Why would the socket-outlet be affected by the current flowing in the supply cable, other than a slight reduction of the heat-sinking effect of that cable?
Kitchen wiring - which circuit is best option, dedicated radial or ring main?
- Thread starter RomanAbramovich
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Which "their" - single sockets or ring final circuits?No, I'm not, but that is their raison d'etre.Yes, but I'm not aware of any suggestion that single sockets can only be used in ring finals, are you?.
Yes, it is a 'niggling worry' for some people, although not something that I personally loose any sleep over. It's not even as if much of the current which is not flowing through the switch contacts (or whatever) will even flow through any part of the accessory terminal - much of it will go straight from one conductor to the other.
I do.
As you know, I think that as well.
Kind Regards, John
I can find nothing in the standard that states that they don't have to. There is only a temperature-rise test, performed at 14A + 6A, but I can't see anything that states that a 13A socket-outlet ceases to be a 13A socket-outlet when it is mounted on the same faceplate as another 13A socket-outlet.
Since we're talking about a temperature-rise, test, I would assume that is the very sort of potential 'effect' that causes the 14A test of a single socket to involve 20A in the supply cable. Rather than a 'slight reduction in heat-sinking effect'. I imagine that the 'heat sinking effect' might well become 'negative' if the supply cable is fairly heavily loaded wrt. its CCC.
Kind Regards, John
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That's probably true, but they could satisfy the temperature-rise test prescribed for when they are both on the faceplate without necessarily being able to safely carry 2 x 13A loads for long periods.
Kind Regards, John
Why would BS 1363 require the temperature rise test for single sockets to involve background current in the cable if it had no relevance?
That's the whole point.
There is no guarantee that a twin socket could pass 2x13A without suffering heat damage because they are not required to.
Sorry - single/double is irrelevant. I meant that ring finals were the reason we got BS 1363 accessories in the first place.
To create standardised conditions for the test. It has quite a small effect.
True, but they do have to conform to all the other provisions of the standard as well.
... but presumably a large enough potential effect for them to feel it needs to be incorporated into the conditions of the test. There's no obvious reason why the conditions for testing single and double sockets have to be the same. As I've said, what I don't understand is why they don't require 32A in the cable (rather than 20A), as part of the conditions of temp-rise tests of both single and double sockets, given that it's very possible that they will be installed in "32A circuits".
Kind Regards, John
Is that the case? I must say that I don't know about the historical chronology of these things. On the face of it, even if all that had existed had been 30A radials, there would still have been a theoretical 'need' for BS1363-like accessories (i.e. fused plugs and FCUs).
Kind Regards, John
"what I don't understand is why they don't require 32A in the cable (rather than 20A), as part of the conditions of temp-rise tests of both single and double sockets"
I suspect the reason was that 'they' were trying to simulate a likely condition, rather than the worst-case. By the time that 3kW loads became commonplace, and materials easily available that would enable twin 13A socket-outlets to withstand a full-current temperature rise test, the standard had been in place for so long that it would not have seemed worthwhile to change, given the small number of real-world problems caused by overheating.
I suspect the reason was that 'they' were trying to simulate a likely condition, rather than the worst-case. By the time that 3kW loads became commonplace, and materials easily available that would enable twin 13A socket-outlets to withstand a full-current temperature rise test, the standard had been in place for so long that it would not have seemed worthwhile to change, given the small number of real-world problems caused by overheating.
So why not standardise on no background current at all, just that going through the socket and dummy plug?
Does anybody know what effect a background load of 18A would have? Or 49A?
Who can assure me that if I have 63A flowing in conductors joined at the terminals of a socket or FCU for several hours the accessory will not suffer heat damage?
Yup - when it was decided that 15A radials using 7/.029 would be turned into 30A rings by connecting the end of the radial back to the fuse box they realised they'd need fused plugs to replace the BS 546 jobbies.
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