Gary your comments is very interesting.  Recently, due to 7671 updates there are significant discussions taking place as to bond or not bond and the requirement to earth back to the main earth,   In other words, if a part is determined an extraneous conductive part ( not forming part of the electrical installation).  In various IET articles this is discussed and reference made to domestic service pipes such as water and gas.  However, as per this picture this is an industrial installation it needs further consideration.  First the extraneous conductive part  - needs to be conductive, not part of the electrical installation and very important likely to introduce earth potential.   Eg metal gantry for crane on the site, large submersible pump with metal walkway and hand rails.  If the resistance is low enough back to the source of the gantry, hand rail.  Then a person touching a metal pumping system under fault condition could be exposed to current flow through the body.   If the resistance is very high then there is no risk. Hence no requirement to connect back to the main earth.   The difficulty is at design stage this is not fully scoped which can led to running of earths post the installation.  Which can be costly. 


In relation to exposed conductive part as per previous posts here it is down to the risk and the what if scenarios. A plastic enclosure with the SWA glanded through to the main earth inside is to ensure all is tied to earth under fault condition.  The mode of failure to make the tray live or the uni strut live must be considered and risk assessed.  In this case it could be considered low from the picture.  


Hence, there is a very strong agreement that neither bonding or connection to main earth is necessary.  The major issue is cart and horse.  At design stage making the determination not to bond or earth can leave the project open to additional earthing when it comes to testing or handover.


A major gap in industrial type projects and the subsequent electrical installation certification is that the determination to earth/bond or not earth/bond is not documented sufficiently.  This can have impact at periodic inspection and testing intervals of the electrical installation and weather the person agreed with the level of earthing / bonding.     


Interested if other people working on industrial side as experiencing the same discussion given the recent articles and updates.

Gary your comments is very interesting.  Recently, due to 7671 updates there are significant discussions taking place as to bond or not bond and the requirement to earth back to the main earth,   In other words, if a part is determined an extraneous conductive part ( not forming part of the electrical installation).  In various IET articles this is discussed and reference made to domestic service pipes such as water and gas.  However, as per this picture this is an industrial installation it needs further consideration.  First the extraneous conductive part  - needs to be conductive, not part of the electrical installation and very important likely to introduce earth potential.   Eg metal gantry for crane on the site, large submersible pump with metal walkway and hand rails.  If the resistance is low enough back to the source of the gantry, hand rail.  Then a person touching a metal pumping system under fault condition could be exposed to current flow through the body.   If the resistance is very high then there is no risk. Hence no requirement to connect back to the main earth.   The difficulty is at design stage this is not fully scoped which can led to running of earths post the installation.  Which can be costly. 


In relation to exposed conductive part as per previous posts here it is down to the risk and the what if scenarios. A plastic enclosure with the SWA glanded through to the main earth inside is to ensure all is tied to earth under fault condition.  The mode of failure to make the tray live or the uni strut live must be considered and risk assessed.  In this case it could be considered low from the picture.  


Hence, there is a very strong agreement that neither bonding or connection to main earth is necessary.  The major issue is cart and horse.  At design stage making the determination not to bond or earth can leave the project open to additional earthing when it comes to testing or handover.


A major gap in industrial type projects and the subsequent electrical installation certification is that the determination to earth/bond or not earth/bond is not documented sufficiently.  This can have impact at periodic inspection and testing intervals of the electrical installation and weather the person agreed with the level of earthing / bonding.     


Interested if other people working on industrial side as experiencing the same discussion given the recent articles and updates.