Why not class 1?

[flyingsparks]

Definitely no plastic inside the cover john. Yes I hadn't thought about the single insulation layer over the connectors.

The metal enclosure encloses it, doesn't it? Have a look inside any ceiling rose - ooh single insulated conductors inside..

A PLASTIC enclosure yes. Metal ones would either have a plastic lining inside or be earthed.

TTC - care to comment on this?

 

[JohnW2]

Definitely no plastic inside the cover john. Yes I hadn't thought about the single insulation layer over the connectors.

Fair enough. As I said, if there are some live conductors which are separated from the metal only by a single layer of insulation, I can't really see how it can possibly qualify as Class II - but maybe I'm just stupid!

Kind Regards, John

 

[mfarrow]

The key ingredient being "...or reinforced insulation". It let's us "get away with" ceiling roses, plastic patresses, accessories, wiska boxes etc.

There's a very good IEC standard which lists and pictorially illustrates the different ways of complying with Class II requirements a I must admit I don't agree with all of them.

The single insulated cores in the OP appear to be cloth sheathed. Presumably this is OK but I doubt normal PVC would comply in the same way.

 

[JohnW2]

The key ingredient being "...or reinforced insulation". ... The single insulated cores in the OP appear to be cloth sheathed. Presumably this is OK but I doubt normal PVC would comply in the same way.

Do you really believe that? I certainly agree that normal PVC insulation could not be seriously described as 're-inforced', and I'm very sceptical about a cloth sheath achieving that (or counting as 'double insulated'), either - aren't you?

Nor do I really understand the motive for stretching 'what they can get away with'. I wouldn't have thought that the market for supplying light fittings for houses without CPCs in their lighting circuits was all that significant - so, for the sake of an earthing terminal, why not just make it Class I (and then not have to have a fancy connector)??

Kind Regards, John

 

[mfarrow]

The use of those cables in units wired by the public should be discouraged certainly. Whether professionally wired the cloth covered ones would be idiot/bullet proof enough I wouldn't like to say. There certainly isn't or doesn't need to be a great deal of insulation between the metal parts of say an electric drill.

Why go to class II indeed for these fittings... maybe it's a continental thing, or testing and ensuring the continuity costs more than different cable and a funny connector. Either way it's here to stay it seems.

 

[stem]

The instructions stated that the fitting was class 2, didn't need an earth and there was a label inside showing the double insulated symbol (Box within a box). Interestingly the fittings integral wiring was not double insulated and appeared to be 'figure of 8' type looking more akin to SELV applications such as that used for garden lighting or loudspeakers.

More than just 'interesting', it surely is not possible for it to really be 'Class II' if there was only a single ('basic') insulation between some conductors and the metal casing? Are we certain that there is not a plastic coating on the inside of the casing?

Kind Regards, John

Here is a link to the manufacturer's website for the light I installed. As you can see it's clearly stated as class 2 and the single insulated cable is just visible through the chain at the top. In reality the insulation is translucent and the conductors can be seen through it. The insulation is quite tough though, I know because I had to shorten the cable as the user wanted the chain shortening and there wasn't enough room to store the spare extra flex in the rose. But even this was difficult because the insulation was formed in one piece with an internal divider formed between the two cores, this meant that the cores could not be separated without one loosing its insulation, so I ended up having to sleeve it inside the terminal box.

 

[JohnW2]

[...As you can see it's clearly stated as class 2 and the single insulated cable is just visible through the chain at the top. In reality the insulation is translucent and the conductors can be seen through it. The insulation is quite tough though, I know because I had to shorten the cable ...

Fair enough. However, I still personally think it is stretching things a bit to say that 'tough' insulation qualifies as 'reinforced', and therefore is able to exist within a Class II item!

I still don't really understand the motive for 'stretching' the rules like that, just so as to enable it to be Class II.

Kind Regards, John

 

[Astra99]

From what I can see of the lamp, it looks very similar to the wall lights I bought in Spain. I do not recall seeing a Class Two identification on them; with metal casings I assumed they were Class One and connected accordingly!

 

[mfarrow]

I still personally think it is stretching things a bit to say that 'tough' insulation qualifies as 'reinforced', and therefore is able to exist within a Class II item!

What would be your definition of reinforced then John?

 

[JohnW2]

I still personally think it is stretching things a bit to say that 'tough' insulation qualifies as 'reinforced', and therefore is able to exist within a Class II item!

What would be your definition of reinforced then John?

I was, of course, talking specifically about a 'tough' single layer of insulation surrounding a single conductor.

I don't have a definition, and I'm not at all sure that there is one - there certainly isn't in BS7671, and I don't know if there is any relevant Standard which does. This, IMO, is one of the problems - if it is going to be permissible to classify an item as Class II because it has "reinforced insulation", there surely needs to be some official definition of it somewhere. I'm not saying that it would be easy to define, but it needs to be!

Thinking by analogy, AFAIAA an accessible live conductor with just a single layer of insulation would never be acceptable to BS7671, no matter how 'tough'(or thick) that single layer of insulation - so I'm inclined to feel that the same should probably apply within an unearthed metal enclosure (i.e. in a Class II item).

Kind Regards, John

 

[mfarrow]

Thinking by analogy, AFAIAA an accessible live conductor with just a single layer of insulation would never be acceptable to BS7671, no matter how 'tough'(or thick) that single layer of insulation

The thing is such arrangements already exist, including Christmas tree lights and just about any plastic box with live terminals moulded into it.

The general requirement for appliances (BS EN 60135) states reinforced insulation should provide at least equivalent as double insulation, though I'm more sure on the specific tests. I'll keep looking.

 

[JohnW2]

Thinking by analogy, AFAIAA an accessible live conductor with just a single layer of insulation would never be acceptable to BS7671, no matter how 'tough'(or thick) that single layer of insulation

The thing is such arrangements already exist, including Christmas tree lights and just about any plastic box with live terminals moulded into it.

I was thinking/talking specifically about the flexible insulation of flexible conductors. I agree that old-fashioned LV Christmas tree light wiring would usually have come into that category, but I don't know what regulations would have related to them, or whether they were necessarily compliant with those regs. I've certainly never seen a flexible cable, per se, sold, or marked, as 'double insulated', despite having only one layer of (flexible) insulation.

I accept that adequately 'reinforced' plastic (whatever the requirements for that may be) is acceptable as the only protection of bare live conductors in the "plastic boxes" situation. As you imply, that is a very common situation in Class II equipment these days - the original 'DI' concept of two physically independent insulation barriers now being much less common.

The general requirement for appliances (BS EN 60135) states reinforced insulation should provide at least equivalent as double insulation, though I'm more sure on the specific tests. I'll keep looking.

One imagines that would be very difficult to define, so I would be very interested to see the definition (or tests) if/when you find them. We are presumably talking primarily about the insulation's resistance to mechanical damage, and there are so many ways it which is could be damaged that I certainly would not want to be the person producing a definition or tests!

Kind Regards, John

 

[plugwash]

I was thinking/talking specifically about the flexible insulation of flexible conductors. I agree that old-fashioned LV Christmas tree light wiring would usually have come into that category,

IME modern LV christmas lights have pretty thick insulation. Often with two distinct layers.

Old ones OTOH often had insulation that was little more than bell wire. I'm not sure when the transition happened but i'm pretty sure it was over 15 years ago. Certainly any set i've personally bought new (i'm 30 and first bought christmas lights as a teenager) had the thick insulation but when I was growing up it was quite common to see the thin stuff.

but I don't know what regulations would have related to them, or whether they were necessarily compliant with those regs. I've certainly never seen a flexible cable, per se, sold, or marked, as 'double insulated', despite having only one layer of (flexible) insulation.

I've seen (and used) test lead wire that claims to meet the specs for double/reinforced insulation (and has the double insulated symbol printed on the insulatoin). Interestingly the PVC stuff seems to use two seperate layers of insulation (inner layer clear outer layer colouted) while the silicone stuff seems to just use a single layer. Maybe silicone is considered less vulnerable to damge than PVC.

 

[securespark]

In my time, I came across loads of pathetic fiddly light fittings.
Many had the increasingly common terminal box with sheath and others had very little space for wiring. It is impossible to attach more than one cable to most wall fittings and those with built-in pull cords are sometimes almost impossible to fit to the wall without fouling the pull cord mechanism.
It is no good making smart looking light fittings if they are a real pia to fit.
The lighting designers should be forced to DIY install their own fittings at home before getting the design signed off for manufacture.

 

[kai]

The big problem here, is that only the UK permits a rats nest at the ceiling rose, with the loop-in system - other countries have just Line Neutral and earth at the ceiling or wall light, with loop in at the junction box or switch.