No earth cable on light fitting

[stillp]

Yes.
There's a clue in my earlier post.

 

[PBC_1966]

You install a class II light fixture, for example, but bolt an earth onto the metalwork anyway. How is the result any different than if you'd just chosen to use a class I fixture instead? Either way you end up with a light fixture on the wall or ceiling which has earthed metalwork.

Because you have introduced a hazard which was not there before.

And if you add a class I wall light to a room, surely you've done exactly the same?

Going back to Winston's points about audio-visual equipment, while many consumer devices might be class II, there are very good reasons for providing an earth to the casings anyway, especially once you have five or six such units all connected up together.

What are those reasons?

For a start, the cumulative leakage due to capacitance which results when numbers of such units are interconnected.

Please let me know when you find a plastic washing machine.

Doesn't that rather make the point? How much consideration has seriously been given to the adoption of double-insulated washing machines, with or without metal casings?

If it's perfectly all right to have something the size of a washing machine sitting there with all that earthed metalwork, what's the problem with something like an earthed light fixture, whether it started out as class II or not?

 

[JohnW2]

Yes. There's a clue in my earlier post.

If you're referring to the fact a manufacturer has chosen to declare a product as Class II, then I really don't think that is relevant. As I understand it, that declaration means that the product satisfies the requirements for omitting the (which otherwise is effectively the default) earthing of any exposed metal, and does not in any way mean or imply that any harm would/could be done to the product by earthing any exposed metal (if that could be done without risk of damaging the product).

More generally, as I wrote to EFLI earlier, I'm really rather confused by this Class I/II business. We seem to be talking as if Class II equipment with exposed metal is common, but that is not my experience. I would think that the majority of Class II products I see are 'all plastic', so I don't fully understand what 'declaring them as Class II' actually achieves - since declaring that they meet the requirements for omitting earthing of exposed metal means nothing if there is no exposed metal.

So, as I asked EFLI, what about items with no exposed metal parts but which don't satisfy the requirements to be Class II (a 'flimsy plastic CU comes to mind, as one of countless examples!) - or, at least, are not marked/labelled as Class II. I can but presume that they are allowed to exist (since they seem to exist), but how are they 'classified'?

Kind Regards, John

 

[stillp]

Yes. There's a clue in my earlier post.

If you're referring to the fact a manufacturer has chosen to declare a product as Class II, then I really don't think that is relevant. As I understand it, that declaration means that the product satisfies the requirements for omitting the (which otherwise is effectively the default) earthing of any exposed metal, and does not in any way mean or imply that any harm would/could be done to the product by earthing any exposed metal (if that could be done without risk of damaging the product).

Not necessarily.
Class II equipment with exposed metal is quite common in industry, usually accompanied by a warning that it shall not be earthed.

 

[JohnW2]

Not necessarily. Class II equipment with exposed metal is quite common in industry, ...

Fair enough, but my experience is not in industry, this is a DIY forum and the context of the discussion has been domestic!

... and usually accompanied by a warning that it shall not be earthed.

As you will be aware, I sympathise with that as part of a general dislike of there being any 'unnecessarily earthed' metal around - but I would not feel inclined to issue a 'warning' that it should not be done. Do you know why the industrial equipment to which you refer comes with such a warning?

Kind Regards, John

 

[stillp]

Not necessarily. Class II equipment with exposed metal is quite common in industry, ...

Fair enough, but my experience is not in industry, this is a DIY forum and the context of the discussion has been domestic!

My experience is in industry. I can't say if such things are common in domestic appliances/accessories.

I would not feel inclined to issue a 'warning' that it should not be done.

Of course, you're not a manufacturer!

 

[stillp]

Do you know why the industrial equipment to which you refer comes with such a warning?

It is a requirement of many product standards.

 

[JohnW2]

I would not feel inclined to issue a 'warning' that it should not be done.

Of course, you're not a manufacturer!

I'm not - but what I was meaning is that I cannot think of an (electrical) reason why, if I were a xxx manufacturer, I would feel the need/ inclination
to issue a warning about this - which is why I was hoping you could educate me as to the reason why manufactures do issue such 'warnings'.

Kind Regards, John

 

[JohnW2]

Do you know why the industrial equipment to which you refer comes with such a warning?

It is a requirement of many product standards.

OK, so we're passing the buck 'up the chain', without getting an 'electrical' answer. In that case, my question becomes "Do you know why many of the product Standards have such a requirement?".

Kind Regards, John

 

[JohnW2]

My experience is in industry. I can't say if such things are common in domestic appliances/accessories.

Apart from your professional experience, you presumably live in a domestic environment, just like the rest of us. You could look around your home and see how many Class II items you have, and then determine how many of them have exposed metal parts - I doubt that it would be many, if any.

Kind Regards, John

 

[EFLImpudence]

but I would not feel inclined to issue a 'warning' that it should not be done. Do you know why the industrial equipment to which you refer comes with such a warning?

As far as domestic products are concerned the wording is usually "This product must not be earthed".

I am sure it just means that "This product must not be earthed (because it is safer that way)" rather than -
"This product must not be earthed (because you shall bring doom and pestilence to my product and the world if you do)". We have made it Class II for your safety; do not negate the benefit of the product.


I don't think there is a catastrophic consequence which you seem to be looking for.

 

[EFLImpudence]

Much the same as if I fitted the ubiquitous metal bath on wooden supports with plastic pipes and placed a sticker on the bath stating "This bath must not be earthed".

 

[JohnW2]

Much the same as if I fitted the ubiquitous metal bath on wooden supports with plastic pipes and placed a sticker on the bath stating "This bath must not be earthed".

Yes - but much as you and I would agree that it would, on balance, be better not to earth it, would you actually use the words "must not"? (particularly given that, as we know, there are at least some people who sincerely believe that, on balance, it is better to earth it)>

Kind Regards, John

 

[JohnW2]

... Do you know why the industrial equipment to which you refer comes with such a warning?

As far as domestic products are concerned the wording is usually "This product must not be earthed".

You've jumped somewhat away from my question, but I know that's what the wording on domestic Class II products usually says, my question (about both domestic and industrial products are concerned), is "why?"

I am sure it just means that "This product must not be earthed (because it is safer that way)" rather than - "This product must not be earthed (because you shall bring doom and pestilence to my product and the world if you do)". We have made it Class II for your safety; do not negate the benefit of the product.

Are you suggesting that they are simply saying exactly the same as me - that, in general (and whether it is an electrical product or not), avoidance of any earthed metal is desirable - or are you suggesting (which I would find more difficult to understand) that they feel that it could/would in some way impair the safety of the product itself?

Kind Regards, John

 

[EFLImpudence]

Yes - but much as you and I would agree that it would, on balance, be better not to earth it, would you actually use the words "must not"?

Yes if I had installed it so that was the case.
Do you expect a sticker to state a long drawn out explanation full of ifs and buts?

(particularly given that, as we know, there are at least some people who sincerely believe that, on balance, it is better to earth it)

In my scenario it isn't; they would be wrong.


If someone installs a metal bath under which are several bare-ended live conductors with minds of their own, they may wish to earth it.