Plastic gas pipe to buried metal pipe...

[Barnet Al]

I have a question which hopefully more experienced Sparkys can help me with.

A gas supply comes to the meter in plastic at the client's property. Then of course goes to copper. The gas pipe used to run under a suspended floor which has now been filled in with floor screed, apparently the gas pipe was protected with pipe Insulation.

According to the OSG it wouldn't need protective bonding as it comes to the meter in plastic. But no mention of the what if it goes back into the ground. I couldn't find anything in the regs.

I am thinking it does as if it is buried in the floor screed, could it pick up potential? Any thoughts appreciated.

 

[binky]

But it's not linked to a metal gas pipe running up the street, which is where some serious issues can occur. So I would say not needed. The boiler will have a CPC anyway, so the short length of pipe within the property will be earthed via that.

 

[Barnet Al]

Good point thanks binky, I didn't think about the boiler having its own bonding anyway.

 

[Andy™]

Good point thanks binky, I didn't think about the boiler having its own bonding anyway.

the boiler is not likely to have its own bonding. the boiler will have a cpc

the gas pipe won't need bonding because it comes in as plastic however if it goes underground o the consumers side then it may need it of its extraneous, you'll have to test it

 

[Barnet Al]

Thanks Andy, I will go around tomorrow and measure it. I found this article that explains what is considered dangerous: https://electricalapprentice.co.uk/...tential,earthing terminal of the installation.

 

[apprentice87]

Thanks Andy, I will go around tomorrow and measure it. I found this article that explains what is considered dangerous: https://electricalapprentice.co.uk/how-do-i-determine-an-extraneous-conductive-part/#:~:text=To assess whether Earth potential,earthing terminal of the installation.

Hi there. I followed the link you provided and it is telling you total crap..







That calculation is totally wrong. When testing to see if a part is "extraneous" and hence needs bonding, you measure the resistance between the part and the MET as they describe, BUT, the MINIMUM reading is about 22kohms in dry conditions to about 50Kohms in wet conditions.. To say it is 7kohms is total crap..

john..

 

[Captain Kirk]

The incoming supply gas pipe to the meter must not be bonded to the electrical installation under any circumstances. Gas meters have an isolating insert to prevent direct electrical connection between the suppliers gas pipe and the consumers installation gas pipe.

This was the result of a number of gas explosions and fatalities in the 1970s when there were many steel underground gas supply pipes. Domestic gas pipes are not isolated when engineers work on them and there were several occasions when cutting through a metal pipe which had been bonded across the meter in consumers premises where the engineer was electrocuted or a spark ignited the gas. It was a particular problem after the introduction of PME.

There are still many steel pipes in service and engineers now fit a temporary bonding jumper across each side of the cut or disconnection to address the risk. I worked with SSEB in the 70s and I had to revisit every job which had a connection application to check and remove any bonding across pipes at the gas meter. So even if the gas supply pipe is metal and is exposed to touch within the building it must not be bonded! - Only the consumers gas pipe on the secondary side can be bonded.

With regard to the consumers metal pipe in question it is a service pipe and therefore requires main equipotential bonding, appropriately sized and close to the point of entry, or at the gas meter box and cannot be substituted by a circuit cpc. The suggested calculation is not applicable.

I am retired now and my last gas qualification expired 10 years ago but the gas requirements at that time was that a gas pipe could not be buried directly in concrete - at best it would have to be enclosed in larger plastic pipe sleeve ventilated at one end to external atmosphere or a used ventilated space. i.e even if a gas pipe runs under or behind kitchen units there should be a ventilator grill in the kick boards.