I'm renovating my bathroom at the moment and currently there is no
supplementary bonding. I have read several threads on uk diy, but I
remain uncertain about some points.

As I understand it

All exposed metal work should be bonded together. This doesn't extend
to things like loo roll holders etc. that are isolated.

Provided the bonding is protected it can be done using 2.5mm cable. In
my case all bonding is going to be carried out within the void under
the bath or within a false wall I am having to build. This will be
accessible, but only by unscrewing an access hatch or bath panel.

I have a light fitted which has a metal case. This is mounted on the
wall, but is fed from a junction box in the false wall. As the junction
box is at the foot of the wall near to where the taps and radiators are
bonded, can I simply connect these to the cpc at the junction box and
avoid having a separate cable from the light down to the radiator.

There is no need to actually link this bonding back to a cpc on the
lighting or shower circuit. But because I have a shower and a light in
the room these will be linked to the bonding anyway.

Please confirm that I have got this right.

Thanks, Tim

Provided the bonding is protected it can be done using 2.5mm cable.

Use 4mm. Providing protection is normally not practicable.

I have a light fitted which has a metal case. This is mounted on the
wall, but is fed from a junction box in the false wall.

An adjacent junction box is an acceptable location for running the
supplementary bonding.

As the junction box is at the foot of the wall near to where the taps
and radiators are bonded, can I simply connect these to the cpc at the
junction box and avoid having a separate cable from the light down to
the radiator.

Personally, I would regard the junction box as too far from the light, so
unacceptable unless the CPC was 4mm, which is VERY unlikely. However, it
would be acceptable if the CPC was protected, such as being in a metallic
conduit, and otherwise met supplementary bonding regulations for minimum
size.

There is no need to actually link this bonding back to a cpc on the
lighting or shower circuit.

There is if you have lighting or a shower.

Christian.

Christian McArdle wrote:

Personally, I would regard the junction box as too far from the light, so
unacceptable unless the CPC was 4mm, which is VERY unlikely. However, it
would be acceptable if the CPC was protected, such as being in a metallic
conduit, and otherwise met supplementary bonding regulations for minimum
size.

Provided that the run from the JB to the light is fairly direct and is
in T&E cable I don't see why bonding to the CPC in the JB wouldn't be
OK. A CPC in a sheathed cable is deemed to be protected for this
purpose [see Regs. 547-03-01 to -03].

Bonding to the lighting circuit's CPC is not required if the light and
any other accessories on the circuit (e.g. shaver point, fan) are
outside the Zones.

--
Andy

A CPC in a sheathed cable is deemed to be protected for this purpose [see
Regs. 547-03-01 to -03].

Ah. I had missed that one. I had thought that protected had the same meaning
as for buried cable runs. That's useful to know.

Christian.

On Thu, 24 Aug 2006 13:07:33 +0100, Andy Wade wrote:

Christian McArdle wrote:

Personally, I would regard the junction box as too far from the light, so
unacceptable unless the CPC was 4mm, which is VERY unlikely. However, it
would be acceptable if the CPC was protected, such as being in a metallic
conduit, and otherwise met supplementary bonding regulations for minimum
size.

Provided that the run from the JB to the light is fairly direct and is
in T&E cable I don't see why bonding to the CPC in the JB wouldn't be
OK. A CPC in a sheathed cable is deemed to be protected for this
purpose [see Regs. 547-03-01 to -03].

Bonding to the lighting circuit's CPC is not required if the light and
any other accessories on the circuit (e.g. shaver point, fan) are
outside the Zones.

....or are Class II equipment?


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

wrote in message
ups.com...

===Clip


Provided the bonding is protected it can be done using 2.5mm cable. In
my case all bonding is going to be carried out within the void under
the bath or within a false wall I am having to build. This will be
accessible, but only by unscrewing an access hatch or bath panel.


Hmm - OK I'm Confused... and on re reading the regs I'm still confused..
I expected one of the Gurus to chip in that 4mm was needed not 2.5mm.

I had thought that 4mm cable in a nice green/yellow cover running round
the bathroom was the way to go..

In sections 547-03-02 & 03 what is the meaning of "sheath" and
"mechanical protection".. These don't get spelled out in the definitions.

Is "Sheath" the green/yellow plastic stuff? What is "mechanical protection"
in this context? The side of a bath? Steel conduit? And why should the
type of protection dramatically affect the diameter of the bonding...

Hmm - I'm obviously confused - could somone please spell out
547-03-02 & 03 in simple terms!

Many thanks,
Roy

Ed Sirett wrote:

Bonding to the lighting circuit's CPC is not required if the light and
any other accessories on the circuit (e.g. shaver point, fan) are
outside the Zones.

...or are Class II equipment?

No, the CPCs of circuits feeding equipment within the Zones should be
bonded, even if all such equipment is Class 2. That was one of the
significant changes made when the new bathroom rules were introduced in
2000. I've always assumed it's so that the bonding is already in place
for when replacement Class 1 fittings get installed.

--
Andy

RzB wrote:

Hmm - OK I'm Confused... and on re reading the regs I'm still confused..
I expected one of the Gurus to chip in that 4mm was needed not 2.5mm.

I had thought that 4mm cable in a nice green/yellow cover running round
the bathroom was the way to go..

It is, usually. You "can't go wrong" if you use 4.

In sections 547-03-02 & 03 what is the meaning of "sheath" and
"mechanical protection".. These don't get spelled out in the definitions.

Is "Sheath" the green/yellow plastic stuff?

No, that's insulation. All separate protective conductors of 6 mm^2 or
less have to be insulated [543-03-02].

Sheath is a second layer of PVC, usually grey, like the outer of
twin-and-earth cable or meter tails.

What is "mechanical protection" in this context? The side of a bath?
Steel conduit? And why should the type of protection dramatically
affect the diameter of the bonding...

I've always assumed it to mean "enclosed in some recognised form of
wiring system" - i.e. conduit (steel or PVC) or trunking (including
mini-trunking). The intent of the regs is to prevent separate thin
easily-broken wires being used. IOW 4 mm^2 is considered sufficiently
robust not to get damaged, even if not enclosed.

Hmm - I'm obviously confused - could somone please spell out
547-03-02 & 03 in simple terms!

547-03-02: For electrical purposes the size of bonding between
electrical circuit earths (CPCs of e.g. shower and lighting circuits)
and extraneous-conductive-parts (e.g. heating pipes) must be at least
half the size of the relevant CPC, but subject to a minimum of 4 mm^2
for reasons of mechanical robustness if not enclosed.

547-03-03: Same thing, but between two extraneous-conductive-parts.
Electrical: 2.5 min, but 4 if not enclosed.

There is another constraint in 413-02-28 which imposes resistance limits
for supplementary bonding. In principle this could mandate larger sizes
than 547-03-xx, - but not in a normal-size bathroom.

HTH
--
Andy

Andy,

Ahh - all a little clearer now.

I'll stick to 4mm and all will be well... :-)

Thanks for your excellent response,

Roy