Earthing of Galv cable tray

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I have to rewire my 36ft attached garage, all the cables curently used run along the timber wall plate supporting the roof.
It would make my life easier to run 6" galv cable tray along the wall under the plate spaced off the wall on unistrut or timber blocks. This would allow me to pre wire most of the new before removing the old cabling.

I have 2 x 2.5mm ring mains, 2 lighting circuits, 1 x 6mm t&e and a 6mm swa which should fit easy on a 6" tray.

So to earthing of the tray? Should I just rely on the section coupling bolts and run say 4mm as a bond from tray end to the CU earthing block, or bond with straps of 4mm cable at each joint? Are the copper plate style straps still used to couple lengths of tray?
 
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If you are using roofing bolts to connect tray together I see no benefit in adding extra links.

If however you are using the spring clips and plastic retainers then bonding between lengths has some advantages.
Only one job of the many I have worked on used the spring clips. They should allow for expansion in the sun and it was only when I had used them that I realised why lengths are ever bonded together.

However one will need to connect end of tray to earth. Not so bad with SWA but using non screened cable you may get some inductance and capacitance between tray and cables it carries and better if any stray voltages generated are lead to earth.
 
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