Electrical bonding

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Electrical bonding and the Earthing system of the mains supply are two different systems. Bonding refers to the fact that in a building served with electricity it is normal for safety reasons to connect all metal objects such as pipes together to the mains earth to form an equipotential zone. This is done in the UK because many buildings are supplied with a single phase supply cable where the neutral and earth conductors are combined. Close to the electricity meter this conductor is divided into two, the earth terminal and the wire going to the neutral busbar in the consumer unit. In the event of a break in a neutral connection this earth terminal provided by the supply company will be at a potential (relative to the true earth) which is the same as the live wire (phase wire) coming to the home.

Here is the situation which the authorities wish to avoid.

If a person was to touch the metal (earthed casing) of an electrical device during the above fault condition and be in contact with a metal object connected to a true earth then they would get an electric shock.

Because all metal objects (such as water pipes) are connected together, all the metal objects in the building will be at the same potential, hence it will not be possible to get a shock by touching two 'earthed' objects at once.

Bonding takes on an important and particular technical significance when it comes to swimming pools and fountains. For these pools and fountains, any conductor, (for example this means bits of metal etc., not the wire conductor wire to a pump,) over a certain size must be bonded to assure that all conductors are equipotential and do not provide a hazardous conductive path. Buried in the ground, and sometimes even having a small leak, a pool can be a better ground than the electric panel ground. With all the conducting elements bonded, it is less likely that electric current will find a path through a swimmer.