Earth bonding size


Postby russellfl » Mon Jun 02, 2008 11:25 am

Hi,

recently moved into a bungalow and found that theres no earth bonding to the metal sink and hot/cold pipes in the kitchen. I want to run in a new earth cable so it's safe. Does anyone know what size of earth cable I need? someone said they thought it might be 10mm, is this correct?

Cheers
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Postby kbrownie » Mon Jun 02, 2008 4:37 pm

Hi russellfl,
If it's the main protective earth bonding, you are looking 16mm, The water supply pipes should be done at the earliest point of entry in to the property within about half a metre and the gas pipes should be agian at the earliest point on the your side (the consumers side) of meter. Kitchen sink does not need to be earth bonded.
But this should be done by a quailified electrician as it will be covered by part p of building regs (see projects under part p: http://www.diydoctor.org.uk/projects/partp.htm) and there will be certain calculations to be made.
Regards
KB
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Postby kbrownie » Mon Jun 02, 2008 4:44 pm

Hi again russellfl,
Just to add if you are talking about supplementary earth bonding that is something different again. i'll be corrected if i'm wrong but this is not required in kitchens. I'd check at your CU and at the Mains Earth Terminals to see if you do have earth bonding it's different supplementary bonding.
Regards
KB
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Postby ericmark » Mon Jun 02, 2008 10:31 pm

Min size of any earth cable no protected is 4mm² 543.1.1 (v) + 544.2.1
The PEN cable has a min size of 10 mm² 543.4.3 (Not really anything to do with you)
Main protective bonding conductor min 6 mm² 544.1.1
Where PME conditions apply it is dependent on supply cable min 10 mm² Table 54.8
Remember I have quoted min sizes from BS 7671:2008 the old BS 7671:2001 may differ. There are other regulations like 543.7.1.3 high conductor currents min 10 mm² since you do not give all details you will have to verify which is why I give regulation number. As kbrownie has said it may not be required I can’t find anything in BS 7671:2008 about sinks and toilets only baths, showers, saunas, swimming pools, and fountains. But you must follow manufactures instructions so if for example the grinder says you need an extra earth then you do need it.

All best Eric
ericmark

Postby russellfl » Mon Jun 09, 2008 4:38 pm

Thanks guys for your responses.

I thought all metal surfaces, appliances and pipes needed to be bonded together and taken back to the CU earth terminal. Is that not right then? and should I not worry about it?

Cheers!
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Postby ericmark » Tue Jun 10, 2008 10:13 am

Not all but the major items need bonding. There have been in the past earthing of window frames the lot but now it is restricted to items which could transmit faults from one area to another. Gas pipes, Water pipes, Central heating pipes and ducts. But where plastic pipes are used radiators etc are not earthed. What is earthed also depends on what earth leakage devices are fitted and can become quite complex. It is easy to make a mistake for example you may not need to earth your kitchen sink but if there was a grinder built in you would. Also if you realized there was high risk for example kettle may fall in sink then there is nothing stopping one from earthing anyway mine is earthed. I tend to use common sense rather than try to follow all the rules.
The rules have changed over the years and when they have changed multiply changes have happened and you can't do one without doing the other but don't have to change so if for example your bathroom is wired to 16th Edition rules it is OK but if you upgrade part to 17th Edition rules then it all must be upgraded not just part. As a result it would be very easy to give wrong information. Which is why I am being a little careful not to say anything which could mislead you.
ericmark

Postby neil deacon » Sun Jun 15, 2008 7:57 pm

[quote="kbrownie"]Hi russellfl,
If it's the main protective earth bonding, you are looking 16mm, The water supply pipes should be done at the earliest point of entry in to the property within about half a metre and the gas pipes should be agian at the earliest point on the your side (the consumers side) of meter. Kitchen sink does not need to be earth bonded.
But this should be done by a quailified electrician as it will be covered by part p of building regs (see projects under part p: http://www.diydoctor.org.uk/projects/partp.htm) and there will be certain calculations to be made.
Regards
KB[/quote] :lol: thats 10mm earth cable not 16 mm thats the main bonding size .......
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Postby neil deacon » Sun Jun 15, 2008 8:06 pm

that is wrong ..... you only need 10 mm cable from fuseboard to water and gas ..... 16 mm is only used from incoming supply to fuseboard
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Postby TOPSPARK » Sun Jul 27, 2008 6:55 pm

Hi russellf
Topspark here Answer to your question about earth bonding sizes
Your main earthing conductor from your mains board to the main earth wether it be pme tns oe tt earthing These are types of supply. this must be equal to the incoming supply tails eg 16mm tails then 16mm earth.If 25mm Tails then min 16mm earth. Now main bonding to gas and water services must be connected within 600mm of stop tap and supply from gas meter. Supplementary bonding of pipes at combiler or in tank cupboard is a min of 4mm earth cable.this includes under the sink or the wash hand basin and radiator in the bath room. I hope this clears up a few of the worries you have.but if all pipework in the bathroom is done in copper thena 4mm earth must be taken from the lightingpullcord or light fiting and continously across the hot an cold of the bath,wash basin and radiator.
all the best
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