Please can someone tell me, is comparing 4mm and 2.5mm cable the same as comparing a chainsaw and a blender?

[EFLImpudence]

We know that, although some people may 'argue'. In fact, provided only that the OPD is adequate to protect the fixed wiring, there's absolutely no reason why someone could not use an OPD rated to satisfy any perceived need for protraction of connected equipment - although that would often/.usually result in an unnecessarily restrictive' OPD rating.

Whilst that might be true, isn't it the case that manufacturers will size the lead and make equipment suitable for where they know it will be connected?
Unless a separate item is manufactured for the UK, then that for a 16A circuit.

That's a bit different. Whilst the 'Wiring Regulations, per se, relate primarily only to the 'fixed wiring' of the installation, there are also requirements for adequate protection of flexible cables 'plugged into' that installation.

Surely that relates only to the rating of plug fuse fitted - so 13A maximum OPD.

To be a little pedantic, it takes at least about 22A to 'blow' a 13A BS1362 (in-plug) fuse, so does not "limit the current to 13A".

True, but do you not think that is taken into account in manufacture?

Yes, but you are now talking ('catastrophic overloads') with what we call 'faults', not overloads. The potential problem (for the flexible cables) relates to 'non-catastrophic overloads', A 32A MCB will allow up to about *** (??? - 36.16A) to flow indefintely, and higher currents than that for appreciable periods of time. If connected equipment results in a high overload current (e.g. an appliance with a 'jammed' large motor) then the flexible cable supply it could find itself carry high currents (much higher than its theoretical 'CCC') for at least long periods, maybe 'indefinitely'. Connection of such an appliance with nothing but a 32A MCB protecting its flexible cable would therefore not be regarded as acceptable in thee UK.

Unlikely to be found in a dwelling, but -

unless, of course, a cable with a CCC of 32A is used.

 

[JohnW2]

Whilst that might be true, isn't it the case that manufacturers will size the lead and make equipment suitable for where they know it will be connected?

One would hope so, but it looks as if you didn't read carefully enough my comment which you quoted and to which you replied, because that's not what I was talking about.

I was merely saying that if one has, say, an appliance which is deemed to require, say 3A protection of its innards (but has no internal protection), then there is nothing stopping one protecting the entire circuit with a 3A MCB. Silly though that would be, my point was that that would be an example of a situation in which the circuit's OPD was not there "only to protect the cables of the fixed wiring'.

Surely that relates only to the rating of plug fuse fitted - so 13A maximum OPD.

In the UK, yes, but that was my very point. In a country where the plugs don't have fuses, the only thing protecting the flex would be the circuit's OPD - which might well be 'inadequate' to provide the usually-expected degree of protection to the flex.

True, but do you not think that is taken into account in manufacture?

One would hope so. However, I was merely pointing out (as I said, a little "pedantically') that a 13A fuse does not "limit the current to 13A".

Unlikely to be found in a dwelling, but - unless, of course, a cable with a CCC of 32A is used.

[ thanks for replacing my asterisks with a number - as you will realise, I intended to go back and do that myself after I had 'checked' the calculation, but forgot! ]
Sure - but, as I said just before you jumped in, unless the load is deemed unlikely to create an overload (which, as you pointed out, I forgot to say!), that would (were it not for plug fuses) require flex of at least 4mm² (per BS7671 tables).

Kind Regards, John

 

[EFLImpudence]

One would hope so, but it looks as if you didn't read carefully enough my comment which you quoted and to which you replied, because that's not what I was talking about.

I was merely saying that if one has, say, an appliance which is deemed to require, say 3A protection of its innards (but has no internal protection), then there is nothing stopping one protecting the entire circuit with a 3A MCB. Silly though that would be, my point was that that would be an example of a situation in which the circuit's OPD was not there "only to protect the cables of the fixed wiring'.

That was exactly my point.
The manufacturer will know there is unlikely to be a 3A circuit OPD, therefore will fit an integral 3A fuse for the equipment and a 16A (or less if overload unlikely) flex.

In the UK, yes, but that was my very point. In a country where the plugs don't have fuses, the only thing protecting the flex would be the circuit's OPD - which might well be 'inadequate' to provide the usually-expected degree of protection to the flex.

Again, my point is the flex will be adequate for the expected circuit OPD.

Sure - but, unless the load is deemed unlikely to create an overload (which, as you pointed out, I forgot to say!), that would (were it not for plug fuses) require flex of at least 4mm² (per BS7671 tables).

Yes, so what? One or the other.

You were talking about a large motor on a 32A circuit.

 

[JohnW2]

That was exactly my point. The manufacturer will know there is unlikely to be a 3A circuit OPD, therefore will fit an integral 3A fuse for the equipment and a 16A (or less if overload unlikely) flex.

As we often discuss, that certainly ought to be the case, but it doesn't seem to stop some manufacturers 'demanding' external 'low'-current protection rather than including it within their product (e.g. extractor fans). As you say, they presumably know that the circuit is (very!) unlikley to have 3A OPD, so 'demand' a 3A FCU to protect their product (which, if it really needs such protection, should have it provided internally!).

Again, my point is the flex will be adequate for the expected circuit OPD.

I think that the problem here is that, in order to make a point (about the main reason why UK plugs have fuses), we are talking about a non-existent (I think) hypothetical situation - namely a country which has ~32A sockets circuits but does not have fused plugs (or sockets). In that situation, any equipment which might produce a significant overload (which probably includes anything which has a significant motor) would have to come with 4mm² (or larger) flex. That would be the case if the UK had its present circuits but no plug fuses - hence, as above, is probably one of the main reasons why we do have fused plugs?

Yes, so what? One or the other. You were talking about a large motor on a 32A circuit.

See above. As for "so what?", I'm not sure it would be very convenient to have to have 4mm² flex on, say, a hair dryer, would it ? As said, the fact that we have fused plugs removes any such need.

Kind Regards, John

 

[EFLImpudence]

As we often discuss, that certainly ought to be the case, but it doesn't seem to stop some manufacturers 'demanding' external 'low'-current protection rather than including it within their product (e.g. extractor fans). As you say, they presumably know that the circuit is (very!) unlikley to have 3A OPD, so 'demand' a 3A FCU to protect their product (which, if it really needs such protection, should have it provided internally!).

As you know, not all of them do demand that.
As for the rest, I obviously have no proof but I have always thought that the manufacturers think that is the regulation in the UK.

I think that the problem here is that, in order to make a point (about the main reason why UK plugs have fuses), we are talking about a non-existent (I think) hypothetical situation - namely a country which has ~32A sockets circuits but does not have fused plugs (or sockets). In that situation, any equipment which might produce a significant overload (which probably includes anything which has a significant motor) would have to come with 4mm² (or larger) flex. That would be the case if the UK had its present circuits but no plug fuses - hence, as above, is probably one of the main reasons why we do have fused plugs?

Well, yes that is why there are fused plugs but as I said your example of a large motor is not likely to be found in a dwelling and commercial premises do have 32A sockets.

See above. As for "so what?", I'm not sure it would be very convenient to have to have 4mm² flex on, say, a hair dryer, would it ? As said, the fact that we have fused plugs removes any such need.

No, of course not but that is not a significant motor and drying one's hair in a fan oven is inconvenient.

What do you think would happen if a hair drier on a 32A circuit did not have a fuse in the plug?

 

[JohnW2]

As you know, not all of them do demand that.

True - but many, perhaps even most,do.

As for the rest, I obviously have no proof but I have always thought that the manufacturers think that is the regulation in the UK.

You may be right. Who knows?!

Well, yes that is why there are fused plugs but as I said your example of a large motor is not likely to be found in a dwelling and commercial premises do have 32A sockets.

The 'significant motors' I was thinking/talking about were those that one would find in WMs, DWs and dryers. I imagine that 'jammed current' is much the same as 'start-up current', and one often sees people saying that the latter may be 10-20 times the running current.

No, of course not but that is not a significant motor and drying one's hair in a fan oven is inconvenient. What do you think would happen if a hair drier on a 32A circuit did not have a fuse in the plug?

I really don't know how 'significant' is the motor (hence, its current draw when not rotating) in a hair drier. However, even if the motor (and its stalled current) is not 'significant in that particular case, as above, I suspect it probably is in some other ubiquitous domestic appliances.

Kind Regards, John

 

[ebee]

"Since you have raised this question, the answer may be one of "chicken and egg" or of "evolution" of standards and practices."

Easy answer to the age old chicken and egg question is - the egg came first

 

[FrodoOne]

"Since you have raised this question, the answer may be one of "chicken and egg" or of "evolution" of standards and practices."

Easy answer to the age old chicken and egg question is - the egg came first

As did the 10 A "Plug" and "Socket-Outlet"

 

[JohnW2]

Easy answer to the age old chicken and egg question is - the egg came first

I'm not sure it's quite that 'easy' - where did that first egg come from?

Kind Regards, John

 

[EFLImpudence]

From something that was not a chicken. Otherwise the egg from which the layer hatched would have been the first chicken egg.

 

[DetlefSchmitz]

I'm not sure it's quite that 'easy' - where did that first egg come from?

I think he's referring to amniotic eggs... (qv)

 

[JohnW2]

I think he's referring to amniotic eggs... (qv)

I realised that - but the question still arises as to where it came from.

As with so many things, I think it probably largely comes down to a matter of 'semantics'/'terminology'. The answer to my question (as the where the first {amniotic} chicken egg came from) is that it came from an animal which was regarded as being 'not quite a chicken', albeit undoubtedly incredibly similar to a chicken. In other words, it is really just a matter of (essentially arbitrary) taxonomic definitions.

Indeed, given that (with only possibly a few exceptions - like 'identical twins') no two (amniotic) eggs, of any species, are identical) this issue does not only operate at the level of species, but also at the level of individuals within each species - i.e. we could regard every individual as being a different 'species' if we so wished!

I suppose a more interesting question (philosophically, if nothing else) is where the very first (amniotic) egg (of any species) came from!

Kind Regards, John

 

[DetlefSchmitz]

Well, I was suggesting that eggs preceded chickens by 340 million years.

 

[JohnW2]

Well, I was suggesting that eggs preceded chickens by 340 million years.

Yes, of course, but the question (essentially down to arbitrary definition) is when the first chicken egg appeared.

As I said, since no 'chicken' is genetically identical to either of its parents, it's really totally arbitrary as to what degree of genetic change is deemed necessary for an animal to cease to be 'a chicken'!

Kind Regards, John

 

[DetlefSchmitz]

but the question

...clearly ebee's answer was to a different interpretation of the question... I assume you missed this, or you would not have responded to his answer as you did.