Class I or Class II ?

[Grizzly]

A Class I IR test ties line & neutral together, then puts 500V dc between them and earth.
A Class II IR test ties line & neutral together, then puts 500V dc between them and a test probe.

If you had a completely insulated item, but one that an earth connection was supplied to (functional etc.), you can see why the CI IR would be more pertinent than the CII IR.

 

[JohnW2]

A Class I IR test ties line & neutral together, then puts 500V dc between them and earth.
A Class II IR test ties line & neutral together, then puts 500V dc between them and a test probe.
If you had a completely insulated item, but one that an earth connection was supplied to (functional etc.), you can see why the CI IR would be more pertinent than the CII IR.

Maybe, but it was you who introduced this additional 'complication' of the functional earth connection.

What if we go back to my original question about a completely insulated item with no functional earth ... I think that most of us are agreed that it isn't clear what Class this is. So, if on that basis, you decided to 'treat it as Class I' what, in practice, would that mean in terms of I&T? The 'Class I IR test' you describe above would not really make any sense in that situation.

Kind Regards, John.

 

[Grizzly]

What if we go back to my original question about a completely insulated item with no functional earth ... I think that most of us are agreed that it isn't clear what Class this is.

Well no, not really.
I'd think it's quite clear that if it didn't have any sort of earthing, and was completely insulated, it's clearly not Class I. So it's Class II.
There are a number of ways you can use to determine that no earth is provided, from identification of inlet connectors, supply cord type, etc.

Now, if the manufacturer hasn't marked it correctly (no double square symbol), or if you don't believe it really conforms to the requirements of Class II construction, that is something for the individual to pursue.

So, if on that basis, you decided to 'treat it as Class I' what, in practice, would that mean in terms of I&T? The 'Class I IR test' you describe above would not really make any sense in that situation.

I personally wouldn't decide to 'treat it as Class I', as it clearly isn't.
The Class I IR test would make no sense in that situation, agreed.

I'm getting a tad confused why there seems to be confusion that an obviously Class II item might not be Class II, unless the manufacturers information was not believed.

 

[JohnW2]

... it's clearly not Class I. So it's Class II.

That's where the issue arises. Class II is not defined as "not Class I" - there are specific requirements for it to be Class II. If it's "not Class I", it could be Class 0 or Class III (as well as class II), or it might not fulfill the definitions/requirements of any Class.

As per the earlier parts of this thread, the issue arises in relation to the (very common) single-insulated all-plastic items. They only qualify as Class II if the insulation is 'reinforced' to the extent that the 'reliability of protection' is at least as good as that which would be provided by double insulation.

Now, if the manufacturer hasn't marked it correctly (no double square symbol), or if you don't believe it really conforms to the requirements of Class II construction, that is something for the individual to pursue.

I think you may have misunderstood the purpose/nature of my initial question. I'm not suggesting that things are incorrectly marked - we are discussing what determines what is required for an item to be Class II, and to bear a Class II symbol.

Specifically, there are all-plastic items which have no earth and which bear no Class II marking - so are they simply 'illegal' (effectively, Class 0), or what?

Kind Regards, John.

 

[Grizzly]

That's where the issue arises. Class II is not defined as "not Class I" - there are specific requirements for it to be Class II. If it's "not Class I", it could be Class 0 or Class III (as well as class II), or it might not fulfill the definitions/requirements of any Class.

I'm sure that most of us are well aware of that.
I'm assuming it's taken as read that our notional piece of equipment is 230V ac powered, so not Class III (or one of the many not-quite-Class III ELV items of equipment that are around these days).
You're right, we could have Class 0, but as a starting point, I'd say we haggle down from Class II.

As per the earlier parts of this thread, the issue arises in relation to the (very common) single-insulated all-plastic items. They only qualify as Class II if the insulation is 'reinforced' to the extent that the 'reliability of protection' is at least as good as that which would be provided by double insulation.

All true.
I feel I must point out, that in certain double-insulated appliances, a layer of air is considered to be sufficient supplementary insulation, so any 'reinforced' insulation might not be as hardcore as you might think/hope.

Now, if the manufacturer hasn't marked it correctly (no double square symbol), or if you don't believe it really conforms to the requirements of Class II construction, that is something for the individual to pursue.

I think you may have misunderstood the purpose/nature of my initial question. I'm not suggesting that things are incorrectly marked - we are discussing what determines what is required for an item to be Class II, and to bear a Class II symbol.

BS 2754, I believe.

Specifically, there are all-plastic items which have no earth and which bear no Class II marking - so are they simply 'illegal' (effectively, Class 0), or what?

Well, we've got 2 options here:

1) The items has been constructed to conform with BS 2754 as Class II, incorporating reinforced insulation, but has not been marked as such by the manufacturer.
Shouldn't be on the market without the correct markings: 'Illegal'.

2) The item does not meet the requirements in BS 2754 for Class II construction, the manufacturer knows this, and has not used the Class II mark accordingly. A Class 0 situation, by the looks of it.
Shouldn't be on the market unless the method of installation provides an environment that will provide protection if the basic insulation fails. Who knows how that may be achieved? If the manufacturer is very specific about this then 'not illegal'? Not sure about that one.
Certainly 'illegal' if it's a plug-in appliance (in the commonly accepted sense).

 

[JohnW2]

Specifically, there are all-plastic items which have no earth and which bear no Class II marking - so are they simply 'illegal' (effectively, Class 0), or what?

Well, we've got 2 options here:
1) The items has been constructed to conform with BS 2754 as Class II, incorporating reinforced insulation, but has not been marked as such by the manufacturer. Shouldn't be on the market without the correct markings: 'Illegal'.
2) The item does not meet the requirements in BS 2754 for Class II construction, the manufacturer knows this, and has not used the Class II mark accordingly. A Class 0 situation, by the looks of it. Shouldn't be on the market unless the method of installation provides an environment that will provide protection if the basic insulation fails. .... Certainly 'illegal' if it's a plug-in appliance (in the commonly accepted sense).

That all sounds logical enough - so are you saying that any piece of equipment is 'illegal' unless EITHER (a) it is totally encased in earthed metal OR (b) it has no exposed-conductive-parts and meets the ('Class II') requirements in terms of 'double insulation' or 'reinforced insulation' and is marked as Class II?

Kind Regards, John.

 

[Grizzly]

That all sounds logical enough - so are you saying that any piece of equipment is 'illegal' unless EITHER (a) it is totally encased in earthed metal

...which is separated from live parts by basic insulation.
Note: not all the metal on a Class I appliance needs to be earthed

OR (b) it has no exposed-conductive-parts and meets the ('Class II') requirements in terms of 'double insulation' or 'reinforced insulation' and is marked as Class II?

OR (c) has exposed-conductive-parts, but these are separated from live parts by either 'double insulation' or 'reinforced insulation' and is marked as Class II.

I reckon that about covers it, for mains powered stuff.
('Illegal' specifically in quotation marks)

 

[JohnW2]

That all sounds logical enough - so are you saying that any piece of equipment is 'illegal' unless EITHER (a) it is totally encased in earthed metal

...which is separated from live parts by basic insulation. Note: not all the metal on a Class I appliance needs to be earthed

OR (b) it has no exposed-conductive-parts and meets the ('Class II') requirements in terms of 'double insulation' or 'reinforced insulation' and is marked as Class II?

OR (c) has exposed-conductive-parts, but these are separated from live parts by either 'double insulation' or 'reinforced insulation' and is marked as Class II.
I reckon that about covers it, for mains powered stuff. ('Illegal' specifically in quotation marks)

OK. I'm not going to quibble about the (c) you've added, since it seems to refer simply to 'irrelevant' bits of isolated metal stuck on the outside of a Class II item, but I don't really think that such bits of isolated metal would actually qualify as exposed-conductive-parts per BS7671 definition ('can become live under fault conditions') - so I reckon it's really the same as (b).

Anyway, according to that we appear to have four (and only four) possibilities for items of equipment - (a), (b), (c) and "illegal". Which of those four possibilites would you say applied to such items of equipment as JBs, ceiling roses, plastic CUs etc. etc.? None of those are encased in earthed metal and (regardless of any considerations of the nature of their insulation) none bear Class II markings (well, none that I have ever seen!) - which, per the above, would appear to make them all "illegal".

Kind Regards, John.

 

[EFLImpudence]

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

If it has no exposed conductive parts it does not require 'double insulation' or 'reinforced insulation' and to be marked as Class II?

Perhaps accessories should not be included in the definition of electrical equipment.

OR (c) has exposed-conductive-parts, but these are separated from live parts by either 'double insulation' or 'reinforced insulation' and is marked as Class II.

That is the definition of class II.

 

[JohnW2]

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

BS7671 does not appear to say that.

If it has no exposed conductive parts it does not require 'double insulation' or 'reinforced insulation' and to be marked as Class II?

It is being suggested that any equipment must either be fully encased in earthed metal OR satisfy the Class II requirements (and be marked accordingly). That actually would make some sense - 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?

Perhaps accessories should not be included in the definition of electrical equipment.

Perhaps (if not only to make this discussion easier), but BS7671 is very clear in explicitly including accessories.

OR (c) has exposed-conductive-parts, but these are separated from live parts by either 'double insulation' or 'reinforced insulation' and is marked as Class II.

That is the definition of class II.

As above, I don't see that the definition of Class II requires there to be any exposed-c-ps. I'm currently sitting looking at a laptop PSU (with a Class II marking) which definitely has no exposed-c-ps.

Kind Regards, John.

 

[Grizzly]

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?

 

[Grizzly]

OK. I'm not going to quibble about the (c) you've added, since it seems to refer simply to 'irrelevant' bits of isolated metal stuck on the outside of a Class II item, but I don't really think that such bits of isolated metal would actually qualify as exposed-conductive-parts per BS7671 definition ('can become live under fault conditions') - so I reckon it's really the same as (b).

I seem to be coming at this from an appliance-based viewpoint, whereas you from accessory-based.
There are many items that I've experienced that are fully metal encased, but are still Class II (Yamaha graphic equalizers, for one).

 

[Grizzly]

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.

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?

 

[EFLImpudence]

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.

As above, I don't see that the definition of Class II requires there to be any exposed-c-ps. I'm currently sitting looking at a laptop PSU (with a Class II marking) which definitely has no exposed-c-ps.

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

 

[EFLImpudence]

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

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 and so, in my view, would not be class II even if the manufacturer used the same parts as the metal cased ones.