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| The Duxtop LCD P961LS Induction Cooktop with the Fellow Stagg Pour-Over Kettle |
In my continuing effort to wean our household off petrochemicals, I have been trying to move our kitchen to use more electricity instead of propane for cooking.
We already have an IKEA electric wall oven with a convection feature that allows faster cooking at slightly lower heat. It works pretty well... except when it broke a year ago three days before Thanksgiving. (Its two thermal fuses burned out when we ran the self-cleaning cycle. Like most things in my home, too much dust and lint had built up in the oven's air vents.)
We also have a propane cooktop by Jenn-Air. It is pathetic. At the time it was installed it was the only model available that would fit the hole in the kitchen counter. The burners often fail to ignite. The oxygen mixture for the burners varies (perhaps based on the propane tank level) and it often burns a yellow candle-like flame (indicating too little air) and it produces less heat. The cooktop has an integrated indoor grill that never gets used -- a testament to its utility. But it has a downdraft exhaust fan which is handy. (It's the only exhaust fan in the kitchen.) Overall, the cooktop performs at the border of acceptability.
It turns out propane and natural gas cooktops have another significant downside besides general greenhouse gas emissions: they produce significant indoor emissions of airborne toxins such as carbon monoxide, formaldehyde and nitrous oxide.
I've considered replacing the propane cooktop with an induction cooktop. But there aren't any 48-inch-wide induction cooktops on the market. And engineering a way to fit a 30 or 36 inch cooktop into the 48 inch hole in the kitchen island and replacing the downdraft fan is a daunting and potentially expensive project.
I decided to try using one or two portable single-burner induction cooktops in conjunction with the existing cooktop. We never use the grill section of the Jenn-Air cooktop. I could place a portable induction cooktop over the grill section, and we would lose nothing.
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| The IKEA Tillreda Induction Cooktop sits on the Jenn-Air's indoor grill next to downdraft vent |
A bit of research revealed a couple portable single-burner induction cooktops I could try. The IKEA Tillreda model is an incredible value at $44. I also ordered a heavy duty stainless steel model (Duxtop LCD P961LS) that was $160 on-line. Both units are rated to draw up to 1800W. Both units have similar features and capabilities, and each can be powered from a dedicated 15 amp 120 V-AC outlet.
I picked up the IKEA cooktop at their store on a trip through Sacramento. And the Duxtop arrived soon thereafter.
I measured the Duxtop's maximum power draw at 1750W and the IKEA's at 1600W using a Kill-A-Watt power meter. The fan alone in the IKEA uses 3W, and the Duxtop's fan uses 4W.
Experiments with our various cookware on the induction cooktops resulted in some successes, some failures and one mystery. All our classic All Clad pots and pans work. Our Revere Ware pans do not work. The All Clad Copper Core pots and pans we have do not work. (All Clad claims their current Copper Core cookware is induction compatible indicating they have changed in their formulation since I acquired mine.) A KitchenAid tea kettle worked fine. An All Clad griddle and an All Clad Wok did not work. The iron skillet worked fine.
Fortunately we have a complete set of classic All Clad pots and pans and some compatible kettles.
induction cooktop
compatible
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magnetic
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Classic All Clad
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yes
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yes
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Revere Ware
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no
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no
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All Clad Copper
Core
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no
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no
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All Clad Griddle
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no
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no
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All Clad Wok
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no
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no
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Kitchen-Aid Kettle
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yes
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yes
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iron skillet
|
yes
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yes
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Fellow Stagg
Kettle
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yes
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no
|
According to the wisdom of the internet, all induction-compatible cookware is ferromagnetic. q.v. https://en.wikipedia.org/wiki/Induction_cooking#Cookware
Each pot or pan that worked with the induction cooktops was also ferromagnetic as testable with a magnet. Each pot or pan that fails was not magnetic. Except one mystery -- the Fellow Stagg Pour-Over Kettle.
The Fellow Stagg Pour-Over Kettle is claimed to be made from 304 18/8 stainless steel. It does not hold a magnet, even a very powerful rare-earth magnet. But it works fine with either of the induction cooktops.
I suspect the key property of the Fellow Stagg kettle that allows it to work with induction yet not be magnetic is the stainless steel's magnetic susceptibility. Magnetic susceptibility is analogous to the difference between resistance in DC electricity vs reactance in AC electricity.
https://en.wikipedia.org/wiki/Magnetic_susceptibility#In_the_frequency_domain
It may be that the 304 steel in the Fellow Stagg kettle has little or no susceptibility at 0 Hz (thus a permanent magnet doesn't stick), but at 24 kHz it has a high enough susceptibility for heating.
Operation
Both induction cooktops have loud fans that operate while the cooktop is operating and after for a short time while they are still hot. The fans are not so loud that they interfere with conversation, but it's more ambient noise. (The Jenn-Air's downdraft fan is so loud it does interfere with conversation.)
The IKEA Tillreda model has a child safety interlock that engages when you first plug the device in. (You just press the "lock" button for 3 seconds to disengage the safety.) You can also engage the lock manually at any time by pressing the lock button. The feature is well thought out, and it isn't a large nuisance after you learn how to unlock it.
The Duxtop also has a "lock" button, but it just locks the current cooking settings and not the On/Off button (which resets the lock to unlocked). So it is not much of a child safety setting. It's more of a "don't mess with my cooking" feature.
My initial cooking experiments have been successful. I'm hopeful this experiment will prove successful over the long term, and we will end up using the electric induction cooktops more than the gas burners.
Measuring efficiency
It turns out that induction cooktops are not all that much more efficient than traditional electric resistance cooktops. But they are definitely faster and easier to clean, and the induction cooktops have efficiency advantages with smaller jobs such as boiling a liter of water.
The Department of Energy has measured induction cooktop efficiency at 71-74% using more sophisticated measurement techniques designed to mimic real-world usage.
https://www.govinfo.gov/content/pkg/FR-2014-12-03/pdf/2014-28212.pdf
The Fellow Stagg kettle boiled 1 liter of 20C water in 4.1 minutes which indicates 78% efficiency.
[Calculation of cooktop's energy efficiency when boiling water]
Energy required to bring 1 liter of 20 C water to 100 C:
Q = c*m*(100 C−T)
c = specific heat capacity of water, which is 1 cal/(g C)
m = mass of water: 1000 g
T = the room temperature in C: 20 C
Q = 1 cal/(g C) * 1000 g * (100 - 20)C
= 1 cal/(g C) * 1000 g * 80 C
= 80000 cal
= 80000 cal * 4.184 J/cal
= 334720 J
= 334720 J * 1 Wh/ 3600 J
= 92.9778 Wh
= 93 Wh * 60 min/h
= 5580 Wmin
Time required to bring 1 liter of 20 C water to a boil on a 1750W cooktop with 100% efficiency:
= 5580 Wmin/1750W
= 3.2 min
Measured time to bring 1 liter of 20 C water to 100 C on the Duxtop 1750W cooktop
= 4.1 min
Efficiency = theoretical time / actual time
= 3.2 min /4.1 min = 0.78
The Kill-A-Watt measured the work to boil the liter of water.
= 120 Wh
Efficiency = theoretically required work / actual work
93 Wh /120 Wh = 0.775
Update:
I ordered an induction diffuser plate to see if it would allow the induction cooktops to work with pots and pans that are directly incompatible with induction to work to some degree.
The first diffuser plate I ordered arrived damaged. So I returned it.
Artestia 9-1/4" Induction Hob Heat Diffuser Aluminum/Stainless Steel Disc with Heat Proof Handle
I then ordered this model.
Gourmia GHP9530 Induction Cooker Diffuser Plate 9.5" – 3.4mm Thick Stainless Steel
The theory is that the diffuser -- a 240 mm-wide stainless steel plate -- gets heated through induction by the cooktop, and the pot gets heated through conduction from the diffuser plate.
I tried to boil 1 liter of water in a large All Clad Copper Core sauce pot (270 mm diameter with a 240 mm flat base) on the Duxtop. The water got hot, but it failed to boil after more than 12 minutes. (A similar All Clad classic sauce pot boiled the liter of water in 4 minutes 22 seconds.) If the diffuser and Copper Core pot had succeeded in boiling the water it would have represented less than 25% efficiency.
I also tried boiling the liter of water in the All Clad Copper Core sauce pot with the diffuser on the IKEA model. It resulted in an overheating error.
Obviously, the diffuser plate is pretty useless with the All Clad Copper Core.