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.

 

[Andy78]

No, they require earthing.

 

[Ian1981]

If they are in good contact with earth(generally below the foundations) and meet the definition of an extraneous conductive part then They will require protective bonding to the MET

 

[Deleted member 9648]

If they are in good contact with earth(generally below the foundations) and meet the definition of an extraneous conductive part then They will require protective bonding to the MET

They cant be an extraneous conductive part by definition if they are part of the electrical system.
As Andy has said. They require earthing.

 

[Ian1981]

Also are they exposed to touch?

 

[Pete999]

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.

Have you tested the conduits to see if they are extraneous?

 

[Deleted member 9648]

Also are they exposed to touch?

Why?

 

[Ian1981]

They cant be an extraneous conductive part by definition if they are part of the electrical system.
As Andy has said. They require earthing.

A fair point

 

[Deleted member 9648]

Have you tested the conduits to see if they are extraneous?

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

 

[Deleted member 9648]

Thanks Ian.

 

[Ian1981]

If the cable installed inside the conduit is insulated and sheathed such as twin&earth , then does it still need to be earthed as you effectively have double insulation unlike singles?

 

[Ian1981]

Thanks Ian.

No problem I’m happy to be corrected.

 

[Deleted member 9648]

Insulated and sheathed is not the same as double insulation.

 

[Pete999]

No problem I’m happy to be corrected.

Me too

 

[Ian1981]

Insulated and sheathed is not the same as double insulation.

No it’s not but do you see were I’m coming from?
The added protection you have with twin & earth is it necessarily needed to earth the conduit?
Perhaps if buried in the floor against impact yes but otherwise I’m not convinced.
Open to discussion

 

[Deleted member 26818]

If the wiring method is T&E, then no the conduit would not require Earthing.

 

[Andy78]

If the wiring method is T&E, then no the conduit would not require Earthing.

Do the regs make this exception ?

 

[ferg]

common sense dictates that if it's metal, contains wires and could be touched then it should be earthed.

 

[Deleted member 9648]

common sense dictates that if it's metal, contains wires and could be touched then it should be earthed.

Not necessarily. There are plenty of all metal class 2 light fittings around.

 

[Ian1981]

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

 

[ferg]

Not necessarily. There are plenty of all metal class 2 light fittings around.

I was waiting for that one.

I'll put it another way. Name a good reason not to earth it.

 

[Ian1981]

I was waiting for that one.

I'll put it another way. Name a good reason not to earth it.

We are not talking personal preference, we are saying is it a requirement of bs 7671

 

[Andy78]

As far as I can see, the reg that requires the earthing of exposed conductive parts is all encompassing and makes no exceptions.

The debate would be whether a part is an exposed conductive one or not.

 

[ferg]

That was my point but you made it in a much less smart arsey way.

I blame too much paperwork.

my apologies to Ian for said smart arse manner.

 

[static zap]

common sense dictates that if it's metal, contains wires and could be touched then it should be earthed.

It's in a kitchen , a chance of wet floors + it gets wet and becomes live !

 

[Ian1981]

Well as per guidance note 8 and regulation 412.2.4.1 A cable complying with the appropriate standards having a non metallic sheath is deemed to provide satisfactory basic protection and fault protection as does an item of class 2 equipment.
Class 2 equivalence aas pvc insulated and sheathed cables.
Hence containment such as metal tray or basket need not be earthed.
Cables in conduit are fully enclosed but I feel meet the same requirement

 

[Ian1981]

That was my point but you made it in a much less smart arsey way.

I blame too much paperwork.

my apologies to Ian for said smart arse manner.

No need pal
I took no offence

 

[Andy78]

411.3.1.1 is the reg that asks for earthing of exposed conductive parts. It makes no exception I can see nor references any of the regs pertaining to reinforced or double insulation.

 

[westward10]

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

T&E does not have reinforced insulation it has one layer of electrical insulation and an overall sheath which provides protection for the electrical insulation.

 

[Deleted member 26818]

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.
410.3.9.

 

[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