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Hands on with Thermador full-surface induction

Posted by PeterH2 (My Page) on
Thu, Feb 14, 13 at 7:50

We went out looking at induction cooktops yesterday and encountered a live Thermador Freedom "full-surface"/"zoneless" unit with a Thermador rep. in attendance. We didn't have time to play with it for very long, but here are some impressions:

The rep claimed that there were "about forty 3-inch coils". I read elsewhere that there are 48 coils.

First off, this thing is a really cool toy, ideal for the iPad generation. The control panel is a color LCD touch screen about 6" diagonal, like a small iPad. It's easy to read, and it responds nicely to touch (not too sensitive - "just right"). I care a lot about user interfaces, and this one is really well done - the developers clearly were very smart people who put a lot of effort into it.

Each pan you put on the cooktop appears in the display as an outline (circle or rectangle) that shows the location, shape, and size of the pan. The current power setting is inside the circle. The accuracy of location seemed to be around 1" or better.

The cooktop will recognize up to six pans at a time, but you can only heat four out of the six simultaneously - a little "X" is shown on the other two. You can switch the active pans without needing to move them - just turn off one of the active pans and turn on one of the inactive pans.

If you move a pan a small distance (for example, you pick a pan up and put it back in not the same spot), the cooktop is smart enough to know it's the same pan - it just moves the circle in the display and keeps the power setting. If you pick a pan up and move it from one side of the cooktop to the other, a little icon appears in the new location to let you transfer the power setting to the new location.

Zoneless is a really Good Thing - it was a real pleasure not to have to worry about which pan matches which ring, or aligning pans exactly - just plunk them down wherever you want and the cooktop figures it out. The ability to use large rectangular cookware such as grills, griddles, and roasting pans is a huge benefit.

Our tests showed that uneven heating/temperatures are a definite issue with cast iron pans on conventional induction cooktops. The zoneless unit was much better in that respect, but still not perfect (see below for more on evenness of heating).

It's not all good news:

It's $%#@! expensive - $5K compared to $3K for the 5-ring Thermador induction cooktop and much less for many other very capable 5-ring induction tops.

The unit is split into two zones; left and right. You can have a maximum of two pans per zone. So, no using three small pans on one side and one huge one on the other. A big pan in the center is considered to be a pan in both zones, so you can only have three pans total if you do that.

Maximum power on a single pan is not as high as "conventional" induction cooktops. That said, it's probably adequate for real-world use, but I'd want to do more testing before I'd consider buying the zoneless.

We saw some signs of uneven heating - bubbles on the bottom of a large stock pot simmering water were clustered on one side of the pan (on a conventional induction ring, you would see a "donut" pattern of bubbles under the same conditions). A quick test with a 12" lodge cast-iron skillet using an IR thermometer showed similar behavior - temperatures varied by about 40F across the pan. For the cast iron pan, that's still an improvement - we saw over 100F variation across the same pan on a conventional induction ring. We didn't have time to do an exhaustive test, but it's possible that the individual coils were not getting the right amount of power to heat the pans evenly. Again, something I'd want to test more before making a buying decision.

Control is not as convenient as the "normal" Thermador/Bosch cooktops - you always have to select the element, then scroll a strip of settings across the screen until you hit the one you want. The conventional models leave the last element selected and have a strip that lets you hit the setting directly, so one touch vs. touch+swipe.

Sure, it's about 36" wide but really it's a 30" cooktop with a wide trim each side and then some dead glass area before you actually reach the cooking area. This ties in with the power rating (only needs a 40A supply, where almost all 36" induction cooktops require 50A), and the fact that you can only heat 4 pans at a time.

The trim looks like a minor dirt trap - we think induction cooktops that have no trim around the edges are the way to go, because you can just sweep debris off the edge. The rep hinted that trim/finish variants might appear after a couple of years if the zoneless sells well enough.

The trim looks like it will get scratched pretty easily, and it will look pretty bad if it gets scratched. The trim is so wide that it reduces the area available to "park" pans, etc. noticeably - it is definitely inferior other 36" induction cooktops in that respect. I am guessing that Thermador put the wide trim on there to make it less obvious that the cooking area is much narrower than the overall width.

This thing has a lot of complex electronics in it (especially that pretty LCD display); I wonder how reliable it will prove to be. I also worry about the availability of parts in a few years time - if it catches on, this is the kind of technology that's likely to evolve fairly rapidly, so the current model may be obsolete within a year or two. I would definitely purchase an extended warranty for this (and I NEVER do that).

In the end, we were sorely tempted, but the conventional 5-ring Thermador still seems like a more sensible purchase for us. It looks like we were right about the power being a bit less than the conventional type for a given pan size. If they ever make a trimless unit that really is 36" and has three zones, we would jump at it. But the current model is just too compromised.

This post was edited by PeterH2 on Sat, Feb 16, 13 at 12:59


Follow-Up Postings:

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RE: Hands on with Thermador full-surface induction

Thanks for this. I still have replacement fantasies -- changing out the electric smoothie for convection -- but waiting for a zoneless that is both perfected and will fit. Hopefully, this will catch on (though price sounds like a barrier with this brand). Or Wolf will do it eventually (which will fit).


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RE: Hands on with Thermador full-surface induction

Edit: moved content from here into my original message.

This post was edited by PeterH2 on Sat, Feb 16, 13 at 12:59


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RE: Hands on with Thermador full-surface induction

"We saw some signs of uneven heating - bubbles on the bottom of a large stock pot simmering water were clustered on one side of the pan (on a conventional induction ring, you would see a "donut" pattern of bubbles under the same conditions). A quick test with a 12" lodge cast-iron skillet using an IR thermometer showed similar behavior - temperatures varied by about 40F across the pan. For the cast iron pan, that's still an improvement - we saw over 100F variation across the same pan on a conventional induction ring. We didn't have time to do an exhaustive test, but it's possible that the individual coils were not getting the right amount of power to heat the pans evenly. Again, something I'd want to test more before making a buying decision."

just curious which IR thermometer was used to determine this temperature variation.

i just went thru the exercise of researching IR thermometers for my lab and found out the measurement spot size can vary quite a lot as a function of distance. the common variety have 1:1 optics (so a 1 foot diameter spot over which the temperature is averaged when measured at 1 foot away!) and the expensive lab grade thermometers have up to 50:1 optics (1 foot spot at 50 feet distance)

in short, just wondering how big the spot was used to determine the 100F variation.


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RE: Hands on with Thermador full-surface induction

The IR thermometer was from Thermoworks (link below). It claims to be 12:1. We held it about 3" from the surface of the pan, so the spot being measured was pretty small. FWIW, I can use it as a stud-finder on external walls by looking for cold spots where the studs bridge the insulation.

We got similar results with a bead thermocouple (Extech). I have now bought a decent contact thermocouple (also Extech) that I can use with my multimeter (you guessed it) for any future tests.

Here is a link that might be useful: Thermoworks IR thermometer


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RE: Hands on with Thermador full-surface induction

Addendum: the Thermador Freedom cooktop has the same internals as the Gaggenau CX480 zoneless induction cooktop. The user interface is slightly different, but otherwise the two are functionally exactly the same. The Gaggenau is 31.5" wide; they didn't attempt to pretend it is a 36" cooktop. I don't have the price for the Gaggenau, but I'll bet it's way more than the Thermador.


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RE: Hands on with Thermador full-surface induction

I found a video on YouTube that shows the insides of the Thermador Freedom.

Here is a link that might be useful: Thermador Freedom CES 2012


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RE: Hands on with Thermador full-surface induction

I went to a distributor to see a demo of the Thermador Freedom induction cooktop. While I think this idea is going to be the future of induction, I didn't buy it for our new kitchen, however for one reason:

I don't like the swipe user interface to adjust the numbers. I have an iPhone and this method works really nicely on the iPhone, but I wouldn't want this on my cooking appliances. Not sure why I feel this way, but it probably doesn't feel right because I'm picturing greasy fingers swiping across the surface and I'm not sure how accurate it and easy to use it will be under dirty conditions. My most bulletproof, long-lasting appliances always had the simplest controls.


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