Replacing ceramic hob for induction - basic questions

[rupertcacatua]

Hi all, planning to replace my electric ceramic hob for an induction one.

Current ceramic hob is:
Baumatic B12SS - 230v/400v 3N 50/60Hz 6kW 26.1A, min fuse protection rating 30A.

The current setup is as follows:
CCU>1xB32 MCB>connected to 2x red cooker switches:

• Switch 1: connected to hob above
• Switch 2: connected to 2x electric Neff ovens, EACH rated 230/240v 50Hz 3.6kW 16A (models B6774N0GB and B1524N0GB)

Question 1) If the B32 MCB is 32A rated, doesn't that mean that it can support up to a max of 230x32=7.4kW, and if so, 6kW (hob) + 3.6kW (oven 1) + 3.6kW (oven 2), far exceeds the maximum tolerance of this single MCB, when all 3 appliances are at full power? Granted, only on very rare ocassions I have used both ovens plus 4 hobs (Christmas...), and nothing actually tripped. Have I miscalculated the tolerance; is this a safe setup for these appliances?

Question 2) Considering swapping the above hob for 32A wired 7.4kW rated Siemens Induction EX675BEB1E. Is the above setup suitable for a direct swap?

Many thanks

Rupert

 

[telectrix]

you need to take diversity into account.this means that the elements willnot all be drawing juice at the same time, except when initial switch on ( thermostats switching on and off). a 32Acircuit with6.0mm cable has been good for coooking appliances upito 15kW for donkeys, so just connect your new hob. if in doubt, get a local spark to test the circuit.

 

[Midwest]

As above. With diversity, I have your old set up as drawing 38A, and the new one as 40A. As the old set runs ok, can't see the new one not either. If it was a new install, you would probably have two 32A supplies or one 40A.

 

[rupertcacatua]

Many thanks guys. For added info, the CCU is 5 meters apart from both red switches (in case this helps).
CURRENT setup on single 32A MCB: 6+3.6+3.6 = 13.2kW
NEW setup on single 32A MCB: 7.4+3.6+3.6 = 14.6kW

Please forgive my ignorance, checking on NEW setup:
14.6/230 = 63.5A (no diversity applied)
10A + 0.3 x 53.5 = 26.03A (with diversity)

Are my calcs above OK? Is this safe basically because 26.03<32? But what happens when I run all 4 hob zones plus an oven (which is something I do on an almost daily basis)? Will the connection not take it?

Thanks again for your time.

R

 

[Midwest]

Nope, I prefer applying diversity to each appliance separately, that’s how you will use them.

 

[Wilko]

Hi - as you’ve calculated, it is possible to overload the circuit with those appliances. The next question - how likely is it? If you were running a restaurant or some such then I’d say it’s not ok and a new circuit is required. If you envisage firing up all 3 appliances together, then for peace of mind I’d run a second circuit if that’s possible.

 

[marconi]

Interactive User Manual - https://media3.bsh-group.com/Documents/siemens.html?matNumber=9001330662&lang=en

The Induction Hob you are buying has a 'power manager' function which enables the installer or user to set an upper limit on the total power consumed - automatically. So with PM off, the factory setting is for a total inductive heating output of 7.4kW and no more. By selecting PM - look at the link - you can see that the total power can be lowered to suit lower capacity supply (down to a 13A plug). Of course this would mean that when all hobs are in use at the same time on high/full power settings it may take a little longer to first heat up the pans and its contents because a smaller amount of electrical power is spread over the same number of hobs.

Take a look at the reference for further information and setting 'C7'.

So, I would connect up to your current supply and if there are problems you can tweek the maximum power limit. This is what I did for my brother-in-law's new kitchen install and he likes cooking for the 5000 and no-one waits overly long.

 

[rupertcacatua]

Thanks all, and thanks @marconi for the very comprehensive and helpful answer.

 

[marconi]

Have you actually used yet an IH? They are a MArmite appliance if you get my comparison.

 

[Zerax]

I love my IH... no gas for me, so it's the best option by some distance !

 

[rupertcacatua]

Have you actually used yet an IH? They are a MArmite appliance if you get my comparison.

Have not tried it and I'm on the fence about it v gas. Watched lots of vids, articles, I'm aware of the benefits, etc, still, to me going for it v gas will be mainly a matter of managing the risk of gas being banned in future (as they say they might due to climate control), not a matter of preference over the gas cooking experience...

 

[Midwest]

I’ve moved to a property, that’s all electric cooking. We have a ceramic hob, whereas we use to have gas hob. Electric bill has gone up several fold. I read that induction hobs are 50% more efficient, and recent developments make them more user friendly.

 

[marconi]

I am an avid Speccie reader. In the Feb 19 edition was this interesting article. I am not sending you it to put you off buying an IH, after all they do not all function and perform in the same way and like most good technology over time is perfected. I expect the IH will be 'gas-like' anyway once you are used to it. I have only used the IH a couple of times on cookery courses and was not familiar with the technology and way it heated and so struggled with it. By nature I like simple, tried and tested technology which has been perfected so I tend to be a late-adopter to new stuff such as IHs.

Gas vs inductions hobs: is there any competition? | The Spectator - https://www.spectator.co.uk/2019/02/gas-vs-inductions-hobs-is-there-any-competition/

 

[Zerax]

I've used all types of hob over the years... without a doubt gas is easier, cheaper, more controllable, more versatile and better in most ways. However if you don't have gas... then Induction is the closest... But if I had gas where I live right now.... I'd put a gas hob in within a week ! The only thing I'd miss I think... is the easy wipe clean surface !

 

[rupertcacatua]

Does the entire pan need to be ferromagnetic or just its base? Is it better if the entire pan is ferromagnetic or will it not matter because the sides will never be heated directly by the hob anyway (only the base will)?

 

[Midwest]

Does the entire pan need to be ferromagnetic or just its base? Is it better if the entire pan is ferromagnetic or will it not matter because the sides will never be heated directly by the hob anyway (only the base will)?

Dunno, but I would guess yes, just the base, whatever ferromagnetic is.

 

[Dan]

I think my old pans (don't have one of those hobs anymore they did my head in!) only had the weird base, not the whole pan was detected. Because if I didn't have the pan just right, it'd pretend to boil my spuds and make me think my tea was nearly ready, but in fact the little blighters were stone cold and rock hard.

So I'm thinking just the pan, or at least on mine. I bet somebody has made better ones now. But it's put me off for life.

Can't beat fire when it comes to man-cooking eh?!

 

[Zerax]

Does the entire pan need to be ferromagnetic or just its base? Is it better if the entire pan is ferromagnetic or will it not matter because the sides will never be heated directly by the hob anyway (only the base will)?

Just the base needs to be... but the best pans to used are cast iron ones... they work really well ! I have a few aluminium pans that have had like a ferro-magnetic matrix inserted into the base... they work well too...

 

[marconi]

Look for this marking:

You can test the base of a pan with a magnet to see if it is ferromagnetic. Do not use pure copper, aluminium or tin pans. Using the wrong pan may damage the hob position.

There is actually quite a lot of interesting physics to 'optimise' for a pan to be good for an IH hob; frequency, skin depth, size, base thickness, permeability, hysteresis, eddy currents and their flux patterns, Joule heating, skin resistance........

If you are interested read this link or if busy just the 'cookware' section:
Induction cooking - Wikipedia - https://en.wikipedia.org/wiki/Induction_cooking

 

[rupertcacatua]

Look for this marking: View attachment 52925

You can test the base of a pan with a magnet to see if it is ferromagnetic. Do not use pure copper, aluminium or tin pans. Using the wrong pan may damage the hob position.

There is actually quite a lot of interesting physics to 'optimise' for a pan to be good for an IH hob; frequency, skin depth, size, base thickness, permeability, hysteresis, eddy currents and their flux patterns, Joule heating, skin resistance........

If you are interested read this link or if busy just the 'cookware' section:
Induction cooking - Wikipedia - https://en.wikipedia.org/wiki/Induction_cooking

Super interesting. Basically paramagnetic metals (Al, Cu) offer less resistance to the induced current thus producing no/less heat whereas Fe based ferromagnetic materials are not great conductors and thus, offer great resistance, thereby heating up! Still, my question was specific about whether a fully magnetic vessel will heat up better than a base-only magnetic vessel. Can't find an answer to that...I guess fully magnetic will be better but not sure the IH plate "cares" about more than the base of the vessel...