Earth Bonding - LPG Pipe That Does Not Go Underground

[aesmith]

Hi,
Our cooker is LPG, fitted on the inside of an outside wall if that makes sense. The gas pipe runs internally then through the wall to the regulator and changeover unit mounted outside, around 4' off the ground. The pipe doesn't go underground at any point.

My understanding is that it doesn't need bonding, the original gas fitter clearly agree as he marked it as "N/A" on the Gas Safety Certificate. However the guy that just did a service wasn't quite happy, he expected to see earth bonding and was a bit dubious.

So my questions are (1) am I correct that bonding isn't needed? And (2) assuming it's not needed, is there any issue with adding it anyway, just to keep any future gas fitter happy?

Thanks, Tony S

 

[Rockingit]

So to be clear, this is a propane tank fed arrangement?

 

[aesmith]

Sorry, the gas supply is two 19kg cylinders each connected by flexible hose to the changeover switch.

 

[Rockingit]

OK, so you're quite correct in thinking that this doesn't need bonding (BS7671 411.3.1.2 refers.....) However, whether you want to attempt to have that conversation time after time with the less informed or just pay to get it done regardless is entirely up to you!!

 

[aesmith]

However, whether you want to attempt to have that conversation time after time with the less informed or just pay to get it done regardless is entirely up to you!!

That was exactly what I was thinking. For example the current certificate notes "Could not see evidence of earth bonding. Instruct an electrician to check gas pipe and add bonding if none present."

I take it from your response that there's no actual disadvantage or safety concern about installing bonding in this case, even if not actually needed?

Strictly we don't actually need to do anything as there's no requirement for a current certificate anyway. But I'd prefer that the installation is such that it would pass if the requirement ever came about.

 

[littlespark]

I posted the same question last week, although my gas pipe was feeding a boiler, and was connected to the water pipework internally at the boiler.

Whatever the regs say, I would be inclined to make sure it’s earthed… just in case some fluke instance happens and your hob becomes live..(electric ignition?) then you would have a live hob, and live gas pipes…

All it would take would be a small spark….

 

[Rockingit]

I posted the same question last week, although my gas pipe was feeding a boiler, and was connected to the water pipework internally at the boiler.

Whatever the regs say, I would be inclined to make sure it’s earthed… just in case some fluke instance happens and your hob becomes live..(electric ignition?) then you would have a live hob, and live gas pipes…

All it would take would be a small spark….

There's actually a counter-argument that by bonding when not actually necessary that we add the potential for an earth fault path to exist where none existed before, so these things do need skilled judgment.

 

[littlespark]

There's actually a counter-argument that by bonding when not actually necessary that we add the potential for an earth fault path to exist where none existed before, so these things do need skilled judgment.

Totally agree.
That's why the OP is asking for our skilled judgement rather than taking the word of a gas engineer.

Not sure of the OP's situation, but certainly my own, there is a parallel path to Earth through the other copper pipes and the flex from the spur to the boiler.

 

[UNG]

That was exactly what I was thinking. For example the current certificate notes "Could not see evidence of earth bonding. Instruct an electrician to check gas pipe and add bonding if none present."

Sounds like the gas engineer has already decided the outcome!!!!

 

[aesmith]

Thanks for all the comments. I don't strictly need a gas safety certificate for our own house, but if the need arises I could use a different gas fitter. This guy also wanted to see a CO alarm, even though the actual guidance says ..

CO detectors to be fitted in all rooms where there is a fixed combustion appliance (excluding an appliance used solely for cooking) or a flue.

However I've not been able to put my finger on the actual legislation governing that requirement. My quote comes from the "Tolerable Standard Guidance
Tolerable Standards

 

[Dartlec]

Thanks for all the comments. I don't strictly need a gas safety certificate for our own house, but if the need arises I could use a different gas fitter. This guy also wanted to see a CO alarm, even though the actual guidance says ..


However I've not been able to put my finger on the actual legislation governing that requirement. My quote comes from the "Tolerable Standard Guidance
Tolerable Standards

The legislation is significantly tighter in Scotland than in England, where we have the catchily titled "The Smoke and Carbon Monoxide Alarm (England) Regulations 2015" which is only for landlords and specifies:

a carbon monoxide alarm is equipped in any room of the premises which is used wholly or partly as living accommodation and contains a solid fuel burning combustion appliance

I'm not expert on the Scotland legislation, but it does seem to match with what you say about carbon monoxide and "tolerable standards" in most places.

From an 'official' page: Fire and smoke alarms: changes to the law - https://www.gov.scot/publications/fire-and-smoke-alarms-in-scottish-homes/

If you have a carbon-fuelled appliance – like a boiler, fire, heater or flue – in any room, you must also have a carbon monoxide detector in that room

Which isn't entirely clear whether it includes cookers.

Though to be honest, they are so cheap I'd probably put one in just for peace of mind.

Re the bonding - It's always useful for when someone demands something, to request in writing the legislation or guidance they are using to base their decision on. A tick box on an inspection report is not a good enough justification.

One possible option going forward would be to get an electrician to inspect - and specify in writing that bonding is not required in your circumstance - something you could show any future gas fitter.

 

[littlespark]

I often wondered why Co detectors were not needed for a cooker...

Is it something to do with the holes that the flame comes from? Or the fact that kitchens should have an extractor?
A boiler is a sealed unit... the only place Co can come from is a leak in the flue or the boiler itself...

Doesnt explain why you need one for an open fire

 

[Dartlec]

I often wondered why Co detectors were not needed for a cooker...

Is it something to do with the holes that the flame comes from? Or the fact that kitchens should have an extractor?
A boiler is a sealed unit... the only place Co can come from is a leak in the flue or the boiler itself...

Doesnt explain why you need one for an open fire

Perhaps the thinking is that cookers are not usually left on while people are sleeping, which a fire/boiler could be?

I'd guess that it needs a prolonged period of formation to build up enough CO to cause a risk to someone (or indeed to set off a sensor)

CO as I understand it is formed from the incomplete combustion of fuel (wood/coal/propane/natural gas), so can't occur unless there is a combustion process, which there isn't when a cooker isn't being used.

I've always been slightly confused by combined CO/Smoke alarms in the ceiling, since I understood that CO was heavier than air, but a quick google suggests that's wrong. Though this site claims the wall a couple of feet below the height of the ceiling is best...

 

[littlespark]

I've always been slightly confused by combined CO/Smoke alarms in the ceiling, since I understood that CO was heavier than air, but a quick google suggests that's wrong. Though this site claims the wall a couple of feet below the height of the ceiling is best...

I know LPG in the calor gas bottles is heavier than air. Leftover knowledge from caravan site days where we had to ensure there was ventilation in peoples decking for just such reason. I assume natural gas, paraffin, propane, butane are all heavier.

Burned exhaust gas must be lighter than air, as some flues exit vertically upwards.

 

[aesmith]

Thanks for all the comments. Can anyone clarify a bit about unnecessary bonding possibly introducing hazards? In this installation the appliance is earthed but I don't think the gas flexible hoses are conductive meaning there's no electrical path to the gas pipework or the cylinders. I can check although that would just be with a multimeter.

 

[LastManOnline]

Thanks for all the comments. Can anyone clarify a bit about unnecessary bonding possibly introducing hazards?

One example.The kitchen sink continued to be bonded in many countries despite the water pipes connected to it no longer been metallic.This meant that under certain fault conditions (open PEN) a piece of metal that was actually electrically isolated from earth and posed no danger to the homeowner is now live at 230 volts and could pose a potential hazard if the floor is poorly insulated.

I can check although that would just be with a multimeter.

You cannot effectively test if metals are extraneous with a multimeter.You need an insulation resistance tester.

 

[aesmith]

OK thanks. We're on a TNS supplier (verified on-site by the DNO) in case that makes a difference. Can a scenario similar to the broken PEN arise?

 

[LastManOnline]

OK thanks. We're on a TNS supplier (verified on-site by the DNO) in case that makes a difference. Can a scenario similar to the broken PEN arise?

A TNS supply?.Congratulations.Thats the "creme de la creme " of available electrical supply systems in my view.
Basically you have all the advantages of a TNCS system but none of the downsides.No worries about open PEN faults.No need for open PEN sensors.

 

[littlespark]

I prefer a PMSL supply myself.