Double insulated downlight with earth connection

[soozypoo]

I bought some bathroom downlights from screwfix a while ago, I already have old low voltage ones in that I did 12 yrs back and all the transformers have gone leaving Just 1 of my 6 lights working.
Anyway the ones I have are double insulated but on the spring clip fittings inside the plastic wiring box there is a connection for an earth.
Now It says in the instructions the light mustn't be earthed, so after researching a lot I'm still confused, sadly my dad (sparky) is no longer here to advise.
So what do I do with the cpc on the twin and earth, do I terminate it in the clip that's there, or just get a wago and connect each end of the earth on the chain into that and pop inside the fitting.
I've seen some electricians saying not to connect to the one provided on the light fitting. And some saying on other brands that don't have the earth terminal despite being double insulated that the manufacturer should have made an earth connector.
So do I just sleeve it and connect in a separate block to the one on the light or is it OK to put it in the fitting on the lamp considering its there already.
Fed up of keep going in the loft and not getting the job done lol

 

[EFLImpudence]

It looks like a terminal to simply 'park' an earth wire if there is one in the supply cable.

It doesn't connect to the cable which goes to the light.

The box looks like plastic; if so, there is nothing that can be earthed.

 

[JohnW2]

It looks like a terminal to simply 'park' an earth wire if there is one in the supply cable. It doesn't connect to the cable which goes to the light. The box looks like plastic; if so, there is nothing that can be earthed.

All agreed. However, despite the "...MUST not be earthed" (sometimes with the upper case word!) which appears in MIs for some Class II items, there's really no electrical reason why one should not earth any exposed metal parts of a 'double-insulated'/Class II item.

As you will undoubtedly respond, there is a theoretical 'risk' associated with introducing any additional touchable earthed metal into an environment, but that's no more true when one is talking about 'something electrical' than anything else -and we do not expect to see "this item MUST not be earthed" on taps, radiators, metal sinks, metal window frames etc.

Kind Regards, John

 

[EFLImpudence]

All agreed. However, despite the "...MUST not be earthed" (sometimes with the upper case word!) which appears in MIs for some Class II items, there's really no electrical reason why one should not earth any exposed metal parts of a 'double-insulated'/Class II item.

We've done this before.

Class II is considered safer than earthing exposed-c-ps and as you have frequently written that it would be better if parts that did not need earthing should not be earthed then your statement is somewhat contradictory.

In this case the Class II refers to the light and not the junction box which (I think) is plastic.

As you will undoubtedly respond, there is a theoretical 'risk' associated with introducing any additional touchable earthed metal into an environment,

I rest my case.

but that's no more true when one is talking about 'something electrical' than anything else -and we do not expect to see "this item MUST not be earthed" on taps, radiators, metal sinks, metal window frames etc.

Were there a Class II electric radiator (or cooker), no doubt it would state that.

The other items you mention are not electrical appliances. Would you expect every spoon etc. to carry such a label?

 

[JohnW2]

.Were there a Class II electric radiator (or cooker), no doubt it would state that. The other items you mention are not electrical appliances. Would you expect every spoon etc. to carry such a label?

That's mu point. If the "MUST not be earthed" were there simply because of the undesirability of having unnecessary earthed touchable metal, then such instructions would be just as valid in relation to non-electrical radiators/cookers or, as you've said, spoons (and sinks, window frames etc. etc.)

I think you are probably giving the authors of these MIs far too much credit for writing these things to minimisise the amount of unnecessarily earthed metal around. I personally think it's far more likely that they do not understand the rules/regulations and actually believe that earthing of exposed metal parts of Class II items is 'not allowed'.

If they do believe that, then they might have to be careful about calling things 'Class I', and requiring their touchable metal parts to be earthed - since if there happened to be "double or reinforced insulation" between that metal and live parts (qualifying the item as 'Class II'), they might be violating what they believe to be 'the rules'!

Kind Regards, John

 

[EFLImpudence]

That's mu point. If the "MUST not be earthed" were there simply because of the undesirability of having unnecessary earthed touchable metal, then such instructions would be just as valid in relation to non-electrical radiators/cookers or, as you've said, spoons (and sinks, window frames etc. etc.)

Ok, but it is much more likely that someone will wrongly connect a redundant CPC than run additional cables to each item of their cutlery.

I think you are probably giving the authors of these MIs far too much credit for writing these things to minimisise the amount of unnecessarily earthed metal around. I personally think it's far more likely that they do not understand the rules/regulations and actually believe that earthing of exposed metal parts of Class II items is 'not allowed'.

Ok, but the desired result is the same.

If you are thinking it is not "not allowed" - i.e. it is allowed - then why do you think it is allowed?
412.2.2.4

If they do believe that, then they might have to be careful about calling things 'Class I', and requiring their touchable metal parts to be earthed - since if there happened to be "double or reinforced insulation" between that metal and live parts (qualifying the item as 'Class II'), they might be violating what they believe to be 'the rules'!

Mistakes are frequently made.

 

[JohnW2]

If you are thinking it is not "not allowed" - i.e. it is allowed - then why do you think it is allowed? 412.2.2.4

Thanks. I must say that I don't recall having noticed that reg. However, I don't really understand why it's there, and there are some aspects which I don't seem to relate to 'exposed parts' and I really don't understand at all. In particular ...

If one accepts that a terminal is a "conductive part", then this would seem to preclude the ('safe') 'parking' of a CPC within a Class II item - so, if the item is part of the fixed installation (e.g. a light fitting) that seems to create a dilemma ('impossibility'?) in relation to the requirement for a CPC to be run 'to every point' in the installation, doesn't it (unless you can find some sort of 'non-conductive something' in which to park the CPC), doesn't it?

Kind Regards, John

 

[EFLImpudence]

I wouldn't think that 'a terminal' is considered a conductive part as such.

Doesn't the rest of the regulation explain and clarify it?

 

[JohnW2]

I wouldn't think that 'a terminal' is considered a conductive part as such.

What do you think it means other than 'a part' which is 'conductive'? BS7671 offers no definition.

Doesn't the rest of the regulation explain and clarify it?

Not really, because although it makes provision for a 'parking terminal' for a CPC, it does so only in relation to CPCs which 'run through the enclosure in order to serve other items of electrical equipment ..." - so would, for example, presumably not be applicable in relation to the example I mentioned. Is that not your understanding of it?

There is some potential confusion about terminology, since I'm far from convinced that touchable metal bits on the outside of a Class II item actually qualify as "exposed-c-ps", per BS7671 definition - are you? If one believes that such parts "can become live under fault conditions" that would seem to undermine the whole concept of Class II equipment, wouldn't it?

Kind Regards, John

 

[ericmark]

It looks like a terminal to simply 'park' an earth wire if there is one in the supply cable.

It doesn't connect to the cable which goes to the light.

The box looks like plastic; if so, there is nothing that can be earthed.

That's all that needs saying, connect the earth wire to where the sign can be seen, end of story.