supplementary bonding bathroom

[buzz light year]

i have read a bit about this subject but it has left me with more questions...
i have a wall mirror and a shaver socket outlet on the bathroom wall which are fed off the upstairs lighting circuit, when i connect up all the other metal pipes, radiators etc. will the earth connection in the back of the shaver outlet be ok for the bond to earth ? also i have a whirpool motor under the bath fed off the upstairs ring main should this be bonded to the supplementary earth or will this cause other problems ??

 

[JohnD]

The idea of the supplementary bonding is that all the electrical circuits which enter the bathroom should be bonded. So if you have a lighting circuit and something that comes off the upstairs ring, you have to bond to both their earth wires.

If you had another circuit, for example an immersion heater or an electric shower, that is not on the lighting or the sockets circuit, you would have to bond that too.

You will not cause a problem by linking them together, because they are (should be) connected together back at the consumer unit, so you are really re-linking them just in case there should be a fault or cable damage that affects the bathroom.

It is quite usual to run the earth wire round the bathroom from clamp to clamp, but it is also permissible to use the copper pipes as part of the bonding, if it is permantly fixed (e.g. soldered) and this can save running visible wires where the basin and the bath supplies are already linked by a copper pipe.

 

[kevindgas]

JOHN D

can't see where your coming from on this

supplementary bonding is rightly the linking of all metal surfaces but you only need to bond to an earth source not all the earth sources as each will go back to the board anyway where they join together.

join water pipes together and then feed to any source of earthing near to them usually the best is under the bath, if the house is wired sensibly and should be 6mm or greater

 

[buzz light year]

JohnD thanks for the reply- any ideas on how to connect 4mm2 earth to 8mm central heating pipes ?

 

[JohnD]

JOHN D

can't see where your coming from on this

I will check my OSG tomorrow in case I've dreamt it... or perhaps someone else will join in.


As for weedy little 8mm pipes, there's a whizzo new earth clamp (I've only used the metal strap kinds) that I saw mentioned on here recently...

 

[Adam_151]

John D is right, the supplimentary bonding is about keeping all parts that could introduce a potential at the same potential, its not a case of earthing stuff (though that is one of the that happens, though the stuff that is bonded is invariably somehow earthed through other paths)

not good enough to say all CPCs are joined at the dist board, you can't guarentee that the impedance is going to be low enough

Bonds should be 4mm² usless mechanically protected

and not all metal surfaces , only those that can introduce a potential, if there is no chance of a potential being introduced, no point in bonding it, and doing so might actually do more harm than good (so no bonding soap dishes )

Think I've addressed all points, but it is late

 

[Qedelec]

JohnD.
The clamps you are referring to are Mem's Ezybond, but I am not sure they go as low as 8mm.
http://www.memonline.com/ezybond.html

 

[buzz light year]

thanks for all the replies with help and advice.

 

[mikely]

JOHN D

can't see where your coming from on this

supplementary bonding is rightly the linking of all metal surfaces but you only need to bond to an earth source not all the earth sources as each will go back to the board anyway where they join together.

join water pipes together and then feed to any source of earthing near to them usually the best is under the bath, if the house is wired sensibly and should be 6mm or greater

JOHN D is correct about all CPCs being required to be connected to the bonding (reg 601-04-01). The connection to the CPCs is not just to provide a 'source of earthing'.

To understand the requirement for supplementary bonding you need to consider what happens during an earth fault. During the fault, before the protective device operates, the voltage developed at the fault rises to approximately half the supply voltage because the resistance of the phase conductors and earth conductors in the fault loop circuit is roughly equal and they act as a voltage divider. The resistance of the circuit within the installation (R1 + R2) is often significant compared to the external impedance Ze. So, even though the main bonding will cause bonded metalwork to rise to the fault potential developed at the MET, a significant voltage can develop across the CPC resistance R2. This will appear between any Class 1 appliance connected to the CPC and any earthed metalwork (e.g. a radiator, or a Class 1 appliance on another circuit). The potential level of this voltage is deemed hazardous in a special location such as a bathroom and it is this that the supplementary bonding eliminates.

This is why the CPCs of all circuits supplying equipment in zones 1,2 or 3 in a bathroom are connected to the supplementary bonding. They are the source of the hazard.

 

[RF Lighting]

Hi, we have been advised by our NIC EIC inspector that we are now required that when carrying out supplementary bonding, to include a connection to the CPC of ALL circuits within the bathroom. It is not crucial however which part of each circuit is bonded. for example to include the lighting circuit you may connect to any of the following: the pull cord, the light fitting, a vanity light, a (lighting fed) shaver point etc.

Rob

 

[JohnD]

... you may connect to ... the pull cord

(don't worry, I think I know what you meant

 

[securespark]

You can sweat the 4mm2 onto the 8mm pipe, that way, it need not be accessible.