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Bonding to Equipotential Bonding Bar (BS EN 62305) or to Main Earthing Terminal (BS 7671)

Simion

Hello,

Could the Equipotential Bonding Bar (as it is illustrated in EN 62305-3 fig. Figure E.45) and Main Earthing Terminal (as it is illustrated in BS 7671-2018 fig. 2.1) be the same bar?

Do they need to be arranged as different (separate) and connected bars in installations where we have an external LPS?

In both figures we have the metal installations bonded to these bars, but the names are different.

Also, i don't understand why the minimum dimensions of conductors connecting internal metal installations are different, for example, in the case of copper conductors:

- in EN 62305-3, Table 9 we have 5mm2

-in BS 7671 we have half the cross-sectional area required for the earthing conductor, but not less than 6mm2 (10mm2 for PME conditions).

The minimum dimensions required by BS7671 are always greater, so we should always use them.

This information is very confusing for me.

Thanks in advance for any clarifications. I hope this question is not too naive for this forum.

Parents
  • +1

    In part it is because the two standards are considering current flows of different magnitudes and duration (lightning tends to be tens to hundreds of microseconds and much higher current that are mostly to do with the height of the building, while mains faults last  at least a good fraction of a 50Hz cycle, and can persist for several seconds and under some conditions a lot  longer, but the currents are likely to scale with the supply rating), and partly perhaps, due to being written by two different committees with different specialists. (thinking of the naming)

    Of course in a building with a lightning system you need to aim to satisfy both, so you need to take the harder conditions from each.

    And yes, a lot of  parts will be common, and if they are not, then they will need to interconnect, but only in a way that satisfies both standards.

    Mike.

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  • +1

    In part it is because the two standards are considering current flows of different magnitudes and duration (lightning tends to be tens to hundreds of microseconds and much higher current that are mostly to do with the height of the building, while mains faults last  at least a good fraction of a 50Hz cycle, and can persist for several seconds and under some conditions a lot  longer, but the currents are likely to scale with the supply rating), and partly perhaps, due to being written by two different committees with different specialists. (thinking of the naming)

    Of course in a building with a lightning system you need to aim to satisfy both, so you need to take the harder conditions from each.

    And yes, a lot of  parts will be common, and if they are not, then they will need to interconnect, but only in a way that satisfies both standards.

    Mike.

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