Garage light -no earth

[iburnell]

Bulkhead light on garage fitted by Electrician years ago has died. I have purchased a replacement and it has no earth - instructions: Class II double insulated, earth is not required

If the existing feed cable has an earth what should I do with it?. Is it enough to simply cut the exposed copper and leave inside the unit?

 

[EFLImpudence]

Put a connector block on the end and position safely out of the way ensuring it does not touch anything.

 

[iburnell]

Thanks. Just had a look at the old light and the earth on that is attached with a small washer to a metal reflector plate. I could use that washer to go over the screw attaching it to the wall and put the earth round that ?

..or as you say you a plastic connector block?

 

[EFLImpudence]

No, you must isolate it - make it so that it doesn't touch anything.

 

[ban-all-sheds]

But don't cut it off - the next light to go there might need it.

 

[DetlefSchmitz]

Or any electrician running standard required tests.

 

[iburnell]

Thanks for advice - very much appreciated. All wired up and working nicely. Put earth into connector out of the way

 

[JohnW2]

No, you must isolate it - make it so that it doesn't touch anything.

The OP's question has been answered correctly and he has completed the job accordingly, so I see no harm in moving to a more general question, which I think we have touched on in the past....

Despite what manufacturer's of Class II equipment often say, and despite the fact that it is 'not needed', is there actually any logical or theoretical reason why one should not earth any conductive parts (including exposed ones) in a Class II piece of equipment (other than the general undesirability of 'unnecessarily' creating any exposed earthed metal, anywhere)?

Particularly when there is an outer metal casing, it could be argued that a combination of "Class II" manufacture and an outer earthed casing would theoretically provide an even greater degree of 'protection'.

Class II is obviously not foolproof. Just a few days ago, I experienced the "double or reinforced insulation" of a wallwart fall apart in-service, leaving live parts exposed.

Kind Regards, John

 

[Adam_151]

I would expect that in 95% of cases, you'd be right john, earthing an externally accessible part which was protected by double insulation, would probably not increase risk in those cases, and would protect against failure of the double insulation (why may be applied in a poor manner and prone to failure)

The problem is that you are taking a piece of CE marked equipment and modifying it from its original design, I see you have two issues:

i) You have to be able to demostrate that your modification was safe AND
ii) If you are modifying it then you are suspecting that the safety precutions adopted by the manufacturer were inadequate (that might well be the case) but should you be installing something that you believe the CE mark to be incorrectly applied to

Now I said in 95% of cases, I think their are exceptions.... I would put a toaster in this category (extra points given working out the the reasoning for that one)

 

[JohnW2]

I would expect that in 95% of cases, you'd be right john, earthing an externally accessible part which was protected by double insulation, would probably not increase risk in those cases, and would protect against failure of the double insulation (why may be applied in a poor manner and prone to failure)

Indeed - that is obviously my thinking.

The problem is that you are taking a piece of CE marked equipment and modifying it from its original design, I see you have two issues: .... i) You have to be able to demostrate that your modification was safe ....

If it were the case that deliberately earthing exposed conductive parts of a Class II item could render it unsafe, then the manufacturer would presumably have to try to 'prohibit' it coming into contact with anything earthed. Not only don't they do that but it would also be pretty impractical.

AND ... ii) If you are modifying it then you are suspecting that the safety precutions adopted by the manufacturer were inadequate (that might well be the case) but should you be installing something that you believe the CE mark to be incorrectly applied to...

True, up to a point. However, no "reinforced insulation" is totally foolproof, and some people are so cautious (or risk-averse) that they would like to add some braces to the belt of what they believed to be a properly designed Class II item.

Now I said in 95% of cases, I think their are exceptions.... I would put a toaster in this category (extra points given working out the the reasoning for that one)

I'm not sure that I've ever seen a Class II toaster. Every toaster I've seen has allowed a large metal object to be inserted into the 'bread hole' and come into contact with the live element. I'd be interest to hear what other sorts of items you might consider to make up that '5%' of exceptions.

I have a more general uncertainty, which I have often voiced, since there seem to be a lot of items of electrical equipment which are in a 'middle ground'. Do you believe that items which have no outer metal casing (and which therefore can't be Class I) are 'not allowed' unless they are designed, manufactured and marked as Class II? I'm sure that there are countless products out there which have no metal casing but which do not bear any Class II marking - virtually all plastic electrical accessories, for a start.

Kind Regards, John

 

[John D v2.0]

is there actually any logical or theoretical reason why one should not earth any conductive parts

This sounds like the old classic debate for this forum. IE choose which of two incredibly unlikely situations is more likely.
So my example would be what happens if you're up a ladder holding the casing with one hand, and the other hand touches live conductor from a fault nearby. RCD trips, but has the good path from live to earth killed you in the mean time?

 

[JohnW2]

This sounds like the old classic debate for this forum. IE choose which of two incredibly unlikely situations is more likely. So my example would be what happens if you're up a ladder holding the casing with one hand, and the other hand touches live conductor from a fault nearby. RCD trips, but has the good path from live to earth killed you in the mean time?

Yes, but that's the general argument (which I have already acknowledged) against having any 'unnecessarily earthed metal' in one's house (whether related to the electrical installation or not), and has nothing to do with whether or not what is 'inside' that earthed metal is Class II or not.

From the point of view you mentioned, it could well be that serious electric shocks would be less likely if one did not earth the exposed metal parts of a Class I light fitting. It's similar to my belief that there will, sooner or later, be electric shocks (fatal or otherwise) as a direct result of the move to CUs which have large earthed metal cases.

Other than that general issue about 'unnecessarily earthed exposed metal' (which could relate to plumbing or metal window frames or baths just as much as 'electrics'), I really do not see how putting a Class II item inside an earthed metal enclosure makes that item any less safe.

Kind Regards, John

 

[EFLImpudence]

Sorry for late reply but my internet has been down for a week.

JohnW2 - You seem to be playing Devil's advocate, as usual - or ...

You have agreed in the past that it would be better if NO metal anywhere (exposed, in our sense, and/or otherwise) needed earthing - yet when an item is manufactured to a standard and method which is deemed 'better' (Class 2 rather than earthing exposed-c-ps) and avoids the necessity you ask why one should not earth the exposed-c-ps anyway and would it be detrimental.
Well, in the accepted reasoning, yes it would be detrimental for the converse reasons to why the item was made to Class 2 standards in the first place.
It makes no difference to the item either way but it is considered safer for people NOT to have earthed metal parts if it can be avoided.

You can quote a blue moon occurrence for any problem where doing the opposite would have lessened the hazard but that does not mean it was wrong as it was.

You may as well say it is not worth making Class 2 items because you want to earth the exposed-c-ps regardless.

 

[EFLImpudence]

I have just found this reply from you to someone who wants to earth metal unnecessarily in another thread -

"The point that often gets missed is that to follow your approach and create lots of unnecessarily earthed metal will increase the risk of electric shock in the event of some types of fault. Yes, it facilitates operation of an RCD if that occurs, but without the earthed metal an appreciable shock would not, in that situation, occur in the first place - and I would personally prefer not to have a shock than to have a shock which an RCD might prevent killing me."

 

[JohnW2]

Sorry for late reply but my internet has been down for a week.

Sorry to hear that. I did wonder, but thought it probable that you had 'gone somewhere' for the festive season. Anyway, I hope you have a happy, heathy and successful 2018!

JohnW2 - You seem to be playing Devil's advocate, as usual - or ... You have agreed in the past that it would be better if NO metal anywhere (exposed, in our sense, and/or otherwise) needed earthing ...

Indeed, and two-thirds of my most recent post was re-iterating that point. Edit .... and in that other recent quote from me which you posted whilst I was writing this!

.... - yet when an item is manufactured to a standard and method which is deemed 'better' (Class 2 rather than earthing exposed-c-ps) and avoids the necessity you ask why one should not earth the exposed-c-ps anyway and would it be detrimental.

Not quite - or, at least, that's not quite what I meant. I was questioning why manufacturers of Class II items should say that one "must not" earth any exposed-c-ps it might have, seemingly implying that to so do would in some way have a detrimental effect on the safety of the item concerned.

I suppose you could argue that they were just being 'public spirited' and were really trying to say "Please do not unnecessarily earth any exposed metal in your home", but I really don't think that is the implication of what they usually write. As I wrote before, that 'plea' would be just as applicable to a metal window frame or floating metal bath as it is to a piece of Class II electrical equipment, yet their warning/instruction usually seems to imply a specific problem associated with earthing their product.

More generally, I would be interested to hear thoughts about what I recently wrote/asked, namely ...

I have a more general uncertainty, which I have often voiced, since there seem to be a lot of items of electrical equipment which are in a 'middle ground'. Do you believe that items which have no outer metal casing (and which therefore can't be Class I) are 'not allowed' unless they are designed, manufactured and marked as Class II? I'm sure that there are countless products out there which have no metal casing but which do not bear any Class II marking - virtually all plastic electrical accessories, for a start.

Any answers/thoughts?

Kind Regards, John