"Lobster" wrote in message
om...
Hi all
I need to install supplementary bonding in both kitchen and bathroom,
as there isn't any at all at the moment! Two queries arise please...
1. I have the luxury of having no ceiling at the moment in the room
below the bathroom, which means all the piping is readily accessible.
I could very easily install earth clamps connecting all the pipework,
very neatly and invisibly. However, is that allowed? Do you need to
be able to see the clamps etc in an installation? Where exactly do I
need to attach the clamps; as close as possible to taps/radiator etc?
2. I need to take an earth cable right through the house to the
kitchen sink. Do I need to have a separate, continuous cable going
from the earthing point at the fusebox all the way to the kitchen
(which means going through the bathroom en route) or is it sufficient
to piggy-back the kitchen earth cable on to a clamp on a bathroom tap,
say?
Thanks
David
You should earth bond from the incoming electrical mains supply cable,
preferably into the Henley block or head block that is used to provide the
main earth to the consumer unit, and then on to the mains supply pipes of
both the water and the gas systems. This bonding should be provided using
10mm csa' (cross sectional area) Green/Yellow sheathed stranded conductors.
This bonding gives you a main earth bond to one end of the pipework on both
systems. Taking the shortest route is better because it saves on cable and
is safest because it provides the shortest path back to the main earth point
on the electrical supply.
The rest of the bonding to the pipework around the house is easiest done
where the pipes come together at the closest points where they come to the
taps or to one side of any metal radiators you have. You should also bond
together all the pipework around the hot and cold water storage tanks.
Making the connections at the closest points also helps to save cable and
gives fault currents the shortest path back to the main earth point at the
electrical supply. All the pipes which connect to the central heating
boiler, including the gas connection, should also be bonded together at the
closest point where they meet at the boiler. The boiler itself should
provide an earthing lug if the casing and chassis have exposed metal parts,
which most do.
All the supplementary bonding should be done using 4mm csa' Green/Yellow
sheathed cable to provide a low resistance path, and should be connected to
the pipework with proper earth straps, not just wrapped around the pipes,
and remembering to clean the pipes with wire wool or fine sand paper at the
point where the strap is to be positioned before putting the clamp around it
and tightening until the strap can not be turned or removed from its
position by accidental mechanical damage. The pipe cleaning helps the
earthing point make a good contact with the metal and it isn't trying to
work through any tarnish or gunge that might have built up on the pipes and
will increase any resistance in the pipework.
If any plastic pipework or joint fittings are used, then the earth bonding
should by-pass it and be connected to the metalwork where any valves or tap
connections have been made to all appliances, this includes all points on
the water and gas distribution systems.
Once you have a main earth point to one end of the main gas and water
supplies from the mains electrical supply, the supplementary bonding between
any gaps or breaks in the rest of pipework act in the same way as looping
everything together so that any fault current can take the shortest, lowest
impedance path back to main earth and cause the fitted safety devices to act
in a correct manner by quickly breaking the current flow to all parts of the
system that are affected by the fault.
Hope this helps answer some of your questions David. :-))
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