Garage light -no earth

[EFLImpudence]

HNY to you too - and everyone.

I don't think there's anything dubious about "must not be earthed"; it just means that it should not be earthed and therefore people are told it "must not be earthed". Instructions never say "please" anything.

As for plastic appliances, I am not sure of any 'Class' classification. I suppose it does not apply as there is nothing to earth.
That's probably why things like plastic light switches are not actually Class 2.
I suppose a Class 2 item is specifically a metal item that does not require earthing.

 

[JohnW2]

I don't think there's anything dubious about "must not be earthed"; it just means that it should not be earthed and therefore people are told it "must not be earthed". Instructions never say "please" anything.

Sure, but I just included the word 'please' to emphasise my point. It is the "must not be earthed" instruction which I am questioning - which, at least to me, implies some potential hazard more specific than would exist if I ('unnecessarily') earthed any other exposed metal. After all, metal baths and window frames do not come with an instruction that they "must not be earthed" (on the contrary, the last one I saw the bottom of actually had an 'earthing point' attached).

As for plastic appliances, I am not sure of any 'Class' classification. I suppose it does not apply as there is nothing to earth. That's probably why things like plastic light switches are not actually Class 2.

Well, that's my question. The regs seem to say/suggest/imply that protection against electric shock must be provided EITH by an earthed metal casing OR by double/reinforced insulation - with no obvious third option that would be applicable to things which had no exposed metal to be earthed, yet were not constructed with double or reinforced insulation.

I suppose a Class 2 item is specifically a metal item that does not require earthing.

That can't be true. I have umpteen Class II items in my house (bearing the appropriate marking), very few of which have any exposed metal at all.

Kind Regards, John

 

[winston1]

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.

It is because, as I have said before, manufacturers instructions are not infrequently wrong.

 

[EFLImpudence]

Sure, but I just included the word 'please' to emphasise my point. It is the "must not be earthed" instruction which I am questioning - which, at least to me, implies some potential hazard more specific than would exist if I ('unnecessarily') earthed any other exposed metal. After all, metal baths and window frames do not come with an instruction that they "must not be earthed" (on the contrary, the last one I saw the bottom of actually had an 'earthing point' attached).

It is because they must not be earthed. That would introduce a hazard unnecessarily because I think people would assume that they should be earthed.
People would not assume window frqames should be earthed and baths (although not earthing) may require bonding.

Well, that's my question. The regs seem to say/suggest/imply that protection against electric shock must be provided EITH by an earthed metal casing OR by double/reinforced insulation - with no obvious third option that would be applicable to things which had no exposed metal to be earthed, yet were not constructed with double or reinforced insulation.

I suppose things that are not possible are not considered - although the wonderful OSG does stupidly say "plastic pipes do not require bonding".
It would be silly to say that something plastic does require earthing.

That can't be true. I have umpteen Class II items in my house (bearing the appropriate marking), very few of which have any exposed metal at all.

Oh, fair enough.
Could they possibly be the same items which sometimes do have a metal case?

 

[JohnW2]

It is because they must not be earthed.

That "must not" is, in my opinion, really too strong. There is no more "must not" about it than in relation to any other bit of metal in a house.

It would be silly to say that something plastic does require earthing.

I am obviously not suggesting that one should earth plastic things. What I am saying is that the regs appear to indicate that people must be protected against electric shock EITHER by a earthed metal enclosure OR by double/reinforced insulation, with no third option offered.

Oh, fair enough. Could they possibly be the same items which sometimes do have a metal case?

How often have you seen a wallwart or laptop charger or an 'electronic transformer'/driver for lighting or a rechargeable battery charger or a toothbrush charger or etc., etc., etc which had a metal case?

Kind Regards, John

 

[EFLImpudence]

That "must not" is, in my opinion, really too strong. There is no more "must not" about it than in relation to any other bit of metal in a house.

Yes there is. It would be more hazardous if it were earthed.

I am obviously not suggesting that one should earth plastic things. What I am saying is that the regs appear to indicate that people must be protected against electric shock EITHER by a earthed metal enclosure OR by double/reinforced insulation, with no third option offered.

What is the third option?

How often have you seen a wallwart or laptop charger or an 'electronic transformer'/driver for lighting or a rechargeable battery charger or a toothbrush charger or etc., etc., etc which had a metal case?

I was only thinking of which appliances they might have been.

All I can say, then, is that they are Class 2 because they have double or reinforced insulation.
I am losing track of what it is you want.
Do you want these wall-warts to have a piece of metal on the outside so you can argue about why it must not be earthed?

 

[JohnW2]

Yes there is. It would be more hazardous if it were earthed.

Indeed (in some scenarios) - but no more hazardous than an other metal object in the house that one unnecessarily earths (none of which, if 'non electrical', come with instructions that they "must not be earthed").

What is the third option?

As I said, none is offered - hence my question. And, to remind you, my question is "if an item of electrical equipment does not have a metal case (so that protection against electric shock cannot be provided by an earthed case) and also does not have double or reinforced insulation to provide such protection, is it actually 'allowed' (and, if so, how/why)?

I am losing track of what it is you want. Do you want these wall-warts to have a piece of metal on the outside so you can argue about why it must not be earthed?

Not at all. I merely want an answer to the question above.

It could well be that a lot of the things I'm talking about (like plastic electrical accessories) are made out of a material that would qualify as 'reinforced insulation', but I'm not sure that makes them 'allowed' if they don't bear the appropriate marking (which plastic electrical accessories don't).

Kind Regards, John

 

[EFLImpudence]

Indeed (in some scenarios) - but no more hazardous than an other metal object in the house that one unnecessarily earths (none of which, if 'non electrical', come with instructions that they "must not be earthed").

Well, that is not an argument. I do not unnecessarily earth metal objects.

No non-electrical items come with instruction on where to connect the line and neutral either - why would they?

my question is "if an item of electrical equipment does not have a metal case (so that protection against electric shock cannot be provided by an earthed case) and also does not have double or reinforced insulation to provide such protection, is it actually 'allowed' (and, if so, how/why)?

Plastic ight switch. BC or ES lamp holders.

Not at all. I merely want an answer to the question above.

It would seem they are alloweed.

It could well be that a lot of the things I'm talking about (like plastic electrical accessories) are made out of a material that would qualify as 'reinforced insulation', but I'm not sure that makes them 'allowed' if they don't bear the appropriate marking (which plastic electrical accessories don't).

They must be allowed because we all have them.

I don't know what else to say.

You want to earth things you shouldn't which say you must not, and
you complain about things which have nothing to earth and
the proverbial spoon which does not have a warning that it must not be earthed.

 

[JohnW2]

Well, that is not an argument. I do not unnecessarily earth metal objects. No non-electrical items come with instruction on where to connect the line and neutral either - why would they?

I am merely saying that earthing the exposed metal parts (if there are any) of an item of Class II electrical equipment is, as far as I can see, no more hazardous than earthing, say, an electrically-floating metal bath, so I think that the "must not earth" instruction in relation to the former is a bit OTT. Something like "preferably should not be earthed" would, in my opinion, be more reasonable.

Plastic ight switch. BC or ES lamp holders. ... It would seem they are alloweed. ... They must be allowed because we all have them. ...

They certainly exist, so presumably are allowed, but what I'm trying to learn iis what 'category' they come into, and how they are necessarily providing the required degree of protection against electric shock. On the face of it, the regs appear to be saying that such protection has to be provided by the item/equipment being either Class I or Class II - yet there seem to be a lot of things which are not (or may be not, and certainly are not marked as such) either. People (including myself) tend to think of things as being either Class I or Class II, but there seem to be an awful lot which are not (or, at least, are not marked as) either.

I don't know what else to say. .... You want to earth things you shouldn't which say you must not

No, I don't, and I wouldn't (unless it were, literally or practicably, 'unavoidable') - but if it were 'unavoidable' I would not lose any sleep or think that I had committed some major crime. I am merely questioning the appropriateness of an instruction that I MUST NOT earth it. If that really were a crucial prohibition, I would expect to also be told that I must not allow it to come into contact with anything earthed.

Kind Regards, John

 

[ban-all-sheds]

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.

That would be a curious thing to say, because there are no exposed-conductive-parts with Class II items.

 

[ban-all-sheds]

How often have you seen a wallwart or laptop charger or an 'electronic transformer'/driver for lighting or a rechargeable battery charger or a toothbrush charger or etc., etc., etc which had a metal case?

Once.

It stopped working when I accidentally earthed the body of the power transistor mounted on the outside of the enclosure which was doubling as a heat sink.

 

[JohnW2]

That would be a curious thing to say, because there are no exposed-conductive-parts with Class II items.

I'm not sure whether or not you are agreeing with me, nor exactly what you mean, because I don't see anything about the BS7671 definitions of a "Class II item" and "exposed-conductive-part" precludes the former having the latter - the definition of the former merely says that there is no "provision for connection of exposed metalwork of the equipment" to a CPC.

A Class II item with an outer metal covering therefore seems entirely possible, and I think we've all seen examples.

Kind Regards, John

 

[ban-all-sheds]

I thought that Class II meant that the exposed metal could not become live in the event of a fault, which is the definition of an exposed-conductive-part?

 

[JohnW2]

I thought that Class II meant that the exposed metal could not become live in the event of a fault, which is the definition of an exposed-conductive-part?

The BS7671 definition of Class II does not say that.

The double/reinforced insulation of a Class II item should, of course, normally prevent any 'outer' metal from becoming live, but nothing is infallible.

Kind Regards, John

 

[Adam_151]

I recall a 240v hammer drill that my father owned (branded under one of the big shed's ranges) that when it expired managaged to put 240v (or at least some fraction of) onto the metal parts of the chuck, dispite it being supposedly class 2.

However is the risk of the odd failure in this manner less of a risk than the old class 1 metal drills, that you might be using outside holding tightly onto the case, possibly on a TNCS earth, possibly with no RCD where a fault would put a voltage onto the that case you are holding for upto 0.4 seconds..... much longer if the earth happened to be broken/not connected (a possibility in portable tools slung into the shed, or not having the plug fitted properly [ insert public information film link ] )