DIY replacement of electrics in kitchen, sanity check & questions

[JohnW2]

I'm attempting to draw the logical conclusions from plain and unambiguously written requirements.

If you are drawing those conclusions totally 'logically', do I therefore take it that you feel that it will often be the case that one cannot have BS1363 sockets supplied by a (Bs7671-compliant) ring final, since there would be "no guarantee that the sockets would remain safe and undamaged"?

Kind Regards, John

 

[EFLImpudence]

I don't understand why, suddenly, two conductors joined in a terminal cause current to heat the whole socket, even if it did heat the terminal which is far larger than the conductors.

What, Bas, would have been your response had Watson or Winston, or anyone else, come up with this hypothesis?

 

[JohnW2]

I don't understand why, suddenly, two conductors joined in a terminal cause current to heat the whole socket, even if it did heat the terminal which is far larger than the conductors.

I feel pretty sure that BAS's personal view of the electrical issue is the same as yours and mine (and, I suspect, the view of the great majority of others).

What appears to have happened 'suddenly' is that he has now decided that he cannot trust his own view, unless it is backed up with a 'guarantee' resulting from tests required by a Standard.

If he has ever installed, or even modified a ring final which was wired in cable which (with its installation method) had a CCC greater than 20A, he would done what he now is saying he would not be happy to do - so something in his mind must have changed.

Kind Regards, John

 

[mwatsonxx]

I don't understand why, suddenly, two conductors joined in a terminal cause current to heat the whole socket, even if it did heat the terminal which is far larger than the conductors.

What, Bas, would have been your response had Watson or Winston, or anyone else, come up with this hypothesis?

It wouldn't have been proposed by me because it is a nonsensical hypothesis. This what I said in post No6

The circuit cable does not run through the sockets. The terminals in the socket (or any other similar device) are for maintaing the circuit connections. As long as those connections maintain the CSA of the conductors there can be no detrimental effects on the socket and the current they are carrying is irrelevant. If it was physically possible to make a connection those cables could be carrying thousands of Amps.

The only current flowing through a socket is that going through the plug.

You're not very good at this, are you?

BAS doesn't know what "through" means.

 

[ban-all-sheds]

If you are drawing those conclusions totally 'logically', do I therefore take it that you feel that it will often be the case that one cannot have BS1363 sockets supplied by a (Bs7671-compliant) ring final, since there would be "no guarantee that the sockets would remain safe and undamaged"?

The behaviour of a socket with > 20A on the supply cable is indeterminate, and there are no requirements for it to undergo any tests of its behaviour in those circumstances.

 

[ban-all-sheds]

I feel pretty sure that BAS's personal view of the electrical issue is the same as yours and mine (and, I suspect, the view of the great majority of others).

My personal view is that the behaviour of a socket with > 20A on the supply cable is indeterminate, and there are no requirements for it to undergo any tests of its behaviour in those circumstances.

What appears to have happened 'suddenly' is that he has now decided that he cannot trust his own view, unless it is backed up with a 'guarantee' resulting from tests required by a Standard.

I cannot trust the behaviour of a socket with > 20A on the supply cable as there are no requirements for it to undergo any tests of its behaviour in those circumstances.

If he has ever installed, or even modified a ring final which was wired in cable which (with its installation method) had a CCC greater than 20A, he would done what he now is saying he would not be happy to do - so something in his mind must have changed.

Surely you aren't suggesting that a cable with a CCC > 20A will somehow make a current of > 20A appear? The tyres on my car are rated for 106mph, but I find that I can drive the car slower than that, and that its speed is not under the control of the tyres.

 

[EFLImpudence]

Perhaps there are no requirements for it to undergo any tests of its behaviour because a socket with > 20A on the supply cable is known not to affect it.

 

[JohnW2]

Surely you aren't suggesting that a cable with a CCC > 20A will somehow make a current of > 20A appear?

Nope, but nor am I suggesting that it prevents a current >20A flowing. Since a designer has no way of guaranteeing what current will flow in any sockets circuit, all we can really do is talk about circuits that would be BS7671-compliant, and, on that basis, I think that your 'logical conclusions' are not all that logical - or, at least, very 'selective'.

Do I take it that you agree (since this is what BS7671 says) that if (as is very common) one has a ring final wired in Method C 2.5mm² cable, that it will be fully compliant if the designer has satisfied himself/herself that no part of the cable is "likely to carry more than 27A for long periods"?

I also assume that, since you keep saying it, that you agree that BS1363 offers no guarantee that a socket to that Standard will "remain safe and undamaged" if the current in the attached cables exceeds 20A. Is that correct?

You have also stated, more than once, that you would not be happy to use an electrical accessory in the absence of such a guarantee, and that you would advise others likewise. Is that correct?

If the answer to all three of those questions is 'yes', then the 'logical conclusion' would seem to be that you would not be happy to connect BS1363 sockets directly to a BS7671-compliant Method C 2.5mm² ring final, and would advise others accordingly - unless, that is, unless you (or they) have some crystal ball that would enable you (or they) to guarantee that none of the cable would ever carry more than 20A.

Do I also take it that you believe that the diagrams of both ring and radial sockets circuits in Appendix 15 of BS7671 are 'incorrect' and unsafe?

Kind Regards, John

 

[ban-all-sheds]

If the answer to all three of those questions is 'yes', then the 'logical conclusion' would seem to be that you would not be happy to connect BS1363 sockets directly to a BS7671-compliant Method C 2.5mm² ring final, and would advise others accordingly - unless, that is, unless you have some crystal ball that would enable you to guarantee that none of the cable would ever carry more than 20A.

Well - ignore for now the issue of the sockets, and the logical conclusion would seem to be that nobody should ever install a BS7671-compliant Method A 2.5mm² ring final unless they had some crystal ball that would enable them to guarantee that none of the cable would ever carry more than 20A.

 

[JohnW2]

Well - ignore for now the issue of the sockets, and the logical conclusion would seem to be that nobody should ever install a BS7671-compliant Method A 2.5mm² ring final unless they had some crystal ball that would enable them to guarantee that none of the cable would ever carry more than 20A.

No, they would simply have to be satisfied that it was not likely that any of the cable would carry more than 20A for long periods.

In any event, you are sidestepping the issue under discussion, which is the view you have suddenly decided to take about the sockets.

Kind Regards, John

 

[ban-all-sheds]

I'm sidestepping nothing.

It seems that you are quite happy for a circuit to have a cable rated at 20A because of the limits imposed by the installation method but not because of the limits imposed by the accessories to which it is connected.

 

[JohnW2]

It seems that you are quite happy for a circuit to have a cable rated at 20A because of the limits imposed by the installation method but not because of the limits imposed by the accessories to which it is connected.

Of course. The current-carrying-capacity of a cable of a certain CSA and installed in a certain way is obviously not going to be dependent upon what it is connected to.

Kind Regards, John

 

[echoes]

Is there anything in BS1363 which stipulates the maximum CCC of the socket terminals?

I am aware of the temperature rise test conditions, but are these not conditions under which the test must be performed, rather than the absolute maximum rating of the terminals?

Given that the A2 radial using BS1363 sockets is a 'standard' circuit in BS7671, and given a socket's terminals are *designed* to accommodate 4 or 6mm cables safely, I find it odd that this would be considered unsafe. Indeed if it was unsafe, then I would expect either standard to be explicit in such a manner as to prohibit the A2.

 

[JohnW2]

Is there anything in BS1363 which stipulates the maximum CCC of the socket terminals?

Not that I am aware of, but that proves little, and I do not have access to the Standard.

I am aware of the temperature rise test conditions, but are these not conditions under which the test must be performed, rather than the absolute maximum rating of the terminals?

That is my understanding.

Given that the A2 radial using BS1363 sockets is a 'standard' circuit in BS7671, and given a socket's terminals are *designed* to accommodate 4 or 6mm cables safely, I find it odd that this would be considered unsafe. Indeed if it was unsafe, then I would expect either standard to be explicit in such a manner as to prohibit the A2.

You say "odd", whereas I would be more inclined to say "ridiculous" !

BAS's 'out-on-a-limb' pronouncement seems to result from the fact that (as far as I am aware), BS1363 does not specify any test relating to the current passing 'through' a socket's terminals (i.e. between two or more attached cables) - and he is, as you say, basing his view on the conditions specified for the temperature rise test.

However, there are any number of other things one can think of which BS1363 might test for but doesn't. In such situations, a sensible person does (should) not assume that the absence of a test for something means that the product must not be used in a particular way. Instead, they apply their knowledge and common sense to make a judgement. In the case in point, I think that the great majority of electricians have (in many cases probably subconsciously) done just that, and have come to the conclusion that the current flowing 'through' a socket terminal (between terminated cables) is, within reason, not a matter of concern.

BAS still has not responded to my suggestion that his view, if shared by others, would mean that very few of the standard socket circuits which have always been installed would be 'acceptable'.

Kind Regards, John

 

[ban-all-sheds]

Of course. The current-carrying-capacity of a cable of a certain CSA and installed in a certain way is obviously not going to be dependent upon what it is connected to.

Really?

Take a look at Note 1 in Table 4E1E 4E1A for example.

[EDIT]Typo corrected.[/EDIT]