Electrical Bonding Ask questions and find answers to many subjects relating to electrics and electrical work

[billobach181]

I have been told that Cross Bonding of Bathroom Fittings, Combie Boiler Pipework, Gas and Water Pipework can be connected to the earthing Bar near the CU from the nearest pipes rather than Run a separate Earthwire all the way through the house to the Earthing Bar. Example my Bathroom, Kitchen and Boiler Pipework are at one end of the house and the CU the other end. So if I bond all together at one end of the house and then connect a shorter earthing wire from the nearest Central Heating pipes to the earthing block it serves the same purpose as running a long eathing cable. Is this true?

Regards
Bill Howells

[sparx]

Hi Bill,
No this is not true!
Your cross bonding MUST NOT be connected back to main earth bar, under any circumstances.
Main 10mm2 bond done at incoming stop cock (your side), also gas/oil etc to main CU bar only.
regards SPARX

[billobach181]

Thanks for your reply. So are you saying that all my pipe cross bonding ,i.e. Gas, Water, Central heating , Bathroom fitting and kitchen sink etc are to be earthed to the CU earth block by separate 10mm earth cable? In other words I cannot make a cross connection via the central Heating pipe to avoid running a separate earth cable?
Regards
Bill

[sparx]

HI Bil I don't think we are on same terminology yet, 'equipotential cross bonding' is carried out in or adjacent to bath rooms to ensure all metalwork in the zone is at same potential(voltage) so strictly local. 'Main bonding' is to keep incoming services at same potential as main earth.
although the pipe work may connect the 2 systems together it is not intended to be so. Indeed if a major earth fault occured at mains you would not want to introduce fault voltage into other zones.
So to summerise 10mm2 cable goes to Gas, Water, Oil at point of entry to building from main incoming earth term. 16mm2. local bonding in 2.5mm2 if protected from mechanical damage or 4.0mm2 if not protected. There is no longer any requirement in regs to bond pipes, sinks , boilers etc except as stated ie bathroom area, too many 'urban myths' abound made worse by NICEIC who have their own idea of what the regs should say, but as they have no legal standing I stick to IET Regs,
regards SPARX

[billobach181]

Dear Sparx
Many thanks for clearing it all up. Now I understand. Having read the Regs I was still confused but not any longer. As a matter of interest my electrician was not sure and he has been around a long time. many thanks again.
regards
Bill