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.