would be NO other convenient point, other than within the garage, where the boiler/CB/and all pipes are together.That would be ideal for me, except for the 600mm rule.If I covered the floor with other type of flooring, under floor access, would be very difficult, without ripping floor up.This is what makes me think the bonding wasn,t done in the first place.The householder before me, who was/and still is a sparky, intended to bond at garage, 15 metres from gas meter.All the pipes are underfloor.and depth of underfloor access reduces from 3 feet at meter,to 6 inches at garage where all pipework terminates at combi .This was 15 years ago.Any opinion on this would be much appreciated.Not trying to cop out of regs, but trying to make my job easier.Cheers
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I have not understood why you are unable to put the earthing clamp within the meter box or housing where ever it is fitted?
Tony
Hi Tony, If I don,t clamp within the meter box, and bring cable 15 metres underfloor to garage, which are opposite ends of bungalow,to consumerboard, nobody can test it,or even locate it unless they take carpet up and scrawl undefloor like me.This was the start of the problem. Homeserve couldn,t locate clamp in box, presumed it was elsewhere, I had no idea,at the time, and then they gave me boiler warning cert.That,s when I found it wasn,t bonded at all.
DONE.Gone from meter, inside box , to water riser, 600mm, then back to MET.20 metre run.cheers all for advice.
Could someone please explain the requirement for a house split into 4 apartments on different levels with each one having its own gas heating and consequently each having its own meter.
Surely the incoming gas pipe should be bonded within 600 mm of entering the building and that should be enough?
Alternatively would it be advisable to bond from inlet pipework to outlet pipework of each individual meter?
Surely the incoming gas pipe should be bonded within 600 mm of entering the building and that should be enough?
Alternatively would it be advisable to bond from inlet pipework to outlet pipework of each individual meter?
You should really start anew thread.
Are the meters secondary meters or primary meters?
If primary, then defo bond from each outlet. I THINK the same applies if they are secondary meters, but would have to have a ponder to be sure.
Thanks and sorry! I thought it might be a follow up to others on similar topic.
As far as I am aware there is no primary meter and the tenants on each floor have their own meters so guess this makes them primary.
Could you please explain "defo bond" and if this requires bonding on each meter outlet, where must the other end go?
As far as I am aware there is no primary meter and the tenants on each floor have their own meters so guess this makes them primary.
Could you please explain "defo bond" and if this requires bonding on each meter outlet, where must the other end go?
I meant “definitely bond” . The bond is from the distribution board to the gas pipe . The gas end is connected within 600mm of the meter outlet or as the pipe (after the meter) enters the property, if the meter is outside. In this context “property” is tge individual dwelling. The connection must be before any branch on the internal pipework.
Isn't there still a potential problem, even if the outlet piping is earthed as you suggest?
The earthing of the length of input piping from where it comes into the house to, e.g. the loft apartment, cannot be guaranteed, because the gas meter may not be conductive.
However, if as would seem possible, BG have bonded the incoming pipe "within 600mm of entering the building", then bonding across meter inlet and outlet pipes would be an answer. See: https://engx.theiet.org/f/wiring-and-regulations/21426/gas-pipe-bonding
The earthing of the length of input piping from where it comes into the house to, e.g. the loft apartment, cannot be guaranteed, because the gas meter may not be conductive.
However, if as would seem possible, BG have bonded the incoming pipe "within 600mm of entering the building", then bonding across meter inlet and outlet pipes would be an answer. See: https://engx.theiet.org/f/wiring-and-regulations/21426/gas-pipe-bonding
A couple of things to consider.
Equipotential bonding requires metal work coming into the premises to be connected ( bonded ) to the Main Earth Terminal ( MET ) of the electrical supply to the premise, Nothing complicated when it is a case of a building containing one premise ( a home or an office ) with one electrical supply.
It could get complicated when the building contains more than one premise. In this case there are 4 premises ( 4 flats ) each with its own MET.
In most case the supply is TN-C-S or PME and the MET is connected to the Neutral of the electrical supply. The exception would be if the supply earthing was TT
If all the premises are fed as TN-C-S from the same electrical cable from the street then all the METs are connected to the same incoming Neutral somewhere in or very close to the building,.
If on the other hand the individual premises are fed from different street cables there is a possibility that the bonding will be connecting the different potentials of two or more Network Neutrals together via a very low impedance sneak path
Neutral 1---MET 1---bond to pipes in flat 1----service pipes common to flat 1 and flat 2----bond to pipes in flat 2 ---MET 2 ---Neutral 2
Equipotential bonding requires metal work coming into the premises to be connected ( bonded ) to the Main Earth Terminal ( MET ) of the electrical supply to the premise, Nothing complicated when it is a case of a building containing one premise ( a home or an office ) with one electrical supply.
It could get complicated when the building contains more than one premise. In this case there are 4 premises ( 4 flats ) each with its own MET.
In most case the supply is TN-C-S or PME and the MET is connected to the Neutral of the electrical supply. The exception would be if the supply earthing was TT
If all the premises are fed as TN-C-S from the same electrical cable from the street then all the METs are connected to the same incoming Neutral somewhere in or very close to the building,.
If on the other hand the individual premises are fed from different street cables there is a possibility that the bonding will be connecting the different potentials of two or more Network Neutrals together via a very low impedance sneak path
Neutral 1---MET 1---bond to pipes in flat 1----service pipes common to flat 1 and flat 2----bond to pipes in flat 2 ---MET 2 ---Neutral 2
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