The main reason for installing an internal LPS is to avoid any dangerous sparking within the building. The internal LPS is important to fully complete the installation to fulfil the requirements of BS EN 62305. The earthing system whether using reinforcing bars or additional conductors or a combination of both must be connected to every down conductor and internal steelwork. The additional network should be connected to the reinforcing bars by clamps or welded joints every 20 m throughout the system. Where a foundation is used as an earth-termination the reinforcing bars must be clamped or welded together to ensure electrical continuity.Īlternatively an additional meshed network of conductors can be installed to ensure continuity. The use of the foundation as an earth electrode is allowable only where the reinforcement network is below any insulating or waterproof membrane. Once all the services are connected its unlikely the installer will be able to measure the earthing resistance of the foundation earth in isolation. If the required resistance cannot be achieved by this method the vertical or radial earthing electrodes can be added to the network.įor ease of testing after installation an inspection pit with an earth bar should be installed where the legs of the ring and conductor routing onto the ring from the each test clamps join (figure 31).Īny internal down conductors should be connected to the internal foundation using a test clamp for ease of maintenance. The reinforced concrete floor slab can be used around the structure. It is recommended that the type B earthing network whichever method is chosen should be integrated as a meshed network buried to a minimum depth of 5 rats. The alternative is to use a foundation earth electrode which can be in a mesh form. The type B earthing is recommended as either a ring conductor outside the perimeter of the structure which it’s recommended should be in contact with the soil for at least 80% of its total length. Structures housing sensitive electronics/equipment.The type B Earthing arrangement is most suitable for: The earth rod should be housed in an inspection pit, commonly concrete or plastic for ease of inspection and registering the location during and after installation figure 30.įull range of copper earth tapes available from stock in range of widths and thicknesses. Type A earth electrodes should be installed so that the top of the earth rod is 0.5 m below the surface, this distance is to reduce the effects of step potential at ground level. If using vertical and horizontal electrodes, the individual earthing electrode lengths should follow the 0.511 and 11 principle respectively. ![]() The surface area of the length of earthing conductor that would need to be used to satisfy the requirement for a lattice mat electrode 11. ![]() The surface area of the length of earthing conductor that would need to be used to satisfy the requirement for a vertical electrode 0.511. If copper plates are to be used the surface area of the plate should be at least equal to either. >11 in the case of a lattice mat measuring the total length of the conductor in the earth mat. It is 11 for horizontal electrodes – usually copper tapes.Ġ.511 for vertical copperbonded rods or solid copper rods. ![]() Minimum length l¹ of each earth electrode according to class of LPS Practically it uses both connected to each down conductor, installed outside the structure (below the foundation) to be protected and housed in a plastic or concrete pit for ease of inspection (figure 30). The type A arrangement uses vertical or horizontal earth electrodes. For an isolated LPS the British Standard BS EN 62305 recommends a type B earthing arrangement where the structure is housing extensive electronic systems. The type A earth termination arrangement is suitable for low structures (below 20 metres in height) or an LPS with rods or stretched wires. This is the conventional type of LPS Earthing System where earthing rods are used to form the earth electrode and usually each down conductor, such as copper earthing tapes, are connected to an earth rod. The foundation electrode system installing the conductors in the concrete foundations of the structure. Type B – The ring electrode sited around the periphery of the structure Vertical or horizontal electrodes such as Type A – The conventional LPS Earthing system using There are three types of LPS Earthing systems types A, B and Foundation Earth Electrodes Driven earth rods manufactured from solid copper and bonded with copper are available from stock – contact Thorne & Derrick
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