Bonding can be a seriously complicated issue.Generally,in domestic work bonding is not required other than in special locations such as bathrooms. However, exceptionally important is the main bonding arrangement. When a fault occurs in an installation the exposed conductive parts will have a potential with reference to true earth. Essentially this is the volt drop along the installation earth and the supply authority earth for the duration of the fault. This same voltage would be apparent between the faulty equipment case and and any un-bonded metalwork in connection with earth. Thus when main bonds are carried out this fault voltage is minimised and equates approximately to the voltage drop along the installation earth (cpc).
Bonding all metalwork in sight can actually introduce a hazard where none formerly existed so great care should be exercised.
