Do Cable Trays in Sydney Car Parks Require Individual Earthing?

In summary: The following methods are permitted for connection of grounding and bonding equipment:(1) Direct connection to grounding electrodes.(2) Connection to an equipment grounding terminal.(3) Connection to a bonding electrode.(4) Connection to an equipment bonding terminal.(5) Connection to a ground bus.(6) Connection to a ground system.The choice of method is based on the location of the equipment, the type of equipment, the grounding system, and the environmental conditions.It is recommended that equipment grounding and bonding be tested and monitored using an appropriate test procedure.In summary, the electrical circuits are run on perforated cable trays at high level
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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.

Advice please ..

Thaks
 
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  • #2
There are hundreds of "standard" earthing practices around the world. There is no universal answer. You must consult your local electrical codes. It is not only wise, but probably legally mandated that you do so.
 
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In my opinion, Australia use IEC standards for electrical installations.
IEC 61537 Annex C Protective Earth [PE] function.
But -as far as I know- no Annex C is detailed still. It is "under consideration".

In U.S.A. NEMA VE 2-2013
3.8.1 Cable Tray Used as an Equipment Ground Conductor (EGC)
3.9 BONDING TO THE METAL FRAME OF THE BUILDING AND EARTH

Metallic cable trays are permitted to be bonded to the metal frame of the building and Earth for signal grounding (“noise” prevention). This may be desirable if the cable tray system is not inherently bonded (connected) to the metal frame of the building and Earth through metallic support systems.

NEMA VE-2 2001 Edition recommended all 60 feet .From 2006 there is not any recommendation of the bonding interval.

The grounding bonding methods are stated in NEC[2017] Art.250.8
250.8 Connection of Grounding and Bonding Equipment. (A) Permitted Methods.
 
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What is "Earthing metal components"?

"Earthing metal components" refers to the process of connecting metal objects or components to the ground in order to eliminate the risk of electric shock and to protect against potential electrical hazards.

Why is earthing metal components important?

Earthing metal components is important because it helps to prevent the buildup of static electricity, which can cause sparks and potentially ignite fires. It also ensures that any electrical faults are directed safely to the ground, rather than posing a danger to individuals or equipment.

How is earthing metal components achieved?

Earthing metal components is achieved by using a conductive wire or rod to connect the metal object to a grounding system, such as a grounding rod or a metal water pipe. This allows any excess electrical energy to be safely dissipated into the ground.

What are the benefits of earthing metal components?

Earthing metal components provides several benefits, including reducing the risk of electric shock, preventing damage to electrical equipment, and protecting against lightning strikes. It also helps to improve the overall stability and reliability of the electrical system.

Are there any safety precautions to consider when earthing metal components?

Yes, there are several safety precautions to consider when earthing metal components. It is important to ensure that the grounding system is properly installed and regularly maintained. All connections should be secure and any damaged components should be replaced immediately. It is also important to follow all safety guidelines and regulations when working with electricity and grounding systems.

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