New rules for equipotential bonding
The 2007 Wiring Rules which came into force on 1 June 2008 make equipotential bonding a requirement for any conductive reinforcing within a concrete floor or wall forming part of a shower or bathroom.
Equipotential bonding is the electrical interconnection of conductive parts that are, or may be, earthed.
Equipotential bonding is put in place to ensure that the conductive parts remain at the same electrical potential (voltage) under all conditions, particularly under fault conditions, so that electrical shock is prevented when people are simultaneously in contact with different conductive parts or materials.
Because equipotential bonding prevents voltage difference between conductive parts, current flow from part-to-part and any attendant electric shock are also prevented.
The 2007 Wiring Rules (clause 5.6) describe requirements for minimising the risks associated with voltage differences between exposed conductive parts of electrical equipment and any conductive parts that may independently be in contact with the earth.
The Wiring Rules highlight water and other conductive piping and taps, conductive cable sheaths and wiring enclosures, conductive reinforcing in showers and bathrooms, exposed conductive parts of swimming pools and spas, and telephone and telecommunication earthing systems.
Equipotential bonding conductors are required to connect the conductive parts of a shower, bathroom, swimming or spa pool and should have a cross-sectional area of not less than 4mm².
Additional equipotential bonding requirements apply for hospitals, medical and dental areas, explosive atmospheres, telecommunications installations, film, video and TV sites, photovoltaic arrays and general access floors, as well as generating systems and separated circuits.
This new provision was inserted in the Standard to recognise the need to remove any potential differences that may occur between conductive piping connected to or in contact with an electrical installation earthing system and a concrete floor or wall.