16amp microwave oven

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Did we ever reach a definite answer as to whether a microwave oven rated at 16amp (usually European) can have diversity applied to be fitted to a 13amp supply?

And if so, what conditions restrict this?
 
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If it really is a 16A microwave, then no, when run at 100% it would draw 16A, and we have to be carful about small overloads of extended duration (especially on fused spurs, they don't tend to handle it well)

But I'd doubt it really is a 16A microwave, assuming 2/3 efficency, that would be an ERP of approaching 2.5kw, domestic ones tend to top out at about half that, and even commericial ones don't tend to get as high as that.

Does it have any other conventional cooking modes?
 
If it really is a 16A microwave, then no, when run at 100% it would draw 16A, and we have to be carful about small overloads of extended duration
I agree - but that would only affect the UK socket, plug and fuse, not the cables.


Sparkwright says "a 13A supply". The supply will not really be 13A, will it?
What that really means is "Can one fit a UK 13A socket, plug and fuse on a truly 16A appliance?"
The answer is clearly no.

However, as said, is the microwave truly 16A or is that just an instruction that it should be connected to a 16A socket, plug and circuit which is what will be available in Europe?
If sold in the UK, does it come with a UK plug? If not, then presumably one should not be fitted.
 
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Did we ever reach a definite answer as to whether a microwave oven rated at 16amp (usually European) can have diversity applied to be fitted to a 13amp supply?
Given the absence of any regulations relating to diversity (beyond a statement in BS7671 along the lines that 'diversity may be applied where appropriate'), all you could hope for would be a number of (probably differing!) opinions - a 'definitive answer' simply does not exist. Most people seem to rely on the OSG for guidance about diversity, but many aspects of that guidance seem to be outdated, and, in particular, doesn't distinguish between microwave ovens and any other sort of 'cooking appliance'.
If it really is a microwave, then no, when run at 100% it would draw 16A, and we have to be carful about small overloads of extended duration
Does not the whole concept of diversity (and, indeed, the concept of ring final circuits) accept that small (maybe even 'appreciable') 'overloads' which are not "of extended duration" are acceptable - and, although "of extended duration" or "for appreciable periods of time" are nowhere explicitly defined, they seem to be generally taken to mean at least half an hour, possibly appreciably more than that (perhaps not unreasonably, give than it seems to be implicitly accepted that the current through an MCB, RCBO, fuse or cable {and, my implication, any connected accessories} can exceed its 'rated maximum' by a factor or 45% for an hour without anything coming to harm).

Usage patterns will obviously vary, but running a microwave oven at '100%' continuously for 30 minutes or more would seem very rare/unlikely (in my personal experience, almost unknown.)
I agree - but that would only affect the UK socket, plug and fuse, not the cables.
Although one cannot knock a cautious approach, I'm not sure that diversity even requires concern about the UK plug/socket/fuse. Would you be saying the same if it were, say, an oven (fitted with a 13A plug) with a before-diversity max current >13A but an after-diversity current <13A - or, indeed, if it were a ~30A (pre-diversity) cooking appliance (which therefore represented a 16A after-diversity load) and which was protected by a B16 MCB?
But I'd doubt it really is a 16A microwave, assuming 2/3 efficency, that would be an ERP of approaching 2.5kw, domestic ones tend to top out at about half that, and even commercial ones don't tend to get as high as that.
That's probably the most relevant point. I don't think I've ever seen or heard of a domestic microwave oven which ought to have a maximum current draw of much more than half of "16A", certainly nothing as high as 13A.

Kind Regards, John
 
Although one cannot knock a cautious approach, I'm not sure that diversity even requires concern about the UK plug/socket/fuse. Would you be saying the same if it were, say, an oven (fitted with a 13A plug) with a before-diversity max current >13A but an after-diversity current <13A
Well, I might because of the nature of UK sockets and plugs rather than the diversity aspect.
However, the OP and my reply is more about whether diversity can be applied or the oven actually is 16A.

What about just connecting the oven to the 32A circuit?

- or, indeed, if it were a ~30A (pre-diversity) cooking appliance (which therefore represented a 16A after-diversity load) and which was protected by a B16 MCB?
I would not be concerned about that as it is the accepted way of doing it and does not involve a socket and plug.


That's probably the most relevant point. I don't think I've ever seen or heard of a domestic microwave oven which ought to have a maximum current draw of much more than half of "16A", certainly nothing as high as 13A.
So, the discussion is moot and is just querying manufacturers' incorrect instructions.
 
Well, I might because of the nature of UK sockets and plugs rather than the diversity aspect.
...... I would not be concerned about that as it is the accepted way of doing it and does not involve a socket and plug.

That's interesting, and I don't recall having seen such a view being expressed explicitly before. Just to be clear, I am right in my understanding that you "might" take the view that diversity cannot be applied if its application could result in a peak current >13A sometimes flowing through a BS1363 plug and socket (or. presumably, also FCU)?

Do I also take it that your concern relates to the presence of a fuse in a BS1363 plug, since I doubt that any other aspects of the "nature of UK sockets and plugs" differ enough from the nature of sockets and plugs in other countries to have a major impact on current-carrying abilities.
However, the OP and my reply is more about whether diversity can be applied or the oven actually is 16A. .... So, the discussion is moot and is just querying manufacturers' incorrect instructions.
I think there are essentially two questions. The first is the hypothetical one as to whether it would (because of diversity) be acceptable to feed something which really was "a 16A microwave" via a 13A UK plug/socket. The second question (the answer to which probably makes the first one hypothetical/moot) is whether there is such a thing as a "16A" domestic microwave oven - which I personally very much doubt.

Kind Regards, John
 
That's interesting, and I don't recall having seen such a view being expressed explicitly before. Just to be clear, I am right in my understanding that you "might" take the view that diversity cannot be applied if its application could result in a peak current >13A sometimes flowing through a BS1363 plug and socket (or. presumably, also FCU)?
Yes, I suppose that is correct - but nothing to do with the diversity aspect.
More to do with some sockets and plugs being not really fit for purpose.
Hence the frequent discussions about how much current they can cope with.

Having said that, I have seen a plug that has been fitted through a plug-in timer to an immersion which has been there 'for ever' with no ill effects.
Others overheat for no apparent reason.

Do I also take it that your concern relates to the presence of a fuse in a BS1363 plug, since I doubt that any other aspects of the "nature of UK sockets and plugs" differ enough from the nature of sockets and plugs in other countries to have a major impact on current-carrying abilities.
Yes, perhaps it is just the fuse holder and rivets.

I think there are essentially two questions. The first is the hypothetical one as to whether it would (because of diversity) be acceptable to feed something which really was "a 16A microwave" via a 13A UK plug/socket.
If you mean a true 16A load which cycled on and off - the diversity being solely time related - I would not be keen.

A 20A load reduces to 13A with diversity, doesn't it?

The second question (the answer to which probably makes the first one hypothetical/moot) is whether there is such a thing as a "16A" domestic microwave oven - which I personally very much doubt.
I agree. I think that is probably not a coincidence.
 
What's attached on the end of the Microwave? I don't see the point in using a 13A plug when one could use a more suitable higher rated connection point fed from a Ring or Radial.
 
Yes, I suppose that is correct - but nothing to do with the diversity aspect. ... More to do with some sockets and plugs being not really fit for purpose. ....... Yes, perhaps it is just the fuse holder and rivets.
It's interesting that this discussion is becoming rather wider and more complicated than the diversity ones usually are. To be sure I'm understanding, can you confirm that the following are your view....

1... Given that a 30A cooking appliance is generally taken to represent a 16A after-diversity load, do I take it that you would be perfectly happy for it to be supplied via a "16A" (unfused) plug/socket fed by a circuit protected by a 16A MCB, despite the fact that 30A would probably sometimes pass (for 'non-extended' periods of time) through the 16A-rated plug/socket?

2... By analogy with the above, if a hypothetical "13A" unfused plug/socket existed, do I take it that you would be equally happy for a 20A Cooking appliance (13A after-diversity') appliance to be supplied via that "13A" unfused plug/socket (with a hypothetical upstream 13A MCB), despite the fact that 20A would probably sometimes pass (for 'non-extended' periods of time) through the 13A-rated plug/socket?

3... That if the Plug/socket in (2) above contained a 13A fuse (any with any rating of upstream MCB), you would then probably not be so 'happy'.

If the above, particularly (2) and (3), are all correct understanding of your views, then, as I said, it sounds as if you problem [with (3)] would relate solely to the plug fuse and it's connections.
... Hence the frequent discussions about how much current they can cope with. .... Having said that, I have seen a plug that has been fitted through a plug-in timer to an immersion which has been there 'for ever' with no ill effects.
Others overheat for no apparent reason.
Yes, I think most of us have seen both of those 'extremes'. Unless there is a surprising amount of manufacturing and/or environmental variation, that seems to suggest that there is no fundamental reason why BS1363 plugs/sockets cannot satisfactorily carry 'full currents' for long periods of time, and that when such service does result in problems, one perhaps needs to look at how well they have been installed (and/or look for unusually harsh environmental conditions)
If you mean a true 16A load which cycled on and off - the diversity being solely time related - I would not be keen.
Fair enough, but I wonder whether you are perhaps making a distinction which isn't necessarily all that 'real'. Given that not many (at least, 'traditional') cooking appliances have any 'modulation' of the heat-producing components (elements etc.) most of the diversity with them is also "soley time-related", with a finite (certainly not zero) probability that all parts of the potential maximum load will be drawing full current simultaneously at times.

Hypothetical though it is, I'm not sure that I would be particularly concerned by the concept of a "20A" (13A after-'diversity') electric kettle supplied via a 13A fused plug, pretty safe in the believe that it would never be used for more than very brief periods at a time (even though drawing 20A continuously during those periods). The 'diversity' I would be then be thinking of would then be the time-diversity over periods of, say, 30 minutes - i.e. the average current over any 30-minute period of even 'improbably heavy use' would undoubtedly be well under 13A.

Kind Regards, John
 
What's attached on the end of the Microwave? I don't see the point in using a 13A plug when one could use a more suitable higher rated connection point fed from a Ring or Radial.
One problem with having an unfused 'connection point' (rather than a plug or FCU with a 13A fuse, if that would be suitable), is that, with a 32A circuit, you might then run into (possibly 'genuine') problems of the adequacy of the microwaves flex to be protected by a 32A OPD) and much more likely to run into issues (which many would suggest could/should be ignored!) of the manufacturer 'insisting' on 16A protection for the appliance!

As has often been said, "FCUs" which could take 16A fuses would often be useful in such situations, but they couldn't really be BS1362-sized fuses, since one wouldn't want people putting them in plugs!

Kind Regards, John
 
Funnily enough I was using a lighting dimmer control today, which had a 16A MCB in it, accessible by the user. It was next to the on/off switch.

I suppose in much the same way that some appliances and extension flex reels (used to) have an overload trip button.
 
Funnily enough I was using a lighting dimmer control today, which had a 16A MCB in it, accessible by the user. It was next to the on/off switch.
What was being dimmed - the lighting of a small sports stadium? :)
I suppose in much the same way that some appliances and extension flex reels (used to) have an overload trip button.
I think that extension flex reels often had (and still have) 'overload trip buttons' if the cable was not capable of supporting 13A (I've certainly still got some "6A" ones which have such cutouts), but I think it's more common these days for reels to have thermal cutouts, to deal with a situation in which the 'overload' (overheating) arises because cable is left on the reel during use, rather than because the actual current is greater than 'what it says on the tin'.

Kind Regards, John
 
Is the solution to this not very simple?

If the oven really is >13A and comes with a 16A plug fitted then one easy solution is to fit a matching 16A socket (presumably Shuko) to the regulations of an EU member state where such sockets are used.
 

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