IET logo
 
IET
Decrease font size
Increase font size
Topic Title: Water Bonding Query
Topic Summary:
Created On: 27 November 2012 10:54 PM
Status: Post and Reply
Linear : Threading : Single : Branch
<< 1 2 Previous Last unread
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 29 November 2012 03:47 PM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 11547
Joined: 13 August 2003

Looked through GN8 and it only shows incoming water pipes being in metal, so I am seeing where your coming from

Look a bit further - there is (or at least used to be) a section talking about determining whether a lump of metal is an extraneous-conductive-part or not (22k Ohms test etc).

but only because they have, for example, cpc's that bring the resistance between pipes and the MET to less than 23k?

Perhaps a slightly better test for an existing installation is to switch off, disconnect the earthing conductor from the MET and test between the part and the end of the earthing conductor (i.e. same as removing all the existing bonding and c.p.c. from the MET first, but less work). Still not foolproof (e.g. due to fortuitous paths to things that really are extraneous), but better.

- Andy.
 29 November 2012 03:50 PM
User is offline View Users Profile Print this message



daveparry1

Posts: 6239
Joined: 04 July 2007

As far as I know it is accepted that the water doesn't need bonding if it comes into the building in plastic. If it then goes on to supply an appreciable amount of copper then I do bond it at the start of the copper, although I suppose this is then classed as supplementary bonding so doesn't necessarily have to be in 10 mm? My argument is that something could happen whithin the installation to cause the copper pipes to become live, an idea which has been discounted several times on here when i've suggested it,

Dave.
 29 November 2012 04:01 PM
User is online View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19744
Joined: 23 March 2004

Originally posted by: leckie

Edit: Sorry Andy I posted this before reading your post. Looked through GN8 and it only shows incoming water pipes being in metal, so I am seeing where your coming from. Must have been written in the 50's



Im sorry for being a moron Oms I will leave myself open to another slating. I haven't been bonding plastic pipes, but I have been bonding copper pipe installations.

Not a moron mate, and no slating intended - i know you haven't bonded the plastic - just the copper that comes after it - becasue that's what many people told you to do - a somple rule that meant you didn't need to check if the water pipe went into the fllor or connected to a boiler that had pipes in the floor or left the property in copper out to a garage or shed.

Are you telling me that all the houses that have been built in the last say forty years, that will have plastic incoming water service pipes need not be bonded unless they introduce an earth potential via being buried underfloor, etc?

Yes, in short

Or do you mean that they do need bonding but only because they have, for example, cpc's that bring the resistance between pipes and the MET to less than 23k?

Nope - the cpc will just defeat the test for extraneous - if the pipe isn't extraneous then it doesn't need bonding - any more than a brass curtain pole would

I have seen literally thousands of new houses over this time and have never seen one not bonded. In many towns by many different contractors. Really.

I'm sure you have - when I've designed housing schemes we include it in the specification - just because I don't know exactly what the mech contractor is going to do with his pipes rather than it being specifically needed - as I said, it;s a simple rule that covers everyones *****


Every assessment (NIC or ECA) I have ever had alway includes a check of the bond to the water, gas, etc, unless the internal pipework has been plastic.

Well, i did tell you that sometimes the great and the good tell you lies for your own good


The OP says he is going to measure for in excess of 23k. Because of the gas pipe, cpc's, he is unlikely to measure higher than 23k, in which case he will have to bond. Correct?

Or disconnect the boiler CPC (and possibly the immersion) - if it's above 23K to the MET without those CPC's then it won't need bonding - drama over


Sorry for being a pleb but its hard to get my brain around the idea of not bonding a copper pipe installation when i have done, and everyone I know has done for a long time.

As I said, it stops you having to think and keeps things safe in future if a pipe strangler or Mr DIY do a bit of alteration (new downstairs WC for example)

Blimey, I could have saved a fortune, anyone want to buy a job lot of 10mm and some clamps?

LoL - you could have I guess - but remember we are talking about minimum compliance with BS 7671, not what is effectively an industry standard - even if it is a bit misguided.

Change comes slowly I'm afraid - the old silver foxes down at Savoy House have only just about come to terms with plastic pipe and metal partitions - it'll take another couple of decades before such things as the regs and the guidance notes spell it all out in simple terms



regards

OMS

-------------------------
Failure is always an option
 29 November 2012 04:12 PM
User is online View Users Profile Print this message


Avatar for rocknroll.
rocknroll

Posts: 8878
Joined: 03 October 2005

LOL

it'll take another couple of decades before such things as the regs and the guidance notes spell it all out in simple terms


Or the schemes proposed 'Domestic Installers Handbook', do it this way, no need to engage brain.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 29 November 2012 04:21 PM
User is online View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19744
Joined: 23 March 2004

Yeah - that'll do it - do as i tell you engineering solutions

I suppose it'll work OK when we get to that two tier system of a few skilled electricians and a shed-full of domestic installers

Regards

OMS

-------------------------
Failure is always an option
 29 November 2012 04:40 PM
User is online View Users Profile Print this message


Avatar for rocknroll.
rocknroll

Posts: 8878
Joined: 03 October 2005

You will no doubt know the support for a prescriptive set of rules for the domestic sector is gathering storm from many players who have been silent until now, maybe because of the perceived mess it is in.

I am not in favour but it wont be up to me, I often think that if all had taken Part P on the chin and got on with the job there would not be the problems we have today, I suspect we will come to the stage where they wish they had.

The only rift at one time was the commercial electricians/engineers regarding the domestic boys as 'housebashers' and looking down their noses at them, but that was jealousy as housebashing commanded often twice or more times the wages than they got, now its everybody tearing each other apart.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------

Edited: 29 November 2012 at 04:55 PM by rocknroll
 29 November 2012 05:17 PM
User is offline View Users Profile Print this message


Avatar for leckie.
leckie

Posts: 1872
Joined: 21 November 2008

Well there is a bit of bad feeling. Its due to electricians who can wire up star delta starters not being qualified to wire a shower in a house

Anyway I'm of to the scrappie now with a load of green and yellow cable
 29 November 2012 06:57 PM
User is online View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19744
Joined: 23 March 2004

Well there is a bit of bad feeling. Its due to electricians who can wire up star delta starters not being qualified to wire a shower in a house


They are qualified to do it - generally not registered to self certify compliance with Part P however.

They can of course use building control notification (or advise the client to do so).

On the flip side - electricians who can put in a shower may be operating ouside of thier scope if they were rigging up star delta starters - although to be fair, a star delta starter isn't rocket science is it

Anyway I'm of to the scrappie now with a load of green and yellow cable


LoL - the future's bright, the future's bluey

regards

OMS

-------------------------
Failure is always an option
 29 November 2012 07:04 PM
User is online View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19744
Joined: 23 March 2004

You will no doubt know the support for a prescriptive set of rules for the domestic sector is gathering storm from many players who have been silent until now, maybe because of the perceived mess it is in.


I can see the point - if we had a quasi 14th edition rule book for houses supported by whoever emerges in the fight to control the Part P scheme and just bludgeoned down to the installers then the whole sorry affair can be quietly forgotten and the sector will sort itself out.

I am not in favour but it wont be up to me, I often think that if all had taken Part P on the chin and got on with the job there would not be the problems we have today, I suspect we will come to the stage where they wish they had.


I'm not in favour either - but it may well be the least bad option left open - lets hope those who still want to do domestic work have a face that fits with the gold card club

Regards

OMS

-------------------------
Failure is always an option
 29 November 2012 07:38 PM
User is online View Users Profile Print this message


Avatar for rocknroll.
rocknroll

Posts: 8878
Joined: 03 October 2005

lets hope those who still want to do domestic work have a face that fits with the gold card club


Interesting statement, but I think that is the area where the biggest problems will be.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 29 November 2012 07:47 PM
User is online View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19744
Joined: 23 March 2004

Interesting statement, but I think that is the area where the biggest problems will be.


For sure - when there's enough gold club afficianados on the inside p**sing out, getting close to the door isn't pleasant -

Still - as always, the advice is "Be careful what you wish for"

Regards

OMS

-------------------------
Failure is always an option
 29 November 2012 07:50 PM
User is online View Users Profile Print this message


Avatar for rocknroll.
rocknroll

Posts: 8878
Joined: 03 October 2005



regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 30 November 2012 12:26 AM
User is offline View Users Profile Print this message


Avatar for spinlondon.
spinlondon

Posts: 4439
Joined: 10 December 2004

Very odd.
I had a conversation with a young lad just yesterday about this very subject.
We're working at one of the Hammersmith Underground Stations, and he's been asked to conduct a Periodic Inspection.
In the kitchen/tearoom, a copper pipe has been bonded, just as it enters the room through the ceiling.
Outside at the end of the covered part of the platform, is the plastic water mains.
This first supplies a tap in copper, then after about 3m runs up the wall to go off feeding whatever including the kitchen/tearoom.
The young lad believes the copper pipework should be bonded near the mains, because the Regs. say so.
I pointed out that the Regs. only require extraneous-conductive-parts be bonded, and that technically the pipework is bonded in the kitchen.
He then went on to state that the bonding should be within 600mm of where the pipework enters the building.
Again I pointed out that the Regs. only require extraneous-conductive-parts be bonded.
Not certain which code it's going to be, probably a C2.

The lad then went on to explain to me that a CPC on a circuit that supplies a computer is a functional earth, and that a computer leaks 5mA to earth, which is why we don't provide such circuits with RCD protection.
 30 November 2012 12:49 AM
User is offline View Users Profile Print this message


Avatar for Legh.
Legh

Posts: 3498
Joined: 17 December 2004

Interesting, the insulated water supply feeding copper piping in an underground installation could become extraneous by being connected to other pipework in the underground location?

It makes some sense to bond all the pipework within the location particularly, if there are leaky appliances...

Legh

edit: just to add, it would be wise to run a long lead around the various metalwork to make sure there is either a level of continuity or not... Don't you think?

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."

Edited: 30 November 2012 at 12:58 AM by Legh
 30 November 2012 12:50 AM
User is online View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19744
Joined: 23 March 2004

It's quite sad really Spin - just what are they teaching the new generation is beyond me, I must confess.

Don't get me wrong, if he's beeen taught that you must have a bond within 600mm of the entry regardless, then so be it - that's all installers need to know - do it that way, every time - don't think, just crack on

But someone must be going through the theory at the same time and explaining why we actually only to bond the pipe if it is extraneous - and why we need to do it

I suppose it's what's been described as underpinning knowledge - you can see some of the knowledge sticking with regard the earth leakage - just that the wrong bits for the wrong reasons

regards

OMS

-------------------------
Failure is always an option
 30 November 2012 07:40 AM
User is offline View Users Profile Print this message


Avatar for ebee.
ebee

Posts: 5725
Joined: 02 December 2004

Bonding (and also its kid brother Earthing) is a very emotive issue, full of myths, half truths and a lot of misunderstanding.

It does need some thought and understanding.

Some just blindly follow rules without any reasoning.

Some get all the reasoning very wrong.

Like AJJ hinted , to blindly bond everything is probably the "least worst" option rather than risk missing bonding something that should be bonded I suppose, although bonding something that does not need bonding introduces a risk that might not otherwise be present.

So then it becomes a clear contest, either bond nothing or bond everything.
Bond everything would probably be the safer of the two options.

whereas bond only if needed is the safest answer of all.

I suppose some might be mindful of a case where a cable wrapped around a pipe especially if jointed with strip connectors might just make a pipe live etc. I can`t say that never happens, I`m sure it will now and again. So some see bonding as "earthing against that possibility"

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 30 November 2012 09:39 PM
User is offline View Users Profile Print this message


Avatar for spinlondon.
spinlondon

Posts: 4439
Joined: 10 December 2004

Legh, neither of the Hammersmith Underground stations are underground.
I wish they were, as it would be a damn sight warmer.
 30 November 2012 09:53 PM
User is offline View Users Profile Print this message


Avatar for Legh.
Legh

Posts: 3498
Joined: 17 December 2004

I knew that ! .....he said
I'm sure some part of it is underground, otherwise they wouldn't have called it such......

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
IET » Wiring and the regulations » Water Bonding Query

<< 1 2 Previous Last unread
Topic Tools Topic Tools
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.