supplementary bonding

[newfutile]

we are allowed to omit supplementary bonding on the 3 conditions (rcd, disconnection times and main bonding adequate )
if we have a plastic insert we may omit main bonding on water for example.
would supplementary bonding have to be added as it no longer has main bonding ?

 

[Ian1981]

Main protective bonding to the water service would not be required where the service enters into the installation in plastic or has a plastic insert then changes to copper.
Regulation 411.3.1.2 - Protective equipotential bonding:

Metallic pipes entering the building having an insulating section at their point of entry need not be connected to the protective equipotential bonding.
Supplementary bonding should not required in this instance but all circuits serving the location (assuming it’s a room containing a bath or shower) require additional protection by an rcd in accordance with 415.1.1

 

[AJshep]

The latest IET wiring matters has an article which goes into a bit more depth regarding bonding and supplementary bonding.

https://electrical.------.org/wiring-matters/issues/76/protective-bonding-habits/

 

[newfutile]

many thanks for the replies
i assume if it has a plastic pipe or insert it not considered an extraneous-conductive-part and is just a piece of metal?

 

[Ian1981]

many thanks for the replies
i assume if it has a plastic pipe or insert it not considered an extraneous-conductive-part and is just a piece of metal?

Yes that would be right

 

[mart spark]

If you are unsure if it's just a piece of metal or an extraneous conductive part you can I.R test. If it's greater than 0.02 MOHM then it's just a piece of metal.

 

[newfutile]

Thanks for all your replies i find earthing and bonding a bit confusing sometimes despite reading GN8.

 

[Bellendian]

If you are unsure if it's just a piece of metal or an extraneous conductive part you can I.R test. If it's greater than 0.02 MOHM then it's just a piece of metal.

But remember that this test will often show a connection to earth via boiler, immersion, water heater cpc's etc. And can send you down the route of thinking it's extraneous, when in actuality it may not be.
To get a true test you need to power off install and disconnect earthing conductor from MET and then test from piece of metal in question directly to earthing conductor.