Roofing Bolts as Earthing studs

[Rockingit]

Cable tray isn't required to have any earth continuity, or even be bonded.
Whereas the connection to the banjo is a connection of the CPC.

Sorry mate, have to disagree!!

From the BEAMA (BS EN 61537) guide:

"2.10.2 Electrical continuity
Cable ladder and cable tray systems that are electrically conductive should have
adequate electrical continuity to ensure equipotential bonding and connections to earth.
Installations shall comply with the requirements of BS 7671 (The Wiring Regulations)."

 

[High Tower]

I bond every tray installation that I do!

 

[Rockingit]

I bond every tray installation that I do!

Likewise. Tray/Ladder/Basket..... I think the only thing I'd say doesn't need it is cable hooks for temporary looms (found mostly in entertainment and TV world for getting looms inside>out to OB trucks and the like).

 

[telectrix]

No. You can't run unsheathed singles on cable tray.

the reason for that is because tray is not an enclosure whereas trunking is. the tray is still an exposed conductive part of the installation.

 

[Guest77]

I agree with all of Rockins posts in this thread, just to add my views.

 

[Lucien Nunes]

To make a reliable connection you need the contact surfaces to be clean, flat, mechanically secure and gas-tight, which means the fasteners ought to be well made, with flat surfaces and effective threads that provide a definite minimum clamping force for a given tightening torque. Roofing bolts are not made to the same spec as hex set screws and I don't trust them to achieve this. The compromise design of the head makes it difficult to torque up accurately and the large diameter makes it easier for movement of the lug to rotate it and loosen the connection.

N/P brass hex for me every time for banjos and cable lugs, BZP steel bolts on tray & trunking where all surfaces are galv anyway.

 

[davesparks]

Sorry mate, have to disagree!!

From the BEAMA (BS EN 61537) guide:

"2.10.2 Electrical continuity
Cable ladder and cable tray systems that are electrically conductive should have
adequate electrical continuity to ensure equipotential bonding and connections to earth.
Installations shall comply with the requirements of BS 7671 (The Wiring Regulations)."

Interesting, I used to insist on all tray and basket being bonded until i was advised otherwise on a forum.

I'll offer up guidance note 8 item 10.11 on page 157 as evidence for my post above.

 

[Risteard]

the reason for that is because tray is not an enclosure whereas trunking is. the tray is still an exposed conductive part of the installation.

I know the reason is because it does not contain the cables - hence is a cable support rather than containment. However, as it cannot have unsheathed cables it is not an exposed conductive part. Usually jobs require cable tray to be earthed so generally it is done, however it wouldn't be correct to state that there is a requirement to do so.

And indeed there could be arguments as to why it shouldn't be.

 

[telectrix]

what about lidded tray?

 

[sparks1234]

So
We all install bolts and banjo's
but
do we all install a cable down to the earth block inside the dis board?

 

[davesparks]

It's a bit of a push to say we all install bolts and banjos, I for one haven't installed banjos on SWA for a good year now at least.

 

[sparks1234]

The reason I ask this is because I was picked up on it a few years ago by another sparks, the board I had installed was an MEM and after phoning them they confirmed that the complete enclosure was tested as an adequate part of the earth and no connection to the earth bar would be required and would not improve the situation

 

[davesparks]

Ok, if you install a banjo with a bolt then you put an earth lead to the earth terminal.
If you are going to use the metal enclosure as the earth then you don't need a banjo in the first place, you just clean it back to shiny metal where the gland will sit.

 

[sparks1234]

Yep, I totally agree with that, the only thing I can think that might improve the situation is if you put the banjo on then a lock nut before putting it through the enclosure, otherwise on a metal dis board it does not improve the reliability of the earth

 

[High Tower]

So
We all install bolts and banjo's
but
do we all install a cable down to the earth block inside the dis board?

If it's glanded Into a painted board then yes, but if I have a few SWA's to gland up, I normally install a length of 4" trunking and bond that back to the earth terminal