RCD consumer unit and lawnmowers

[ericmark]

The question is will two RCD's be safer than one assuming both are in working order.

Answer must be no as the current differential between line and neutral will be the same or less at the plug as it is at the consumer unit so with a 30ma unit in both places the consumer unit device is likely to act first as likely there are some leakage paths between the consumer unit and the socket which will likely make the consumer unit one more sensitive.

With both 2 core and 3 core cable cutting the cable with a lawn mower or hedge trimmer is so quick it is unlikely the RCD will trip. It only really helps when some one picks up the cable and tries to repair it without first turning off the supply. As to if having a resistive path through the ground or a near non resistive path through a earth wire goes both are likely to trip the RCD but through the earth wire is likely to give a far higher current until it does trip. So I would say keep with the two core cable.

As to using a 10ma RCD on the plug, yes some caravan suppliers do stock them, but time will be the same so since under fault conditions unlikely less than 30ma will flow there is no point as likely both will trip in nearly the same time. In any case less than 40ms.

So answer is simple no point in doubling up on RCD's

Which leaves the question why when any caravan site has a 30ma RCD on the supply should there also be one within the caravan? Sorry have no answer. Likely a TT supply with rod at the supply post so just can't see any point in fitting two RCD's unless the earth is not imported as would often be the case with boats. But never seen an isolation transformer or a diode in the earth wire with a caravan that only happens with boats.

 

[EFLImpudence]

I don't see anything strange in the absence of a cpc in such items.

The regulations do not stipulate a cpc is required because the rcd is for additional protection of persons which will operate should a person come into contact with a live part.
None of the parts will become live.
The only way a person can come into contact with a live part is through a faulty cable.

The appliances are double insulated and as such must not be earthed therefore the manufacturer do not fit one in the cable.

Should the cable be cut it will operate the opd.
If it does not because the blades do not contact both conductors simultaneously, then it may not contact the cpc at the same time (as the others) either.
Less likely because of the positioning of three, I suppose, but not really worth the expense

Should a person pick up a still live cable and touch either live conductor the rcd will operate and so a cpc is of no advantage.

 

[bernardgreen]

Presumably so, although as said, there was earth in the extension lead.

The amount of current through the water depends on the area of contact between the water and the conductor. The cut end of a cable CPC is small ( typicall 1 sq mm ) so the impedance of the CPC to water interface is high compared to a foot on wet ground.

 

[JohnW2]

I don't see anything strange in the absence of a cpc in such items. The regulations do not stipulate a cpc is required because the rcd is for additional protection of persons which will operate should a person come into contact with a live part.
None of the parts will become live. The only way a person can come into contact with a live part is through a faulty cable.

You are presenting what I assume to be the 'official thinking' which results in a CPC not being required. However, do you deny that, in some cases of cable damage, the presence of a CPC (and RCD) would result in the individual concerned not receiving a shock at all?

The appliances are double insulated and as such must not be earthed therefore the manufacturer do not fit one in the cable.

The fact that something is double insulated and therefore must not be earthed does not mean that the cable feeding it cannot, or should not, have a CPC. Indeed, in terms of fixed wiring, the regs now require a CPC, even if the load is not to be earthed. That may partially be because something else (which does require an earth) may one day be connected to the cable, but I suspect it is also at least partially because it facilitates operation of protective devices in the event of damage/penetration of the cable.

Should the cable be cut it will operate the opd. If it does not because the blades do not contact both conductors simultaneously, ...

As you will have seen, I've been told that it is not uncommon for an OPD not to operate. This may be due to what you describe, but it might also be a question of the duration of the contact between L & N. That's one aspect of the specification/behaviour of both OPDs (certainly MCBs) and RCDs that I haven't seen documented (have you?) - i.e. data on the duration, as well as magnitude, of a fault/overload current required to operate the device (we tend to think about 'continuing faults', not ones of very brief duration). In the case of a fuse, it is certainly apparent that even a very high current will not cause it to operate if the duration of that current is too short - since it's all a question of the amount of energy required to melt to fuse wire. I have an unfounded 'gut-feeling' that an RCD might well respond to briefer durations of fault current than would be needed for MCB operation, but that may be totally wrong.

... then it may not contact the cpc at the same time (as the others) either. Less likely because of the positioning of three, I suppose, ....

Obviously true, but it's surely the case that with both an OPD and a RCD/CPC, the chances of disconnection at the time of the cable being cut will be appreciably increased (albeit obvioulsy not to "100% guarantee") - particularly if, as I'm being told, it is quite common for an OPD not to operate.

...but not really worth the expense

That may be your (and 'their') opinion - but we're down to risk-benefit (really cost-benefit, since I can't think of any significant downside of the CPC other than cost) assessment and the age-old question of "what is a human life worth".

Should a person pick up a still live cable and touch either live conductor the rcd will operate and so a cpc is of no advantage.

I doubt that the RCD would operate if the person touched just the neutral (unless, perhaps, there were standing in a pond at the time!), but that's just a detail.

In summary, I don't really think there is any escaping the fact that the risk of a shock (following cable damage), hence also the risk of death (even with an RCD) will be reduced, at least to some extent, by having a CPC (and RCD). I personally think it better to take steps to reduce the chance of a shock, rather than to rely on the hope that an RCD will prevent that shock being fatal. As you imply, someone has presumably decided that the number of lives potentially saved does not justify the cost of requiring a CPC - maybe because they are 'confident' (more confident that I am, and IMO more confident that they should be!) that a 30mA RCD will always prevent a shock being fatal.

I sometimes get accused of considering the vanishingly improbable. However, I would imagine that people cutting through garden tool cables is a more-than-daily occurrence - and I'm being told that OPDs will often not operate. That probably means, on average, at least some cases every day of live cables with exposed ends lying on the ground with the hope that an RCD will avoid fatality if someone touches it. Do you not feel there would be a case for having requirements which reduced (at least to some extent) the number of such live exposed conductors lying on the ground, 'waiting to be touched'?

Kind Regards, John

 

[JohnW2]

The question is will two RCD's be safer than one assuming both are in working order. Answer must be no ...

Indeed - but, as you say, that relies on the assumption that both are 'in working order'. If you believe the oft-cited claim that a high proportion (is it '1 in 7' or 7%?) of in-service RCDs are faulty, that could obvioulsy be an argument for the 'belt and braces' of having two - but that would obviously have to be balanced against the inconvenience of having two RCDs in different locations operating (and maybe taking out other circuits/services).

With both 2 core and 3 core cable cutting the cable with a lawn mower or hedge trimmer is so quick it is unlikely the RCD will trip.

With a 2-core cable, it obvioulsy could not trip unless there was some other path to earth involved. With 3-core cable, I'm not sure I agree. I've certainly experienced RCD trips in that situation and, as I've just written to EFLI, I have a gut feeling that RCDs may be sensitive to shorter durations of transient faults than are MCBs (and certainly fuses).

Kind Regards, John

 

[bernardgreen]

It always puzzled me why the metal case of some double insulated electrical items " must NOT be earthed "

When it is garden equipment it is likely to be because of the risk of exporting an "earth" that is derived from the Neutral and cannot be ensured to be at ground potential. If the neutral bounced then the metal work would be a shock hazard.

For tools used inside the equipotential zone the earthed case would provide a path to earth thus increasing the risk if the user came into contact with a live wire while holding the tool.

 

[JohnW2]

It always puzzled me why the metal case of some double insulated electrical items " must NOT be earthed "

You say that, but then go on to give explanations as to why earthing the casing could represent a hazard both outdoors and indoors. Are you really puzzled?

Of indoor tools, you say that an earthed casing increases the risk of shock if a person comes into contact with a live wire whilst holding the tool. That's obviously correct, but is equally true of Class I tools (for which the earthing of the case is clearly required) and, indeed, of any metalwork which is earthed (directly, or indirectly via bonding).

Kind Regards, John

 

[EFLImpudence]

It always puzzled me why the metal case of some double insulated electrical items " must NOT be earthed

The same reason that isolated metal parts (e.g. bath) should not be earthed.

 

[JohnW2]

It always puzzled me why the metal case of some double insulated electrical items " must NOT be earthed

The same reason that isolated metal parts (e.g. bath) should not be earthed.

... which I suppose is a subset of the generalisation that, if it could be achieved (which is nearly always impossible, except in very specialised situations), a totally earth-free environment (hence necessarily with no exposed-conductive-parts) would probably be the safest situation of all.

Kind Regards, John

 

[EFLImpudence]

I don't see anything strange in the absence of a cpc in such items. The regulations do not stipulate a cpc is required because the rcd is for additional protection of persons which will operate should a person come into contact with a live part.
None of the parts will become live. The only way a person can come into contact with a live part is through a faulty cable.

You are presenting what I assume to be the 'official thinking' which results in a CPC not being required. However, do you deny that, in some cases of cable damage, the presence of a CPC (and RCD) would result in the individual concerned not receiving a shock at all?

If, by that, you mean because the opd/rcd is more likely to be activated by the increased chance of contact, you are obviously correct.
I do not have any data regarding this but, following your thought process and bearing in mind the very low figures of death/injury because of this, I don't think it necessary.
If there were need then why is earthed metal covered or concentric flex required?

The appliances are double insulated and as such must not be earthed therefore the manufacturer do not fit one in the cable.

The fact that something is double insulated and therefore must not be earthed does not mean that the cable feeding it cannot, or should not, have a CPC. Indeed, in terms of fixed wiring, the regs now require a CPC, even if the load is not to be earthed. That may partially be because something else (which does require an earth) may one day be connected to the cable, but I suspect it is also at least partially because it facilitates operation of protective devices in the event of damage/penetration of the cable.

Penetration of a mower flex by a screw/nail is unlikely.
However, I think the reason is more to do with overheating and contacting the bare cpc which is not the case with flex.
The rcd would operate when only one live conductor was penetrated and touched by a person.

Should the cable be cut it will operate the opd. If it does not because the blades do not contact both conductors simultaneously, ...

As you will have seen, I've been told that it is not uncommon for an OPD not to operate.

I have done it myself.

This may be due to what you describe, but it might also be a question of the duration of the contact between L & N. That's one aspect of the specification/behaviour of both OPDs (certainly MCBs) and RCDs that I haven't seen documented (have you?)

No.

- i.e. data on the duration, as well as magnitude, of a fault/overload current required to operate the device (we tend to think about 'continuing faults', not ones of very brief duration). In the case of a fuse, it is certainly apparent that even a very high current will not cause it to operate if the duration of that current is too short - since it's all a question of the amount of energy required to melt to fuse wire. I have an unfounded 'gut-feeling' that an RCD might well respond to briefer durations of fault current than would be needed for MCB operation, but that may be totally wrong.

... then it may not contact the cpc at the same time (as the others) either. Less likely because of the positioning of three, I suppose, ....

I am not sure but 0.1 or 0.01 seconds is fairly quick.

Obviously true, but it's surely the case that with both an OPD and a RCD/CPC, the chances of disconnection at the time of the cable being cut will be appreciably increased (albeit obvioulsy not to "100% guarantee") - particularly if, as I'm being told, it is quite common for an OPD not to operate.

If desired, and as above, a cable which would definitely cause operation of the opd could be used.
If time is the problem then perhaps there is nothing that can be done.

...but not really worth the expense

That may be your (and 'their') opinion - but we're down to risk-benefit (really cost-benefit, since I can't think of any significant downside of the CPC other than cost) assessment and the age-old question of "what is a human life worth".

But - is it really necessary?

In summary, I don't really think there is any escaping the fact that the risk of a shock (following cable damage), hence also the risk of death (even with an RCD) will be reduced, at least to some extent, by having a CPC (and RCD). I personally think it better to take steps to reduce the chance of a shock, rather than to rely on the hope that an RCD will prevent that shock being fatal.

Once the cable has been cut without the opd operating the presence of a cpc is irrelevant.
The rcd will operate in the event of a shock without the cpc.

As you imply, someone has presumably decided that the number of lives potentially saved does not justify the cost of requiring a CPC - maybe because they are 'confident' (more confident than I am, and IMO more confident that they should be!) that a 30mA RCD will always prevent a shock being fatal.

Isn't that the wrong way around?
According to you they are not employing the rcd to the full extent.

I sometimes get accused of considering the vanishingly improbable. However, I would imagine that people cutting through garden tool cables is a more-than-daily occurrence - and I'm being told that OPDs will often not operate. That probably means, on average, at least some cases every day of live cables with exposed ends lying on the ground with the hope that an RCD will avoid fatality if someone touches it.

It would, therefore seem to be working.

Do you not feel there would be a case for having requirements which reduced (at least to some extent) the number of such live exposed conductors lying on the ground, 'waiting to be touched'?

I admit that it would be desirable to reduce the number of such cables but it does not appear to be a huge problem and would a cpc have helped?

 

[Spark123]

The main reason I think that the scenario you described (getting a shock from severed cable end) is pretty unlikely is that, despite all that gets said about him, the average Joe Public has more sense than to touch the exposed end of a cable (s)he's just cut!

I think you have too much confidence in Joe Public, the last few I can recall seeing have had bare wires wrapped together as a repair, a plug that a monkey could have wired better but the best one by far was the person who went to plug the severed cable in to show me what had happened

 

[JohnW2]

... do you deny that, in some cases of cable damage, the presence of a CPC (and RCD) would result in the individual concerned not receiving a shock at all?

If, by that, you mean because the opd/rcd is more likely to be activated by the increased chance of contact, you are obviously correct.

I mean that, if an OPD does not operate, disconnection in response to a cable cut is more likely to occur if there is a CPC (and RCD) than if there isn't.

I do not have any data regarding this but, following your thought process and bearing in mind the very low figures of death/injury because of this, I don't think it necessary.

Hmmm. The problem here is that we're talking about such low risks in the first place. The total number of deaths and serious injuries due to electric shock is so (amazingly, IMO) small (and has been, during the period of the last few editions of the regs) that the same argument could be used to say that most of the ('additional safety') requirements that have appeared in the regs over the last few decades are 'unnecessary'. Even the introduction of RCDs, per se, has probably saved far fewer lives than would have been saved by very minor changes in the enforcement of laws related to driving. Electrical regs therefore necessarily have to think in terms of reducing risks which are already incredibly small - which leads to some of them being criticised by some for being 'unnecessarily' strict.

Let me ask you, as an example - which do you think would be more likely to reduce (even if only by a small degree) the number of electric shocks suffered - requiring a CPC in garden tool cables, or filling in 2mm diameter holes in the tops of enclosures?

Obviously true, but it's surely the case that with both an OPD and a RCD/CPC, the chances of disconnection at the time of the cable being cut will be appreciably increased (albeit obvioulsy not to "100% guarantee") - particularly if, as I'm being told, it is quite common for an OPD not to operate.

If desired, and as above, a cable which would definitely cause operation of the opd could be used.

It could, indeed, but that's going even further - requiring 3-core cable would perhaps be a 'reasonable' compromise in that direction - but I would not be averse to the idea of requiring an earthed sheath.

If time is the problem then perhaps there is nothing that can be done.

True, but it's clearly not always a problem, if ever - I've certainly tripped RCDs by 'hedge trimming' cables!

...but not really worth the expense

That may be your (and 'their') opinion - but we're down to risk-benefit (really cost-benefit, since I can't think of any significant downside of the CPC other than cost) assessment and the age-old question of "what is a human life worth".

But - is it really necessary?

As I said, it's down to a decision as to the value of a human life - a difficult decision, but one which has to be made.

Once the cable has been cut without the opd operating the presence of a cpc is irrelevant.

Eh? If a CPC is present, it's fairly likely that an RCD will have operated, even if the OPD didn't - thereby achieving disconnection that wouldn't have been achieved without the OPD. Is thatreally 'irrelevant'?!

The rcd will operate in the event of a shock without the cpc.

It will indeed and, as I keep saying, that shock may possibly result in death, even in the presence of an RCD. Do you really believe that allowing a shock to occur, hoping that the RCD will prevent death, is as good as making it less likley taht teh shock will occur in the first place?

As you imply, someone has presumably decided that the number of lives potentially saved does not justify the cost of requiring a CPC - maybe because they are 'confident' (more confident than I am, and IMO more confident that they should be!) that a 30mA RCD will always prevent a shock being fatal.

Isn't that the wrong way around? According to you they are not employing the rcd to the full extent.

I don't really understand your comment. Just as I've just written, they are relying on the RCD only to reduce (but not eliminate) the risk of death if a shock occurs. They are 'missing' an opportunity to also use the RCD to reduce the risk of the shock occurring in the first place.

Do you not feel there would be a case for having requirements which reduced (at least to some extent) the number of such live exposed conductors lying on the ground, 'waiting to be touched'?

I admit that it would be desirable to reduce the number of such cables but it does not appear to be a huge problem and would a cpc have helped?

As above, in terms of the big pictures of 'life risks', deaths and serious injuries due to electric shock are anything but a 'huge problem' - but that doesn't stoip us from introducing increasingly demanding safety-based electrical regulations.

Given it's Friday evening, and the fact that yoiu keep invoking the concept of "very low risk, therefore measures unnecessary", I might be tempted to enter the debating chamber and ponder the question of how many additional serious injuries and deaths we would see if we abolished the Wiring Regs (and Part P) today - or maybe reverted to a 50 year-old edition of the Wiring Regs! The fact is, of course, that for better or for worse, we have decided that we want incredibly demanding safety-based regulations, even though the risks being addressed are, in most cases, incredibly small!

I'm off to open a bottle

Kind Regards, John

 

[EFLImpudence]

Hmmm. The problem here is that we're talking about such low risks in the first place. The total number of deaths and serious injuries due to electric shock is so (amazingly, IMO) small (and has been, during the period of the last few editions of the regs) that the same argument could be used to say that most of the ('additional safety') requirements that have appeared in the regs over the last few decades are 'unnecessary'. Even the introduction of RCDs, per se, has probably saved far fewer lives than would have been saved by very minor changes in the enforcement of laws related to driving. Electrical regs therefore necessarily have to think in terms of reducing risks which are already incredibly small - which leads to some of them being criticised by some for being 'unnecessarily' strict.

Agreed but that's what 'they' do.
That they haven't done 'xyz' yet is not a mystery.

Let me ask you, as an example - which do you think would be more likely to reduce (even if only by a small degree) the number of electric shocks suffered - requiring a CPC in garden tool cables, or filling in 2mm diameter holes in the tops of enclosures?

Well, some posters often 'pick holes' in the regulations and then want more.
Perhaps there are no shocks, other than a jump, suffered by cut cables to reduce.

Once the cable has been cut without the opd operating the presence of a cpc is irrelevant.

Eh? If a CPC is present, it's fairly likely that an RCD will have operated, even if the OPD didn't - thereby achieving disconnection that wouldn't have been achieved without the OPD. Is that really 'irrelevant'?!

I was considering the cable having been cut and not disconnected by either device.
You are thinking that an rcd will operate when the opd does not.
I think I stated that a cpc would lead to a greater chance of two cables being connected by the blades.

The rcd will operate in the event of a shock without the cpc.

It will indeed and, as I keep saying, that shock may possibly result in death, even in the presence of an RCD. Do you really believe that allowing a shock to occur, hoping that the RCD will prevent death, is as good as making it less likley taht teh shock will occur in the first place?

Obviously not but then fit metal sheathed cable rather than increasing the probability slightly.

As you imply, someone has presumably decided that the number of lives potentially saved does not justify the cost of requiring a CPC

Maybe there is none to save.

As above, in terms of the big pictures of 'life risks', deaths and serious injuries due to electric shock are anything but a 'huge problem' - but that doesn't stop us from introducing increasingly demanding safety-based electrical regulations.

Perhaps they haven't got round to this one yet.
Guaranteeing they still have a job next year.

Given it's Friday evening, and the fact that you keep invoking the concept of "very low risk, therefore measures unnecessary", I might be tempted to enter the debating chamber and ponder the question of how many additional serious injuries and deaths we would see if we abolished the Wiring Regs (and Part P) today - or maybe reverted to a 50 year-old edition of the Wiring Regs! The fact is, of course, that for better or for worse, we have decided that we want incredibly demanding safety-based regulations, even though the risks being addressed are, in most cases, incredibly small!

Have we decided? Is that a cross every four or five years?
I have often wondered why, in some instances, the 'powers that be' don't like us hurting ourselves then in others they don't give a toss about us.

You only have to compare the figures before and after part P and, indeed, before that.


I have since thought that you're previous statement that cabling to unearthed appliances and fixtures do require a cpc is not correct.
That only applies to the fixed wiring for protection from screws and nails.
Should the unearthed appliance or fixture be supplied with its own flex/wiring no cpc will be present and so, in this respect, a lawn mower is no different than a light pendant or another plastic appliance.

For whatever reason they don't.

 

[JohnW2]

Let me ask you, as an example - which do you think would be more likely to reduce (even if only by a small degree) the number of electric shocks suffered - requiring a CPC in garden tool cables, or filling in 2mm diameter holes in the tops of enclosures?

Well, some posters often 'pick holes' in the regulations and then want more. Perhaps there are no shocks, other than a jump, suffered by cut cables to reduce.

Fair comment. I suppose it's really 'inconsistency of spirit' that I try to comment on. There certainly are at least some shocks from cut cables to reduce (I know that because my neighbour suffered one a couple of years ago!), but I agree there might not be many. However, I find it very hard to believe that the risk of someone managing to get a shock via a 2mm diameter hole in the top of an enclosure is greater - yet the regs have requirements to prevent the latter, but do not impose the additional requirements which would reduce the (perhaps already very low) risk in the 'cut outdoor cable' scenario. It's this inconsistency, or seemingly odd sense of priorities, that I often feel inclined to comment upon.

In any event, if one (or 'they') were working on the premise that there were no shocks due to cut cables to reduce, then one (or 'they') would not have a requirement for RCD protection at all.

Eh? If a CPC is present, it's fairly likely that an RCD will have operated, even if the OPD didn't - thereby achieving disconnection that wouldn't have been achieved without the OPD. Is that really 'irrelevant'?!

I was considering the cable having been cut and not disconnected by either device.

Well, yes, if both devices failed to operate, even with a CPC in the cable, then the absence of that CPC obvioulsy would be irrelevant. However, the point is that with (but not without) the CPC, the RCD may well operate when the OPD hadn't....

You are thinking that an rcd will operate when the opd does not. I think I stated that a cpc would lead to a greater chance of two cables being connected by the blades.

Exactly - and you did,indeed, say that - so are you now agreeing with me?

Do you really believe that allowing a shock to occur, hoping that the RCD will prevent death, is as good as making it less likley taht teh shock will occur in the first place?

Obviously not but then fit metal sheathed cable rather than increasing the probability slightly.

I've agreed that an earthed sheath would be even better, and that I'd have no real problem with such a requirement, but a CPC is at least a step in that direction.

As you imply, someone has presumably decided that the number of lives potentially saved does not justify the cost of requiring a CPC

Maybe there is none to save.

Possibly - but, as I said, what about those 'non-compliant' 2mm holes in enclosures?

Given it's Friday evening, and the fact that you keep invoking the concept of "very low risk, therefore measures unnecessary", I might be tempted to enter the debating chamber and ponder the question of how many additional serious injuries and deaths we would see if we abolished the Wiring Regs (and Part P) today - or maybe reverted to a 50 year-old edition of the Wiring Regs! The fact is, of course, that for better or for worse, we have decided that we want incredibly demanding safety-based regulations, even though the risks being addressed are, in most cases, incredibly small!

Have we decided? Is that a cross every four or five years?

The identity of that 'we' is, indeed, an interesting question. Whatever, with an incredibly small number of arguable exceptions, the degree of stringency of the Wiring Regs has, in the apparent name of safety, has moved only in one direction over the evolution of many editions/amendments, and there is no sign of a change in direction being likely to happen any time soon!

I have often wondered why, in some instances, the 'powers that be' don't like us hurting ourselves then in others they don't give a toss about us.

I agree totally. The logic of why the law allows me to smoke, drink, have unprotected sex with strangers, jump out of planes and climb mountains, but not drive a car without a seatbelt is totally lost on me!

I have since thought that you're previous statement that cabling to unearthed appliances and fixtures do require a cpc is not correct. That only applies to the fixed wiring for protection from screws and nails.

I'm not sure why you say I was incorrect. I wrote:

The fact that something is double insulated and therefore must not be earthed does not mean that the cable feeding it cannot, or should not, have a CPC. Indeed, in terms of fixed wiring, the regs now require a CPC, even if the load is not to be earthed.

.. and, in any event, is a screw or nail really conceptually any different from a mower or hedgecutter blade?

Kind Regards, John

 

[EFLImpudence]

You are thinking that an rcd will operate when the opd does not. I think I stated that a cpc would lead to a greater chance of two cables being connected by the blades.

Exactly - and you did,indeed, say that - so are you now agreeing with me?

Well, I don't actually disagree with anything you have written just whether it is necessarily worth introducing further regulation and trying to explain the likely reasons.

what about those 'non-compliant' 2mm holes in enclosures?

Just one of the many inconsistancies. I don't know.

I have since thought that you're previous statement that cabling to unearthed appliances and fixtures do require a cpc is not correct. That only applies to the fixed wiring for protection from screws and nails.

I'm not sure why you say I was incorrect. I wrote:
The fact that something is double insulated and therefore must not be earthed does not mean that the cable feeding it cannot, or should not, have a CPC. Indeed, in terms of fixed wiring, the regs now require a CPC, even if the load is not to be earthed.

I acknowledge that but the point I was making was of the supplied flex with such items.

.. and, in any event, is a screw or nail really conceptually any different from a mower or hedgecutter blade?

The difference, surely, is that a person will not be holding the blade when it contacts the live conductor