Amp rating of this oven

[JohnW2]

So you are putting in a new circuit. Have you notified building control? You cannot add a circuit to a CU without doing that.

Those are most certainly not answers to any questions which have been asked

 

[Jupiter01]

Does that help?

Yes, immensely. Typically helpful.

Having said all that, you have (greatly oversized) 10 mm² cable, so it's totally unnecessary (from the point of view of cable protection) to consider OPDs anything like as small as 16/20 A (as has been said, you could probably have a 63A one!).

We’ve established that the oven requires a minimum of 20a and that the cable is oversized.
Based on your response, I am inclined to go with a 32a MCB but what would be the drawback of using a 20a MCB?

 

[JohnW2]

Yes, immensely. Typically helpful.

Gret. You're welcome

We’ve established that the oven requires a minimum of 20a and that the cable is oversized.

Exactly. 20A (or, at least 16A if one applies diversity) is the minimum for the oven, but much higher than that 9maybe 63A) would be OK for the 'oversized cable

Based on your response, I am inclined to go with a 32a MCB ...

If you did that, then one could say that none of this discussion was really necessary, since you would merely be doing "what almost everyone does" for a 'cooker circuit' (albeit that's commonly 4 mm² or 6 mm² cable).

... but what would be the drawback of using a 20a MCB?

None I can think of, really, in the present situation - other than that I suppose it is 'nicer' not to be running an MCB right up to, or close to, its rated current. The upside of going with a 32 A one (so, I suppose, a 'downside' of not doing so) is that, with the future in mind, you'd then have a fairly standard 'cooker circuit' which could (assuming diversity was considered) be used 'as is' for cooking appliance loads up to a total of around 19/20 kW in the future.

Kind Regards, John

 

[DetlefSchmitz]

but what would be the drawback of using a 20a MCB?

To my mind the disadvantage to using a lower MCB value than you need to, is that for someone in the future to increase it depends on their knowing the complete installation method which may not be information available at that time. So they may not be able to take advantage of the incredibly generous circuit cable. And as John said, 32A is a nice 'standard' circuit to have in the cooker location. Maybe a note inside the CU would be a good idea in any case.

 

[Jupiter01]

To my mind the disadvantage to using a lower MCB value than you need to, is that for someone in the future to increase it depends on their knowing the complete installation method which may not be information available at that time. So they may not be able to take advantage of the incredibly generous circuit cable. And as John said, 32A is a nice 'standard' circuit to have in the cooker location. Maybe a note inside the CU would be a good idea in any case.

And this future scenario would presumably result in nuisance tripping?

 

[JohnW2]

And this future scenario would presumably result in nuisance tripping?

Possibly, but probably not.

If you used, say, a 20A MCB, that would allow 29A to flow for about an hour without tripping, whereas a large cooker (say 15 kW at 240V) would only draw, on 'average' (i.e. 'after diversity') about 25 A (at 230V).

Kind Regards, John

 

[JohnW2]

... and the only reason for going any lower than 32A is if you wanted to 'obey' the MIs - but, as has been said, if they really felt that their appliance (rather than the cable) required "25A protection", it should be provided internally in the oven.

It's difficult to know how the minds of these manufacturers work.

If they truly believe that their 4.8 kW oven needs to be protected with a "25A fuse", then if they took the same oven, added a 4.8 kW hob and sold it as a "9.6 kW cooker", one might expect that they would then require that cooker to be protected with a "50 A fuse".

Not only would that be pretty daft, per se (and probably would require 10 mm² cable), but the oven that they believed needed '25 A protection' would then only be protected by a 50A fuse!

In terms of the oven, one can't help but wonder whether their reference to "25 A fuse" was perhaps meant to read/mean "at least 25A"!

Kind Regards, John

 

[Harry Bloomfield]

Would any native-English-speaking person who knew anything about electrical installations use the phrase "energy-isolating device"?

In what way, I wonder, would not having an "energy-isolating device" and/or not "identifying the live and neutral conductors in the mains socket" result in "damage to the appliance"?

It is likely a warning notice which covers a wide range of appliances and issued with every one of them. Likely a translation from some other language, where the person doing the translation's first language is not English.

 

[JohnW2]

It is likely a warning notice which covers a wide range of appliances and issued with every one of them. Likely a translation from some other language, where the person doing the translation's first language is not English.

Quite so.

Kind Regards, John