Earth Bonding, what size wire?


Postby WHYDIY » Wed Mar 18, 2009 5:54 pm

HI, Can someone please advise me on the correct size of wire to use for supplementary earth bonding in bathrooms and is it different to the size used for the Earth Bonding on the stop cock and gas????

Sorry if this has been covered before!

Cheers
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Postby kbrownie » Thu Mar 19, 2009 8:02 am

Hi whydiy,
The Main bonding on your mains supply pipework is larger and depends on earthing system being supplied to property.
4mmsq is normal for supplementary bonding.
KB
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Postby WHYDIY » Thu Mar 19, 2009 9:05 pm

Thanks for the info! Just taken a look at the project related to Earth bonding on DIY DOC and it suggests the supplementary earth must be connected to a local earth to the bathroom such as a socket or shower, which creates some questions;

Can this earth point be a lighting circuit earth??? (because I have no other electrical connection in the bathroom to take it to)

Does this need to be done by a part P qualified person?
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Postby kbrownie » Fri Mar 20, 2009 12:29 pm

if circuit rcd protected, disconnection times comply as fixed equpiment your breaker should operate within 5 seconds and mains earth bonding is effective to bathroom pipework.
supplementary bonding not required.
KB
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Postby kbrownie » Fri Mar 20, 2009 5:39 pm

May I also add as I didn't cover this point that installing or upgrading supplementary bonding is not notifiable work. the logic behind this I fail to see as I personally consider the earthing the most important part of the installation and if not done correctly can cause more harm than good.
If the light fitting is outside of the zones it is also not needed.
KB
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Postby Steve the gas » Sat Mar 21, 2009 6:58 am

My understanding is :-

Main earth at cut out ( PME or TNCS) is now 16mm2.
Bonding to services - gas and water services is 10mm2.

But I'm a gasman not a sparky.
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Postby rosebery » Sat Mar 21, 2009 8:06 am

Just to add further confuson, bless the penpushers and regulators, if your house is wired to the 17th with a shedload of RCDs in your consumer unit supplementary bonding is no longer required in a bathroom. Pre 17th wiring it is required.

However if the circuits in the bathroom are RCD protected (as they will be if a new fan, lights etc have been fitted in a recent upgrade under the 17th) and the rest of the house is to the 16th supplementary bonding is still NOT required although there is no reason not to do it if you so wish.

Just for completeness there has been no need to provide supplementary for metal kitchen sinks and sink pipes since the 15th.

Edited for correction.
Last edited by rosebery on Sat Mar 21, 2009 1:04 pm, edited 1 time in total.
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Postby WHYDIY » Sat Mar 21, 2009 9:35 am

I agree that it must be the most important thing to get right in a bathroom. It also seems to be one of the most confusing areas of work for the DIYer.

I recently replaced all the bathroom plumbing for plastic pipes so all taps and so on are supplied by plastic pipe. From what I read this would mean I do not have to supplementary earth bond in the bathroom.

cheers
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Postby kbrownie » Sat Mar 21, 2009 1:57 pm

WHYDIY
If you have palstic pipes through-out the the bath room, supplementary bonding is pointless as it will have no effect on the earth bonding continuity regarding the main earth and supplementary bonding within this area and the installation.
KB
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Postby rosebery » Sat Mar 21, 2009 2:35 pm

"From what I read this would mean I do not have to supplementary earth bond in the bathroom."

You are correct but what you are talking about is NOT an EARTH bond. Its an equipotential bond. Quite different.
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Postby WHYDIY » Fri Mar 27, 2009 5:49 pm

Thanks for the help!
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