Earthing in Buildings & 50310 Equipotential Bonding

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EN 50310 Equipotential Bonding & Earthing in Buildings with IT Equipment:


What is supplementary bonding?


Supplementary bonding  involves establishing an extra connection between exposed metal parts of different equipment and devices to ensure electrical safety. This technique creates a low-impedance path for electrical currents, preventing hazardous potential differences and reducing the risk of electric shock to users and potential damage to sensitive IT equipment. Its primary goal is to equalize electrical potential across all connected metal surfaces, enhancing safety measures in IT installations and complying with electrical codes and regulations.

Equipotential Bonding Networks (EBNs) are defined to protect IT equipment, cabling and telephone cable wiring from electrical hazards, such as:
– Electric shock
– Risk of fire
– Damage to equipment
– Under normal operating or fault conditions within the equipment or power distribution system
– Due to the impact of induced voltage or current (e.g. by lightning)


EBNs are also intended to alleviate EM disturbance and EN 50174-2 is referenced for EM cable segregation.
EN 50310 needs to be aligned with EN 50174 Ed.2 with regards to containment systems, power separation and the necessity for earthing and bonding.

The installer should refer to EN 50310, 50174 & BS7671 IEE 17th edition electrical regulations.
For regions outside the UK local electrical codes along with ISO/IEC 14763 and ANSI/TIA/EIA-607A may also apply.

The size of earthing leads is dictated by the CSA of the power cables, e.g. the supply neutral conductor.
IEE Clause 544.2.3 states that the minimum size of supplementary bonding conductor shall have a CSA of no less than 2.5 mm2 if sheathed or mechanically protected or 4mm2 if not sheathed or mechanically protected.
IEE Clause 544.1.1 states that the minimum size of the main earthing conductor shall be no less than 6 mm2 and need not exceed 25 mm2 if the earthing conductor is copper.

IEE Table 54.8 provides guidelines for sizing the bonding conductors.

3 5mm2 or less – 10 mm2
35 mm2 to 50 mm2 – 16 mm2
50 mm2 to 95 mm2 – 25 mm2

This would cover cabinet or rack to telecoms bus-bar earthing conductors.

For the main equipotential bonding network sizing the same approach would need to be taken.
95 mm2 to 150 mm2 – 35 mm2
Over 150 mm2 – 50 mm2


Brand-Rex requirements

The Brand-Rex requirements are for 2.5mm earth leads from each patch panel, whether UTP or shielded, to a grounding point in the cabinet or rack and then a main earthing lead to the dedicated telecoms earthing bus-bar
All connections must be made using a crimped connection, to prevent the earth wire becoming loose, causing stray currents. These will negate the effectiveness of the earth wire.
Daisy chaining is not permitted.


Read ACCL’s Structured Cabling Guide to learn more about data cabling


Get in touch

If you are interested in discussing earthing solutions for your Company, the experts are just a phone call away. Following an initial chat, a site visit will be scheduled at the earliest opportunity

For more information on ACCL’s cabling services call:

0333 900 0101



Related topics:

Power monitoring system Standards

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