So what?
Can you do sums? 4800/240 = 20A (that's actually 19.2A at 230V which you are supposed to use for design).
Does that mean you would not buy it because you have MCBs?
Amp rating of this oven
- Thread starter Jupiter01
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Can you do sums? 4800/240 = 20A (that's actually 19.2A at 230V which you are supposed to use for design).
Does that mean you would not buy it because you have MCBs?
Was responding to your earlier comment re. actual manufacturers specifications.
If Bosch state 25amp, that’s the way to go I assume. Yes, I could increase to 63a given the size of my cable.
As is so often said, if the manufacturer feels that the equipment requires a particular degree of overcurrent protection, then such protection 'should' (one could easily say 'must') be provided within the equipment.
That's surely a situation in which the equipment 'must' have the internal protection deemed necessary by the manufacturer - since I would have thought that it would be extremely unlikely that the supply to the equipment would be protected ('eternal' to the equipment) by a "semiconductor fuse", isn't it?
Kind Regards, John
I am personally comfortable working on the basis of that assumption.
However, as we know, the problem is that Sunray and bernard, to name but two, will scrape barrels (maybe even with anecdotes relating to extremely rare occurrences) and come up (very rare) situations in which an oven could result in an overload current.
I remain 'comfortable' on the basis of viewing that possibility in the light of the extremely low probability of it happening (aka 'risk assessment') - but it seems that others can't.
Since they are essentially untestable, we don't have any idea as to what is the in-service 'failure rate' of MCBs, but it wouldn't surprise me if the probability of that were greater than the probability of an oven resulting in an 'overload current' - if so, I wonder what those mentioned above would want to do to address that (undoubtedly extremely small) 'risk'?
Kind Regards, John
When designing something the designer has to "scrape the barrel" in order to find all the possible failure modes that could affect the item, system or installation being designed.
Only when all possible modes are known can each mode be given a calculated / estimated factor of probability
An appliance using resistive heating elements can have a failure mode that causes the current flowing on the Live wire to be higher than the designed current. If an RCD is in the supply then this will trip and cut the supply, Without an RCD the current will continue to flow until a fuse or an MCB operates. ( or the overheating section of element melts.
Wouldn’t the “safest” option be to use a 25a breaker in my situation? That covers all bases?
Whilst I could use a 63a breaker in my situation (as I have a 10mm cable), I am unclear as to the benefits of this. Other than future proofing, if I fit a higher rated oven and want to avoid nuisance tripping.
Can you help me out with the above consideration please.
All that technical data applies to the oven. One can assume it means 25a built in fuse protection.
How many times do you have to be told the breaker is to protect the cable not the oven?
Anyway 25a breakers are difficult to source.
With respect, there is a divergent of views on this.
A 32a breaker would also be protecting the cable?
Yes but the manufacturer states you must use a 25A fuse.
If you think the manufacturer's "instructions" so important, you cannot say you must have a 25A overload device because the manufacturer says so and then ignore the type the manufacturer states.
You can't have it both ways.
Either you follow the manufacturer's "instructions" or you work it all out for yourself.
I suggested 32a instead of a 25a MCB as @winston1 indicated that the latter is hard to source
Back to my question. What size MCB should I use in this situation?
Sorry, I’m still unclear on this.
They do indeed. Then, as you go on to say ....,
Quite so, but it is the next stage in the process which is relevant here. On the basis of that estimated probability, one has to decide whether 'addressing' the potential risk is necessary, or even necessarily 'justified'. Implicit in that decision is an acceptance that leaving non-zero (but extremely small) risks unaddressed is sometimes the sensible and rational course - particularly given that the 'addressing' will nearly always be associated with some sort of 'costs', sometimes even definite 'downside'.
As often discussed, it can. It therefore comes down to the risk assessment' mentioned above - and it is my personal opinion (which you don't appear to share) that the probability of such an event is so low as to not require (or really justify) addressing it in any way.
It's really similar with diversity - since that, by definition, is a probabilistic concept. Even in the absence of any faults, with a large (say "19-20 kW") cooker, there is theoretically a non-zero (but incredibly small) probability that it could draw in excess of 80A for a significant period of time - but no-one in their right mind would consider it necessary to feed it with 16 mm² T+E (if Method C) or 25 mm² singles if not Method C.
Determining "all possible failure modes" is not all that difficult - it just requires knowledge and thought. 'Determining' the probabilities of each of those failure modes is more difficult, but one can at least have a stab at estimates. However, translating that into a 'decision' is entirely down to a personal (or, in some cases, 'societal') decision as to what degree of non-zero (but incredibly small) 'risk' is acceptable - that's where opinions may vary widely, and where you sometimes seem to be somewhat 'out on a limb'. One can't say that you are 'wrong', but one can identify situations in which you are seemingly in a very small minority.
Kind Regards, John
For the umpteenth time the one you have is OK. No need to spend money, time, or effort
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