Bonding of conduit in kitchen floor

[Lagentium]

Bit of a debate today, advice please as regs book not possible to get in my hands until tomorrow. New job, apartments, in the kitchen there are 2 x 25mm conduits from an external wall to an island within the kitchen that is free standing, to be able to get the hob supply across and lighting with a spare in case any sockets are added at a later date. My question is, do these require bonding? Thanks in advance.

 

[Ian1981]

Regulation 412.2.4.1 I feel covers it in conjunction with ref 412.2 so I don’t think it’s a requirement.

 

[Andy78]

There are exceptions to the requirement to Earth exposed-conductive-parts. One of which is where the wiring system is deemed to be double insulated.

Can you point me in the right direction for that ?

 

[Deleted member 26818]

410.3.9.

 

[Andy78]

410.3.9.

Thanks. So 410.3.9 negates 411.3.1.1 as long as 412 is satisfied. Next question for me is does twin and earth satisfy 412 as double insulated ?

 

[Ian1981]

Well it’s deemed to provide satisfactory basic and fault protection as does an item of class 2 equipment.
I’m aware that every one bangs on about twin and earth is not class 2 blah blah but there it is.
Check out guidance note 8

 

[Deleted member 26818]

On second thoughts, I don't think T&E does satisfy the requirement to deemed double insulated.
I believe the CPC has to also be insulated and sheathed to comply.

 

[Andy78]

On second thoughts, I don't think T&E does satisfy the requirement to deemed double insulated.
I believe the CPC has to also be insulated and sheathed to comply.

I've heard that before in respect of bringing cable into class 2 accessories. Flex is acceptable because the cpc is insulated to the same voltage as the live conductors.

 

[Deleted member 26818]

In this instance though, the CPC of the T&E is not exposed within the enclosure.

 

[Ian1981]

The cpc only needs to carry fault current so it’s irrelevant if it’s not sleeved in this case as it’s not classed as a live conductor

 

[Risteard]

Try regulation 412.1.1 double or reinforced insulation
Basic protection and fault protection are provided by reinforced insulation between live parts and accessible parts.
Regulation 412.2.

Singles don’t have reinforced insulation so understandably need containment as per regulation 521.10.1,where as twin and earth does, so I’d say it’s not necessarily a requirement to Earth the conduit if metal containing insulated and sheathed cables

Insulated and sheathed cables do not provide either double or reinforced insulation. They merely provide mechanical protection.

 

[Deleted member 26818]

The requirement now is for any CPC that traverses an enclosure to be insulated as though they were live parts.

 

[Deleted member 26818]

Insulated and sheathed cables do not provide either double or reinforced insulation. They merely provide mechanical protection.

Wiring systems are deemed to be double insulated if adequate mechanical protection of the basic insulation is provided by a non-metallic sheath or non-metallic conduit.

 

[Ian1981]

Wiring systems are deemed to be double insulated if adequate mechanical protection of the basic insulation is provided by a non-metallic sheath or non-metallic conduit.

Yes that’s how I read it sort of
Yet to be convinced otherwise

 

[Ian1981]

Insulated and sheathed cables do not provide either double or reinforced insulation. They merely provide mechanical protection.[/QUOTE I would say that any non metallic sheathed cable whether single core, multi or flat t&e affords protection against basic and fault protection contact much like class 2 equipment but isn't to be regarded as class II in itself.

 

[westward10]

To be double insulated you require two layers of "electrical" insulation or a single layer or more of reinforced insulation.

 

[LewisM]

I'm guessing at some point the conduit joins a metal pattress just earth the pattress thus earthing the conduit it may or may not be needed but doing it isn't exactly a strenuous task.

 

[stevethesparks]

Conduit is part of the electrical installation, it doesn't compare with a double insulated (class2) metal light fitting. So would the disbelievers run a 3 core (L,N&E) swa under the floor without earthing the armour?

 

[Ian1981]

Conduit is part of the electrical installation, it doesn't compare with a double insulated (class2) metal light fitting. So would the disbelievers run a 3 core (L,N&E) swa under the floor without earthing the armour?

The armour needs glanding so by definition is always an exposed conductive part so it’s not the same is it

 

[stevethesparks]

Could be glanded into a wiska box, same scenario.

 

[Ian1981]

The armour is part of the overall construction of the cable
Conduit is not
Insulated and sheathed cables gives satisfactory protection against basic and fault protection is all I’m saying

 

[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.