Accidental Earthing of Class II Equipment

[EFLImpudence]

I'm getting to the stage where I hope you are being awkward.

I find it hard to believe that it is as simple as that. If they just meant 'an insulating material', they would surely just say so - they have surely added "reinforced" for a reason?

The definition only includes "supplementary insulation" - no thicker than the original, I presume.

How about 'chockboxes', particularly the opaque white (rather than transulcent) ones, which appear to be particularly brittle? I've just done this, just with my fingers (no tools) to one of them ...

Could you have received a shock before breaking it...
...and after breaking, would you have got a shock from the wires properly terminated in the connector block?

... do you really regard that as "reinforced insulation"?

It's you who keeps bringing up "reinforced". It was a second - supplementary layer.
I suppose if you don't bite your nails, you could even tear off normal insulation.

Indeed. I said nothing about it preventing contact with live conductors. I was saying that it afforded 'protection against electrical shock' - which is the same language that the regs use.

So would a plastic exterior.

Do you really mean that?

Yes. If one can't get a shock from something, Why does it have to be Class I or II?

'Basic protection' (e.g. the insulation of a 'single-insulated' cable) alone is not allowed, otherwise 'single-insulated' singles would be allowed. One has to have additional protection against electric shock, the two most common methods being double (or reinforced) insulation or an earthed metal barrier.

That additional layer only has to be the same as the first layer.
Or merely the carcass of a plastic consumer unit. Were they Class II?

The hazard only "does not exist" (is deemed not to exist) if there is something acceptable in addition to 'basic protection' (if, indeed, there is 'basic protection').

A second layer.

I really don't understand that.

You seem to prefer earthed metal covering to plastic, yet you don't seem keen on metal CUs.

I am merely asking whether, for example, the chockbox that I have just shattered with my fingers is or is not, per BS7671, adequate protection against electric shock if it contains live parts .

Had it contained wires and connectors, it was, two faults were needed before a shock became likely

(which may not even have 'basic protection')

Then it wouldn't have been double insulated, would it?

 

[JohnW2]

I'm getting to the stage where I hope you are being awkward.

Sorry, but I'm afraid that your hope is not fulfilled. I am genuinely trying to learn about something that I have never really understood.

The definition only includes "supplementary insulation" - no thicker than the original, I presume.

You're talking about the BS7671 definition of double insulation. An alternative to that is reinforced insulation, in which case there is no 'original insulation' - and the definition of reinforced insulation requires that it "provides a degree of protection against electric shock equivalent to double insulation". However, deciding what would be regarded as "similar protection against electric shock" is not obvious (and not defined).

Yes. If one can't get a shock from something, Why does it have to be Class I or II?

Maybe it doesn't - BS7671 does not talk in such terms - but a live part does need something in addition to 'basic protection' (otherwise 'SI singles' without conduit would be allowed), whatever language one uses.

You seem to prefer earthed metal covering to plastic, yet you don't seem keen on metal CUs.

Not at all. In all cases, I would prefer the primary protection to be provided by adequate insulation, and certainly to avoid touchable earthed metal wherever possible.. There is no electrical need to encase an adequately-insulated (e.g. 'Class II') item in metal - but I suppose there might sometimes be aesthetic or 'design' reasons for wanting to.

Had it contained wires and connectors, it was, two faults were needed before a shock became likely ... Then it wouldn't have been double insulated, would it?

It seems that you may be missing my point. IF it had reinforced insulation (and I don't know whether that, alone, is enough for it to be called 'Class II') it would be acceptable for it to contain totally unprotected live parts - i.e. not just acting as a 'second layer'. If (as you implied) you regarded my chockbox as qualifying as "reinforced insulation", then it ought to have not been possible for me to break the box and come into contact with (otherwise unprotected) live parts within (i.e. with only a single 'fault') - but I clearly could have done.

Kind Regards, John

 

[EFLImpudence]

You're talking about the BS7671 definition of double insulation. An alternative to that is reinforced insulation, in which case there is no 'original insulation' - and the definition of reinforced insulation requires that it "provides a degree of protection against electric shock equivalent to double insulation".

Yes, but I don't think you have quoted anything which had reinforced insulation.

However, deciding what would be regarded as "similar protection against electric shock" is not obvious (and not defined).

It says it must be equivalent to double insulation.

Maybe it doesn't - BS7671 does not talk in such terms - but a live part does need something in addition to 'basic protection' (otherwise 'SI singles' without conduit would be allowed), whatever language one uses.

...but tails have what is often said NOT to be double insulation yet they are allowed so it must be DI.

It seems that you may be missing my point. IF it had reinforced insulation (and I don't know whether that, alone, is enough for it to be called 'Class II') it would be acceptable for it to contain totally unprotected live parts - i.e. not just acting as a 'second layer'.

Not sure I underestand that but -
I think reinforced counts as Class II, I have never seen anything else in the way of markings.
I mentioned yesterday cable restraint but, these days, that applies to everything - not much point having complicated protection if the wires can just be pulled out.
As for totally unprotected live parts, I presume they must be enclosed in the reinforced insulation - i.e. the body of a drill.

If (as you implied) you regarded my chockbox as qualifying as "reinforced insulation",

I didn't mean to imply that. It could just be the second layer.

then it ought to have not been possible for me to break the box and come into contact with (otherwise unprotected) live parts within (i.e. with only a single 'fault') - but I clearly could have done.

That depends whether the box is reinforced or just the second layer.
Then that brings up how strong does it have to be - my point about finger nails.
You wouldn't be able to break a J501/801 like that. Perhaps it was just rubbish.

Either way, do you not consider the connector block as insulation?

 

[JohnW2]

Yes, but I don't think you have quoted anything which had reinforced insulation.

As I've said, unless it bears a Class II marking (and has only one layer) I don't know what does and doesn't qualify as "reinforced insulation". In post #14, you said/implied that "any plastic casing which is strong enough for its purpose" would probably qualify.

...but tails have what is often said NOT to be double insulation yet they are allowed so it must be DI.

Quite - as I've always said when there is quibbling about "DI" cables, the fact that they are allowed seems to imply that the outer sheath is regarded as a second layer of insulation.

Not sure I underestand that but - I think reinforced counts as Class II, I have never seen anything else in the way of markings.

My point is that, if a live part is protected by reinforced (not 'double') insulation, that live part is not required to have an other protection/insulation - e.g. a bare bus bar within an enclosure which qualified as reiunforced insulation would be permitted/acceptable.

That depends whether the box is reinforced or just the second layer.

As I keep saying, I'm talking about the former.

Then that brings up how strong does it have to be - my point about finger nails.
You wouldn't be able to break a J501/801 like that. Perhaps it was just rubbish.

Precisely - but they are extremes. My (perhaps 'rubbish') chockbox certainly doesn't qualify in my mind as being adequate (reinforced) to be the sole barrier between me and a live part, but the sort of enclosure used by a J501/801 probably would (although might not even need to, because there is other insulation within) - but how, regulatory-wise, am I meant to know where to draw the line? I say 'regulatory-wise' because, in practice, I would personally make a common sense judgement - but things should not really rely on that (particularly given that some people seem to possess limited 'common sense')!

Either way, do you not consider the connector block as insulation

Yes, but you seem to be missing my point/question again. I'm asking how I am meant ('regs-wise') to determine whether a certain non-conductive enclosure is or not acceptable as the sole protection between a person and a bare live part within.

One has to assume, for example, that (despite the lack of Class II, or any other relevant, markings) the casing of something like a traditional round JB is considered acceptable (if accessible, these days!) to be the sole protection of a person from the totally uninsulated lumps of 'live brass' within - but that is just a deduction based on the fact that 'it is allowed to exist' - so I can find nothing within BS7671 which allows me to confirm that it satisfies BS7671's requirements for "protection against electric shock" within an electrical installation (even though the JB itself undoubtedly satisfied the requirements of some Standard).

In practical terms, it's far from unknown for me to put things with 'bare live parts' inside 'plastic boxes'. Although I would always satisfy myself, on the basis of common sense, that I had provided adequate protection, it would probably be rather nice to know whether the 'plastic box' actually satisfied some 'requirements' regarding its adequacy for the purpose to which I had put it!

Kind Regards, John

 

[sparkwright]

Not sure if this counts, but I encountered a metal class 2 light fitting the other day.

Transformer inside, one secondary lead going to the lampholders (4 I think), the other secondary lead going to a big ring terminal on the metalwork of the fitting.

So the metalwork is the negative for the lampholders, I suppose.

The 230 v connector was not enclosed.

No doubt someone without thinking would have liked to have earthed the metalwork.

 

[JohnW2]

Not sure if this counts, but I encountered a metal class 2 light fitting the other day. Transformer inside, one secondary lead going to the lampholders (4 I think), the other secondary lead going to a big ring terminal on the metalwork of the fitting. So the metalwork is the negative for the lampholders, I suppose. The 230 v connector was not enclosed.

That introduces an additional level of complication/complexity, given that it involves ELV (something we have not so far considered in this discussion).

Is there any 'exposed' 230V within the metal enclosure?

No doubt someone without thinking would have liked to have earthed the metalwork.

They might. Even if they did some thinking they still might, given that PELV is not unthinkable.

I suspect that you will not have seen the instructions but, if by any chance you have, was there any reference to earthing ("This must not be earthed" or otherwise)?

Kind Regards, John

 

[mattylad]

Can I just point out, that if your looking for the specifics of the safety regulations aspects for within appliances, drills etc. then BS7671 is NOT the std you need to be looking at.
Read the scope of it, it applies to the installation - NOT the manufacture of these items. 7671 comes into play only when the items are being installed and for how it is installed - not the specifics of within the items.

There are other standards that apply (that BS7671 says you should go off and apply) such as the various parts of BSEN60335, the low voltage directive, BSEN601010 (not sure on the last number - its something like that).

Expand the scope of the standards your looking at, read more - although they are all basically saying the same basic thing - be safe.

 

[JohnW2]

Can I just point out, that if your looking for the specifics of the safety regulations aspects for within appliances, drills etc. then BS7671 is NOT the std you need to be looking at. ... Read the scope of it, it applies to the installation - NOT the manufacture of these items. 7671 comes into play only when the items are being installed and for how it is installed - not the specifics of within the items.

Indeed - and if you plough back through this thread, you will see that I've said all that - and have pointed out that one of the problems with this discussion have been that none of us participating really knows much/anything about the requirements in relation to equipment/items which is/are not part of an electrical installation.

There are other standards that apply (that BS7671 says you should go off and apply) such as the various parts of BSEN60335, the low voltage directive, BSEN601010 (not sure on the last number - its something like that). ... Expand the scope of the standards your looking at, read more - ....

See above.

However, this does not alter a lot of what I've been saying and asking. For example, I recently wrote ....

In practical terms, it's far from unknown for me to put things with 'bare live parts' inside 'plastic boxes'. Although I would always satisfy myself, on the basis of common sense, that I had provided adequate protection, it would probably be rather nice to know whether the 'plastic box' actually satisfied some 'requirements' regarding its adequacy for the purpose to which I had put it!

Many of those "things with 'bare live parts' inside 'plastic boxes'" are (or become) part of my electrical installation, and I therefore presume come within the scope of BS7671 - but I can't find anything in BS7671 which really tells me about the requirements for my 'plastic boxes'. Are you saying that some other Standards and/or cregulations do cover that?

.... although they are all basically saying the same basic thing - be safe.

Indeed. As I've said, this issue is not really of any concern to me, since I always apply 'common sense', and I would be surprised if I do not end up with things which would at least satisfy (and probably surpass) the requirements of any Standards or regulations. However, I've been talking about regulatory etc. requirements', which may be more important to some people other than myself, who may not be as able as myself to 'do their own thinking' and/or confident enough to rely on their own thinking.

Kind Regards, John

 

[mattylad]

Common sense does prevail and they often overlap and say the same basic thing.
BS7671 is I think a single standard with how many pages? 1 book would cover it.

BSEN6033 on the other hand has way way more sections,I dare not try and even think about getting printouts of them all - Ill stick to the few that apply to me (1, 2, 49 & 50 to start) and that's gonna print out far more than 7671 lol

Either way, no matter which we follow - there are always those that won't understand either, nor follow them.

 

[JohnW2]

Common sense does prevail and they often overlap and say the same basic thing.

... although they sometimes diverge a little - i.e. there are, for example, some things in BS7671 which do not seem to correspond very closely with common sense.

However, that aside, there are clearly some people who do not have the knowledge (or, in some cases, maybe not even enough common sense) and/or confidence to do the 'common sense' thinking for themselves, so they will probably be looking for external guidance - from Standards, regulations or whatever.

P.S. The current version of BS7671 is, I think, just a little under 500 pages.

Kind Regards, John