Extraneous conductive parts

[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.

 

[Devonchris]

A "dry riser" is a vertical pipe that usually starts at ground floor level and has an outlet on each floor. Its purposes is to allow firefighters to connect at ground level and the fire level without having to run hose in stairwells.

At no point would it enter the "ground". Effectively, its just a bit of metal within the building. Unless someone has made some sort of connection, then I would be surprised if it tests as extraneous.

 

[Which One’s Live?]

...that seems to be the £64,000 question.

I nearly fainted then; I thought that was a job quote!!

 

[bigspark17]

In relation to the OP i think @Devonchris is right and at no point should that dry riser be in the ground apart from fixed to it, but the OP is the man on the job and an experienced one at that.

 

[johnduffell]

could be explained maybe someone else in the building has already bonded it to their MET? making it an ECP for all other equipotential bonding zones it enters

 

[ipf]

could be explained maybe someone else in the building has already bonded it to their MET? making it an ECP for all other equipotential bonding zones it enters

Shut it down Marvo.
It's getting ridiculous.

 

[Ian1981]

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.
View attachment 43000

Didn’t realise it’s thread is still running but yes Richard you are correct

 

[Ian1981]

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.

Correct again

 

[Ian1981]

A "dry riser" is a vertical pipe that usually starts at ground floor level and has an outlet on each floor. Its purposes is to allow firefighters to connect at ground level and the fire level without having to run hose in stairwells.

At no point would it enter the "ground". Effectively, its just a bit of metal within the building. Unless someone has made some sort of connection, then I would be surprised if it tests as extraneous.

The dry riser comes out of the ground all metallic in construction and does introduce an earth potential.
It is a separate service entering the building and not in anyway connected to the main buildings water supply.

 

[johnduffell]

Shut it down Marvo.
It's getting ridiculous.

don't get it? was it a joke and I'm being thick or just you quoted the wrong post?

 

[bigspark17]

don't get it? was it a joke and I'm being thick or just you quoted the wrong post?

Agree!! If you dont like the post just ignore it!!