Fitting a DB without updating the main bonding.. Bad crack or safer than before?

[snowhead]

“Mums going to belt me when she sees the chalk dust on my blazer!”

Been done the same myself, but nowadays Mum wouldn't be belting you she'd be rubbing her hands together and dashing off to a No Win No Fee appointment.

 

[Deleted member 9648]

I would disagree with you there,
Being that the bonding 'within 60mm' is a recommendation, I think the worst you could code the above scenario is an observation, In fact the worst you can code any effective bonding is an observation.

With gas I think a valid point has been made about it being continuous...the same can not be said of water. If bonding has been installed incorrectly at the time of the original installation there's no excuse for it not being at the point of entry....if it's added to an existing install I concede there is justfiication for it not being at the point of entry.

The two key words in the reg oldtimer quoted are, 'Practicable'. (x2)
So, ripping half the house apart to connect a cable, in my eyes, isn't practicable, as long as where ever the connection is made affords the same protection.
You're allowed to deviate from the regs anyway.

True....however in the case of a bond to a water service a connection made some where at a random place nowhere near the point of entry cant be garanteed to remain effective after the electrician has finished.

Archy hit the nail on the head and it was the basis for me doing the calculations. “Why rip a house to bits to install the bond to the gas supply point?”
It doesn’t make the installation safer earthing at the incoming of a gas service. 9 times out of 10 it makes it worse.Dont understand how it can be worse...please explain. And you are not earthing it.

As for imported faults, only ever had one to get worried about. But as I’d done my house to the 14[SUP]th[/SUP] I wasn’t that bothered. 25A coming in through the water pipe and leaving via the gas and earth rods.
The NWEB as it was then, went in to panic mode for some reason when I phoned them. Faulty line tap on the OH supply and an N>E fault next door but one.

With everything cross bonded where is the potential touch voltage going to come from?


Tony Cockburn

 

[Knobhead]

With gas I think a valid point has been made about it being continuous...the same can not be said of water. If bonding has been installed incorrectly at the time of the original installation there's no excuse for it not being at the point of entry....if it's added to an existing install I concede there is justfiication for it not being at the point of entry.

Dont understand how it can be worse...please explain. And you are not earthing it.

Using the calculation I gave

Where:
Od = outer diameter
Id = inner diameter

π*(Od/2)²-π*(Id/2)²=CSA/mm²
15mm ≡ 39.69mm² ∴ 248.06%↑
22mm ≡ 53.28mm² ∴ 362.75%↑

%↑ improvement based on 16mm²

To run an earth to the origin of the gas supply rather that a point on the gas pipe near the MET doesn’t improve the situation. My original thread about this was purely a hypothetical point based on the laws of physics.
There are reasons for the 600mm recommendation but they are based on convention and not sound principals.

 

[Geordie Spark]

You miss the whole point of bonding,it should be bonded at the point of entry because it's purpose is to deal with a potential introduced by the pipe from externally.
Conductivity of the pipe etc is totally irrelevant.It should be bonded at the point of entry because there,whatever alterations to the pipework take place in the property it will still serve it's purpose.This is not the case if bonding takes place elsewhere.

Ok ..... so here we have a garage and there's a steel pipe emerging from its floor. This is the point of entry for the gas supply.

The pipe now rises up the garage to a height of about 2 metres wall and is clipped to it. At the top of the pipe is the Emergency Control Valve and connected to that is the Semi Rigid pipe that connects to the Governor which in turn is connected to the meter.

To follow the argument "It should be bonded at the point of entry ...." WHY do we fix the bond on the copper pipe on the outlet side of and within 600 mm of the meter??

 

[Tuttle]

Ok ..... so here we have a garage and there's a steel pipe emerging from its floor. This is the point of entry for the gas supply.

The pipe now rises up the garage to a height of about 2 metres wall and is clipped to it. At the top of the pipe is the Emergency Control Valve and connected to that is the Semi Rigid pipe that connects to the Governor which in turn is connected to the meter.

To follow the argument "It should be bonded at the point of entry ...." WHY do we fix the bond on the copper pipe on the outlet side of and within 600 mm of the meter??

I went to a house recently where the gas meter was on a shelf high up, just below the ceiling, in a utility room. There wasn't any bonding so I bonded after the meter, within 600mm as recommended. Perhaps I should have bonded the supply pipe as well.

 

[Deleted member 9648]

Using the calculation I gave

Where:
Od = outer diameter
Id = inner diameter

π*(Od/2)²-π*(Id/2)²=CSA/mm²
15mm ≡ 39.69mm² ∴ 248.06%↑
22mm ≡ 53.28mm² ∴ 362.75%↑

%↑ improvement based on 16mm²

To run an earth to the origin of the gas supply rather that a point on the gas pipe near the MET doesn’t improve the situation. My original thread about this was purely a hypothetical point based on the laws of physics.
There are reasons for the 600mm recommendation but they are based on convention and not sound principals.

Have to disagree.
The purpose of bonding is to deal with an external PD being introduced to a building. There is no better place to deal with it than the point where the PD enters the building.
I accept that in the case of a gas pipe bonding can be elsewhaere than the point of entry and remain effective....but there IS a sound principle for bonding at the point of entry,it's not just convention or making life difficult.

 

[Deleted member 9648]

Ok ..... so here we have a garage and there's a steel pipe emerging from its floor. This is the point of entry for the gas supply.

The pipe now rises up the garage to a height of about 2 metres wall and is clipped to it. At the top of the pipe is the Emergency Control Valve and connected to that is the Semi Rigid pipe that connects to the Governor which in turn is connected to the meter.

To follow the argument "It should be bonded at the point of entry ...." WHY do we fix the bond on the copper pipe on the outlet side of and within 600 mm of the meter??

To be effective in the situation you describe the bonding should be on the service pipe at the point of entry,and that is what I would do in the above situation....and have done in the past. As already stated the regs are not statutory,and if I know that bonding at a point on the consumers side of the meter will leave a long unbonded ECP then I'll ignore the fact that it's unconventional and bond it where I know it will serve it's purpose.
Had a similar instance on a water service recently. The service was saddled around a utility room for about 4m before the stopcock,and there was poor continuity through the stopcock....I bonded it where it needed bonding,at the point of entry,not on the consumers side of the stopcock.
Sometimes you have to think for yourself and ignore convention.

 

[Geordie Spark]

I went to a house recently where the gas meter was on a shelf high up, just below the ceiling, in a utility room. There wasn't any bonding so I bonded after the meter, within 600mm as recommended. Perhaps I should have bonded the supply pipe as well.

I've seen this done in the past and have done it myself - only to find on a later visit the bond to the supply pipe removed by a gas bloke .....

 

[Geordie Spark]

To be effective in the situation you describe the bonding should be on the service pipe at the point of entry,and that is what I would do in the above situation....and have done in the past. As already stated the regs are not statutory,and if I know that bonding at a point on the consumers side of the meter will leave a long unbonded ECP then I'll ignore the fact that it's unconventional and bond it where I know it will serve it's purpose.
Had a similar instance on a water service recently. The service was saddled around a utility room for about 4m before the stopcock,and there was poor continuity through the stopcock....I bonded it where it needed bonding,at the point of entry,not on the consumers side of the stopcock.
Sometimes you have to think for yourself and ignore convention.

I agree and have done it myself - only for someone to remove it later!!

In most cases I've seen, the bond has been after and within 600 mm of the meter regardless of how much steel pipe there's been between the ground and the meter.

As it happens, just to pass the time during my retirement, I've been helping my builder mate with his own house renovation project and in the next few days will be running the gas pipework through his garage from the recently installed new meter which is about 2 metres up the garage wall.

 

[Rockingit]

I think this whole thread serves to prove only one point: The world and its various buildings and M&E within them rarely present as textbook. The reason for healthy under-pinning knowledge and depth of training is to enable the proper electrician to be able to think on their feet and provide an engineering solution to any problem, rather than the Electrical Trainee approach of joining the dots in the My First Colouring book.

"Give a man a fish and he eats for a day. Teach a man to fish and he feeds the world forever".

 

[Geordie Spark]

Surely its a good point re: gas pipes usually not being altered, and isn't there some rule about it being in copper? Never ever seen a domestic gas pipe, in a premises, that wasn't.

You haven't seen Tracpipe yet have you?

Here it is: Tracpipe Gas Pipe - www.colglo.co.uk

 

[specs]

You haven't seen Tracpipe yet have you?

Here it is: Tracpipe Gas Pipe - www.colglo.co.uk

Many thanks for the link, never heard of this stuff.

 

[Geordie Spark]

Many thanks for the link, never heard of this stuff.

Well you know we're not allowed to use the plastic stuff indoors for gas, and you know that one of the advantages of the plastic stuff is you can thread it through drilled holes in joists - like you do with cable? Well this stuff being stainless steel allows it to be used for gas and being flexible on a coil it can be threaded through drilled joists - just like the plastic stuff.

I have to say; I've never used it and only seen it when attending courses in the training centre & now being retired it's unlikely that I ever will. I notice the prices of the fittings are a bit on the expensive side too.

 

[bigbaddave]

you say pricey.. More than copper im guessing

 

[specs]

Well you know we're not allowed to use the plastic stuff indoors for gas, and you know that one of the advantages of the plastic stuff is you can thread it through drilled holes in joists - like you do with cable? Well this stuff being stainless steel allows it to be used for gas and being flexible on a coil it can be threaded through drilled joists - just like the plastic stuff.

I have to say; I've never used it and only seen it when attending courses in the training centre & now being retired it's unlikely that I ever will. I notice the prices of the fittings are a bit on the expensive side too.

Maybe on the high side for fittings but methinks a bit of a saving on labour. Once again a big thanks for the link.