John Rumm wrote:
On 22/04/2017 10:50, Ivor Nastychestikov wrote:
Firstly, no such thing as "earth bonding" - the phrase makes no sense.
You can have earthing, and you can have equipotential bonding. Two
different systems that work in different ways and are designed to
provide shock protection by different mechanisms. (reduced shock
duration for earthing, and reduced shock magnitude for EQ bonding).
Bathroom has hot and cold water pipes, electric towel rail and an
electric shower, what bonding is required?
That depends...
If the main equipotential bonding[1] is in place, and all the circuits
that feed the bathroom are RCD protected (with 30mA trip devices), then
since the 17th edition of the wiring regs, none is actually required.
If the above requirements are not met (say the lighting circuit is not
RCD protected), then you will need to equipotential bond the earth
conductors of all the circuits that feed anything in the bathroom, along
with any other metalwork that is capable of introducing a potential into
the room (and that includes an earth potential).
So typically that would include hot and cold water pipework, and
possibly central heating pipework.
You don't need to bond pipes that are plastic, or are just isolated bits
of metal "show" pipework feed from plastic pipes. Nor do you need to
bond radiators, baths or any other lump of metal that by itself is not
able to introduce a potential into the room.
You may need to bond waste pipes if they are metal and ultimately
connected to earth. (if unsure measure the resistance between them a a
known good earthing point)
For more information see:
[1] http://wiki.diyfaq.org.uk/index.php/...ng_and_Bonding
I have a strange situation in my bathroom, all the copper water pipes
are bonded to earth externally but I sometimes get a tingle to taps when
standing in the shower, (About 5 volts measured from metal round drain
to taps)
I can only assume that when the house was built(on concrete slab) the
reo steel in the concrete was not bonded to earth which is a requirement
today