Extraneous conductive parts

[Ian1981]

Hi all.
Looking for opinions on here.
I’ve identified during an eicr that a dry rise pipe used for firefighters in the building is in fact an extraneous conductive part and that it is not bonded back to the MET.
However what I’m questioning is it’s accessability to be touched in the event of a fault.
Pipework is installed in boxing with a key for an access panel for the riser water inlet to be used for the firefighters.
Only person with access is the building manager.
What’s people’s opinions does it require protective bonding or is it deemed not accessible to touch and that’s the end of the matter?
It’s worth pointing out bs 7671 doesn’t mention the fact it needs to be accessible however it’s common sense that says it needs to be if your going to be in contact during a fault between say an exposed conductive part and said pipework.
Thanks

To add the dry riser pipe comes up from the floor in metal and is separate from the cold water pipe entering the building in plastic.
A completely different service it seems.

 

[Pete999]

How exactly have you determined this pipework to be extraneous?

 

[Dillb]

Surely if someone can get to it then it is accessible?

 

[Ian1981]

How exactly have you determined this pipework to be extraneous?

Testing from the MET or rather the source of earthing to said pipe.
Main earthing conductor disconnected from source earth
IR set to 500v reading of 0.00 Mohms
Also no continuity between said pipework and a known earth source

 

[Ian1981]

Surely if someone can get to it then it is accessible?

The likelihood of someone coming into contact with the pipework during fault conditions is minimal to say the least but yes if the access panel is opened by key if say during an inspection or servicing of the pipework then it can be touched, perhaps this is my answer.

 

[Pete999]

Testing from the MET or rather the source of earthing to said pipe.
Main earthing conductor disconnected from source earth
IR set to 500v reading of 0.00 Mohms
Also no continuity between said pipework and a known earth source

This is a block of flats or a tall multi user building I take it?

 

[Ian1981]

This is a block of flats or a tall multi user building I take it?

It’s the communal/landlords supply for elderly living accommodation

 

[Wilko]

The Last Electrician probably didn't look tooo hard, but I think it should be bonded as that door could be left open.

 

[telectrix]

might be worthwhile finding out why it's extraneous. bit of a grey area without some further info.

 

[Deleted member 26818]

Doesn’t the fact that there is zero IR between the MET and the riser mean that the riser is reliably connected to the MET?
Thought the maximum resistance allowed between bonded parts and the MET was 0.05 Ohms?

 

[Pete999]

Doesn’t the fact that there is zero IR between the MET and the riser mean that the riser is reliably connected to the MET?
Thought the maximum resistance allowed between bonded parts and the MET was 0.05 Ohms?

Are you getting mixed up between main and supplementary bonding?

 

[Pete999]

Doesn’t the fact that there is zero IR between the MET and the riser mean that the riser is reliably connected to the MET?
Thought the maximum resistance allowed between bonded parts and the MET was 0.05 Ohms?

That is for main Equipotential bonding the OP is on about extraneous two different Animals, please see the vids I have posted.

 

[Deleted member 26818]

Not sure what the videos are telling you, but if it’s that MEB is not intended to to equalise any possible differences in potential between extraneous-conductive parts then they are mis-informing you.

 

[Ian1981]

Doesn’t the fact that there is zero IR between the MET and the riser mean that the riser is reliably connected to the MET?
Thought the maximum resistance allowed between bonded parts and the MET was 0.05 Ohms?

No it means there’s little to no resistance between them or little to no resistance between the source of earthing and the metallic pipe which is introducing an earth potential.
If it was higher than say 23Kohms then I’d consider the pipework as not being extraneous.
There’s no such maximum resistance between bonded parts. 0.05 ohms is a value from GN3 which determines that testing between any two points such as metallic pipes can be considered reliably earthed/bonded

 

[Pete999]

Not sure what the videos are telling you, but if it’s that MEB is not intended to to equalise any possible differences in potential between extraneous-conductive parts then they are mis-informing you.

Why is that Spin?

 

[Deleted member 26818]

No it means there’s little to no resistance between them or little to no resistance between the source of earthing and the metallic pipe which is introducing an earth potential.
If it was higher than say 23Kohms then I’d consider the pipework as not being extraneous.
There’s no such maximum resistance between bonded parts. 0.05 ohms is a value from GN3 which determines that testing between any two points such as metallic pipes can be considered reliably earthed/bonded

Have you not just said the same as me, but in a more convoluted manner?

 

[Deleted member 26818]

Why is that Spin?

Seriously?
Are you telling me you are unaware of the purpose of Main Equipotential or Protective Bonding conductors?

 

[Pete999]

Extraneous conductive parts are considered as water, Gas, Oil, fire fighting pipework in high rise blocks, or large buildings, lightning conductors, structural steelework etc, ie they do not form part of an electrical installation

Seriously?
Are you telling me you are unaware of the purpose of Main Equipotential or Protective Bonding conductors?

 

[Ian1981]

Have you not just said the same as me, but in a more convoluted manner?

No not really.
It indicates that the metallic pipe is in contact with earth but as I’ve said, it’s not connected to the MET and has no continuity to it when using a wander lead to test it from the MET to the pipework.
The test I’ve done says to me it’s extraneous as it has a very low resistance to earth.
If it was connected to the MET then I’d have continuity.
Also the IR test I did was with the earthing conductor disconnected from the source of earthing and the test made between metallic pipe and the DNO source earth.
TN-S in this case on the side of the 3 phase Lucy unit with the earthing bolt.

 

[Pete999]

No I just wanted you to explain your statement, it seems we are getting mixed up here Spin, of course I know the reason, it was just I thought your statement was a bit far reaching. And why you feel the vids are misinforming people that's all.

 

[Deleted member 26818]

No not really.
It indicates that the metallic pipe is in contact with earth but as I’ve said, it’s not connected to the MET and has no continuity to it when using a wander lead to test it from the MET to the pipework.
The test I’ve done says to me it’s extraneous as it has a very low resistance to earth.
If it was connected to the MET then I’d have continuity

No, it does not indicate that metallic pipe is connected to earth. It indicates that there is a reliable connection between the metallic pipe and the MET.

Your second posts states: you have zero resistance between the metallic pipe and the MET and no continuity between the metallic pipe and a known earth.
Now you appear to be saying the opposite.
Please clarify.

 

[Ian1981]

No, it does not indicate that metallic pipe is connected to earth. It indicates that there is a reliable connection between the metallic pipe and the MET.

Your second posts states: you have zero resistance between the metallic pipe and the MET and no continuity between the metallic pipe and a known earth.
Now you appear to be saying the opposite.
Please clarify.

Right there’s no continuity between MET and pipe when carrying out a continuity test.
There a reading of 0.00 Mohms between the source of earth to the installation (not at the MET as I disconnected it doing the IR test).
Conclusion is that the metallic pipe is in good contact with earth(externally) and is extraneous but it is NOT connected to the buildings earthing.
Got it??

 

[Pete999]

Right there’s no continuity between MET and pipe when carrying out a continuity test.
There a reading of 0.00 Mohms between the source of earth to the installation (not at the MET as I disconnected it doing the IR test).
Conclusion is that the metallic pipe is in good contact with earth(externally) and is extraneous but it is NOT connected to the buildings earthing.
Got it??

I have thanks

 

[Ian1981]

The discussion isn’t or isn’t it extraneous , it’s if it’s accessible in the sense that it requires bonding and it probably should.

 

[Deleted member 26818]

So why did you say this:

Testing from the MET or rather the source of earthing to said pipe.
Main earthing conductor disconnected from source earth
IR set to 500v reading of 0.00 Mohms
Also no continuity between said pipework and a known earth source

If you tested IR between the MET (with the Main earthing conductor disconnected) and the pipe, to obtain a reading of 0.00 Mohms, that would indicate a reliable connection between the pipe and the MET.
To then state there is no continuity between said pipe work and a known earth source, would indicate no connection to earth.
Are you now saying, you did not test IR between the MET and the pipe, that in fact you tested between the Earthing conductor and the pipe?
If so what does the statement that there is “also no continuity between said pipework and a known earth source” mean?

 

[Ian1981]

So why did you say this:

If you tested IR between the MET (with the Main earthing conductor disconnected) and the pipe, to obtain a reading of 0.00 Mohms, that would indicate a reliable connection between the pipe and the MET.
To then state there is no continuity between said pipe work and a known earth source, would indicate no connection to earth.
Are you now saying, you did not test IR between the MET and the pipe, that in fact you tested between the Earthing conductor and the pipe?
If so what does the statement that there is “also no continuity between said pipework and a known earth source” mean?

The source of earthing is what the DNO provide for the installation.
A known earth source is exactly that, a point in the installation such as the MET that’s connected to the earthing arrangement in the building.
My 2nd post in the thread is clear enough.
Testing the metallic pipe was done in accordance with gn8 pages 74 and 75.
Testing between earth and the suspect pipework using an insulation resistance tester set at 500 volts D.C. and the reading being less than 22Kohms or as displayed on my instrument 0.00 Mohms.
Have a read up on it why don’t you?

 

[magnoliafan89]

Guys im confused. If you wanted to know if a pipe or say tap could have a potential difference. What tests would you do? What results would you expect? You'll have to make the answer simple as im still just a trainee

 

[Ian1981]

Guys im confused. If you wanted to know if a pipe or say tap could have a potential difference. What tests would you do? What results would you expect? You'll have to make the answer simple as im still just a trainee

Check out pete’s uploaded videos.
Generally the formula is 230/0.01 amps (10mA being the let go threshold)
To assess whether Earth potential is liable to be introduced by a conductive part that is connected to the general mass of Earth through a resistance, a measurement should be made of the resistance between the conductive part and the main earthing terminal of the installation.
As generally our continuity meters won’t read that high say (22Kohms) then an insulation resistance meter is used set to 500v D.C. and a measurement is taken between the suspect pipework and the earth arrangement to the installation.
Also For a better technical explanation check out gn8.

 

[westward10]

The discussion isn’t or isn’t it extraneous , it’s if it’s accessible in the sense that it requires bonding and it probably should.

Bet you are glad you asked now
I think you have to say it is accessible, amen.

 

[Ian1981]

Bet you are glad you asked now
I think you have to say it is accessible, amen.

I don’t post very often problems on site and this experience has put me right off

It’s gone down as a C2 on the report

 

[westward10]

Don't be put off you are a forum member who knows his eggs.

 

[Deleted member 26818]

Be useful if he explained himself better.

 

[Pete999]

No I just wanted you to explain your statement, it seems we are getting mixed up here Spin, of course I know the reason, it was just I thought your statement was a bit far reaching. And why you feel the vids are misinforming people that's all.

What do you think Spin?

 

[Deleted member 26818]

I would be surprised if the vids are mis-informing people.
Was concerned that you appeared to be unaware that Main Equipotential Bonding relates to extraneous-conductive parts.

 

[Pete999]

I would be surprised if the vids are mis-informing people.
Was concerned that you appeared to be unaware that Main Equipotential Bonding relates to extraneous-conductive parts.

Not unaware at all Mate, maybe a wrongly worded question.

 

[DPG]

I'm sure Pete knows full well what it refers to.

 

[Deleted member 26818]

You said this:

That is for main Equipotential bonding the OP is on about extraneous two different Animals, please see the vids I have posted.

If the vids are telling you that Main Equipotential Bonding and bonding of extraneous-conductive parts are two different animals, they are mis-informing you.

 

[Pete999]

You said this:

If the vids are telling you that Main Equipotential Bonding and bonding of extraneous-conductive parts are two different animals, they are mis-informing you.

I don;t think the vids are saying that, I think what caused the confusion especially in JW's Vid is that the different Animal, comes from the description of the differences of exposed conductive parts ie part of an electrical installation that is NOT normally live, electric metal heater framework , and an Extraneous conductive part, as in water,gas, oil pipework etc that doesn't form part of the electrical installation.

 

[Deleted member 26818]

As far as I am aware, the OP was referring to a dry riser, which would not be part of the electrical installation.
The OP started off stating there was an IR of 0.00 Mohms between the riser and the MET and that there was no continuity between the riser and a known earth.

I stated that 0.05 ohms is the maximum resistance for parts bonded to the MET.
In the OP’s case, I would use a low ohm meter to determine whether the IR reading of 0.00 Mohms is below 0.05 ohms.

 

[DPG]

Is this the 5 minute argument or the 10?

 

[Deleted member 26818]

Is this the 5 minute argument or the 10?

Getting a little ----ed off that people are disagreeing with me, then either posting vids or replying with posts that say the same thing I have said.

 

[Marvo]

Thread closed for a one hour cooling off period.

Deep breaths everyone, in through the nose, out through the mouth.

We'll be back shortly and in the meantime here's some soothing music.

 

[Marvo]

Thread reopened early because I'm off to bed.

By the way, did anyone notice the Pink Floyd song they sneakily slipped into that Muzak track?

 

[AJshep]

By saying no continuity do you mean low ohms measurement between MET and riser is off the scale (Im guessing greater than 200 ohms)

But insulation resistance between MET and riser is 0.00 Mohms.

Is that right? otherwise the information contradicts itself because no continuity wouldnt give a reading of 0.00 Mohms and maybe where the confusions is.

 

[Richard Burns]

The key point of the original question I think is is there an exposed conductive part, a live part (even if covered), or another bonded extraneous conductive part within 2.5 m of the hatch giving access to the riser.
The majority of the riser is inaccessible and therefore cannot introduce a potential; if the access hatch is not near any conductive part that may become live and can be simultaneously touched by a person or livestock, then the part at the hatch will also not be able to introduce its potential into the installation and bonding would not be necessary.

I think what Ian1981 is saying about measurements is as described in the below diagram. The riser is connected to true earth, but not connected to the installation protective conductors.

 

[telectrix]

no i'm confused ( doesn't take much). in OP's post #4, he says:
Testing from the MET or rather the source of earthing to said pipe.
Main earthing conductor disconnected from source earth
IR set to 500v reading of 0.00 Mohms
Also no continuity between said pipework and a known earth source
so... riser is 0.00 M to MET and no connection to earth. that says it's not extraneous.?????

 

[Deleted member 26818]

no i'm confused ( doesn't take much). in OP's post #4, he says:
Testing from the MET or rather the source of earthing to said pipe.
Main earthing conductor disconnected from source earth
IR set to 500v reading of 0.00 Mohms
Also no continuity between said pipework and a known earth source
so... riser is 0.00 M to MET and no connection to earth. that says it's not extraneous.?????

The OP has apparently changed his mind.

 

[DPG]

Maybe some of the wording wasn't clear. No need for things to get offensive though.

 

[Richard Burns]

no i'm confused ( doesn't take much). in OP's post #4, he says:
Testing from the MET or rather the source of earthing to said pipe.
Main earthing conductor disconnected from source earth
IR set to 500v reading of 0.00 Mohms
Also no continuity between said pipework and a known earth source
so... riser is 0.00 M to MET and no connection to earth. that says it's not extraneous.?????

I think perhaps the post might be worded better as

Testing not from the MET but from the source of earthing, whilst it is disconnected from the MET, to said pipe.
IR set to 500V reading 0.00MΩ.

When testing from a known earth internal to the installation to the said pipework there was no continuity.

This is what has been said in post 19.

The pipe is (presumably) buried in the ground and so has very good contact with the ground and therefore shows up as an effective earth rod. However the pipe according to the continuity readings is not connected to the installations earth wiring i.e. it has not been bonded nor has it got a connection with any cpc.
Therefore the pipe is at earth potential but the issue is does it introduce that potential into the installation.

 

[telectrix]

Therefore the pipe is at earth potential but the issue is does it introduce that potential into the installation.

or does it introduce an earth potential into the building? and if so, can it be touched? that seems to be the £64,000 question.