Extraneous and bonding etc

[uksparks]

Hi,

something that cropped up yesterday on my assessment was that I'd done a load of work on a house and new CU etc.

the old boiler had been taken out and a new one fitted but the gas supply had not been put into the new boiler.

the old gas pipe was left where the old boiler was in a different part of the house.

i didn't bond the old pipe as it was about to be removed and a new one put in.

he said why have you not bonded the gas pipe?

i said it was about to be removed.

i said I have done an IR on it to the MET and it suggested it was not extraneous or already bonded somewhere so was not bothered as I felt it to be satisfactory.

he said what do you mean you have done an IR test in it?

so I explained it was less than 0.03M ohms, it was 0.00 as it happens, so it was less that 23,000 ohms. He said that it should be well over 1 meg ohm. I had to agree to disagree, I said yes but I'm proving it's not extraneous....

am am I right or am I being thick?

 

[uksparks]

Re: Extraneous and binding etc

I think the NIC bloke was trying to pull the wool over my eyes saying it needed bonding....

 

[uksparks]

Re: Extraneous and binding etc

As this job was the 4th in the day and had just been trying to explain to him about the fault currents between line and neutral and max conductor temp under a fault and the charts with squiggly lines on in the back of BS7671 I'd had enough so just agreed with him.

 

[Richard Burns]

Re: Extraneous and binding etc

I think the NIC bloke was trying to pull the wool over my eyes saying it needed bonding....

Come on think, (this is not what I am doing at them moment though)

Bonding conductors are there to connect to the MET all accessible conductive parts, whether exposed or extraneous or cpc so as to reduce touch voltages in the case of a fault.

The minimum csa of the bonding conductors is determined by the size of the incoming neutral.

If I connect a 1.5 m long 1.0 mm² cable from the MET to the nearby extraneous conductive part, then the resistance of that cable would be 0.0435 Ω.
Would you consider that was correctly bonded?
No, because even though the resistance is low the csa does not comply.

You did not know the csa of the electrical connection to the gas pipe so in order to be sure you either find the connecting cable and confirm the csa or bond the pipe with an appropriately sized bonding cable.

That is the correct thing to do, however in your case I would not have bothered either.
Just put a plastic bucket over it then it is no longer accessible and does not need bonding!
Losing the plot here I think:54:

 

[Silly Sausage]

Re: Extraneous and binding etc

Making assumptions here...
The boiler has been removed and the gas pipe there has been capped and hasn't been chopped between this point and the meter.
Presumably the gas is already bonded at the meter, so it doesn't need bonding at the old boiler location, so it's a complete pointless point, from the NICEIC muppet.
Do these goons know anything about anything electrical???

 

[HappyHippyDad]

Re: Extraneous and binding etc

Come on think, (this is not what I am doing at them moment though)

Bonding conductors are there to connect to the MET all accessible conductive parts, whether exposed or extraneous or cpc so as to reduce touch voltages in the case of a fault.

The minimum csa of the bonding conductors is determined by the size of the incoming neutral.

If I connect a 1.5 m long 1.0 mm² cable from the MET to the nearby extraneous conductive part, then the resistance of that cable would be 0.0435 Ω.
Would you consider that was correctly bonded?
No, because even though the resistance is low the csa does not comply.

You did not know the csa of the electrical connection to the gas pipe so in order to be sure you either find the connecting cable and confirm the csa or bond the pipe with an appropriately sized bonding cable.

That is the correct thing to do, however in your case I would not have bothered either.
Just put a plastic bucket over it then it is no longer accessible and does not need bonding!
Losing the plot here I think:54:

But is this not the same scenario when we are testing other questionable metal parts in special locations? We test to see if extraneous, and if it is then it needs to be bonded. We check continuity with the MET and as long as the reading is satisfactory we are satisfied? It would be pretty difficult to trace the entire path of that extraneous part back to its orgin (floorboards etc) to make sure it has a 10mm attached to it.

 

[Geoffsd]

Re: Extraneous and binding etc

But is this not the same scenario when we are testing other questionable metal parts in special locations?

In a way but there the main bonding will have been verified first.

We test to see if extraneous, and if it is then it needs to be bonded. We check continuity with the MET and as long as the reading is satisfactory we are satisfied?

To check if main bonding is required the pipe should be disconnected from all other connections.
This is not practical so, as it is already connected to the earthing arrangement, it is as well to main bond.

It would be pretty difficult to trace the entire path of that extraneous part back to its orgin (floorboards etc) to make sure it has a 10mm attached to it.

We disconnect and test that it is a continuous conductor.


This thread, it now appears, concerns the plumbers' favourite "cross-bonding" under the boiler which is not required in the first place.

 

[DRG]

I was under the impression you checked:
Main protective bonding - if the clamp/conductor was not visible at stopcock or gas meter if you did an r2 test and the reading was 0.05 ohms or below it was deemed as being adequately bonded and classified as just being a deviation due to not being visible.

Protective supplementary bonding - any other metal work (whatever it may be) regarded as being extraneous was needed to be tested 22kohm or IR'd too see if it needed bonded or not depending upon the results of that test.

Am I correct in thinking this?

 

[Geoffsd]

I was under the impression you checked:
Main protective bonding - if the clamp/conductor was not visible at stopcock or gas meter if you did an r2 test and the reading was 0.05 ohms or below it was deemed as being adequately bonded and classified as just being a deviation due to not being visible.

That's a bit different to what is being discussed.

The main bonding should be visible. If it is not then, as said above the connection could be by any unknown thing which may not be an adequate conductor.
The stopcock is irrelevant; the main bonding should be applied at the point of entry where practicable so may be elsewhere.
The 0.05 ohms is just an accepted value for negligible impedance between the conductor and part.
If the pipe was bonded right next to the MET this value could still be found elsewhere on the pipe.
The bonding conductor itself should be tested.

It wouldn't be a deviation as that is another accepted satisfactory method.

Protective supplementary bonding - any other metal work (whatever it may be) regarded as being extraneous was needed to be tested 22kohm or IR'd too see if it needed bonded or not depending upon the results of that test.

I'm not certain what you are asking.

That applies to main bonding. If greater than 22kohm (or whichever value you consider safe) to the MET then it is not regarded as extraneous.
This also, obviously, applies to supplementary bonding parts in a special location.

Am I correct in thinking this?

Partly ?