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Metal parts within the house are bonded for two reasons, one it stops a fault in one room being taken into another room, so if a dog knocked over a standard lamp and the bulb smashed on a radiator it would not make all radiators in the house live, the second is so if there is a supply fault items earthed in the house are same polarity throughout the house so present no danger even if at 230 volt above true earth.
The second fault means if a gas pipe is bonded before the insulating pipe it would try to carry the current due to the faulty TN-C-S supply, this could melt the gas pipe which is clearly a danger, it is unlikely to melt a water pipe as they are water cooled. Where the water supply is in a metal pipe that would likely stop the current going through the gas pipe, and with a TT supply it really does not matter where the earth goes, houses are now RCD protected so bonding to stop faults passing from room to room is no longer really required.
So the point is the bond must be were if the TN-C-S supply is damaged that the earth current will not damage the gas pipe. Never mind regulations look at common sense. It also needs to be where some one working on the meter will not get a shock, so all metal within an enclosure should be insulated or bonded, having one pipe bonded to house earth and other pipe bonded to true earth within an enclosure is clearly not right.
There must be a procedure for gas workers, it may be that a earth clamp is fitted before removing meter, I am not gas so don't know the procedure, I know with my house the gas pipe is bonded as it enters the garage, this was to 16th Edition, the only earth at the meter is from the gas pipe that goes through the wall into the garage. So unless the person working on the meter is given assess to garage they would not know if bonded or not.
I assume there is an insulating section to stop TN-C-S faults damaging the gas pipe, although there have been a number of reports of fire when copper is stolen from sub-stations so it would seem this is not always the case.
So over to the gas guys to explain their safety procedure.
The second fault means if a gas pipe is bonded before the insulating pipe it would try to carry the current due to the faulty TN-C-S supply, this could melt the gas pipe which is clearly a danger, it is unlikely to melt a water pipe as they are water cooled. Where the water supply is in a metal pipe that would likely stop the current going through the gas pipe, and with a TT supply it really does not matter where the earth goes, houses are now RCD protected so bonding to stop faults passing from room to room is no longer really required.
So the point is the bond must be were if the TN-C-S supply is damaged that the earth current will not damage the gas pipe. Never mind regulations look at common sense. It also needs to be where some one working on the meter will not get a shock, so all metal within an enclosure should be insulated or bonded, having one pipe bonded to house earth and other pipe bonded to true earth within an enclosure is clearly not right.
There must be a procedure for gas workers, it may be that a earth clamp is fitted before removing meter, I am not gas so don't know the procedure, I know with my house the gas pipe is bonded as it enters the garage, this was to 16th Edition, the only earth at the meter is from the gas pipe that goes through the wall into the garage. So unless the person working on the meter is given assess to garage they would not know if bonded or not.
I assume there is an insulating section to stop TN-C-S faults damaging the gas pipe, although there have been a number of reports of fire when copper is stolen from sub-stations so it would seem this is not always the case.
So over to the gas guys to explain their safety procedure.