Earth Banjo Securing Practices

These are not ordinary self-tapping screws, but self-drilling screws. These leave unnecessary cut hazards for initial construction work associated with this part of the installation after the screws are installed, similarly no consideration of safety for future maintenance work - demonstrating lack of risk assessment (or supervision/management under H&S legislation, including CDM Regs).

This arrangement is almost certainly unsuitable to bean effective electrical connection during temperature changes etc - Regulation Group 526.

In the past it was commonly accepted that a single self-tapping screw usually isn't effecting for earthing and bonding connections. Whilst some product standards might permit self-tapping screws to secure protective conductors in certain circumstances, I certainly wouldn't recommend it as an installation practice. I understand it's specifically prohibited to use self-tapping screws for making ground connections in NEC (wiring rules in USA).

Now to debate of whether the banjo should be on the inside or the outside of the enclosure 

Hi Graham, I recall that many years ago, our NICEIC field engineer at the time explained that the banjo should be placed on the inside of the enclosure if it’s plastic, as it is considered an exposed conductive part. What are your thoughts on this?

Additionally, regarding the self-drilling screws used in the installation, what action would you take? Would you recommend having them replaced to address the concerns about cut hazards and the suitability of the metal thickness for maintaining an effective electrical connection?

Graham,

I agree with your comments, and forgot about NEC criteria. Looking at picture closely again there looks as if at least tow if not all of the cables have a seperate integral cable conductor sleeved in green/yellow sleeing so a seperate CPC. 

Personally dont like earth tags on the inside as depending on how things are done can equally be as messy and have earthed parts now closer to live parts. Use of serrated washers and a lock nut with earthing grub screw could actually be better and save the earth tag full stop.

I really do worry where this has been carried out once how many times has it already been done or will be done, or others "Learn" from it and then think its appropriate practice.

GTB

Graham,

I agree with your comments, and forgot about NEC criteria. Looking at picture closely again there looks as if at least tow if not all of the cables have a seperate integral cable conductor sleeved in green/yellow sleeing so a seperate CPC. 

Personally dont like earth tags on the inside as depending on how things are done can equally be as messy and have earthed parts now closer to live parts. Use of serrated washers and a lock nut with earthing grub screw could actually be better and save the earth tag full stop.

I really do worry where this has been carried out once how many times has it already been done or will be done, or others "Learn" from it and then think its appropriate practice.

GTB

GTB said:

I agree with your comments, and forgot about NEC criteria. Looking at picture closely again there looks as if at least tow if not all of the cables have a seperate integral cable conductor sleeved in green/yellow sleeing so a seperate CPC. 

Yes, in addition, I pointed out in my reply to AMK why it's acceptable for products to product standards (in some cases), but not installations.

GTB said:

Personally dont like earth tags on the inside as depending on how things are done can equally be as messy and have earthed parts now closer to live parts.

Agreed - it all depends on the arrangement.

GTB said:

Use of serrated washers and a lock nut with earthing grub screw could actually be better and save the earth tag full stop.

Agreed, where the case of the equipment meets the thermal requirements for protective conductors. Otherwise, I really like 'earthing nut' type products, but again there are sometimes cases where there are limits to space inside modern equipment. Some more thought in the design given to practical installation limitations wouldn't go amiss occasionally.