Unexpected coloured wires and two going into L1 on dimmer switch

[terryplumb]

Does this mean the existing switch is wired dangerously then?

Yes, the switch plate is not earthed. Other things on the circuit may also be unsafe.
Engage an electrician.

 

[Benjic]

Okay thanks guys. TBH I was in two minds about paying for an electrician to do what looked like simply swapping one switch for another but knowing your concerns here makes me feel happier splashing out on a professional.

 

[Adam_151]

Okay, so that earth connector (bottom left on attached photo) seems to go nowhere (or is the fact the clip on metal front touches the switch plate enough to do the earthing?).

Its not going nowhere, its going to the metal plate of the switch, which in the case of whats pictured, is the bit that forms the enclosure for the internals and connections, the decorative front plate will end up earthed through clipping on but is not really the bit you are primaraily earthing, it can only really pick up a potential from the metal behind it (which means that if you dont earth that, and it becomes live through a fault, the front will too)

Yes, previous switch was not correct either

Switch off, pull all loose coonnector blcoks back into the box, and fit a flylead from the earths to the switch, you'll have to dress the connector blocks to the side to allow the body of the switch back, quite likely

 

[EFLImpudence]

I was told, that even though class 2 products don’t require and Earth/cpc, that it needs to be there should anyone accidentally cut through the live and or neutral wires.

That is not the reason.

It is merely (unjustifiably) allowing for future need.

 

[flameport]

Does this mean the existing switch is wired dangerously then?

It's incorrect. Dangerous if a wire touches the metal parts.
Easily fixed by connecting the earth wires which surely must exist in the backbox to the switch.

Post a picture of the other wires in the backbox.

 

[Benjic]

Okay, here’s what the backbox looks like…

 

[CBW]

Okay, here’s what the backbox looks like…

The green/yellow should be your earth/cpc.

 

[securespark]

That's a real rat's nest....

 

[JohnW2]

I was told, that even though class 2 products don’t require and Earth/cpc, that it needs to be there should anyone accidentally cut through the live and or neutral wires.

As I wrote, the reg (as quoted by EFLI in post #19) requires only that a CPC ('earth#) be 'run to each point and accessory) - hence,if more than one cables go to an accessory and one has an 'earth', that reg theoretically means that any other cables do not have to have an earth. In any event, there is no immediate safety issue in having no earth 'available' at an accessory/item that does not need one - as I said before (and as the note to the reg says) the requirement exists in case the accessory/item is subsequently changed to one which does require an earth.

As for what you suggest, it would make sense, but I cannot off the top of my head think of any reg which requires every cable to have a CPC ('earth'). Indeed, there are still plenty of ancient installations around whose lighting circuit wiring does not have a CPC and, although that means that "Class I"/metal accessories and fittings can't be used, I don'gt recall people citing a regulation that would be violated by the ('earthless') cable itself.

In fact, the most common situation probably is that the cable does have a CPC, but that since the accessory (e.g. switch) does not require it, it has been 'cut short' at the end, and is therefore not immediately 'available' at the accessory.

Kind Regards, John

 

[JohnW2]

That switch is a low profile ,clip on metal front. The switch plate is metal with a plastic edging,and clearly has an earth terminal as shown by Johnw2 above.

The irony is that seems to be that it looks as if, were it not for that earth terminal, any 'clip on metal front' (IF there is one) would be separated from anything electrical by plastic which was at least as insulating, thick and 'reinforced' as that of a Class II item - so that, even though it probably does not bear a Class II marking, in common sense terms it would not require an earth were the earth terminal not there

Kind Regards, John

 

[DetlefSchmitz]

that reg theoretically means that any other cables do not have an earth.

Well, not really, that cable must be going somewhere that also needs an earth.

 

[JohnW2]

Well, not really, that cable must be going somewhere that also needs an earth.

... but that 'somewhere' might be getting it's (required) earth through a different cable, mightn't it?

As I said, the common 'issue' is that the cable does have a CPC, which is connected to earth at one end, but that that CPC has been 'cut short', hence inaccessible, at the other end.

KInd Regards, John

 

[DetlefSchmitz]

... but that 'somewhere' might be getting it's (required) earth through a different cable, mightn't it?

I consider this a bit fanciful. I am finding it hard to imagine a genuine situation where the earth wires were not all needed in a legitimate installation.

 

[JohnW2]

I consider this a bit fanciful. I am finding it hard to imagine a genuine situation where the earth wires were not all needed in a legitimate installation.

I agree that its a bit contrived,but one has to wonder why the regs 'merely' require that a CPC be run 'to each poiint and accessory', rather than simply requiring that every cable must have a CPC.

I don't think it's too difficult to think of practical situations in which this issue could arise, particular in relation to old CPC-less lighting circuits that have been partially modified. For example, if there are multi-gang light switches, at least one gang of which is '2-way', then if the accessories are 'receiving a CPC' from one of the other cables, I think that the reg can be taken to mean that the cable connecting a pair of two-way switches theoretically doesn't have to have a CPC.

Kind Regards, John

 

[terryplumb]

The irony is that seems to be that it looks as if, were it not for that earth terminal, any 'clip on metal front' (IF there is one) would be separated from anything electrical by plastic

On the contrary John ,the metal clips of the decorative, clip on front, connect directly to the metal switch plate,not any plastic . Take a look at the op's picture of the front of the switch plate. The 2 square holes are where the springs connect the decorative front to the switch plate.