Extraneous conductive parts

davidl · Apr 24, 2009

Good morning everyone,

I have a really silly question here, mainly for clarification. A bathroom has an exposed section of cast iron soil pipe, a radiator and short pipes from the floor, and all other exposed copper pipework is fed via plastic pipework under the floor and inside pipe boxing and all circuits,( in this case only lighting) are protected by an RCBO.

The supplymentary equipotential may be ommitted where certain conditions are met, they include rcd protection etc, but the one that is a bit ambiguous is ' all extraneous-coductive parts of the location are effectively connected to the protective equipotential main bonding according to reg 411.3.1.2.'

I intend to bond the soil pipe but what about the rad? Seems easier to carry out supplymentary bonding, or am I reading it all wrong.

Thanks in advance for the replies.

Kind regards

David

extension15 · Apr 24, 2009

If the radiator is fed via plastic (or the copper pipework is broken up with plastic fittings) do not supp bond..

But all circuits protected so no need to bother, in this instance.

(As far as I can see here)

Janice · Apr 25, 2009

helluva big clip round the soil pipe.

One coat of bitumastic, followed by a coat of gloss should ensure this is no longer an extraneous conductive part.

The rad is fed by plastic so this, also, is not an extraneous conductive part.

Unless I am reading this wrong?

J.

davidl · Apr 25, 2009

Hi Extension15 and Janice,

Thanks for the replies, in fact the rad is fed completely by copper pipes, with metal joints, soldered or compression thoughout, as far as I can tell,

An NICEIC inspector was of the opinion that the soil should be bonded back to the met, but the point that confuses me is that if supplementary bonding can be ommitted in this case but extraneous conductive parts have to be bonded to get this ommission, is the rad an extraneous part that needs to bonded back to met as well. If it is then supplementary bonding is probably more easy to carry out, in this case. Am I making sense? or completely raviing.

Thanks again.

Have A nice weekend everyone

David

Oracle · Apr 25, 2009

i think you are getting confused by main and sup bonding.

They are say the soil pipe needs main bonding (just like a service) as it goes direct into the ground. Where as the rad needs sup bonding - to ensure its all at the same potential (the water system is already main bonded)

O.

SPECIAL LOCATION · Apr 25, 2009

Hi Extension15 and Janice,Thanks for the replies, in fact the rad is fed completely by copper pipes, with metal joints, soldered or compression thoughout, as far as I can tell,

An NICEIC inspector was of the opinion that the soil should be bonded back to the met, but the point that confuses me is that if supplementary bonding can be ommitted in this case but extraneous conductive parts have to be bonded to get this ommission, is the rad an extraneous part that needs to bonded back to met as well. If it is then supplementary bonding is probably more easy to carry out, in this case. Am I making sense? or completely raviing.

Thanks again.

Have A nice weekend everyone

David

Hello David..

Don't get confused between Exposed conductive parts & Extraneous conductive parts. (see page 24 of the big red book for definitions).

Extraneous, COULD introduce an earth potential and MUST have "main protective bonding" as per 411.3.1.2 e.g. a metal soil pipe going into the ground.

Exposed conductive parts, conductive metal parts that don't normally introduce an earth potential but may go live during a fault.

these are the stuff what have "supplementary bonding" e.g. the radiator.

But supplementary bonding can be omitted if all bathroom circuits RCD protected, see page 166 Reg 701.415.2, bottom quarter of page, bit that reads "supplementary bonding may be omitted if point i, ii, & iii are met"

Andy™ · Apr 25, 2009

But.... are we then not adding more of a risk by bonding the soil stack? mostly if the house is PME. soil stack is likely to be cast iron to ground then clay onwards, so if it is bonded and there is a fault... you have just made that pipe outside live when i otherwise wouldnt be. kinda getting back to the unnecessary bonding of metallic window frames mentioned here

or could it be argued that it cant be extraneous because its not metallic into the ground, it stop at the ground

SPECIAL LOCATION · Apr 25, 2009

But.... are we then not adding more of a risk by bonding the soil stack? mostly if the house is PME. soil stack is likely to be cast iron to ground then clay onwards, so if it is bonded and there is a fault... you have just made that pipe outside live when i otherwise wouldnt be. kinda getting back to the unnecessary bonding of metallic window frames mentioned hereor could it be argued that it cant be extraneous because its not metallic into the ground, it stop at the ground

ONLY if you can prove that it stops, but if its Cast iron up the side of the building and it touches the ground...

It is an extraneous conductive part...

normally clay bits are not visible above the ground?

unless of course you can confirm electrically there is no path or you can visibly see suitable insulated section?

A window is NOT an extraneous conductive part... (it don't go into the ground introducing an earth potential)

But a metal soil stack IS and does. thus reg 411.3.1.2 protective bonding to all Extraneous conductive parts inc Gas / Water / Oil / Metal waste pipes / Structural steel etc..

p.s. If it was my house I would have put a plastic waste stack in now..

stop the thing corroding and all the poo seeping outBlushing:O

Andy™ · Apr 25, 2009

A window is NOT an extraneous conductive part... (it don't go into the ground introducing an earth potential)

But a metal soil stack IS and does. thus reg 411.3.1.2 protective bonding to all Extraneous conductive parts inc Gas / Water / Oil / Metal waste pipes / Structural steel etc..

easy enough to say, but if the stack doesnt go into the ground, and is therefore insulated from 'earth', just like the window, then you are introducing a potential that was never there, so anyone outside could get a shock.

but by not earthing it, you could allow a potential inside the building between that and something else... where do you stop

SPECIAL LOCATION · Apr 25, 2009

easy enough to say, but if the stack doesnt go into the ground, and is therefore insulated from 'earth', just like the window, then you are introducing a potential that was never there, so anyone outside could get a shock.

If it IS insulated it is NOT and extraneous conductive part (page 24 big red) therefore you don't bond it!?

but by not earthing it' date=' you could allow a potential inside the building between that and something else... where do you stop[/quote']

You only earth it if it is already in contact with earth (extraneous) to ensure a GOOD earth path to maintain disconnection times & not exceed 50v touch voltage.

Otherwise if not in contact with earth, no bond and it cannot introduce any potential.

and any Simultaneously accessible "Exposed" parts will either be supplementary bonded OR RCD on all circuits.

an insulated metal stack on the outside of the building will be no more hazardous than a metal push bike standing in the garage.

BUT a metal stack in contact with the ground with metal exposed pipe work entering the bathroom would be extraneous and that could introduce and earth potential.

as said personally I would have put plastic pipework in...

or at least where it come through into the bathroom..

thus any other metal is outside the building and outside the equipotential zone.!

Andy™ · Apr 25, 2009

probably best to get the plumber in and add a piece of plastic instead where it goes through the wall... problem solved!

Oracle · Apr 25, 2009

if unsure can't you test the resistance - using an ir test between the soil pipe and an earth. If its around 20k (can't remember the exact and can't be arsed to calc it) or less then bond it.

O.

SPECIAL LOCATION · Apr 25, 2009

if unsure can't you test the resistance - using an ir test between the soil pipe and an earth. If its around 20k (can't remember the exact and can't be arsed to calc it) or less then bond it.O.

Quite so Oracle!

Applaud Smiley

green-hornet · Apr 25, 2009

I find it interesting that the owners have allowed a great lump of metal soil pipe to be exposed in the bathroom (ugly) springs to mind.

Box it in, obstacles in place, no need to bond.

Andy™ · Apr 25, 2009

but 417.2 says obstacles are for basic protection only and locations that are controlled by supervised by skilled persons. so either im missing something, or that idea doesnt work.

even if you did put a tick in obstacles box on EIC, what happens if they remove boxing for DIY purposes, and then get a shock (if it really is extraneous). Dont think even adding a note behind boxing would comply either. if it was a live in normal use part, then possibly warning them to isolate would do, but you cant 'isolate' the pipe so wont be able to make it safe

green-hornet · Apr 25, 2009

Most metal soil pipes are and have been from the earliest I can remember boxed in.

It would not be required, to expose such pipes in order to bond "if" it was found to be metal.

Another major problem is effective bonding on cast iron is not the best.

If boxed in and a tool was required to remove then I see no problem with not bonding a pipe that should not be seen anyway.

Janice · Apr 25, 2009

All these posts about the soil pipe being an extranoeus conductive part. As I said earlier, the easiest way is to make it NON-CONDUCTIVE and get it out of the equation.

J.

Andy™ · Apr 25, 2009

All these posts about the soil pipe being an extranoeus conductive part. As I said earlier, the easiest way is to make it NON-CONDUCTIVE and get it out of the equation.J.

but i cant see customer being too happy about 'and would you mind getting a plumber in to cut a section of your bog pipe out and replace with a short plastic section to make things easier for me?'

SPECIAL LOCATION · Apr 25, 2009

I think the key problem you may encounter with "metal waste pipes" is actually the ones that join directly onto a plug waste in a sink or bath..

not the big carry the poo from the back of the toilet one!

As the toilet is generally ceramic and persons don't very often go groveling around the back of the pan!Blushing:O

IMHO the risk associated with a toilet waste is minimal!

However "extraneous metal waste" from a sink or bath with an electrically continuous path to the metal rim around the plug hole.....

that persons do touch .. quite frequently..

does pose a more realistic risk...

and in that case bonding should be put in place.... or metal removed! ; \

Janice · Apr 25, 2009

OP only referred to the toilet outlet.

J.

Extraneous conductive parts

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