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Double sockets
- Thread starter JohnW2
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Yes, I could; in fact, it's only about 1.5h - but, as I assumed the posted quote was a copy-and-paste, I didn't bother (although there's a possibility that it is out-of-date).
I agree totally. It would seem that MK, just like so many people who write on this issue, have missed the whole point about what a BS (Bristish Standard, not necessarily b******s
) is all about - (e.g all these incorrect asserions that double sockets are 'rated' at 20A).Despite what mikhailfaradayski says, it still does seem a little odd/silly to me that a company should choose to 'rate' their product at 13A when they are confident enough about their product and testing to publically state that an 'indefinite' load of 19.5A is OK - but that's obviously their business. Maybe, and a little ironically, they feel it might confuse, since people might think it is no longer a '13A socket' if it has some other rating stamped on the back.
I'll be interested tgo hear if you find anything more relevant in youyr MK catalogue.
Kind Regards, John
BS 1363 Part 2 1995 defines a socket-outlet as "An accessory having a set of three socket-contacts designed to engage with the pins of a corresponding plug and having means for the electrical connection of approriate cables or flexible cords".
To me, this confirms that the 13A rating applies to each socket-outlet, i.e. the set of three socket-contacts, even if there are multiple 'sets-of-three' mounted on a socket-outlet plate.
If twin socket-outlets were to be rated at 13A total, what would be the point of BS 1363 demanding that the heat-rise test for a twin is performed at a total load of 20 A?
To me, this confirms that the 13A rating applies to each socket-outlet, i.e. the set of three socket-contacts, even if there are multiple 'sets-of-three' mounted on a socket-outlet plate.
If twin socket-outlets were to be rated at 13A total, what would be the point of BS 1363 demanding that the heat-rise test for a twin is performed at a total load of 20 A?
To me, too, until things started confusing me! People here have asserted, and the wording of the MK catalogue seems to concur, that the term 'socket-outlet' applies to a whole physical unit - whether that has one or more 'sets of three'. That's certainly not what I would have said.
Well, there would be nothing unusual about a Standard requiring a test to be undertaken at conditions more arduous than the 'rating' of the product (e.g. testing a 13A rated product at 20A). What obvioulsy would not be possible would be for the standard to specify a test which was less arduous than the 'rating' - so, whatever else, BS1363 cannot regard a double socket as being OK ('rated') for 2x13A (which is what 99.99% of the general public probably believe) if at least one of the specified tests requires only 20A for a 'double socket'.
For something so basic, this whole situation is amazingly confused!
Kind Regards, John
JohnW, sorry but I don't agree with either of those statements!
The temperature rise test does not verify the rating of the socket-outlet, that is done (with a safety margin) by the breaking capacity test and normal operation test. The temperature rise test is to verify that the following requirement is met "Socket-outlets and their surroundings shall not attain excessive temperatures in normal use". This is clarified by table 4, which states the permissible temperature rise. For accessible external surfaces that is 52K, for terminals 47K.
The key words are "in normal use", which imply that the responsible committee considered that a double socket-outlet having 2X13A loads plugged into it would not be considered normal.
That might not be so realistic an assumption today as it was when the standard was written.
MK's technical literature states 13A per socket-outlet (except 3 gang). Define 'socket-outlet' ?
I quoted the definition from BS 1363 a couple of posts up. I assume MK have a copy of the standard, and also that their literature uses the same definitions.
To John and Stillp,
Do you mind if i ask what you both do for a living? Is it in any way related to product development or testing of electrical equipment?
If the answer is yes, i can understand your depth of analysis into what seems to be a simple question.
If the answer is no, might i respectfully ask what is it that has drawn your enthusiasm for this subject?
Three pages ago, i thought this was a very simple concept to get to grips with. I still think the same now, but now i am also slightly bemused at how much of a kafuffal it seems to be causing with some folk.
Do you mind if i ask what you both do for a living? Is it in any way related to product development or testing of electrical equipment?
If the answer is yes, i can understand your depth of analysis into what seems to be a simple question.
If the answer is no, might i respectfully ask what is it that has drawn your enthusiasm for this subject?
Three pages ago, i thought this was a very simple concept to get to grips with. I still think the same now, but now i am also slightly bemused at how much of a kafuffal it seems to be causing with some folk.
I don't really understand how you can disagree with the first statement. In terms of safety-related issues, it is probably the rule, rather than the exception that 'safety margins' are built in to standards - i.e. that products have to pass tests undertaken at conditions more severe than those for which the product is 'rated'
Yes, but I suppose I'm guilty of not having said the rest of it, since I thought it was 'obvious' - namely that I can but assume that each of the 'sets of three' will pass all of the other tests (breaking capacity etc.) in the same way that a 'single' socket would - since there is no reason on earth why putting two or more on one plate should alter that. In practice, therefore, if there is a difference in rating between two separate 'single' sockets and one 'double socket', I can but presume that it must be due to the temperature rise - and even that surprises me.
I agree with all of that - but see above.
Kind Regards, John
Exactly. As stillp has indicated, there is a definition in BS1363, but it appears that not everyone is working to that definition - and the MK catalogue confuses things even more by talking in terms of 'units' - which appears to refer to the whole product (whether it will accept 1, 2, 3 or more plugs).
Kind Regards, John
As I indicated in my post which started this thread, I was merely curious to know why so many electricians, here and elsewhere, were asserting that 'double sockets' were 'rated' at 20A ("except MK ones, which were 'rated' at 26A"), when I could not really find a basis for any of that. I thought it was a simple question which would yield a simple answer (I know you think the answer is simple, but you've only got to look at this thread to see something other than 'simplicity'!)
It has emerged that these assertions probably arise mainly because of a misunderstanding of what Standards are all about and also that there is no consensus of opinion amoungst electricians as to what the 'ratings' of sockets really are. I find that surprising.
Kind Regards, John
If you are an electrician tasked with installing these devices, Which do you feel is the most relevant standard to work to BS1363 or BS7671:2008?
Are they in agreement with each other, or do they contradict each other?
How do you deal with any contradictions found?
If you were in a customer house, having just installed one of these devices, and then this question is asked, how would you choose to respond to the customer? (bear in mind that you probably want to get home before midnight
)Would you engross them with hours of moot techno babble, given your knowledge of testing methods, or do you just tell them something far more simple, that also errs on the side of safety?
Hi John,
If you thought this subject was complicated and confusing, take a look at this question:-
http://www.diynot.com/forums/viewtopic.php?t=265550
Its gonna mash your melon
If you thought this subject was complicated and confusing, take a look at this question:-
http://www.diynot.com/forums/viewtopic.php?t=265550
Its gonna mash your melon
Of course you may.
In a way.
However my motivation in this thread is that there were several bits of misinformation that were stated as fact, and also that John had posed an interesting question.
With hindsight, you're probably right that tests are often more arduous that the parameter being verified. Not always though.
Tests less severe than the rating are quite common, for example when testing at the full rating would be dangerous or destructive. The committee has to judge how severe a test is necessary to verify that the requirements of the standard are met.
I think that you (John) and I are in agreement, that the rating of each "set of three" is 13A, regardless of how many are attached to a mounting plate. They are likely though to overheat if a multiple socket-outlet has all outlets loaded to the full rated current - a situation that the standard does not consider to be normal.
BS7671 is of course the standard for installations. It requires socket-outlets for a.c. to comply with BS1363, with a few exceptions listed in 533.1.5.
Neither. They do however complement each other.
I wouldn't be in that situation, not being an electrician. However if someone were to ask the question (what was it again?) I would reply along the lines that a dual 13A socket-outlet, whatever the make, may reach an uncomfortable temperature if two 13A loads are connected to it for a long period.
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