Earthing In Bathrooms & Dual Rcd Boards

I have been to different areas of sites to earthing in bathrooms and each area is different.With a dual rcd you dont have to cross bond in the bathroom,with a split load board you do this is between hot and cold under bath panel, under the sink hot and cold plus radiator.I have also seen 4mm earth off the light in the bathroom linked to the shower,under the bath panel hot and cold with a dual rcd board.I have stated all this because im getting a little confused of how to earth depending on the board used etc could you help?

Earthing of any class I fittings in a bathroom will be the same irrespective of any types of CU fitted. The exposed metal parts will have an earth termination point that will be connected to the CPC of the supply circuit to that accessory. Supplementary equipotential bonding will be done in accordance to the regulations applicable at the time that the bathroom wiring was installed. The specific requirements will be found in the current edition of BS7671. There is no specific conditional requirement for different bonding methods defined by the type of CU installed.

Doc H.

I think what the OP is finding is different requirements for different versions of the regs.

Under really old versions there was no cross bonding at all. you will still find plenty of houses like that.

16th edition required cross bonding between for instance the light, shower, radiators etc regardless of what type of CU and that was usually done with 4mm

17th edition allows you to omit the cross bonding if certain conditions are met like all circuits on an RCD

If you are doing new work it should be to 17th edition.

dual rcd boards omit cross bonding but what about split load boards one side of the breakers normal other side of the breakers rcd protected does this omit or does it require cross bonding?

sorry r.b. I don't understand your post.

r.b said:

dual rcd boards omit cross bonding but what about split load boards one side of the breakers normal other side of the breakers rcd protected does this omit or does it require cross bonding?

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I have merged this with your previous question on a near identical subject, duplicating thread topics only clutters the forum. Please continue your existing threads if they are recent topics. I have also moved it to the more appropriate sub forum.

Doc H.

r.b said:

dual rcd boards omit cross bonding but what about split load boards one side of the breakers normal other side of the breakers rcd protected does this omit or does it require cross bonding?

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The cross bonding can only be omitted if ALL circuits in the bathroom are on an RCD

So the conventional (16th eddition) board would almost certainly not have the lighting on an RCD.

ProDave said:

The cross bonding can only be omitted if ALL circuits in the bathroom are on an RCD

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Providing the test results are within the limits Dave

ProDave said:

The cross bonding can only be omitted if ALL circuits in the bathroom are on an RCD

So the conventional (16th eddition) board would almost certainly not have the lighting on an RCD.

Click to expand...

Exactly as Dave says, its nothing to do with boards, which edition of the regs its previously wired to.  Under the 17th if ALL the circuits in the bathroom are RCD protected then supplimentary bonding can be omitted!  Allthough I would double check that all extraneous pipe work is under 1667ohms to the MET as I beleive that is also part of the conditions of omitting the bonding

When it says all circuits need to be RCD protected that includes the pipework.

The pipework is a conductive part of the Central Heating circuit or a water heater element circuit if there is a hot water cylinder.

If a fault appears on the pipework this is where it may come from. This is why these circuits also need to RCD protected.

So with your split DB where other circuits are not RCD protected, this is the reason the bonding requirements are different.