Supplementary Bonding


Postby PhilB » Tue Sep 25, 2007 3:47 pm

Hi there Everyone,
I would like to know the correct procedure for supplementary bonding, in my bathroom,
i'am aware that i can not carry out this work myself but would just like to know more about it before calling out electrician

Q1- what size earth conductor will be used 4mm or is it 6mm
Q2- once all pipe's & metal parts are bonded together, am i correct in thinking that the earth conductor does not go back to consumer unit but instead is taken to a nearby socket and connected to earth there.
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Postby sparx » Tue Sep 25, 2007 9:31 pm

Hi, in turn,
2.5mm2 if 'mechanically protected' or 4.0mm2 if not.
no need to connect to anything else unless there is say an electric towel rail or other fixed electrical equipment in room. when you should connect to the outlet plate / Fused spur ect.
Also it is not required to cross bond in the room itself if you can connect to hot/cold/heating pipes in local area IE airing cupboard/loft space.
Earthing MUST NOT go back to consumer unit as a fault on another circuit "could be introduced into a previously safe area", regards
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Postby Shay Farrell » Fri Oct 05, 2007 3:36 pm

Hi - can you explain the comment "Earthing MUST NOT go back to consumer unit as a fault on another circuit "could be introduced into a previously safe area"

If this is the case then any fault on any appliance / installation could potentially 'liven' any earthed appliance / installation ? Where else should the earth go back to. -

Shay
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Postby sparx » Sat Oct 06, 2007 10:04 pm

for Shay farrrell:
we are talking about supplimentary bonding, not circuit protective conductors which do go back to board but which if a fault developed could raise the potential at the end of a long circuit sufficiently to be hazardous before operating the protective device. ie a cable melting against a hot central heating pipe could connect live to the pipe & thanks to increasing use of 'push-fit' plastic connections the local pipe could rise enough to be a shock hazard but if all metal in the area is tied together then all would rise the same amount so no voltage difference to give a problem,
It requires a potential difference of around 50V to cause a lethal current to flow in a healthy dry human being, somewhat less if skin is wet hence the extra precautions for 'special locations'
regards SPARX
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