Understanding the new regulation regarding Main Bonding.

[HappyHippyDad]

Regulation 411.3.1.2 states ....

Main bonding conductors shall connect to the main earthing terminal extraneous conductive parts.

It then goes on to say...

'Metallic pipes entering the building having an insulating section at their point of entry need not be connected to the protective equipotential bonding'.

Lets say we have a water pipe coming into the house in the plastic blue pipe, from then on its metal. The above reg makes me believe this does not need Main bonding, is that correct?

The above reg does not suggest we test the water pipe to see if it extraneous. It just says we have to bond extraneous parts, then it says not to bond if they come in to the house in an insulating section.

If we do test the water pipe it is likely that it will test at 1 or 2 ohms to earth (probably as it is usually connected to earth somewhere within the premises). Does this reg still imply not to bond in this case when we can clearly see an insulating section at point of entry?

 

[Deleted member 9648]

As you have mentioned already, measure resistance to MET from metallic pipework. <22Kohms = bond.

Obviously make sure parellel patha are disconnected first.

It's almost impossible to eliminate parallel paths, if there's a combi for example the gas service will be mechanically joined to the water pipes. The test for extraneousness (I just made that word up) is generally unreliable and I prefer to combine it with a visual assessment of how likely a water pipe is to become extraneous when entirely within a building. Unless the building is steel framed the likelihood is minimal.

 

[buzzlightyear]

No mate he had an Apache on his head, and ut wasn't his own hair never had Head and Shoulders in those days

no prisoners for that man .

 

[GBDamo]

It's almost impossible to eliminate parallel paths, if there's a combi for example the gas service will be mechanically joined to the water pipes. The test for extraneousness (I just made that word up) is generally unreliable and I prefer to combine it with a visual assessment of how likely a water pipe is to become extraneous when entirely within a building. Unless the building is steel framed the likelihood is minimal.

Especially in a 32nd floor flat!!

 

[ChrisElectrical88]

It's almost impossible to eliminate parallel paths, if there's a combi for example the gas service will be mechanically joined to the water pipes. The test for extraneousness (I just made that word up) is generally unreliable and I prefer to combine it with a visual assessment of how likely a water pipe is to become extraneous when entirely within a building. Unless the building is steel framed the likelihood is minimal.

I had the on site plumber take a small section out right after the stop tap so i could test it which eliminated all parellel paths lol. Serched everywhere are there was no other extraneous parts. I thibk the reason i got 30KOhms was resistance through the wat or i would have had greater than 99MOhms

 

[The Ghost]

Ever since I started electrics back in 1961 bonding/equipotential cross bonding extraneous metal has been it seems a dark art. With a myriad of opinions on it most wrong. And an almost superstitious "...if it's metal bond it!.." approach. I think in this case it is simpler than we may overthink it is. One caution though, I have been in houses that start with plastic to copper. The copper wends its way through the property to the back bath and or kitchen but goes sub floor in cement so in such a case...??? It is only that there is not one rule fits all a careful survey needs to be done to be sure bonding is not needed as @wirepuller said "...a careful visual inspection..." is required.

 

[buzzlightyear]

And an almost superstitious

you can sing this when you thinking about it Vort.

 

[TJ Anderson]

It's almost impossible to eliminate parallel paths, if there's a combi for example the gas service will be mechanically joined to the water pipes. The test for extraneousness (I just made that word up) is generally unreliable and I prefer to combine it with a visual assessment of how likely a water pipe is to become extraneous when entirely within a building. Unless the building is steel framed the likelihood is minimal.

Loving Extraneousness!! That should definitely be a word lol

 

[HappyHippyDad]

Some good posts!

I agree, it can be almost impossible to eliminate all parallel paths so an extraneousness test (pinched from @wirepuller ) isn't going to be that reliable.

I think I'll have a chat with my assessor when he comes and see what he says. Until then, I'll flip a coin to see if I'm going to bond!

 

[TJ Anderson]

I don't think it is so hard to determine.

Parallel paths via cpc's will be a low impedance back to MET. You therefore won't know if it was extraneous as you now can't sensibly prove it anymore without disconnecting too much stuff.

If pipework it is at earth potential via a cpc even though it was not extraneous in its own right, you won't do any harm by bonding it, you are just safeguarding if it is truly extraneous.

Most of the sparks at firm I work for don't understand the difference between earthing and bonding lol........let alone making a decision if they should to install it haha

 

[telectrix]

I don’t think I’d like to be the one taking that photo - he seems a little miffed!

he has every right to be miffed, as Sitting Bull and the S0iux took all the credit for wiping out Custard and his blue bellies at Little Big Horn

 

[freddo]

Why are you all still going on about this subject? There is nothing to question as all the answers are already in this book.

 

[snipersmith87]

I thought aslong as it exceeded 7.67k ohms it is not to be considered an extraneous conductive part.

 

[Dave OCD]

Surely if there is an insulated incoming service pipe or even a 3 inch insulating piece between metal incoming and installation pipework then it's impossible for a potential to be introduced from outside the building ? And therefore bonding is not required in such circumstances ?

 

[chrisdungan]

You can't earth plastic end of story. don't be a dick.
Do you earth isolated sections of any sort of pipe.... water/oil etc etc??
My answer is probably not, it's your call.
BUT BUT
I have 2 tests to ask
1 IS IT EXPOSED METAL( OF ANY KIND) THAT HAS THE POTENTIAL TO BECOME ALIVE??????
If yes then the answer must be to earth bond it
2 What would be your defense in the coroners court?

Remember the regs are designed to confuse sparkies by legal numpties.

 

[telectrix]

I thought aslong as it exceeded 7.67k ohms it is not to be considered an extraneous conductive part.

no. the figure is 22K Ohms. 7.67K is the value of a L-E earth fault or leakage that would trip a 30mA RCD.