Central Heating Earth Bonding

As a CORGI registered installer, I have been podering upon the stated need
for cross bonding between the pipes connected to a newly installed gas
central heating boiler.
Assuming a typical UK domestic household, where the services are correctly
connected to earth as close to the entry point of the dwelling. I install a
new central heating boiler. With the make of boiler I install, the central
heating flow / return, hot / cold water and gas pipe are connected to metal
compression fittings that are in turn mechanically fastened to a metal
bracket that forms part of the boiler's casing.
It seems to me that this metal to metal contact between all of the pipes is
better and more robust than using earth bonds and a cable connecting them.
It is possible that the earth cable or bonds could become slack, or due to
the possibility of corrosion, become less effective. The metal bracket of
the boiler is a solid piece of equipment and to me, provides a more than
adequate cross bond between the connected pipes.
Reply to
Harry Willis
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Cross bonding is usually done in close proximity to areas that could have a different potential to earth.
Even though the system you have just fitted is very well bonded to the metal of the boiler, what if someone was to fit some form of plastic coupling in the system.....
That's why bonding is usually done around areas that you are likely to have contact with.
Reply to
It is a long time since I worked with compression fittings but if my memory is correct then the compression rings are nylon or some such so the electrical contact will not be as good as you might imagine.
Reply to
John G
Some types of compression fittings are metal/metal, and you're right that would be a pretty good electrical connection. But the system will be maintained for quite some time, and not always by someone with an *electrical* background. As the others have suggested, not all couplings are 'equal'. Plastic or some non-conductive sealant used in the joints could compromise the electrical conductivity. So, apparently, the UK 'rule makers' have decided it is safest to have a second, bonding wire cable.
Reply to
There is no such requirement in the UK electrical regs unless the boiler is fitted in a room containing a bath or shower. Some trade bodies (such as CORGI in this case) sometimes specify their members should do things which are not required by the regs. I don't know if this is the case here as you have not said where you saw this need 'stated'.
Reply to
Andrew Gabriel

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