Class I or Class II ?

[Grizzly]

If you mean the 'square in square', mine doesn't but a very small wall wart camera charger does.

So your laptop charger probably has an IEC C14 or C6 inlet (or some other comparable connector)?
So it probably uses the earth for functional purposes.
Which is why it can't be classified as Class II.

The camera wallwart charger maybe has an ISOD (Insulated Shutter Opening Device - aka a plastic earth pin), and if so, is quite clear that the Class II mark is correct (although not all have plastic earth pins).

 

[EFLImpudence]

So your laptop charger probably has an IEC C14 or C6 inlet (or some other comparable connector)?
So it probably uses the earth for functional purposes.
Which is why it can't be classified as Class II.

It does, but that doesn't make it Class I, so what class is it?

The camera wallwart charger maybe has an ISOD (Insulated Shutter Opening Device - aka a plastic earth pin), and if so, is quite clear that the Class II mark is correct (although not all have plastic earth pins).

It may contain Class II insulation but it is not really necessary, is it.

If a normal plug had a metal casing it would have to be earthed and so Class I or constructed to make it Class II, but a normal plastic plug is not Class II.

 

[JohnW2]

If the item of equipment has no exposed conductive parts it does not come under the definition of class II equipment.

I reckon it does. Certainly for appliances. Anyone got a copy of BS 2754, so that can be checked?

As I've said, I agree that Class II classification does not require there to be any exposed conductive parts. The definition of Class II in BS 7671, which cites BS EN 61140, certainly does not require exposed-c-ps.

In fact, having thought about it, doesn't the presence of exposed-conductive-parts (as defined in BS7671) automatically make an item Class I? There may, of course, be 'irrelevant isolated metal' stuck to the outside of a Class II item, but if the metal "can become live under fault conditions" (the definition of an exposed-conductive-part), it surely must be connected so something within the item - hence Class I??

Kind Regards, John.

 

[JohnW2]

I seem to be coming at this from an appliance-based viewpoint, whereas you from accessory-based.

No, I'm coming from the viewpoint of BS7671, which defines Class II in relation to items of 'electrical equipment' - which, in turn, it defines as including accessories. I gave examples of accessories since they were the ones which first came to mind.

There are many items that I've experienced that are fully metal encased, but are still Class II (Yamaha graphic equalizers, for one).

Indeed they are (provided that the metal is not connected to anything), but that doesn't alter any of my arguments.

Kindest Regards, John.

 

[JohnW2]

As above, I don't see that the definition of Class II requires there to be any exposed-c-ps.

True, it doesn't require it, but it does include it.

As I've just written, I don't think that's true. Sure, a Class II item can have (isolated) metal stuck on the outside, but if it is an exposed-conductive-part (as defined in BS7671), then I think it automatically becomes Class I,doesn't it?

I'm currently sitting looking at a laptop PSU (with a Class II marking) which definitely has no exposed-c-ps.

The connector that plugs into the laptop?

It's actually a very old one, which doesn't have a connector (just a wire-in power cable) - but that doesn't alter my point. I was reinforcing the point that Class II does not require any exposed-conductive-parts to be present.

Kind Regards, John.

 

[JohnW2]

one would not really want it to be acceptable to have something with no exposed-c-ps but with some very flimsy single layer of plastic being the only thing preventing live parts being touched, would one?

But that is what we are discussing. The purpose of class II insulation is to prevent shock from the exterior of the item. I don't think it covers breakage and exposure of the live parts inside.

Eh? The fact that, if not 'double', the insulation of a Class II item has to be 'reinforced' surely means that we are talking about potential "breakage and exposure of the live parts inside"??

Kind Regards, John.

 

[JohnW2]

Yes, but I think you are sort of missing the fundamental point. Your GE definitely is Class II but if the casing were plastic or wood it would not need the protection of the class II insulation ....

Eh? If the casing were plastic or wood, that plastic or wood would (or could) surely be the 'Class II insulation".

As I understand it, to be 'legal' an LV item has to be either Class I or Class II (there are no other options) - which was the reason for my initial question, since some things don't appear to fulfill the requirements for either. If the wood/plastic casing you hypothesise were for some reason inadequate as 'Class II insulation' (hence the item not Class II), what would you say it was - surely not Class I?

Kind Regards, John.

 

[JohnW2]

So your laptop charger probably has an IEC C14 or C6 inlet (or some other comparable connector)? So it probably uses the earth for functional purposes. Which is why it can't be classified as Class II.

So what are you saying it is - surely not Class I?

The camera wallwart charger maybe has an ISOD (Insulated Shutter Opening Device - aka a plastic earth pin), and if so, is quite clear that the Class II mark is correct (although not all have plastic earth pins).

You seem to be assuming that the fact that a connection to CPCs does not enter an item automatically makes it Class II - which is surely not necessarily correct?

Kind Regards, John.

 

[EFLImpudence]

As I've said, I agree that Class II classification does not require there to be any exposed conductive parts. The definition of Class II in BS 7671, which cites BS EN 61140, certainly does not require exposed-c-ps.

Although fundamental, we will have to agree to disagree on this.

In fact, having thought about it, doesn't the presence of exposed-conductive-parts (as defined in BS7671) automatically make an item Class I?

NO. that's the whole point of Class II - metal exposed parts which are NOT connected to a cpc.
I don't understand how you can say that after all the discussion.

There may, of course, be 'irrelevant isolated metal' stuck to the outside of a Class II item, but if the metal "can become live under fault conditions" (the definition of an exposed-conductive-part), it surely must be connected so something within the item - hence Class I??

I have a class II metal drill (and other tools) which does not have a cpc in the cable.
Even a plastic cased drill will have a metal chuck sticking out of it.

 

[EFLImpudence]

Eh? The fact that, if not 'double', the insulation of a Class II item has to be 'reinforced' surely means that we are talking about potential "breakage and exposure of the live parts inside"??

Again, I don't understand how you can say that.

Nothing can prevent exposure of live parts by breakage - be it Class I, Class II or even enclosed in resin.

TVs (CRTs), for example, have a quite flimsy back on them which may be broken and expose some very high voltage parts.

 

[JohnW2]

As I've said, I agree that Class II classification does not require there to be any exposed conductive parts. The definition of Class II in BS 7671, which cites BS EN 61140, certainly does not require exposed-c-ps.

Although fundamental, we will have to agree to disagree on this.

I don't think we can 'agree to disagree'. As you say, it's so fundamental that we need to reach resolution!

In fact, having thought about it, doesn't the presence of exposed-conductive-parts (as defined in BS7671) automatically make an item Class I?

NO. that's the whole point of Class II - metal exposed parts which are NOT connected to a cpc. I don't understand how you can say that after all the discussion.

Are you not confusing "metal exposed parts" with "exposed-conductive-parts" (as defined in regs). If the metal is not connected to anything within the item, then it can't 'become live under fault conditions', and therefore does not qualify as an exposed-conductive-part.

I have a class II metal drill (and other tools) which does not have a cpc in the cable.

Well, if it's Class II, it obviously does not need a CPC. However, as above, although it is metal-cased, I don't think it could be Class II if that metal was in electrical continuity with any part of the 'electrical' part of the contents (e.g. motor parts) - i.e. if it were an 'exposed-conductive-part'.

Even a plastic cased drill will have a metal chuck sticking out of it.

Maybe I'm wrong, but it had always been my understanding that the chuck of a Class II drill had to be electrically isolated from 'the works' (i.e. motor) by means of non-metallic gears or shafts. Otherwise, a single fault between armature winding and shaft would result in the chuck (and probably also the casing, if metal) becoming live.

Kind Regards, John.

 

[JohnW2]

Eh? The fact that, if not 'double', the insulation of a Class II item has to be 'reinforced' surely means that we are talking about potential "breakage and exposure of the live parts inside"??

Again, I don't understand how you can say that. Nothing can prevent exposure of live parts by breakage - be it Class I, Class II or even enclosed in resin.

There is obviously a limit to how much trauma anything can be subjected to without breaking and exposing live parts but my understanding is that the requirements for Class II seek to ensure that substantial trauma is required for that to happen.

Otherwise, why do you think there exists the requirement that if the insulation is not 'double', it has to be 'reinforced'?

Kind Regards, John.

 

[JohnW2]

TVs (CRTs), for example, have a quite flimsy back on them which may be broken and expose some very high voltage parts.

You're giving away your age These days, I think you'd be lucky to find much above 12V, other than the 230V AC in the PSU!

Kind Regards, John.

 

[securespark]

Surely CRT's have still got high voltages present?

 

[JohnW2]

Surely CRT's have still got high voltages present?

Of course, but not many surviving TVs (and certainly no TV you're likely to be able to buy today) have CRTs

Kind Regards, John.