A simple question

[JohnW2]

It is for you to judge the lesser of two evils, but, then I would suggest that your arguments are the equivalent of Bernard's to earth (wrongly bond) metal parts that do not require it.

Certainly not 'equivalent', since I am talking about parts which I believe might (because it is not 'properly Class II) be at risk of becoming live as a result of a single fault (since I regard the product as 'not necessarily better than Class I') - whereas many of the things that Bernard feels should be bonded (like otherwise electrically 'floating' metal baths) would/could only become live in extraordinarily unlikely situations. The balance of risks is therefore totally different in 'his' and 'my' scenarios.

The products in question may also be as poorly made in other respects so perhaps a better choice would be to not use at all but send to Trading Standards.

That could well be the case, but I was obviously talking about a situation in which, despite one doubts about the 'Class II' classification, one had decide to use the product.

If, for example, one's concerns relate only to the fact that one finds it hard to believe that a flimsy plastic layer (which represents the only 'protection against electric shock') really qualifies as "reinforced insulation" (a definition of which I've never seen), and everything else about it seems fine, to earth exposed metal parts is no different from what you would do if the manufactured had not made the 'Class II claim' about which one is not convinced.

It is, of course, in no way more hazardous to earth exposed metal parts of a product which bears a Class II marking than there would be to earth the exposed metal parts of an identical product which did not bear that marking - and no-one forces any manufacturer to claim that a product is Class II, and mark it as such - event if they could. Indeed, I suspect that there are products around which would/could satisfy the requirements for Class II, but the manufacturer has chosen not so to do (maybe to avoid the hassle of 'proving'/'justifying' the Class II status).

Kind Regards, John

 

[JohnW2]

That may be true but it is a false argument because you have made them 'more hazardous' than they are intended to be.

We've discussed this umpteen times before, and I think that "false argument" is putting it far too strongly - we are, rather, talking about two different points of view.

I seriously doubt that (m)any manufacturers make Class II items because they "intend" that this avoids the creation of unnecessarily earthed metalwork.

If one is allowed to invoke common sense, there is, in my opinion, little of that involved in saying that one "must not" earth exposed metal parts of a light fitting to be attached to a ceiling (because it would avoid the 'hazard' {to someone who went up a ladder and touched it} of introducing 'unnecessarily earthed metal') if we do not also say that much larger, and much more accessible/touchable (often with wet hands) bits of exposed metal (like metal sinks) "must not be connected to earth".

Kind Regards, John

 

[EFLImpudence]

Ah. That's interesting.

Why do they bother to make Class II items?

As I understand it, it is considered safer - less hazardous - but that doesn't explain why the manufacturers bother.

 

[JohnW2]

Ah. That's interesting. Why do they bother to make Class II items? As I understand it, it is considered safer - less hazardous - but that doesn't explain why the manufacturers bother.

Yes, interesting questions, and it leads me to another interesting question which I've often asked, but never really got an answer to ...

... I would think that the great majority of Class II (and Class II marked) items I posses have no external touchable metal parts so, whatever else, they couldn't really be Class I. However, that question I keep asking, if it can't be Class I (no external metal to earth) and does not have 'double or reinforced insulation' (hence can't be Class II), then what is it? .... 'not allowed', or what?

Kind Regards, John

 

[SimonH2]

... one finds it hard to believe that a flimsy plastic layer (which represents the only 'protection against electric shock') really qualifies as "reinforced insulation" (a definition of which I've never seen), and everything else about it seems fine, to earth exposed metal parts is no different from what you would do if the manufactured had not made the 'Class II claim' about which one is not convinced.

I put a couple of pendant fittings (chromed rose and lampholder, fancy cable) up for a friend - supposedly Class II. However the MIs instructions said to use a chock block for the connections and "wrap it with a few layers of insulating tape". Lets just say that I was a bit dubious about the idea of a few layers of tape round a chock block being properly Class II.

 

[EFLImpudence]

... I would think that the great majority of Class II (and Class II marked) items I posses have no external touchable metal parts so, whatever else, they couldn't really be Class I. However, that question I keep asking, if it can't be Class I (no external metal to earth) and does not have 'double or reinforced insulation' (hence can't be Class II), then what is it? .... 'not allowed', or what?

I suspect 'what'.

I still don't know the answer. Think plastic light switch etc.; it is just impossible for it to become live.

I have just looked at the definition of Class II and contrary to what you keep quoting, it does not mention 'reinforced' insulation (where did that come from?), merely 'precautions such as supplementary insulation' and 'there being no provision for the connection of exposed metalwork of the equipment to a [C]PC and no reliance upon precautions to be taken in the fixed wiring. (See BS EN 61140)'.

 

[JohnW2]

I suspect 'what'. ... I still don't know the answer.

As I said, nor do I - which is why I keep asking the question. However, it's really a pretty important question - since there are many products which can't be Class I (not exposed metal to earth) and don't claim to be Class II - in essence, any plastic-enclosed item which does not bear a Class II marking.

Think plastic light switch etc.; it is just impossible for it to become live.

We've discussed that one before. If anything qualifies as "reinforced insulation" (see below), the very 'difficult to work with' urea-formaldehyde resin they use for standard white accessories surely must qualify - so, as we've discussed before, the real question is why it doesn't bear a 'Class II' marking - because I'm sure it would qualify.

As for "....just impossible for it to become live", we're talking about protection from electric shock in general, not just the possibility of the outer casing of something 'becoming live' (which is obviously impossible if it's not a conductor). If, for just a moment, we forget about regulations, definitions and Class I/Class II, and instead talk 'common sense', I hope we could agree that an item in a very flimsy/brittle plastic case (no touchable metal) that one could "push one's finger through" (and then touch live parts), with no claim of Class II, would not be acceptable, and hence hopefully would fall foul of some rules/regulations.

I have just looked at the definition of Class II and contrary to what you keep quoting, it does not mention 'reinforced' insulation (where did that come from?), merely 'precautions such as supplementary insulation' and 'there being no provision for the connection of exposed metalwork of the equipment to a [C]PC and no reliance upon precautions to be taken in the fixed wiring. (See BS EN 61140)'.

The definition in Part II does, indeed, say that, and it seems very odd. If 'supplementary insulation' means something separate from, and additional to, the 'basic insulation', then a high proportion of items out there which are marked as Class II would not actually qualify by that definition - since, these days, they almost always rely on a single layer of (presumably) "re-inforced" insulation - not a second layer of insulation ('supplementary' to the basic insulation)! AS for ...

... it does not mention 'reinforced' insulation (where did that come from?) ...

... the short answer is that it 'comes from' BS7671 . Although, as you say, the definition in Part 2 of BS7671 does not mention it, the entirety of section 412 is about protection from electric shock by "DOUBLE OR REINFORCED INSULATION".

Kind Regards, John

 

[Furthy34]

Guys
Being a novice, can you explain why I have 4 red and 4 black and 4 earth wires in this ceiling rose instead of the expected 3? There is only one light here but it can be operated by 2 switches. I thought that normally the two switches would be connected so I am wondering if in this case the light is directly connected to both switches, but this is just a novice's guess!

 

[John D v2.0]

can you explain why I have 4 red and 4 black and 4 earth wires in this ceiling rose instead of the expected 3?

Could be the circuit branches off at that point and feeds two downstream lights.

 

[Furthy34]

Could be the circuit branches off at that point and feeds two downstream lights.

Ah ok, thanks very much. Either way I have copied the wiring shown in the photo for my new light fitting and everything is working so hopefully all will be ok.

 

[jg321]

Ah ok, thanks very much. Either way I have copied the wiring shown in the photo for my new light fitting and everything is working so hopefully all will be ok.

Yep - my landing light is the same. At least it was until the top of some old, reused metal conduit cut into the cables running into it. A quick trip into the loft turned into some strategic rewiring given that I don't want to take any plaster off on the landing just yet!

I've only been in the house 18 months and that's twice that a "quick trip into the loft" has resulted in an afternoon of rewiring.