Metal Class 2 Wall Lights.

So what is your risk assesment there Zoom?

Likelihood of your theoretical fault occuring? Pretty low I would venture.

Consequences of touching a livened up chrome light fitting? Surprising but unlikely to be fatal.

And as you say, pretty common, so where are the corpses?

I would be a bit doubtful as to the validity of the “double insulated" marking in such a case, this sometimes being applied to lights or other appliances that are clearly not in compliance with the standards.

In doubtful cases I would consider adding an earth connection if reasonably practical. I appreciate that some people are opposed to so doing, and state that adding an earth is “altering the design” or “voiding the CE marking”

I disagree, unless there is some specific reason to prohibit adding an earth connection. But how would they feel about mounting said light fitting on an earthed metal conduit box ? or on an earthed metal partition ? Are we really expected to supply an insulated mounting so as to ensure that the light CAN NOT become earthed.

Grumpy: 
 

So what is your risk assesment there Zoom?

Likelihood of your theoretical fault occuring? Pretty low I would venture.

Consequences of touching a livened up chrome light fitting? Surprising but unlikely to be fatal.

And as you say, pretty common, so where are the corpses?

The risk of shock should be minimised by earthing the said light fitting I say.

The risk of fatality will be increased if the fitting becomes live, as there will be no way of knowing that until it is too late, perhaps when somebody touches the live metal light whilst also in contact with an earthed radiator. This is especially dangerous in old non R.C.D. protected installations.

We certainly don't want to see piles of bodies, we don't want to see even one fatality do we?

As John Donne said:

"Any man's death diminishes me because I am involved in Mankind. And therefore never send to know for whom the bell tolls: it tolls for thee.

"Mary Wherry, the Daughter of MP Jenny Tonge was tragically killed when she was electrocuted in her own home.

The circumstances of her death were a direct result of shoddy workmanship and bad luck. A new kitchen had been fitted in her home back in 1999. 2 years later her husband had fitted a drainer below the extractor fan. A cable connected to the fan had been fitted at a 5 degree angle meaning it veered into an area he did not expect it to be. When he screwed the drainer into the wall the screw was left almost touching the wire. As the drainer moved slightly over the years it finally came into contact with the wire electrifying it.  This in itself would not usually result in a deadly shock, however Mrs Wherry's shock proved fatal because her leg was touching a metal-fronted dishwasher door, completing the circuit."

Z.

The connector block in Class II fitting is usually fixed and/or shrouded so that conductors with only basic insulation (including the installation side ones) cannot come into contact with the metalwork. Sounds like the installation might have been botched with this one (or possibly incorrectly manufactured). When done correctly Class II should be at least as safe, if not safer, than Class I (no risk of ADS being compromised by broken c.p.c.s, bad earthing or sticky RCDs).

   - Andy.

broadgage: 
 

 

In doubtful cases I would consider adding an earth connection if reasonably practical. I appreciate that some people are opposed to so doing, and state that adding an earth is “altering the design” or “voiding the CE marking”

 

Are there any real technical disadvantages to adding an earth connection?

ietmgreen: Are there any real technical disadvantages to adding an earth connection?

So someone's changing a light bulb - there's some sort of problem getting the new bulb in, so they stick a finger inside the bayonet holder to feel for any obstruction (because they know the light switch is off). The other hand is holding the metal light fitting. What would have been a tingle has now been upgraded to a fatal shock.

That risk has to be weighed against the risk of the fitting itself becoming live if unearthed.

Zoomy, you have mentioned that the light fittings are chrome, but what is the chrome plated on to?

wallywombat: 
 

ietmgreen: Are there any real technical disadvantages to adding an earth connection?

So someone's changing a light bulb - there's some sort of problem getting the new bulb in, so they stick a finger inside the bayonet holder to feel for any obstruction (because they know the light switch is off). The other hand is holding the metal light fitting. What would have been a tingle has now been upgraded to a fatal shock.

That risk has to be weighed against the risk of the fitting itself becoming live if unearthed.

If the light switch is off, where is the voltage providing the fatal shock.???

ietmgreen: 
 

If the light switch is off, where is the voltage providing the fatal shock.???

That's why I put “know” in italics - because the householder is convinced that the light switch is off, but with a dead/missing bulb and no test equipment, it's easy to get it wrong - especially with 2-way switching. Or someone else switches it on right after the householder checks that it's off.

Or it's looped in at the light fitting I suppose