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?

 

[Simonslimline]

Re: Extraneous and binding etc

A reading greater than 22k ohms would prove it is not extraneous. Show him GN8 if he thinks you are wrong, it is all explained in there.

Edit...

It is 23k i believe but 1k is deducted for the body resistance.

230V / 23000 Ohms = 0.01A

 

[Richard Burns]

Re: Extraneous and binding etc

I can see why you would not bond something that was about to be removed, even thought the regulations would have otherwise (what happens if a fault occurs before it is removed!!).

Electrically you are actually conducting a high value resistance test that is most easily done with an IR tester.

You proved that it was an extraneous part because the resistance to the MET was less than 23 kohms and so it would require bonding.
If you measured with a low resistance ohmmeter and got a very low value (hundredths of an ohm) then you could assume it was electrically connected to the installation, but whether with a large enough conductor is another matter.

Overall from what you say I would say it should have been bonded but this would be redundant in a short time and so had been left as it was electrically (perhaps) connected to the MET anyway.

 

[Baker1988]

Re: Extraneous and binding etc

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?

i think it should be more than 22k so the 0.00ohm reading is too low

 

[uksparks]

Re: Extraneous and binding etc

Greater than or less than? I'm confusing myself now, if I measure a pipe, any pipe and it's say 0.03M then that's greater than 23k.

if it's 0.02 for example then that's less than 23k.

 

[Simonslimline]

Re: Extraneous and binding etc

worth a watch




https://www.youtube.com/watch?v=v38PfIVy2rI

 

[uksparks]

Re: Extraneous and binding etc

Yes you are right, I'm confusing myself that's the issue.

I did explain to him it was less than 0.05 ohms between them on continuity which to me suggests it's bonded.

the pipe is coming out this week anyway.

 

[HappyHippyDad]

Re: Extraneous and binding etc

Was the test 0.00 as in first post UK or 0.05 as in last post? First post suggests it is connected to MET somewhere but I'm confused with the 0.05 figure, that would be 50,000Ω. I guess you could have done a continuity check just to see if the figure was below 1667Ω then if RCD protected it would be ok.

 

[Richard Burns]

Re: Extraneous and binding etc

I think the first is 0.00 Mohms the last is 0.05 ohms.

RCD protection doe not remove the requirement for bonding, bonding is there so that in the case of a fault to earth all accessible conductive parts will be at the same voltage prior to the disconnection occurring.

 

[uksparks]

Re: Extraneous and binding etc

Sorry I realise what I've said.

it was 0.00Mohms IR between the water and gas so zero M ohms.

IR tester will only go down to 10,000 ohm resolution yes?

anyway when I tested with a low resistance ohmmeter between the same two bits of pipe it was less than 0.05 ohms, which would obviously show as zero on IR as it's less than 0.01M ohms ok.

Ok, so can you not say there's clearly continuity between the two pipes yes? Sufficiently to say they are well connected somehow ?

am I just being a total spanner here?

 

[uksparks]

Re: Extraneous and binding etc

Oh just for the record I'm not one for saying it's rcd protected so it's ok.

 

[HappyHippyDad]

Re: Extraneous and binding etc

You're quite right Richard. UK clearly states 0.05ohms on a continuity check. Also quite right about the bonding.. I was getting confused with supplementary bonding. It's too late for me!

 

[uksparks]

Re: Extraneous and binding etc

He was trying to suggest if was extraneous and needed bonding but I could only see that it was like touching the same bits of pipe together from the readings?

 

[HappyHippyDad]

Re: Extraneous and binding etc

Sorry I realise what I've said.

it was 0.00Mohms IR between the water and gas so zero M ohms.

IR tester will only go down to 10,000 ohm resolution yes?

anyway when I tested with a low resistance ohmmeter between the same two bits of pipe it was less than 0.05 ohms, which would obviously show as zero on IR as it's less than 0.01M ohms ok.

Ok, so can you not say there's clearly continuity between the two pipes yes? Sufficiently to say they are well connected somehow ?

am I just being a total spanner here?

I would have thought so! Hopefully Richard will tell us :smiley2:

 

[Silly Sausage]

Re: Extraneous and binding etc

You're quite right Richard. UK clearly states 0.05ohms on a continuity check. Also quite right about the bonding.. I was getting confused with supplementary bonding. It's too late for me!

Time to hit you with this then!

http://www.copperalliance.org.uk/do...thing-practice-pdf.pdf?Status=Master&sfvrsn=0

 

[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 ?