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#138643 - 09/20/03 03:43 AM earthing
james S Offline
Member

Registered: 05/13/03
Posts: 102
Loc: West England
i would just like to see how many electricians bond metal pipe work, metal furniture, sinks or draining boards within kitchen areas even though according to bs7671 is not required?

and if yes is the bonding connected to a cpc in a nearby circuit or are the pipes just bonded together?

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#138644 - 09/20/03 04:38 AM Re: earthing
PaulCornwall Offline
Member

Registered: 06/02/03
Posts: 112
Loc: England
Personaly... i dont bother earthing sinks anymore,, with the exception when there is an under sink water heater.. just feels its adds a bit more protection..

I think this is now becoming a problem,, i have just finished a new house where the plumber has mixed PVC pipe with copper,, so what is the point of bonding anything?? the IEE will have to issue some proper guide lines on this.

dont think you are allowed to bond to a near by circuit ant more,, maybe someone could confirm this

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#138645 - 09/20/03 06:49 AM Re: earthing
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Gidday there James,
Over here, it is up to the Installing Electrician.
Personally, I bond and earth anything that could cause an electrical hazard, should it be livened, with a 6mm2 wire.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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#138646 - 09/20/03 10:10 AM Re: earthing
j a harrison Offline
Member

Registered: 05/22/02
Posts: 112
Loc: southampton, england
Trumpy,

i am the same, if its matal and its near an outlet, it gets bonded!!

i would rather be safe than sorry, irrespective of BS7671. !!

John H

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#138647 - 09/20/03 10:48 AM Re: earthing
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
John,
You're quite right there.
Who cares what the Regs say?, we are qualified people, we SHOULD know how the story goes by now!.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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#138648 - 09/20/03 11:17 AM Re: earthing
lyledunn Offline
Member

Registered: 06/30/02
Posts: 159
Loc: N.Ireland
Bonding can be a seriously complicated issue.Generally,in domestic work bonding is not required other than in special locations such as bathrooms. However, exceptionally important is the main bonding arrangement. When a fault occurs in an installation the exposed conductive parts will have a potential with reference to true earth. Essentially this is the volt drop along the installation earth and the supply authority earth for the duration of the fault. This same voltage would be apparent between the faulty equipment case and and any un-bonded metalwork in connection with earth. Thus when main bonds are carried out this fault voltage is minimised and equates approximately to the voltage drop along the installation earth (cpc).
Bonding all metalwork in sight can actually introduce a hazard where none formerly existed so great care should be exercised.
_________________________
regards

lyle dunn

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#138649 - 09/21/03 06:39 AM Re: earthing
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
The Electrician's Guide to BS7671 suggests that a metal item should be bonded if its measured resistance to earth is under 50K.

The reasoning is that if adjacent bonded metalwork rises in potential during a fault condition, a resistance of over 50K to earth will allow under 5mA or so to flow as shock current.

If the resistance is lower than 50K, the shock current would exceed 5mA, so they say bond it so that it rises to the same potential as the adjacent item.

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#138650 - 09/21/03 02:30 PM Re: earthing
james S Offline
Member

Registered: 05/13/03
Posts: 102
Loc: West England
thanks for your views all. very interesting! i like to follow the reg as much as possible i just wish they where a bit more clear to understand !

[This message has been edited by james S (edited 09-21-2003).]

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