Bonding of conduit in kitchen floor

[Risteard]

I would always consider galvanised trunking and conduit containing low voltage cables to be an exposed conductive part. (Likewise the armour of an SWA.) It's not the same scenario as cable tray which is not intended to be used with non-sheathed cables.

 

[Ian1981]

I would always consider galvanised trunking and conduit to be an exposed conductive part. (Likewise the armour of an SWA.) It's not the same scenario as cable tray which is not intended to be used with non-sheathed cables.

I never said non sheathed cables I said sheathed

 

[Risteard]

I never said non sheathed cables I said sheathed

I know. I pointed out that comparing trunking/conduit with tray is wrong as tray is not intended to be used with non-sheathed cables whereas trunking and conduit are.

 

[Ian1981]

I know. I pointed out that comparing trunking/conduit with tray is wrong as tray is not intended to be used with non-sheathed cables whereas trunking and conduit are.

I think the op is saying twin and earth cables installed in conduit and not singles.
Singles would always need containment and if metallic then always earthed as it only has one layer of insulation (basic protection) only

 

[Risteard]

I think the op is saying twin and earth cables installed in conduit and not singles.
Singles would always need containment and if metallic then always earthed as it only has one layer of insulation (basic protection) only

I am aware of that. I am saying that the fact that trunking and conduit are designed for non-sheathed cables means that they must always be regarded as exposed conductive parts. I am aware that singles aren't being used in the conduit in this instance. (T&E in conduit is generally something to be avoided to be honest, as that isn't what conduit is designed for. I accept that sometimes it is handy to improve the look of drops or provide extra mechanical protection or whatever though.

T&E also only has one layer of insulation though - the insulating properties of the sheath are not the same as the insulation and it is only there to provide mechanical protection.

 

[stevethesparks]

A maybe unlikely but possible scenario is with a non-earth conduit, even if wired in T&E, someone drills through it making the whole section live - as we know rcd's, rcbo's are not infallible.

 

[Ian1981]

I am aware of that. I am saying that the fact that trunking and conduit are designed for non-sheathed cables means that they must always be regarded as exposed conductive parts. I am aware that singles aren't being used in the conduit in this instance. (T&E in conduit is generally something to be avoided to be honest, as that isn't what conduit is designed for. I accept that sometimes it is handy to improve the look of drops or provide extra mechanical protection or whatever though.

T&E also only has one layer of insulation though - the insulating properties of the sheath are not the same as the insulation and it is only there to provide mechanical protection.

But it would take the basic insulation to fail and the sheath to fail for it to become a hazard not taking impact into account.
Rather than people saying it’s metal it must be earthed my interpretation is not necessarily if using cables such as twin and earth.

 

[Ian1981]

Must have hit a nerve there with that ‘dumb ‘ rating ?

 

[stevethesparks]

Touche
And not so much of the old

 

[Deleted member 26818]

T&E also only has one layer of insulation though - the insulating properties of the sheath are not the same as the insulation and it is only there to provide mechanical protection.

We have already done this.
It's deemed to be double insulated if the sheath provides adequate mechanical protection.

 

[telectrix]

my tuppence worth. similar scenario is metal tray/basket carrying T/E. that tray/basket does not have to be earthed.

 

[Pete999]

Pete they are conduits, part of the electrical installation, They cant be extraneous!!!

Yes realised that what a Dork I am

 

[Ian1981]

Hmm after much thinking taking everyone’s comments and digging in the regulations again I’d be inclined to agree that it’s an exposed conductive part and would require earthing.
I hope your all happy

 

[Risteard]

Hmm after much thinking taking everyone’s comments and digging in the regulations again I’d be inclined to agree that it’s an exposed conductive part and would require earthing.
I hope your all happy

Glad you agree!

 

[telectrix]

so why do we not earth tray when it's carrying T/E?

 

[Ian1981]

Because I guess the tray isn’t part of the electrical installation that’s to say it’s not classed as an exposed conductive part it’s only a cable management system.
If you have GN8 I’d have a read of page 164&165.

 

[Pete999]

So is the conduit isn't it? cable management I mean.

 

[Ian1981]

Conduit is containment.
Where tray basket is a support system.
That’s my understanding anyway.
As I say have a read of GN8

 

[telectrix]

Conduit is containment.
Where tray basket is a support system.
That’s my understanding anyway.
As I say have a read of GN8

good point. can you now advise IET on some of their more obscure ambiguous regs.?

 

[Andy78]

I have earthed basket and tray many times before to follow specification.

 

[telectrix]

I have earthed basket and tray many times before to follow specification.

so. up aladder checking for a damaged cable. one hand in contact with the esrthed tray. other hand fishing round contacts a live conductor ( insulation damage?). ZAP.

 

[Ian1981]

Usually through parallel paths the basket ends up earthed anyway such as metal framed structures when you mount the brackets to them.

 

[David M]

so. up aladder checking for a damaged cable. one hand in contact with the esrthed tray. other hand fishing round contacts a live conductor ( insulation damage?). ZAP.

Would that not apply only if the tray was extraneous?

 

[Risteard]

I have earthed basket and tray many times before to follow specification.

Indeed. For right or wrong it's commonly required by clients.

 

[Midwest]

Should of just used plastic conduit. It would of saved all this arguing

 

[Midwest]

I remember reading this article some time back on cable tray

Does a metallic cable tray require earthing or bonding? - https://www.tradeskills4u.co.uk/posts/metallic-cable-tray

Not that I've installed any for 30 odd years.

 

[westward10]

Got a belt off a tray with T&Es on it in a ceiling void a few years back. One length run across the void and was isolated from any earth. The cables dropped through the perforations with no protection and one must have been cut through because the tray was live which I discovered when I provided a path for it to the ceiling grid, never say never.

 

[sam400]

Good thread!

Do we have to earth the old conduits that we reuse during a rewire?

 

[Deleted member 26818]

Thinking again about this subject, it will only require earthing, if part of it is exposed.

 

[Deleted member 26818]

What is it you disagree with Risteard?
That we already done it 3 or 4 posts back, or is it the Regulation you disagree with?

 

[Guitarist]

I asked a similar question of Elecsa a couple of years ago regarding T&E running through a backbox to identify a drop, before going through a wall. They told me that as long as the T&E is continuous, then the backbox does not need to be earthed, as the cable is insulated and sheathed.

 

[Octopus]

Maybe ditch the steel conduit idea and use something plastic?

And we shouldn't have to by Guidance Notes to understand the regs.