Class I or Class II ?

[JohnW2]

In another thread, someone who should not need telling is being told about the difference between Class I and Class II appliances - and what he has been told what one would expect.

However, there seems to be a group of items which do not actually fall into either of these categories (or any other IEC Class). The IEC definition of Class II more-or-less demands double insulation, such that no single fault can leave live parts exposed, whilst Class I essentially requires an earthed conductive casing ....

So what about something containing live parts which is 'single insulated' but without a conductive casing? (e.g. many/most domestic accessories {which I assume qualify as 'equipment'} would presumably fall into this category) In this situation, breakage of the (single) insulating cover/case would leave live parts exposed - so it does not qualify as Class II, but there is nothing to earth, so it can't sensibly be called Class I, either.

Kind Regards, John.

 

[Risteard]

Class II is not double insulation - it is double OR reinforced insulation.

 

[JohnW2]

Class II is not double insulation - it is double OR reinforced insulation.

I realise that, but I'm not clear what 'reinforced' means in that context (and I haven't got access to IEC 61140) - can anyone help? I imagine that most of us have seen accessories (e.g. ceiling roses, JBs, plate switches, even CUs etc.), if not also appliances, in which the insulated casing was clearly not 'reinforced' enough to prevent mechanical breakage, with a consequential exposure of live parts.

It actually seems that, in practice, people tend to think of something as Class II if it has an entirely insulated casing and Class I if there are any exposed-conductive-parts, without further reference to the actual definitions.

Kind Regards, John.

 

[EFLImpudence]

It actually seems that, in practice, people tend to think of something as Class II if it has an entirely insulated casing and Class I if there are any exposed-conductive-parts, without further reference to the actual definitions.

I agree with what you have written...

...but Class II equipment has exposed conductive parts which should/must not be earthed.

Equipment having entirely insulated casing is not Class II and, obviously, there are no parts which could be earthed.

I can't think of a classification for these items.

Surely, anything can be broken to expose live parts.

 

[JohnW2]

I agree with what you have written... but Class II equipment has exposed conductive parts which should/must not be earthed. Equipment having entirely insulated casing is not Class II and, obviously, there are no parts which could be earthed.

If that were all true, then things would be much simpler. However, there are surely countless examples of equipment which have entirely insulated casings and no exposed-conductive-parts which bear "Class II" markings/symbols, and which many/most people would regard as Class II?

I can't think of a classification for these items.

That was my point. Although often marked 'Class II', it's not clear (at least, not to me) how they actually do, or should, fit into the IEC classification

Surely, anything can be broken to expose live parts.

Of course, but I thought the idea (at least, of 'double insulation') was that of 'belt and braces' - i.e. if the outer insulating casing broke (one 'fault'), one would then be confronted by a second insulating barrier which would also have to be broken before live parts were exposed.

Kind Regards, John.

 

[ebee]

There is a class III too - sorry just thought I`d mention it - SELV.

We do tend to think about conductive being class I and non conductive + double (or reinforced) insulation as class II but there are some manufacturers who make conductive class II fittings too

 

[Grizzly]

Equipment having entirely insulated casing is not Class II and, obviously, there are no parts which could be earthed.

Are you absolutely sure about that?
Both Class I and II equipment/appliances can be entirely insulated...

 

[stillp]

I'm not clear what 'reinforced' means in that context (and I haven't got access to IEC 61140) - can anyone help? It actually seems that, in practice, people tend to think of something as Class II if it has an entirely insulated casing and Class I if there are any exposed-conductive-parts, without further reference to the actual definitions.

Seems like I'm needed here!

3.10.2
supplementary insulation
independent insulation applied in addition to basic insulation, for fault protection
[IEV 195-06-07]
3.10.3
double insulation
insulation comprising both basic insulation and supplementary insulation
[IEV 195-06-08]
3.10.4
reinforced insulation
insulation of hazardous-live-parts which provides a degree of protection against electric shock
equivalent to double insulation
NOTE Reinforced insulation may comprise several layers which cannot be tested singly as basic insulation or
supplementary insulation.
[IEV 195-06-09]

Does that help? I thought not. Remember 61140 is for use by product committees, who will set the requirements for how their products meet the objectives of 61140, or as the standard puts it:
"The requirements of this standard apply only if they are incorporated, or are referred to, in the relevant standards. It is not intended to be used as a stand-alone standard."

 

[wingcoax]

Further to this thread, What do you do when PA Testing a class 1 that has no exposed conductive parts when you need to connect your lead to earth?

 

[stillp]

Further to this thread, What do you do when PA Testing a class 1 that has no exposed conductive parts when you need to connect your lead to earth?

You don't need to, because you can't.

 

[wingcoax]

Exactly. You have to go against principles and test as class 2.

 

[JohnW2]

Seems like I'm needed here!

Yes, I was hoping you'd see the implicit call for your help! Many thanks.

<quotes snipped>Does that help? I thought not. Remember 61140 is for use by product committees, who will set the requirements for how their products meet the objectives of 61140, or as the standard puts it: "The requirements of this standard apply only if they are incorporated, or are referred to, in the relevant standards. It is not intended to be used as a stand-alone standard."

I see! OK, in that case what about BS 2754?

Kind Regards, John.

 

[JohnW2]

There is a class III too - sorry just thought I`d mention it - SELV.

Indeed, and a Class 0 - although sale of that was banned in the UK a few decades ago.

We do tend to think about conductive being class I and non conductive + double (or reinforced) insulation as class II but there are some manufacturers who make conductive class II fittings too

Indeed, but it is the opposite which interests me more. What about the equipment which has 'single insulation' in the form of a casing which is totally non-conductive, but such that no-one could seriously describe it as 're-inforced'. I suspect that most of us would think of it as Class II, but it would actually seem that, safety-wise, it would not qualify as either Class I or Class II. Are such items 'banned'??

Kind Regards, John.

 

[stillp]

Indeed, but it is the opposite which interests me more. What about the equipment which has 'single insulation' in the form of a casing which is totally non-conductive, but such that no-one could seriously describe it as 're-inforced'. I suspect that most of us would think of it as Class II, but it would actually seem that, safety-wise, it would not qualify as either Class I or Class II. Are such items 'banned'??

Kind Regards, John.

If they fail to meet the requirements of the Low Voltage Directive then they are illegal. How they meet those requirements is up to the manufacturer.

 

[EFLImpudence]

Equipment having entirely insulated casing is not Class II and, obviously, there are no parts which could be earthed.

Are you absolutely sure about that?

Not entirely, hence the discussion.

By 'entirely insulated casing' I meant all plastic (as in the OP) - not just insulated from the wiring.

Unless you mean something else -

Definitions state -
Class II - additional safety precautions provided...there being no provision for the connection of exposed metalwork of the equipment to a protective conductor...and no reliance on the fixed wiring.

Class I - More or less the opposite.

Both Class I and II equipment/appliances can be entirely insulated...

A plastic item which had additional safety precautions (double insulation) may be called class II but I don't think it really is.

How can an all plastic item be Class I if there is nothing to which a cpc can be connected?