DIY Doctor

earth bonding

Postby misery » Sun Feb 01, 2009 7:34 pm

Hi guys,
Have just had new combi boiler fitted hence all pipework and tanks in loft now redundant.
The main earthing wire from the cu was cross bonding all the pipework up there have pulled it through wall to under bathroom floor level,have had 2 new rads ,new bath and sink in bathroom so have used said cable to cross bond all existing and new pipework.
My question is ,is that ok now ,I,m a bit confused because in the projects section it states that earthing should terminate at a near socket,immersion etc and not back to the cu as could be dangerous ,or does it mean dont take back to cu thus forming a ring?
Would appreciate any advice,thanks
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Simply Build It

Postby kbrownie » Mon Feb 02, 2009 12:51 pm

This sounds like a strange configuration, Water and gas pipes are connected via the mains earth terminal (MET) for main protective bonding, this termination will take place where the pipes enter the building after the meter for gas and after the stock-cock for water no more than 600mm after that point.
Earth bonding is not taken fron the CU but circuit protective conductors are this should run with neutrals and line/live conductors of that circuit.
Supplementary bonding is when pipe/metal work may be used to earth electrical epuipment ie shower/whirlpool bath.
So I can only assume by what you have quoted, that this earth bonding is not needed. Unless it is the main protective bond from MET but this must be connected where the pipes enter the building as mentioned above and not from CU but MET This cable is normally 10mm2 if TN-S or TN-C-S, 6mm2 for TT earthing arrangements
Last edited by kbrownie on Mon Feb 02, 2009 7:43 pm, edited 1 time in total.
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Postby kbrownie » Mon Feb 02, 2009 1:12 pm

me again, main earth bonding normally 10mm2 on TN-S and TN-CS- or 6mm2 on TT earthing arrangement think I but 16mm by mistake.
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