Supplimentry Bonding 17th Edition

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I would like some advice regarding Supplimentry Bonding of taps and fittings in Bathrooms and Kitchens. Do I require it? All ccts are protected by RCD. All Service pipes (water) and Main isolator are pvc
Thank you
 
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The purpose of bonding (Main & Supplementary) is to connect together all pipework and other conductors such as structural steel etc that might introduce a potential - usually earth potential.
So if all is plastic it is not needed - and you would have no conductor to bond too anyway.

The purpose of Supplementary bonding such as in a bathroom is to also connect the earths of the circuits together along with such pipework/structure therefore any two conductive parts that you can touch are always at substantially the same potential and any shock risk would therefore be minimal at all times.

Supp bonding in kitchens has not been a requirement for quite some time however you might feel it is safer to do so.

Supp bonding may be omitted anyway if ALL three of certain conditions are met:-

Automatic disconnection times are met.

All circuits of the location are 30mA RCD protected

All pipework of the location (if conductive) is effectively connected to any bonding required in the installation .

You might however feel it safer to supplementary bond (at least the earths of circuits in your case) to mitigate against possible failure of an RCD or indeed the rise of an earthwire potential occurring from a fault upstream of a local RCD (Note - the Reg actually says "All circuits of the location" not "Part of a circuit feeding the location")
 
I think only professional electricians should make the call as to whether to supplementary bond in kitchens or not.

The IEE thought it was better to earth most metallic things that did not move from the 14th Ed. onwards.

The 14th Ed. even had a list of items it deemed acceptable not to connect:

Isolated lengths of metal used for cable protection other than overhead spans or those protecting HV cables in discharge lighting installations, metal cable clips, metal lamp caps, small metal parts such as screws or nameplates isolated by insulating material, metal chains for the suspension of light fittings, metal light fittings using filament lamps installed above a non-conducting floor and so mounted or so screened by non-conducting material that they cannot readly be touched by a person standing on or within reach of earthed metal.

The 15th got a reputation for supplementary bonding: if it doesn't move, it's metal and you can touch it, bond it!

In my grandmother's kitchen in Guildford, the window had a 4mm link between the metal window frame and the opening lights while the frame was connected to the nearest pipe....

Whether this was right or wrong, I don't know, but let's just say that the IEE's Paul Cook wrote many articles on the subject. He was concerned supplementary in the kitchen was introducing multiple earth paths into the installation and in any case, the kitchen is not such a high risk area (generally no denuded bodies with greatly reduced body resistance - I did say generally! ;) ) and he may well have had a hand in the reigning back of supplementary from the 16th Ed. onwards.

Obviously the regs are a fluid thing: I feel we are sometmes guinea pigs trialling a new set of regs. The IET will decide as time goes on whether certain regs work, whether others need tweaking or removing all together.

Some regs you can recognise, even from the 1st Ed. back in 1882.

Others, looking in the 14th Ed, from the year I was born (1966) remain largely unchanged today.

But SEB is one area of the regs where there has been much change down the years.
 
I will depend on the regulations in Gibraltar, which (most likely) none of us here in the UK will know.
 
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If folk are going to post questions in Electrics UK using locations outside the UK, it is assumed they are in the UK: lots of users here have non-UK locations.

If the OP is really from outside the UK, they should repost in the correct place.
 
If folk are going to post questions in Electrics UK using locations outside the UK, it is assumed they are in the UK: lots of users here have non-UK locations.
If folk post here saying that they are outside the UK then I assume that they are telling the truth, not lying to us.
 
Not quite fair, Ban. Countless people use (or at least used to) use a location that implied they were abroad when they were not.
 
Correct me if I'm wrong, but I thought that BS 7671 did indeed apply in Gibraltar. Although really part of Spain, it is classed by the British Government as a "UK Overseas Territory".
 
Supp bonding may be omitted anyway if ALL three of certain conditions are met:-
1...Automatic disconnection times are met.
2...All circuits of the location are 30mA RCD protected
3...All pipework of the location (if conductive) is effectively connected to any bonding required in the installation.
That is indeed what the regs say, and they say nothing directly about how (1) has to be achieved. That make me wonder why they bother to specify condition (1), since the required disconnection time will inevitably be achieved by (2).

Kind Regards, John.
 
As the RCD may only be considered additional protection I maintain '1' should be met without reliance on the RCD although I admit, as is so often the case, it doesn't say that.

The same as, I believe, 'Max.Zs allowed' on certificates should still be that relating to the MCB and not 1667 for every circuit.
 
As the RCD may only be considered additional protection I maintain '1' should be met without reliance on the RCD although I admit, as is so often the case, it doesn't say that. The same as, I believe, 'Max.Zs allowed' on certificates should still be that relating to the MCB and not 1667 for every circuit.
What you say is not unreasonable but, as you say "it [the regs] doesn't say that".

Kind Regards, John.
 
I think the fact that ALL conditions must be met enhances the point that RCD is supplementary and without it being present then supp bonding must still be carried out.

The only time I think this would occur though is to an existing bathroom with non RCD circuits having a new (RCD) circuit added although this seems to conflict with Mark Coles at the IET insisting that all bathroom circuits must be brought up to current regs when installing a new circuit.

Like I`ve said before I still prefer to sup bond even though I may omit it because of the possible failure rate of RCDs and the fault before it syndrome . Even when disconnection times are met then touching two bits at different potentials until the fault clears might still give quite a sting and to a person who might be hot naked and sweaty then even more so.
 
As the RCD may only be considered additional protection I maintain '1' should be met without reliance on the RCD although I admit, as is so often the case, it doesn't say that.

The same as, I believe, 'Max.Zs allowed' on certificates should still be that relating to the MCB and not 1667 for every circuit.

A resounding agreement on both counts!

I also think it should be 1666, as 1667 goes over....



hot naked and sweaty

Have you been reading 50 shades of Grey again?

;)
 
I think the fact that ALL conditions must be met enhances the point that RCD is supplementary and without it being present then supp bonding must still be carried out.
I think you may have missed my point. No-one is denying that all conditions must be met in order for supplementary bonding to be omited - it's a question of how they are met.

For a start, under what circumstances do you feel that it is acceptable/compliant to have any final circuit which does not fulfill the requirements of the regs in terms of disconnection times?

Kind Regards, John.
 
Hi John,
to me it seems pretty clear that the RCD (including its trip time) might have been the "crowning glory" that allowed this relaxation.

The final circuit should have a disconnection time of 0.4 secs for TN systems (as well as the RCD for "back up) . Previous regs allowed for circuits with a 5.0 seconds disconnect time (though not for bathrooms).

Although it should not be the case it may well happen that an existing bathroom is on a lighting circuit that allowed a 5.0 second time and therefore the bathroom disconnection time is exceeded.

So at best you could have a bathroom with a compliant 0.4 secs disconnection time but a fault elsewhere on that circuit could raise the cpc to say half supply voltage for that time. That 0.4 seconds time is clearly longer than the RCD trip time of 300mS (or the better old BS time of 200mS) during which time the RCD would not trip if it is protecting only the bathroom part of the circuit and not the entire circuit right from the DB.

Anyway that`s my take, the RCD is supplementary and providing it is in place then bonding may be omitted but the other two conditions must still applyin their own right.

I`ve probably complicated ot by the way I just explained it. If so , sorry.
 

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