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#### Futsal1st

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I am looking at a building with a car park in Sydney. Electrical circuits are run on perforated cable trays at high level.

I understand that the trays require earthing, however, I'm trying to determine the extent.

The trays are made from galvanized sheet and come in 3 meter lengths and are butted to each other. Two short straps (around 100mm long), one on each side, are used to join the lengths together. 10mm bolts and nuts are used for the connection.

Should the trays be individually earthed or only one at each run end or some thing in between? I have been told by one contractor that one earth per tray is adequate. I've been told by an electrical engineer that each 3m length of tray should be individually earthed.

Thanks

#### mbednarik

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without a code book in front of me i would think just one on the end of each run being that they are all bonded together. Do you have a EGC in the tray or are you using the tray itself?

#### nolabama

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Futsal1st said:
I am looking at a building with a car park in Sydney. Electrical circuits are run on perforated cable trays at high level.

I understand that the trays require earthing, however, I'm trying to determine the extent.

The trays are made from galvanized sheet and come in 3 meter lengths and are butted to each other. Two short straps (around 100mm long), one on each side, are used to join the lengths together. 10mm bolts and nuts are used for the connection.

Should the trays be individually earthed or only one at each run end or some thing in between? I have been told by one contractor that one earth per tray is adequate. I've been told by an electrical engineer that each 3m length of tray should be individually earthed.

Thanks
IMHO your engineer is an idiot. By definition the tray is bonded thru how it is constructed. As far as Aussie code, I cannot comment
They tray being earthed at on end or the other is sufficient for cable tray. If however your engineer is paying for the job.......

#### al_smelter

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I can't answer your question directly, but at the chemical facilities in our valley, tray splices are specified to have one bolt per inch of height (i.e. 4" tray= four bolts per side on each piece= 8 bolts per splice per side). However, most of the plants also require a bonding jumper or strap across each splice. Bonding jumpers are also required when spilling into another tray.

These requirements apply only to electrical trays, not tubing bundle trays.

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