CPC as live conductor now OK?

[ban-all-sheds]

Bare conductors is another but is the centre conductor of twin and earth really considered as a bare conductor?

No, but it is not insulated and sheathed, and so may it be used as a live conductor without with more mechanical protection?

lets see if any one can find a regulation stopping the use of the centre conductor for other than earth?

134.1.1.

 

[OwainDIYer]

How could you do that and still comply with regulation 411.3.1.1 "A circuit protective conductor shall be run to and terminated at each point in wiring and at each accessory except a lampholder having no exposed-conductive-parts and suspended from such a point"

Are fans and light fittings no longer a point in wiring or an accessory?

If it's a double insulated fan it doesn't need a cpc in its flex, which is part of the appliance not part of the fixed wiring. The cpc must be taken as far as the flex outlet. A double insulated light fitting would comply as a lampholder having no exposed-conductive-parts and suspended from such a point, again the cpc must be taken as far as the ceiling rose.

 

[JohnW2]

If it's a double insulated fan it doesn't need a cpc in its flex, which is part of the appliance not part of the fixed wiring.

In common sense terms, it's quite difficult to argue with that but, regs-wise, there clearly is some scope for discussion/argument as to what does, and does not, count as being part of 'fixed wiring'.

If we were talking about a length of T+E or 3C+E which left a JB, switch, isolator or whatever, I don't think many people would try arguing that it wasn't part of the fixed wiring - regardless of where the other end of the cable went. It's not obvious (at least, not to me) why things would change significantly if that T+E/3C+E were replaced with flexible cable.

Kind Regards, John

 

[mfarrow]

Let's take a look at some standards shall we...

BS 6004

This standard recognises a PVC insulated, PVC sheathed cable with circuit protective conductor.
...
Position of circuit protective conductor:
Twin - centrally placed between cores in the same plane
3-core - centrally placed between black and grey cores in same plane

The standard therefore recognises the uninsulated core as a CPC. Therefore it should be used as such, whatever mechanical protection or otherwise you apply.

For multicore cables without an uninsulated core, the standard recognises that it is understood that that colours green/yellow when they are combined as specififed are recognised as identifying exclusively the core intended for use as an earth conductor or similar protection. I think the key word there is intent. There is no further reference, although it also recognises the use of blue for identifying the core intended to be used as a neutral.

BS 5467

Pretty much the same as BS 6004. Obviously there is a prime candidate for a CPC already in these cables (the armour) and no provision is made for an uninsulated core.

BS 7671

I'll forget 411 regulations, as it's not relevant if you're not using a CPC and therefore not relying on automatic disconnction of supply.

412.1.3 advises that where Double or Reinforced Insulation is the sole protective measure, it shall be verified that the installation or circuit concerned will be under effective supervision in normal use so that no change is made that would impair the effectiveness of the protective measure. One may be able to argue that there aren't that many Class 1 fans or thermostats on the market (or even any) but this is at the discretion of the electrician or designer to assess whether this departure would be acceptable.

514.4.2 to me is very clear. It's not telling you that green yellow cores should be used exclusively as a protective conductor, as it appears to be read as.

It's saying that the combination of the colours green and yellow shall be used only to identify a protective conductor. In my opinion this is to avoid people reading the 70/30 rule and using a 90/10 sleeving and calling the cable line. Strictly speaking this should also mean that coloured number markings shouldn't be used where green and yellow sit together, again to avoid confusion.

There is nothing saying you can't oversleeve a pre-coloured core to identify it as something else, except on single core g/y cables that will ultimately be likely to run through conduit and be intercepted along their length.

 

[JohnW2]

There is nothing saying you can't oversleeve a pre-coloured core to identify it as something else, except on single core g/y cables that will ultimately be likely to run through conduit and be intercepted along their length.

Indeed. When this issue was originally thrashed out (ad infinitum!), I think that most/all people ended up agreeing that (no matter what one might feel about the practice), there is (with the one exception you mention) no regulation preventing the oversleeving of a G/Y-insulated core at its terminations for use as a live conductor.

However, that shifted the discussion to the need for a CPC - and it is clear that, in nearly all situations, BS7671 effectively requires that every 'fixed-wiring' cable has a CPC. In practice, therefore, that means that the issue about overseeving a G/Y is pretty moot, since it will be required for its 'intended purpose'. However,per my lst post (and OwainDIYer's comment), thereis clearly scope for some discussion as to what constitutes 'fixed wiring'.

Kind Regards, John

 

[mfarrow]

In practice, therefore, that means that the issue about overseeving a G/Y is pretty moot, since it will be required for its 'intended purpose'.

I've seen SWA with Brown, Blue and Green/Yellow, so I don't think it's quite as clear cut as that.

 

[Monkeh]

In practice, therefore, that means that the issue about overseeving a G/Y is pretty moot, since it will be required for its 'intended purpose'.

I've seen SWA with Brown, Blue and Green/Yellow, so I don't think it's quite as clear cut as that.

Let me guess, B&Q or Wickes.

 

[JohnW2]

In practice, therefore, that means that the issue about overseeving a G/Y is pretty moot, since it will be required for its 'intended purpose'.

I've seen SWA with Brown, Blue and Green/Yellow, so I don't think it's quite as clear cut as that.

Fair point (although those are unusual colours for 3-core SWA). However, this particular discussion is clearly not about SWA but, rather, about flexible cables in which the only possible thing to act as a CPC is a G/Y-insulated core. Hence my comment.

Kind Regards, John.

 

[mfarrow]

Let me guess, B&Q or Wickes.

eBay

 

[securespark]

Bare conductors is another but is the centre conductor of twin and earth really considered as a bare conductor?

I would say so!!

 

[doitall]

CPC as live conductor now OK?

No Eco it's always been ok.

Oversleeving a green and yellow as a switch phase is, how shall we say, "Not outside the regs" according to the suits that write them.

 

[RF Lighting]

But you have to supply every single wiring point and accessory with a CPC. How are you going to acheive this if you've over-sleeved the green and yellow wire to use it for something else?

 

[Iggifer]

But you have to supply every single wiring point and accessory with a CPC. How are you going to acheive this if you've over-sleeved the green and yellow wire to use it for something else?

Oversleeve a line conductor in G/Y?

 

[EFLImpudence]

I didn't want to get embroiled in this again but the original query was raised because of fitting a thermostat which required a neutral where the previous one did not, thus being short of conductors.
I.e. someone has bought and fitted the wrong item.

Now though, three core flex is being discussed.
Surely this is just a short length between an item and the wiring centre of a central heating system or the fixed wiring of the installation.

Therefore, why cannot four core flex be supplied ?
It would seem that some people are intent on doing it wrong on purpose.

 

[doitall]

It would seem that some people are intent on doing it wrong on purpose.

How can that be when it isn't wrong.

I don't think you sparky types will accept you are wrong because you've been ripping the public off for so long and generating extra work under false pretenses.