No earth cable on light fitting

[JohnW2]

Only in the event of two failures.

That would surely only be true if the exposed parts of the Class II item were earthed? I'm talking about the (normal) situation in which, in accordance with manufacturer's instructions, those parts were not earthed (but allegedly safe to touch at the same time as touching something earthed).

If you disagree, what 'two failures' did you have in mind?

Kind Regards, John

 

[JohnW2]

Only in the event of two failures.

You mean both parts of the double insulation fail?

I suspect that he was thinking of one of the failures being failure of protective devices to respond to the exposed-c-ps become live (if earthed) - but, as I've just written, that is irrelevant to the situation I was talking about, in which those parts were (per instructions) not earthed.

Kind Regards, John

 

[PBC_1966]

To inject a little light relief regarding manufacturer's instructions, it might be difficult to tell if you've complied with some of these instructions or not!

//www.diynot.com/diy/threads/bad-translations.449886

 

[JohnW2]

Undoubtedly. But we tend not to hear about injuries which never happened, so who knows how many such incidents may have been avoided because somebody ignored the manufacturer's instructions?

We obviously don't know - that's why I said "if it were possible". However, the fact that such cases would be next-to-impossible to detect does not mean they don't happen. The point is that 'in either directly', extremely rare (and quite probably 'extreme') anecdotal events (whether detectable or not) mean essentially nothing about the overall picture.

Kind Regards, John

 

[PBC_1966]

However, the fact that such cases would be next-to-impossible to detect does not mean they don't happen.

Certainly - I was suggesting that such cases do indeed happen.

 

[stillp]

Only in the event of two failures.

That would surely only be true if the exposed parts of the Class II item were earthed? I'm talking about the (normal) situation in which, in accordance with manufacturer's instructions, those parts were not earthed (but allegedly safe to touch at the same time as touching something earthed).

If you disagree, what 'two failures' did you have in mind?

Kind Regards, John

Failure of both layers of insulation.

 

[JohnW2]

However, the fact that such cases would be next-to-impossible to detect does not mean they don't happen.

Certainly - I was suggesting that such cases do indeed happen.

I'm sure they do - and in some cases, it's actually possible to get a good handle on these 'non-events' ....

... not all that long ago I was involved in a situation in which, after several thousands of copies had got into the hands of purchasers, it was discovered that a typo in the instruction leaflet for an over-the-counter medication had resulted in the 'recommended dose' appearing as "12 tablets every four hours" instead of "1-2 tablets every 4 hours". It seems that everyone who read those instructions had the good sense to ignore them ("knew better than the manufacturer"), since there were no reports of any cases of the harm one would have expected to befall anyone who had complied with the instructions.

... which, of course, reminds us of another reality. Even a 'good and reputable manufacturer' is not immune from accidental errors in instructions, such as in this case.

Kind Regards, John

 

[PBC_1966]

Failure of both layers of insulation.

Then as John said earlier, surely if you consider that a significant risk in terms of the result of the failure damaging the equipment if the casing were earthed, it's just as much of a significant risk in terms of a shock hazard to somebody using the equipment if the case were not earthed?

If, for example, you are seriously suggesting that the properties of the insulation provided are such that a breakdown is likely if the casing were earthed, then as far as I'm concerned I would not want to be using that device and coming into contact with its unearthed casing anyway.

 

[JohnW2]

Failure of both layers of insulation.

Oh, I see - or presumably failure of the one layer of 'reinforced insulation'?

Whatever, that is surely irrelevant - no matter how many layers of insulation have to fail, you have implied that it may happen, since otherwise I cannot conceive of any way in which connecting the outside (outside of the layers of insulation) of the product to earth could cause the workings of the item (within all the layers of insulation) to "fail", in the manner you have suggested could happen.

Kind Regards, John

 

[stillp]

OK then, you keep earthing them then, as you obviously know better.

 

[JohnW2]

OK,m you keep earthing them then, as you obviously know better.

But, as I've said countless times, I don't earth them, because I do not approve of any unnecessarily earthed metal around the place.

However, you have got me worried by suggesting that the outer casing of a Class II appliance could possibly come into sufficient 'electrical connection' with live parts inside (beneath however many layers of insulation) as to cause the item to "fail" if that casing were earthed. If that really were the case, I would find it almost impossible to see how (if, per instructions, not earthed) that item could be relied upon to be safe for me to touch (whilst also touching something earthed).

Kind Regards, John