Another "BONDING" Question

[STI]

I have read with interest many of the discussions on earthing earth bonding equipotential bonding etc but i still cant find an answer to this.

Is Supplementary bonding the same as Supplementary Equipotential bonding.

 

[holmslaw]

..

 

[STI]

The reason i ask is because in an earlier post BAS posted some very usefull links see below:

NICEIC Earthing & Bonding leaflet


What's an extraneous-conductive-part?


Bonding & plastic pipes


Bathrooms & the 17th


Supplementary Equipotential Bonding

When i looked at these the final diagram in the first brochure ie the NICIEC leaflet shows supplementary bonding in a bathroom which to me is not the same as the supplementary Equipotential bonding shown in the last document titled accordingly. The main difference being the lack of attachment to an accessories earth.

I ask because i have asked in the past, if you have a bathroom that is not RCD protected AND has copper pipes for water and central heating with a metal rad and lets say contains a light, an electric towel rail and a shower. To put supplementary bonding in here do i need to run an earth wire form the pipes to the earth of the towel rail AND to the earth of the Lights AND to the earth of the shower. Looking at the NICIEC document which is again a simple one electrical accessory example it would appear yes but in the last document i could just run earth wire across the pipes and NOT connect directly to the earth terminal in any of the accessories.

I think i asked this question on this forum and on the voltium forum and to be frank i have never received a definitive answer.

 

[STI]

The other topic where the links are posted is Earth Bonding POSTED BY ALANTHOMASWATSON

 

[dingbat]

... i have never received a definitive answer...

Maybe because every scenario is unique and requires consideration of the reason why it may need to be done in the first place.

Read Regulation group 415.2, including the notes. It's pretty straightforward.

 

[STI]

Hi Dingbat ive read it and if i ve understood it, a different matter all together, then 415.2.1 to me would mean bond all the pipes rads etc together then run this back to the CU and the earth bar in it. That way its "connected to the protective conductors of all equipment including socket outlets".
However i was told you cant do this. Thats why i started asking the question as the only way i could see it meeting the needs of 415.2.1 using my central heating radiator supply pipes as an example in a bathroom with no RCD would be to run from the pipes, one earth wire to the shower. Then another earth wire to the lights then another to the electric towel rail. So 3 wires coming from the radiator pipes to the CPC connections. This cant be right.

 

[ban-all-sheds]

I think at least part of the reason for the "pedantry" over terminology is that there is widespread confusion and lack of understanding of the difference between earthing and equipotential bonding, and mixing the terms in random ad-hoc ways does nothing but exacerbate the problem.

That said, the IET keep changing the names but the cables remain the same....

When i looked at these the final diagram in the first brochure ie the NICIEC leaflet shows supplementary bonding in a bathroom which to me is not the same as the supplementary Equipotential bonding shown in the last document titled accordingly. The main difference being the lack of attachment to an accessories earth.

They are the same, and the diagram in the last document does show connections to accessory/appliance earths, but being an IET document it labels the latter "exposed conductive parts".

To put supplementary bonding in here do i need to run an earth wire form the pipes to the earth of the towel rail AND to the earth of the Lights AND to the earth of the shower.

Yes.

Looking at the NICIEC document which is again a simple one electrical accessory example it would appear yes but in the last document i could just run earth wire across the pipes and NOT connect directly to the earth terminal in any of the accessories.

No - read 701.415.2.

Hi Dingbat ive read it and if i ve understood it, a different matter all together, then 415.2.1 to me would mean bond all the pipes rads etc together then run this back to the CU and the earth bar in it. That way its "connected to the protective conductors of all equipment including socket outlets".

That last sentence refers to the location where the supplementary bonding is, so if you have sockets there then you'd connect to their cpc terminals.

the only way i could see it meeting the needs of 415.2.1 using my central heating radiator supply pipes as an example in a bathroom with no RCD would be to run from the pipes, one earth wire to the shower. Then another earth wire to the lights then another to the electric towel rail. So 3 wires coming from the radiator pipes to the CPC connections. This cant be right.

It doesn't have to be 3 - it could be one, going from one point to another - it all depends on the positions of items relative to each other. Also, don't forget that the cpcs themselves can be part of the bonding, so it isn't necessary to connect directly to the cpc terminal on each appliance.

 

[STI]

BAS,
Thanks for the reply it helps a lot but i am with you until your last sentence
Also, don't forget that the cpcs themselves can be part of the bonding, so it isn't necessary to connect directly to the cpc terminal on each appliance
I am probably being thick but i cant follow that, could you give a verbal illustration..

 

[ban-all-sheds]

You could accomplish the bonding of the light by connecting to the lighting circuit cpc at the switch.

 

[dingbat]

BAS,
Thanks for the reply it helps a lot but i am with you until your last sentence
Also, don't forget that the cpcs themselves can be part of the bonding, so it isn't necessary to connect directly to the cpc terminal on each appliance
I am probably being thick but i cant follow that, could you give a verbal illustration..

All that bonding does is to reduce the resistance between parts of an installation.
This can be achieved by using separate conductors, or by existing, permanent reliable conductive parts such as pipework, cable armour, CPCs, etc (Reg 544.2.4)

Reg 415.2.2 gives a method for determining whether you actually need to use supplementary conductors.

 

[STI]

Just read 701.415.2 and sorry this is my enquiring mind, i understand that it says it should be done preferably close to the point of entry of extraneous-conductive parts but i dont understand why. Is it so there is less likely hood of a disconnect occuring by changes to the pipe runs (i would have thought a direct link to the CU would actually be less likely to be "removed" ) or is there another reason to do with Zs and the fact that the Extr. Parts arent in themselves protected by any device at the CU.

 

[STI]

BAS,
Thanks for the reply it helps a lot but i am with you until your last sentence
Also, don't forget that the cpcs themselves can be part of the bonding, so it isn't necessary to connect directly to the cpc terminal on each appliance
I am probably being thick but i cant follow that, could you give a verbal illustration..

All that bonding does is to reduce the resistance between parts of an installation.
This can be achieved by using separate conductors, or by existing, permanent reliable conductive parts such as pipework, cable armour, CPCs, etc (Reg 544.2.4)

Reg 415.2.2 gives a method for determining whether you actually need to use supplementary conductors.

Got it thanks on the 544.2.4 but still not on the why not run it back to the CU in fact 544.2.5 more or less implies it is acceptable ie use of a socket outlets earth connection when using a short piece of flex.