Just to start an argument.

[supasparxs]

The whole purpose of bonding the Gas and any other services coming into a premises is to stop fault currents coming in from outside.

You guy must know about cows, or even what happened last year race horses getting electrocuted from a fault in another installation. A fault elsewhere can travel though the ground and cause a shock or even worse.

The 10mm Earth to the Gas, Water etc is to protect your installation from a fault outside your installation.
If a fault occurs the 10mm Main Earth will cause the fault to go down to the earth on the service head.

This is why the 17th edition regs state that if the circuits in a bathroom are RCD protected there is no need for the equipotential bonding

 

[supasparxs]

Wire
A 1m length of 6mm² =0.0358Kg
A 1m length of 10mm² =0.089Kg
A 1m length of 16mm² = 0.142Kg

Pipe (from tables)
A 1m length of 15mm = 0.391Kg
A 1m length of 22mm = 0.587Kg

Tony your forgetting the copper content of cable compared to the content of 15 or 22mm pipe

 

[Deleted member 9648]

The whole purpose of bonding the Gas and any other services coming into a premises is to stop fault currents coming in from outside.

You guy must know about cows, or even what happened last year race horses getting electrocuted from a fault in another installation. A fault elsewhere can travel though the ground and cause a shock or even worse.

The 10mm Earth to the Gas, Water etc is to protect your installation from a fault outside your installation.
If a fault occurs the 10mm Main Earth will cause the fault to go down to the earth on the service head.

This is why the 17th edition regs state that if the circuits in a bathroom are RCD protected there is no need for the equipotential bonding

Have I been hibernating?...is it April 1st already?

 

[needasparks]

Do we have to take the bonds off during the winter so the meter reader can warm his hands up on the gas meter. ?

 

[Knobhead]

Tony your forgetting the copper content of cable compared to the content of 15 or 22mm pipe

Well unless someone has started making copper pipe out of something other than copper, the weight per meter is the copper content be it pipe or wire.

Based on a wall thickness of 1mm:
15mm pipe = 44mm CSA
22mm pipe = 66mm CSA

All pipe figures from Copper Plumbing Tubes & Copper Water Supply Tubes - Metal Agencies Ltd

 

[Knobhead]

I’m not saying go against the regulations but I’m trying to point out using physics that the regulations aren’t always right.

If there is an exported or imported fault it will travel through the gas meter whatever method you use, unless you fit a jumper across the meter (electrical, not a bit of fancy bit of plumbing to bypass the meter).

This drawing is based on a typical installation based on the GAS pipe only.

View attachment 8835

Give a nominal resistance value of 10Ώ for drawing A. The “correct way according to the regulations”.
Where as B has a resistance of 3.21Ώ.
(10 / 66 x 8 = 1.21 for the pipe + 2 for the bonding.)

QED the regulations aren’t always right.

View attachment 8836

Every installation is different. Service positions can be any where. I based this on Tel’s post #4

 

[sambotc]

Surely the regulation is there to standardise the requirement for each installation to ensure that it is fitted in a position where it will provide adequate protection in all installations? That's not to say that there may be an alternative which could preform better in a fault current situation, but without a specific requirement, the onus would be on the installer to assess the resistance and pipework routing to ensure there are no tee's before the connection etc. Whilst most people on here seem to know what they are doing, I certainly wouldn't like to assume that everybody with the relevent tickets are?

Sam

 

[telectrix]

it's always good to query the status quo. just because it's a regulation doesn't mean it's right. just look at the smoking ban in pubs for one.

 

[telectrix]

that ban has been in force now for 4 years?. have we seen a fall in the cases of lung cancer?... NO. have we seen an increase in the number of bankrupt publicans with their pubs demolished and old folks homes built on the sites ... YES.

 

[alarm man]

that ban has been in force now for 4 years?. have we seen a fall in the cases of lung cancer?... NO. have we seen an increase in the number of bankrupt publicans with their pubs demolished and old folks homes built on the sites ... YES.

your right tel..biggest causes of cancer are not smoking/drinking which are all natural substances i add but the preservatives/pesticides modified foods we eat,add mobile phones etc,people have smoked and drank for thousands of years,but the food chain remained untouched and fresh.

 

[PC Electrics]

another way of looking at it , apart from comparing weights is:

15mm copper pipe has a circumference of 15 x pi = 47mm . times by 1mm thick gives it a csa of 47sq.mm which is just under 3 x the csa of 16mm cable. compares favourably with your figure of 2.76.

figures approximate and roughly correct at the time of printing. no responsiblity accepted for injuries caused by trying to split gas pipes open to check my findings.

Just for info, 15 and 22mm copper tubing to the relevant BS has a wall thickness of 0.8mm.
Also bear in mind that the copper used in tubing is less pure than that reequired for cable, so the specific resistance will be greater (but not by much, about 10-15% I would guess).

 

[Knobhead]

Thanks I’d looked for UK standards but couldn’t see the wood for the trees with Google. (And before anyone says anything, I did find wooden pipes).

With .8 wall thickness then it should be

π x (Do/2)² - π x (Di/2)² = CSA mm²
Where:
Do = outside diameter
Di = inside diameter

Therefore:
15mm pipe = 35.69mm²
22mm pipe = 53.28mm²

Still better than a bit of 10mm singles and less prone to damage or disconnection.

The revised figures for drawing B
Pipe 10/53.28 x 8 = 1.5 + Bonding 2 = 3.5Ώ

 

[Richard Burns]

Absolutely right Tony, I have thought this before, the only disadvantage (which I consider lower than disconnecting bonding cables) is the pipework discontinuity. Having the bonding after a branch makes no difference because electricity will flow either way in a conductor so all pipework will maintain the same voltage across the system wherever you bond.
Oh yes but the regs do not allow this; ah! but is this a better method and therefore safer than BS7671 so OK:hurray:.

 

[cornburn]

your right tel..biggest causes of cancer are not smoking/drinking which are all natural substances i add but the preservatives/pesticides modified foods we eat,add mobile phones etc,people have smoked and drank for thousands of years,but the food chain remained untouched and fresh.

Oh dear. Yes life expectancy 1000 years ago was much higher than today, due to the fact we didn't have pesticides or mobile phones. In fact everyone protected themselves by smoking and drinking natural substances like opium, tobacco and cocaine and as a race we'd never been healthier :S

Re the bond, surely it's where there's entry to the building so that when you spur a tap off the pipe using a pushfit T piece you don't break the bond?

 

[Engineer54]

Errrr!! I don't think so, life expectancey 1000 years ago was in fact considerably lower than it is today!! Average life span back then was around 35 to 45 years or lower.... That's if you managed to live beyound 3yrs from birth. Infant mortallity rate was very high back then....