Some implications for bonding
In a well-designed system, all metallic/conductive services, such as water and gas pipes, power, telecommunications and data cables would enter the building in the same locality and be connected to a single earth bonding bar. Which, in turn, would be connected to the earth termination network, as well as the conductive parts of the building.
However, life isn’t that simple and services enter and exit at different places. It is recommended that services are bonded at their point of entry to/exit from the building.
Equipotential bonding can be achieved through:
Utilising earth bonds, earth clamps and bonding conductors which link the various metallic services and parts of the structure to Earth Bars.
The standard outlines the minimum cross-sectional area of conductors to be used in these applications.
Earth Bars act as collection points for the various lightning protection and earth continuity bonds and their subsequent connection to the earth termination. Each Earth Bar would be connected to earth.
Surge Protection Devices (SPDs)
It is recommended that the live cores of power, telecommunication and data cables are equipotentially bonded through using appropriately rated Surge Protective Devices.
A simplified illustration of equipotential bonding using SPDs is demonstrated here . . .
Guidance for the selection of equipotential bonding or lightning current SPDs can be found HERE.
Isolating Spark Gaps (ISGs)
Are suitable for use where the direct connection of an external Lightning Protection System and other metallic parts or earthing system is not allowed due to operating reasons. For example, earthing systems for heavy current and telecommunications systems or bridging isolated flanges on pipe connections.
When a difference in potential occurs between these parts, the Isolating Spark Gap (ISG) will provide a temporary conductive connection to earth, thus reducing dangerous potential difference issues (a simple explanation of potential difference).