Supplementary Bonding in Bathrooms Ask questions and find answers to many subjects relating to electrics and electrical work

[peterconnolly]

Hi,

I read on your 'projects' area that supplementary bonding in bathrooms should be done using 4mm cunductors and I am looking for this to be confirmed as I was under the impression that is should be 10mm.

I got the 10mm from the On Site Guide page 37 table 3.3.3 where the protective conductor is 16mm. I'm presuming that this is referring to the main protective conductor at the CU. However I must admit that a 4mm or even 6mm supplementary earth bonding would seem to be more appropriate.

Thanks in advance ... Peter

[sparx]

Hi Peter, you & 1000's of others are a little confused by the long winded terminology used by the IET in the regs. so here goes,
Main incoming protective conductor on all systems except TT (earth rod) must be 16mm2 from supply cable/cut out to your consumer unit earth bar (either inside con.unit or seperate block outside it on older systems.
MAIN Bonding conductors from the earth bar go to incoming services; ie Gas, Water, Oil, Stuctural steel (if exposed to the touch), Lightning conductors etc & must be 10mm2.
Supplementary, equipotential bonding (cross-bonding) as sometimes required in bathrooms with 'current using equipment' can be 2.5mm2 if 'mechanically protected' or 4.0mm2 if exposed to damage.
hope this helps, regards SPARX

[peterconnolly]

Thanks Sparx ... as a newly defined 'competent person' under Part P of the building regs I don't always feel that competent.

Perhaps you can assisit on a related topic ... I've seen conflicting reports on internet forums (fora?) regarding supplementary bonding along with the old bonding of pipework back to the MET at the CU.

As I understand it the water pipes at baths etc had to be bonded back to the CU. This has now been superceded with supplementary bonding. If an exisitng bathroom is being modified and therefore supplementary bonding is added, what do the regulations state regarding the old bonding conductors? Is there a requirement to remove them? What happens if they can't be located ... under tiled floors or behind tiled walls?

Any guidance or thoughts would be appreciated.

Regards ... Peter

[sparx]

Hi peter , welcome to the much maligned Part P brotherhood!
I believe you should cut it off at bathroom,(as long as main bonbs ok of course), regs now say as you quote ie cross bond, but not back to mains as a prob. elsewhere on system could introduce a voltage in bathroom, not exactly what we want!!
regards SPARX