5A BS 1363 plug?

[stillp]

I guess I'm just going to have to remain confused!

I'm not really sure what 'rated at 6A' (in relation to a cordset) really means if it doesn't mean that it is deemed 'unsafe' for it to carry more than 6A, in which case, I would expect the required protective device to reflect that. Nor do I really understand why the 'CCCs' (the maximum current deemed to be 'safe') of a flexible cable of a given CSA should be appreciably different if it is part of an electrical installation or part of a moulded 'cordset' - indeed, if anything, I would expect the CCC (hence In of required protective device) to be lower for the latter, given the sort of treatment it might receive in service.

Yes, I suspect you probably will!
As I wrote earlier, a rating is a value assigned by a manufacturer. The manufacturers and regulatory bodies have sat around a table and reached a consensus about what protective device is appropriate and available for products dealt with in their standard. Similarly for BS1363 plugs. The same for those responsible for electrical installations. There is no reason why they should reach the same conclusions, and no reason why they should reach different conclusions. Of course their requirements will be broadly consistent, since "ye cannae change the laws of physics Jim", but you have to accept that each of those committees has access to empirical data and to basic safety standards, as well as knowing what is acceptable for their products.
I don't agree that CCC should be lower for cables likely to be subjected to rough treatment in service - the two things are not related. One might argue that the CCC of a cordset could be much greater than for the equivalent cable used as part of an installation, since it is unlikely to be installed in conduit, or bunched with other cables, and and tendency to overheat is likely to be noticed by the user.

 

[JohnW2]

I guess I'm just going to have to remain confused! ...

Yes, I suspect you probably will!

So it seems, but I have to say that I find it pretty frustrating when I cannot really understand the logic behind something.

As I wrote earlier, a rating is a value assigned by a manufacturer. The manufacturers and regulatory bodies have sat around a table and reached a consensus about what protective device is appropriate and available for products dealt with in their standard. ... There is no reason why they should reach the same conclusions, and no reason why they should reach different conclusions.

If we were talking about different products/items, that would obviously make total sense. However, I am talking specifically about a flexible cable, which will be identical whether it is part of an electrical installation, part of a made-up cable-set or whatever - and I find it difficult to understand that the situations are sufficiently different to explain the relatively large difference (particularly for 0.75mm² cable) between the protection required by the same cable in those two situations. However, people more clever than myself appear to have decided that such is the case.

In view of what you keep saying about 'ratings', I suppose one thing that I am now very confused/uncertain about is how to interpret the manufacturer's 'ratings'. If I have a cordset 'rated' at 6A, but with a 13A fuse in it, does that mean that I can use it to supply a 13A load, or only a 6A one?

... and what about the difference between a factory-manufactured and user-manufactured cordset? If I join together a re-wireable BS1363 plug, a short length of 0.75mm² flexible cable and and IEC connector, is it OK for me to put a 13A fuse in the plug - and, if so, what current am I 'allowed' to use it to supply?

I don't agree that CCC should be lower for cables likely to be subjected to rough treatment in service - the two things are not related. One might argue that the CCC of a cordset could be much greater than for the equivalent cable used as part of an installation, since it is unlikely to be installed in conduit, or bunched with other cables, and and tendency to overheat is likely to be noticed by the user.

Again, I am talking specifically about flexible cables. As part of an electrical installation, they would rarely be installed in conduit or bunched - and, indeed, (in contrast with the situation for all other cable types) BS7671 does not give CCCs for them under such circumstances; one assumes that, if they did, CCCs in those situations would be even lower than the CCCs they give for 'normal' usage of flexible cables (which, apparently by co-incidence, just happen to be identical to the 'current ratings' stated in BS1363). On the other side of the fence, cables in cordsets can be subjected to considerable flexing, bending, stretching and even impact, abrasion and compression which will not normally be the case when the cable is part of an electrical installation. Again, it appears that my intuition is wrong.

Kind Regards, John

 

[stillp]

However, I am talking specifically about a flexible cable

That's part of the problem. You seem to be seeing the cable as the subject of the standards, rather than the moulded plug (in the case of BS1363) or the installation (in the case of BS 7671).

And by the way "flexing, bending, stretching and even impact, abrasion and compression " do not alter the CCC of a cable, although they might affect it's suitability for a given application.

 

[JohnW2]

However, I am talking specifically about a flexible cable

That's part of the problem. You seem to be seeing the cable as the subject of the standards, rather than the moulded plug (in the case of BS1363) or the installation (in the case of BS 7671).

Not really - but I am seeing the cable as something which I would have expected to probably require similar (not necessarily identical) protection against overload in the two situations we are talking about.

And by the way "flexing, bending, stretching and even impact, abrasion and compression " do not alter the CCC of a cable, although they might affect it's suitability for a given application.

It obviously does not alter the CCC of an intact cable, as manufactured. However, it's far from beyond the realms of possibility that 'they' would decide that they needed to 'adjust' the specified CCC to account for the possibility that, say, some strands of the conductors might be broken in service.

Kind Regards, John

 

[ban-all-sheds]

About the assumption (that JohnW2 implied) that the fuse values were those to be used for the tests.

I didn't assume that. I think it's you and he who are making incorrect assumptions.

[give or take the abomination of formatting, which I've had to partially correct above!]

Sorry about that - I noticed on my next visit, but by then it was too late to be worth fixing, as you'd already posted your reply.

Anyway...

In that case, I'm lost - what did you mean when you wrote:

Because that table describes test conditions, and since 3A is the only other preferred value for BS 1362 fuses, if you want to test a pre-wired plug & cable rated at 6 or 10A then you have to use a 13A fuse.

?

OK - the mist (or is it smoke laid down by stillp ?) has cleared.

The reason I said "no I didn't" after this sequence:

but it appears he was wrong.

About what?

About the assumption (that JohnW2 implied) that the fuse values were those to be used for the tests.

was that I thought (quite reasonably, IMO) that he was talking about something in this topic, and I knew I'd not made any assumptions about what I thought you'd meant about something, or had decided you were implying something, somewhere, so I thought "no - I didn't do that, nothing like that happened".

As for your question, I'll address that in the topic to which it relates, i.e. the one where you got that quote of mine from.

 

[ban-all-sheds]

And by the way "flexing, bending, stretching and even impact, abrasion and compression " do not alter the CCC of a cable, although they might affect it's suitability for a given application.

I disagree.

I can quite see how the possibility that legitimate uses for a cable might lead to "flexing, bending, stretching and even impact, abrasion and compression" could, perhaps should, alter the CCC, because the insulation and sheathing might become too soft to adequately resist damage from flexing, abrasion, compression etc if it carried enough current to raise the conductor temperature to 70°.

 

[JohnW2]

... was that I thought (quite reasonably, IMO) that he was talking about something in this topic, and I knew I'd not made any assumptions about what I thought you'd meant about something, or had decided you were implying something, somewhere, so I thought "no - I didn't do that, nothing like that happened".

Fair enough.

As for your question, I'll address that in the topic to which it relates, i.e. the one where you got that quote of mine from.

Again, fair enough.

Kind Regards, John

 

[JohnW2]

There are still two (genuine, not rhetorical) questions I posed to which I would very much like to know the answers ....

In view of what you keep saying about 'ratings', I suppose one thing that I am now very confused/uncertain about is how to interpret the manufacturer's 'ratings'. If I have a cordset 'rated' at 6A, but with a 13A fuse in it, does that mean that I can use it to supply a 13A load, or only a 6A one?

... and what about the difference between a factory-manufactured and user-manufactured cordset? If I join together a re-wireable BS1363 plug, a short length of 0.75mm² flexible cable and and IEC connector, is it OK for me to put a 13A fuse in the plug - and, if so, what current am I 'allowed' to use it to supply?

Kind Regards, John

 

[stillp]

As I'm sure you realise, a cordset rated at 6A is for use at a current not exceeding 6A.

If you manufacture a cordset as you describe, then you are responsible for its rating. Table 2 of BS 1363 would suggest that you should not rate it at greater than 6A, and that it would be quite in order to fit a 13A fuse as the SCPD.

 

[JohnW2]

As I'm sure you realise, a cordset rated at 6A is for use at a current not exceeding 6A.

That's certainly what I would have expected, but recent discussions have confused me.

If you manufacture a cordset as you describe, then you are responsible for its rating. Table 2 of BS 1363 would suggest that you should not rate it at greater than 6A, and that it would be quite in order to fit a 13A fuse as the SCPD.

You will probably say it's because I am 'obsessed' with BS7671 and/or electrical installations, but, yes, I would 'rate' it at 6A (because of the cable) but, no, I wouldn't personally dream of protecting a 0.75mm² flexible cable (being part of a cable assembling which could be used for a load of any type) with a 13A fuse, because I cannot convince myself that the situation is all that different from when the same cable is used 'as part of an electrical installation'. BTW, what do you mean by 'SCPD' - does that 'SC' mean 'short-circuit'? If so, does this mean that you do not see the need for any overload protection?

Kind Regards, John

 

[stillp]

BTW, what do you mean by 'SCPD' - does that 'SC' mean 'short-circuit'? If so, does this mean that you do not see the need for any overload protection?

Yes, and no.

 

[ban-all-sheds]

433.3

 

[stillp]

And by the way "flexing, bending, stretching and even impact, abrasion and compression " do not alter the CCC of a cable, although they might affect it's suitability for a given application.

I disagree.

I can quite see how the possibility that legitimate uses for a cable might lead to "flexing, bending, stretching and even impact, abrasion and compression" could, perhaps should, alter the CCC, because the insulation and sheathing might become too soft to adequately resist damage from flexing, abrasion, compression etc if it carried enough current to raise the conductor temperature to 70°.

If the insulation and sheathing become too soft to resist damage if the conductor temperature is raised to 70 degC then that cable is not suitable for such use. That is not directly related to the CCC.

 

[JohnW2]

433.3

Do I take it that you are thinking primarily of 433.3.1(ii)? If so, that's the reason I wrote:

... a 0.75mm² flexible cable (being part of a cable assembling which could be used for a load of any type)

["assembling" obviously should have read "assembly"!!]
If I know nothing about, and have no control over, what load may be supplied by the lead (hence cable), I surely cannot be satisfied that the cable is "not likely to carry overload current", can I??

Kind Regards, John

 

[JohnW2]

BTW, what do you mean by 'SCPD' - does that 'SC' mean 'short-circuit'? If so, does this mean that you do not see the need for any overload protection?

Yes, and no.

OK - so dos that mean that (in the context we are talking about) you believe that the 13A fuse affords sufficient overload protection for the 0.75mm² flexible cable?

Kind Regards, John