Gas supply earth bonding

[Fallout]

I guess if we really want to get into it, there is probably more overall danger withfrom installations missing bonding that need it, than the cost of bonding unnecessary (most will be effectively bonded via the boiler)
So the question is probably alright and better than just not mentioning it, in the minds of those who added it.

Does the boiler have its own earth so would earth the pipework too as all metallic?

 

[EFLImpudence]

Does the boiler have its own earth so would earth the pipework too as all metallic?

It almost certainly does have its own earth and would therefore earth the pipework - thus making incorrectly applied bonding immaterial - BUT -

it would be safer if the pipes were not earthed by anything - ground, boiler or other appliances.

 

[Fallout]

Thanks could you explain why it would be safer if pipes were not earthed by anything?

 

[EFLImpudence]

Yes. Earthing is not a good thing in its own right; it is a necessary evil - and bonding is, where necessary, to equalise potential between parts which ARE earthed.

It would be better if NO metal part anywhere was earthed and allowed a path to earth that a person might touch while also touching a live conductor.

Unfortunately, metal parts of appliances have to be earthed to cause the OPD to disconnect the supply when they are made live by contact with a stray live conductor or fault, and

as above, some metal parts are earthed by their connection to appliances which are earthed.

 

[Harry Bloomfield]

Yes. Earthing is not a good thing in its own right; it is a necessary evil - and bonding is, where necessary, to equalise potential between parts which ARE earthed.

It would be better if NO metal part anywhere was earthed and allowed a path to earth that a person might touch while also touching a live conductor.

Whilst agreeing with that up to a point, I take the opposite view of as so much metalwork is earth bonded - it then becomes essential to enure all large pieces of metal is earth bonded. My reason for thinking this way, is that if you have one large metal item which is bonded, with a second large un-bonded item and that second item should become live and someone makes contact with both...

In my bathroom, which has a metal bath and a shower - the bath is bonded to both handles on the bath, to the shower, to the bath taps, to the wash basin taps and the radiator. Likewise round the rest of the house, all taps and radiators are bonded.

 

[SUNRAY]

Whilst agreeing with that up to a point, I take the opposite view of as so much metalwork is earth bonded - it then becomes essential to enure all large pieces of metal is earth bonded. My reason for thinking this way, is that if you have one large metal item which is bonded, with a second large un-bonded item and that second item should become live and someone makes contact with both...

In my bathroom, which has a metal bath and a shower - the bath is bonded to both handles on the bath, to the shower, to the bath taps, to the wash basin taps and the radiator. Likewise round the rest of the house, all taps and radiators are bonded.

That takes me back to the 70's

 

[Gasguru]

As gas workers we are always advised to notify homeowners in the absence of meter bonding.

We have a very specific law regarding continuity when removing meters/pipework (fittings in the legislation)...achieved with 10mm csa cable and huge croc clips.

https://www.legislation.gov.uk/uksi/1998/2451/regulation/10/made

Remember boilers can have the most abysmal designs in terms of electrical safety (especially those of the past).
For example the Potterton Puma had a 5A connector strip (with multiple 240V cables) in the base that would regularly become immersed in water from the leaks above,
the auto air vent top left would happily leak water straight down and into the 240V gas valve connector.
It's quite common to find boilers drowning in their own condensate and only finally when they die do we get called to attend.
Also consider the public that think nothing of boiling their kettles directly under boilers (few are IP rated to any worthwhile level).

 

[EFLImpudence]

Whilst agreeing with that up to a point,

Then you are correct up to a point.

I take the opposite view of as so much metalwork is earth bonded - it then becomes essential to enure all large pieces of metal is earth bonded.

Not so. If a metal part has no connection to earth then it should not be bonded.
In fact, if the metal part has no connection to earth then you are not bonding it; you are earthing it unnecessarily. once earthed unnecessarily; it might then need bonding. Think metal spoon.

My reason for thinking this way, is that if you have one large metal item which is bonded, with a second large un-bonded item and that second item should become live and someone makes contact with both...

If that second item is likely to become live then it should be earthed, and then perhaps bonded - but is it likely to become live? Think metal spoon.

In my bathroom, which has a metal bath and a shower - the bath is bonded to both handles on the bath, to the shower, to the bath taps, to the wash basin taps and the radiator. Likewise round the rest of the house, all taps and radiators are bonded.

The 'bonding' of the handles to the bath is pointless. If they are connected to the bath by their fixings, then they will be at the same state as the bath; if they are not, then it doesn't matter.
It is unlikely that the bath needs bonding and unlikely the shower will have exposed-conductive-parts.

As for the rest of the house - you say 'bonded' but it depends on what you have done.

If you earth all your pieces of cutlery, they then may need bonding together; instead of all being quite safe to handle before.

 

[EFLImpudence]

As gas workers we are always advised to notify homeowners in the absence of meter bonding.

It is the incoming pipe that should be bonded.

We have a very specific law regarding continuity when removing meters/pipework (fittings in the legislation)...achieved with 10mm csa cable and huge croc clips.

That is to ensure the same potential between the incoming pipe and consumer side pipe - which would not be necessary if the bonding conductor were connected to the correct pipe; the incoming pipe rather than the consumer's side pipework.

 

[bernardgreen]

There is also the situation where a metal item that is not earthed or bonded but does have a conductive path to the Earth.

Consider when a person is for some reason touching a Live wire and this metal item.

The impedance of the conductive path to the Earth is now critical.

It may be low enough that the current flowing through the person is enough to trip an RCD and limit the duration of the shock to that which is non fatal. The shock may stop the heart but, like when stopped by a defibrillator, the heart will in most cases restart after a short duration shock.

It may be high enough that the current flowing through the person is NOT enough to trip an RCD in which case the current will continue to flow through the person until that person or some other person breaks the contact.

What happens to the person depends on the amplitude of the current.

 

[EFLImpudence]

There is also the situation where a metal item that is not earthed or bonded but does have a conductive path to the Earth.

Then it IS earthed and should be treated as such.

 

[bernardgreen]

Then it IS earthed and should be treated as such.

No it is NOT Earthed, it has a significant impedance to Earth, an example is a damp wall where a conductive path can exist from a metal shelf bracket to the Earthed metal back box of a socket in the wall.

 

[Gasguru]

It is the incoming pipe that should be bonded.


That is to ensure the same potential between the incoming pipe and consumer side pipe - which would not be necessary if the bonding conductor were connected to the correct pipe; the incoming pipe rather than the consumer's side pipework.

Each trade has their own requirements, the gas regs are as daft as the electrcial regs...we've got far too many shiny suits (open to lobbying by those with the largest brown envelopes) making jobs for themselves tinkering with the standards.
Then of course the networks have their own requirements, it's common to find galvanic isolators on the steel service just before gas meters...they don't want us exporting currents.

 

[EFLImpudence]

it's common to find galvanic isolators on the steel service just before gas meters...they don't want us exporting currents.

Yes, I know, but that does not alter the fact that -

it is still the incoming pipe that should be bonded to achieve the electrical protection, and

in such a situation, with the isolator, the consumer's pipework being bonded achieves nothing.

 

[EFLImpudence]

No it is NOT Earthed, it has a significant impedance to Earth,

Like an earth electrode you mean?

an example is a damp wall where a conductive path can exist from a metal shelf bracket to the Earthed metal back box of a socket in the wall.

So - what are you proposing? Giving the shelf a negligible path to earth instead?

That does not detract from anything I have written.


What about stopping the damp or not having accessories in damp walls?