Induction Hob Ratings

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I'm looking to replace a hob with a Bosch induction.

I'm hoping someone can explain to me the difference in ratings between different models. I've copied the specs for three nearly identical Bosch models below.

So I'm aware the ratings of 3 kW are for a 13A plug (which comes pre-fitted on this model), 4.6 kW for a 20A supply and 7.4 kW for a 32A supply. The ratings in brackets I assume are for the Boost function and on the 3 kW model these are obviously capped at 3 kW.

My question is more along the lines of how the lower rated hobs can operate at these kind of power levels given the rating of each individual ring. I understand diversity can be applied to cooking appliances however with four rings rated at 1.8 kW as an average, it doesn't seem unfeasible for more than 3 kW to be needed at times - what will happen if I turn on all 4 rings simultaneously to bring cold pans full of cold water to the boil? Equally if I put one of the larger rings onto Boost mode, does that mean no other ring could be used at the same time?

Are induction hobs so efficient that diversity really means the first of the three models below will operate just fine on a 13A supply, or are the higher rated ones a better choice?

PUE611BF1B
Connected load: 3 kW
1 x Ø 180 mm, 1.8 KW (max. Power levels 3 KW)
1 x Ø 180 mm, 1.8 KW (max. Power levels 3 KW)
1 x Ø 145 mm, 1.4 KW (max. Power levels 2.2 KW)
1 x Ø 210 mm, 2.2 KW (max. Power levels 3 KW)

PUE611BB1E
Connected load: 4.6 kW
1 x Ø 180 mm, 1.8 KW (max. Power levels 3.1 KW)
1 x Ø 180 mm, 1.8 KW (max. Power levels 3.1 KW)
1 x Ø 145 mm, 1.4 KW (max. Power levels 2.2 KW)
1 x Ø 210 mm, 2.2 KW (max. Power levels 3.7 KW)

PIE651BB1E
Connected load: 7.4 kW
1 x Ø 180 mm, 1.8 KW (max. Power levels 3.1 KW)
1 x Ø 180 mm, 1.8 KW (max. Power levels 3.1 KW)
1 x Ø 145 mm, 1.4 KW (max. Power levels 2.2 KW)
1 x Ø 210 mm, 2.2 KW (max. Power levels 3.7 KW)
 
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I know my induction pulsed to limit output, so there is no reason why they should not share as one hot spot turns on, another turns off, however only the manufacturer can tell you how it actually works.

It has surprised me how low an output will cook food, I have a very cheap Lidi induction for use in the caravan which I used when looking after mother, it turned on at 1 kW and could be turned up to 2 kW or down I think to around 150 watt, and in the main I would turn it down. Most cooking did not need over 750 watt.

The main thing I would say is you want knobs, not touch control, with knobs one can turn it off or down quickly, but with touch controls they are too slow, and you have to lift pan rather than turn it down.

Also some of the touch controls you can't see if your low down, so can't use in a wheel chair, and children can't see the word hot because too low of an angle.

The main cooker has boost, but except for plain water it can't be used, it is too much and simply burns food onto the pan.
 
So I'm aware the ratings of 3 kW are for a 13A plug (which comes pre-fitted on this model), 4.6 kW for a 20A supply and 7.4 kW for a 32A supply. The ratings in brackets I assume are for the Boost function and on the 3 kW model these are obviously capped at 3 kW. ... My question is more along the lines of how the lower rated hobs can operate at these kind of power levels given the rating of each individual ring. I understand diversity can be applied to cooking appliances however with four rings rated at 1.8 kW as an average, it doesn't seem unfeasible for more than 3 kW to be needed at times - what will happen if I turn on all 4 rings simultaneously to bring cold pans full of cold water to the boil? Equally if I put one of the larger rings onto Boost mode, does that mean no other ring could be used at the same time?...
'Diversity' helps quite a lot. A 4.6kW cooking appliance is considered as about 3kW after application of diversity. However, I think you'll find that they are 'intelligent' and limit the total power that can be drawn simultaneously (from all 4 rings) - so, although the rings are individually of identical power in the three models you quote, you'd be able to get a lot more heat out of all four simultaneously with the "7.4 kW" model than the "3 kW" one.

With the models you mention, it sounds as if the 7.4 kW one imposes no limitation on the rings (which only add up to 7.2 kW), but that progressively more 'restrictive control' is applies as you move down through the 4.6 kW one to the 3 kW one.

You can't beat the laws of physics. If the average power going in is limited to 3kW then, even if it were '100% efficient' in terms of cooking (i.e. no heat lost into the environment), you'd only get an average of 3kW of heat into your cooking pots/pans (and 7.4kW of heat if the electrical power were allowed to go as high as 7.4 kW)!

Kind Regards, John
 
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As others have said, the higher rated ones are a better choice if you have the supply to do so.

Its kind of an 'Enforced Diversity' if the power levels you ask it for, are more than the total, then it'll do the best it can while not trying to let you down too much, it depends on ow the manufacturer has done the firmware, but expect for example that while a ring is in 'P' the power levels of the others might be dropped a little until it drops out of 'P' or that 'P' might not be as powerful as it normally is. Or might not be available at all. I wouldn't expect it to lock out rings entirely, just that they might not go as high as you want.

What I don't get though, is why there are three separate models, I have an induction hob of another make, and you set the max power level on installation. I cant remember how, as I left it as its default as the maximum. As these ones in your post are not adjustable, go for the biggest you can with the supply you have available (get the 32A one even if your cooker circuit is shared with the oven, diversity will mean its not a problem) I know places with limited ones because they had to be supplied off a fused spur and it does cause problems if doing a lot of cooking together
 
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I use the auto boil then simmer, don't this my wife does, the knobs have a de-tent in both directions, turn to max and hold goes into boost, turn off and hold then to simmer rate, it goes to standard max then to simmer after I think set time. Heat areas a paired so boost only available if other ring of pair is off. Never use boost. However the options like auto boil/simmer will likely not work if power limited.

Personally after having both induction with knobs, and with touch controls, if touch controls I would auto reject it. The Belling IH60R Rotary Control 60cm Induction Hob would be my selection for hob only, I have the Belling FSE60DOi 60cm Electric Double Oven with Induction Hob, so much better with knobs on it.
 
What I don't get though, is why there are three separate models, I have an induction hob of another make, and you set the max power level on installation.
Yes, that was one of my first reactions, and I started wondering whether they really were different (rather than all being the same, with different default max power settings having been set in the factory). However, they are significantyly different prices (£530, £580 and £675 on Bosch website) - but I suppose it's possible that there are other differences/'features' as well.

If anything, I would have expected the 'highest power' one to be cheaper - since, as I said, it sounds as if that does not need to have any 'intelligent' power control.

Whatever, as you've said, it certainly sounds as if it would be best to go with the 'highest power' one for which one has an adequate supply. Of course, if one is restricted to 'plugging it in', then that would force one's hand!

Kind Regards, John
 
I have a larger size (nearly 90cm) Bosch Induction hob and it can be set to limit power from max down in various steps to 3kW using an installer feature in software. I suspect they all can from the BSH group (and maybe other brands)?

My son has a no-name brand 60cm 4-ring hob on a 13A circuit and it rarely impedes any cooking he does... but obviously all 4 'rings' can't be on full at the same time.
 
Thanks all for the replies.

It's an interesting point some make about why Bosch sell three different hobs that are seemingly the same. The higher rated ones can all be downrated in the settings, i.e. the 7.4kW can be "tuned" down to 4.6kW or 3kW if necessary, which implies they probably are all the same hobs but simply with different electronics which stop you tuning up the lower rated ones...

Given I have a dedicated 32A supply for the hob it seems to make sense to go for the highest rated one then I can be sure I'm not going to hit any limitations at any point.
 
The higher rated ones can all be downrated in the settings, i.e. the 7.4kW can be "tuned" down to 4.6kW or 3kW if necessary, which implies they probably are all the same hobs but simply with different electronics which stop you tuning up the lower rated ones...

Could simply be a 'paywall' or could also have lead to smaller terminals, and tracks on the PCB etc. I suuspect that even if the former then its unlikely to be as simple as a jumper on the board, probably a flag in the firmware so while there are going to be some who could probably get past it, for the most part it cant't be done and even those that could, would end up spending more time than its actualy worth to do so
 
Could simply be a 'paywall' or could also have lead to smaller terminals, and tracks on the PCB etc. I suuspect that even if the former then its unlikely to be as simple as a jumper on the board, probably a flag in the firmware so while there are going to be some who could probably get past it, for the most part it cant't be done and even those that could, would end up spending more time than its actualy worth to do so
As I said at the start, what surprises me is that, of the three models described by the OP, I might have guessed that the highest powered ("7.4 kW"), and actually most expensive, could actually be the cheapest, since it doesn't look as if it needs any (or any significant) control circuitry or firmware at all.

Kind Regards, John
 
As I said at the start, what surprises me is that, of the three models described by the OP, I might have guessed that the highest powered ("7.4 kW"), and actually most expensive, could actually be the cheapest, since it doesn't look as if it needs any (or any significant) control circuitry or firmware at all.
It might not 'need' any to our thinking but surely it must have some to limit the 12.1kW to 7.4kW.

Presumably they think it would otherwise require a 50A supply.
 
It might not 'need' any to our thinking but surely it must have some to limit the 12.1kW to 7.4kW.
You're working with those "max. Power levels" in brackets, and I'm not sure what they represent - so, if those figures really are the maximum loads, then you might be right.

I was talking about the 1.8, 1.8, 1.4 and 1.2 kW figures quoted, the total of which (7.2 kW) is less than 7.4 kW.

What do you think that the two sets of figures represent? I initially thought that the 1.8kW etc. figures might be 'after diversity' versions of the figures in brackets,. but they are somewhat too low for that.

Kind Regards, John
 
I assumed they were the boost mode to which the OP referred. I haven't looked for the manual.

Whether they can all be boosted at the same time, I don't know; probably not which might be what the electronics do.
 
Also, I presume the electronics limit the boost time as well - otherwise they would just be the maximum rating of the particular ring.
 
I assumed they were the boost mode to which the OP referred. I haven't looked for the manual. ... Whether they can all be boosted at the same time, I don't know; probably not which might be what the electronics do.
As you say, we don't know enough.
Also, I presume the electronics limit the boost time as well - otherwise they would just be the maximum rating of the particular ring.
True, if your assumption is above is correct.

Kind Regards, John
 

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