Earth funnies and phantom voltages on lighting circuit

[yartin]

Q1. Apart maybe from wet rooms such as bathrooms and the likes; is there any advantage of installing class ii light when E is available in the circuit?

Q2. Isn't it safer connecting CPC cable to metal light casing rather than having metal casing class ii light with no E connection?

 

[JohnW2]

Q1. Apart maybe from wet rooms such as bathrooms and the likes; is there any advantage of installing class ii light when E is available in the circuit?

If anything, the opposite, since it is theoretically undesirable to have any more touchable earthed metal in a house, since it theoretically increases the risk of electric shocks (for someone touching something else which is 'live').

Q2. Isn't it safer connecting CPC cable to metal light casing rather than having metal casing class ii light with no E connection?

As above.

 

[Harry Bloomfield]

If anything, the opposite, since it is theoretically undesirable to have any more touchable earthed metal in a house, since it theoretically increases the risk of electric shocks (for someone touching something else which is 'live').

If everything metal, taps, sinks, cookers, fridges, freezers, switch plates, pipes, radiators, and so on, could be replaced with none electrically conductive versions. Unfortunately, that cannot be achieved, so they are earthed/bonded for safety, to ensure they can never at risk of becoming live.

 

[yartin]

Say you get class ii ceiling light, you have L & N coming down from the ceiling to be connected to the protected wires of the light, what connector do you use to maintain the double insulation? I doubt wago are suitable? Also L & N wires from the ceiling are not double insulated.

 

[Harry Bloomfield]

Also L & N wires from the ceiling are not double insulated.

You have the blue/brown coloured wire insulation, and the outer insulation.

 

[JohnW2]

If everything metal, taps, sinks, cookers, fridges, freezers, switch plates, pipes, radiators, and so on, could be replaced with none electrically conductive versions. Unfortunately, that cannot be achieved, so they are earthed/bonded for safety, to ensure they can never at risk of becoming live.

All true. I don't think anyone has suggested that Class I items should (sensibly) not be earthed.

However, that doesn't alter what I said, that to create additional touchable ('unnecessarily') earthed metal is always going to (very slightly) increase the risks of electric shocks - so 'why do it?'

 

[yartin]

You have the blue/brown coloured wire insulation, and the outer insulation.

I know that but that's single insulation; the grey standard insulated cables aren't class II double isolated.

How about the connectors? Wago or bloc connectors aren't class II.

 

[EFLImpudence]

Say you get class ii ceiling light, you have L & N coming down from the ceiling to be connected to the protected wires of the light, what connector do you use to maintain the double insulation?

The double-insulated connections in the enclosure the manufacturer has designed and stated are double-insulated.

I doubt wago are suitable?

No.

Also L & N wires from the ceiling are not double insulated.

Well they are insulated and sheathed but anyway they are not part of the double-insulated appliance.
The sheathed insulated cable will enter the enclosure.

 

[yartin]

The double-insulated connections in the enclosure the manufacturer has designed and stated are double-insulated.


No.


Well they are insulated and sheathed but anyway they are not part of the double-insulated appliance.
The sheathed insulated cable will enter the enclosure.

Stranded cable are class II according to this vid

 

[EFLImpudence]

Stranded cable are class II according to this vid

The first thing he says is they are single-insulated.

 

[JohnW2]

Stranded cable are class II according to this vid ....

In a literal sense, cables with both insulation and sheath obviously are, since the conductor is surrounded by two layers of non-conductive ('insulating') material (the 'insulation' and the 'sheath'). That's why they are deemed to be safe to touch, whereas a cable with only single insulation would not be, unless surrounded by 'earthed metal'. ....but "So What?"

 

[SUNRAY]

Where was this quoted from

 

[EFLImpudence]

I made it up - hence the "Oh no he didn't".

 

[SimonH2]

I was taught by my parents (both English grads from UCL, one an English teacher, the other an English lecturer and TEFL teacher) the same rule about fewer and less, but English is, as my Mum says, a moveable feast, so how it is used changes with the times.

Agreed, language changes over time. But that's no excuse for not caring.
What irks me more than the sort of thing we're discussing here - is when people make no attempt to follow the extant rules of grammer, and doubly so those with a "it doesn't matter, people know what is meant." The problem with that latter attitude is that it often causes confusion.

The sheathed insulated cable will enter the enclosure.

But then the sheath is stripped and the cores are no longer double insulated. Unless the inside of the metal enclosure is fully insulated then you've lost your DI compliance.
IIRC, the last fitting I worked with came with a chock block - the instructions said to wrap it with tape.

 

[Ragnar_AT]

It would make a lot more sense if it was „even if the circuit only supplies one or more class II fixtures“. In that case it would be pretty clear that all the fixed wiring needs to have a CPC, in case someone wants to install class I fixtures in the future.