- Thread starter edexlab
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- 18th 18th edition bonding edition
The requirement to earth or bond tray is the same as it’s always been
Yes I thought it might be ...
When he mentioned it I asked him what had changed in regard to this , he just said it was a new requirement and in future we'd probably have to do it.
To be fair he's never used BS7671 so I did think that maybe he's mistaken.
In the job I do, we run tray fixed to steel box section frames (powdercoated) and generally it's the customers responsibility to ensure bonding is suitable to that particular countries regs
ie in China and India they do nothing, but other countries have varying amounts of bonding to frame and tray
One company insists we link every single join in tray and bond repeated intervals to all steelwork so in view of this it's always agreed in the contracts that all power supplies and bonding are carried out by a local contractor
When he mentioned it I asked him what had changed in regard to this , he just said it was a new requirement and in future we'd probably have to do it.
To be fair he's never used BS7671 so I did think that maybe he's mistaken.
In the job I do, we run tray fixed to steel box section frames (powdercoated) and generally it's the customers responsibility to ensure bonding is suitable to that particular countries regs
ie in China and India they do nothing, but other countries have varying amounts of bonding to frame and tray
One company insists we link every single join in tray and bond repeated intervals to all steelwork so in view of this it's always agreed in the contracts that all power supplies and bonding are carried out by a local contractor
D
Deleted member 26818
Is the tray extraneous or an exposed conductive-part?
These make zero sense.
Usually there is no need to either earth or bond traywork. If the cabling is insulated and sheathed, Class 2 equivalent construction, the traywork won't be an exposed conductive part so no earthing required. Traywork doesn't usually introduce an earth potential that isn't already present, so no bonding required.
That being said, inspectors love to snag traywork which isn't earthed or bonded.
That being said, inspectors love to snag traywork which isn't earthed or bonded.
Heard that argument a couple of times!
One firm I worked with had us go round checking all the tray on a big job with a long lead and test to show the Clerk that the tray continuity was ok , potential to earth was no worse than sll the metal work around the place etc and that bonding at couple of points was sufficient
Still ended up having his way and bonding every thing even after a Chartered Engineer agreed that it wasn't needed
One firm I worked with had us go round checking all the tray on a big job with a long lead and test to show the Clerk that the tray continuity was ok , potential to earth was no worse than sll the metal work around the place etc and that bonding at couple of points was sufficient
Still ended up having his way and bonding every thing even after a Chartered Engineer agreed that it wasn't needed
T
Toneyz
It makes me wonder what the world these clerks of works and electrical consultants live in the other day I was doing some testing with a contracts manager and the consultant asked if the classroom sink needed bonding they still have in some of these specs about bonding window frames and suspended ceilings.
Yes true ,it has to be continuous any cut in the tray will hinder that hence you put another link to make it continuous.
D
Deleted member 26818
Can anyone quote the Reg. No. that requires tray to be bonded?
Would probably help if we knew whether the tray is extraneous or an exposed conductive-part.
Would probably help if we knew whether the tray is extraneous or an exposed conductive-part.
Why does it have to be continuous? It's generally just another bit of steelwork, neither extraneous nor exposed conductive part.
I would say it is extraneous.
Well does it introduce a potential to the location it serves?
Is it in good contact to an outside earth at true earth potential?
I doubt it’s going to be extraneous but then I’m not on site.
Is it an exposed conductive part ie does it form part of the electrical installation or is it mearly a support system for the cables ?
Is it in good contact to an outside earth at true earth potential?
I doubt it’s going to be extraneous but then I’m not on site.
Is it an exposed conductive part ie does it form part of the electrical installation or is it mearly a support system for the cables ?
It is a safety precation,it might introduce potential depending on wher and how it is istalled.
I thought by bonding it you are establishing contact with the outside earth
Bonding randomly can create its own hazards
Often when installed the tray supports are fixed to say the metallic structure of the building so are connected to earth that way if the structural frame is bonded by being an extraneous conductive part
T
Toneyz
Cable tray couplers.
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