Stoves without thermostats

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To add, in a 400, 600 1000 watt scenario I could see why 6 positions would suffice as 400 + 600 = 1000 /// so it would be redundant.

This of course if for the stove top burners.

Hard part for me will be calculating the heat loss (for the oven) such that X watts will maintain 375-400 degrees steady state.

If I apply the same concept, I could achieve 350, 400 and 450 degrees.

.............

Cookies in my experience cook better at 375 then 350

I'd argue when temperatures are steady the actual temperature is of less importance.

My Breville smart oven has taught me that.

Lets not kid ourselves a typical oven, even a GE "true temp" fluctuates some 50* if not more.

On/Off is crude even when done with relays...
 
And my bad- 350+650 is also equal to 1000 lol.

Still confused why no 1000 watt setting.

Anyway, a modern US burner with two elements. Two elements are common in flatops for giving you a cookware size options, but what is odd here is that these two elements appear to both scale the full unit.



This is typical, where on element runs the center another the perimeter:



Another example of a dual wattage burner:

 
I have never seen a household oven that varies 50 F as it cycles on and off unless it had a bad thermostat etc.

 

It is Impossible to build a decent oven that does not have a thermostat, in order for it to work properly it needs to reach temperature quickly, work in different temperature rooms from 50F-120 F and recover quickly from unpredictable oven door openings and vastly different temperatures of food being added from frozen [ 0 F ] to boiling or more, if you are out to reinvent the wheel an oven without a thermostat is not going to be the invention that wins you any recognition, LOL.

 

John L.
 
But it can win you $$$$$. Everything around you exists because people were capable of thinking outside the box, adding to what existed prior. We may not know the names of the engineers at Whirlpool or their patents but they sure are enjoying handsome pay. So yes, it won't win anyone recognition even if successful to the point of mass production.

In your experience, by how much do ovens vary as they cycle?
 
I can believe that. But also keep in mind you have hot and cold spots along with uneven temperature distribution. Breville went to great lengths to eliminate that too and the difference is night and day.

An oven with more even, steady temps can make up for overall high or low temps.
 
>> why the double elements? What was Whirlpools reasoning behind this?

That's probably one of the "rapid boil" or "turbo boil" elements.
They let you put a LOT of heat, or a smaller amount of heat, into the same size cookware... with much more stable temperature regulation when using lower heat settings.
 
Yes- but my point was having your name on a patent is an accomplishment even though most people could not put an individual name to a patent.

Considering how much stoves vary in temperature and how uneven they are, it is indeed out of the box thinking how to correct it.

Breville smart ovens cook better then most 2,000 dollar ranges.
 
Why not an variable voltage solution? Or high power PWM solution?

Most safety systems could be run on timed modes as well, and no relays to fuse shut.

Would still include a one shot thermostat for fires though.

The shorter the operating times will be the more exact it will, the longer the more you draft off.
 
I find it weirdly ironic that you keep mentioning the Breville smart ovens.

Yes, they *do* work very well, that's true.

And they do have multiple elements.

But they are very possibly the or one of the most over controlled ovens -- the microprocessor even sports anywhere from 6 to 13 (possibly more by now) different programs to deal with cookies, pizza, regular baking, roasting, toasting, some have slow cooking, or air frying features etc.

The entire thing is basically a demonstration of what a few highly sensitive low inertia sensors plus a microprocessor can do with 5 to 6 elements.

It's possibly the furthest thing one could have from a handful of elements coupled to a switch that puts the elements in series or parallel to achieve different power levels, each element on the Breville is connected to circuits that vary the power very closely according to the program and temperature sensors, and, if you look at the elements during a cycle, even for toast, for example, you'll see them cycling from off to several different power levels to achieve multiple different functions, like raise the temperature of the toast, dry it, then they turn on the central broil element to toast the surface etc.
 
100% true- however- the temperature is inside is steady and very even.

My theory is that if you do not open the door to a none thermostat oven, the temps inside will remain rather stable and not bob up and down.
 
Keep getting hotter

Sorry but this really is tit for tat. You don't understand thermodynamics even in the most fundamental sense. Which is why someone with a more advanced understanding would appear dumb to you. Because its going over your head.

At any given wattage you will eventually reach an equilibrium.

The temperature will rise such that heat loss will equal element's heat input.

It is physically impossible for a 250 watt element to bring a typical stove to 600*F. But it will get warm inside for sure.
 
>> My theory is that if you do not open the door to a none thermostat oven, the temps inside
>> will remain rather stable and not bob up and down.
>> ...
>> At any given wattage you will eventually reach an equilibrium.

Again, Yes, it could be done, and Yes, you could bake things in an oven made this way.

But you're still missing the big picture. That equilibrium equation includes losses due to opening the door (necessary to put food inside to cook, or to check cooking progress), the thermal mass of the cold food and cookware you put in, the temperature, humidity, drafts, etc of the external environment in your kitchen, the materials and insulation of your oven, the insulating value and thermal mass of surrounding floor and cabinetry, whether your nearby refrigerator is running, whether the lights are on, whether the sun is shining through the window, what season it is, whether the oven light is on, etc.

It is very easy to design a simple temperature-regulated control circuit to hold an oven at a specified temperature +/- a tolerance, regardless of the outside conditions. It is near impossible outside of a carefully controlled lab environment to reach that same temperature at an equivalent level of temperature stability by equilibrium alone.

So what do you do?
If you set the heater wattage to reach that theoretical equilibrium point at a sane cooking temperature, you have to deal with an oven that for practical purposes never reaches temp. Because with cold food put in, the time it takes to recover is on par with the total time you cook for.

If you set the heater wattage to be higher to account for that, to bring the temp up faster and keep cook times in check, then your equilibrium point is a much higher temperature and leaving it on will burn your food if left alone.

If you increase the thermal mass of the cooking appliance to improve temp stability (cast iron stove walls, etc), you increase the warm-up time considerably, worsening the problems above. If you reduce the thermal mass of the cooking appliance to improve warm-up-to-equilibrium time, you worsen the impacts of opening the door or inserting food.

See the problems?
 
Just to throw this in the mix, how about the old wood stoves with the oven built in. The fire was going constantly to keep heat going, but you could adjust the fire to hold a pretty constant temperature. We had one in the basement at my parents house and if it was on my mother would bake down there all the time and the results were outstanding whether it was cakes cookies chicken or roasts.

Jon
 
I think they should build passenger cars that only have enough horsepower to only drive 65 mph...

Same idea. And it would work equally well.

I may have missed a comment as to why in the hell would this idea have any merit, I scrolled by half of the thread.

I LOVE any system that has feedback control that allows it to be adaptive to work better. This is what a thermostat system is, closed loop feedback control. This is the reason why computer controlled appliances are adaptive and superior to old crude mechanical controls too.
 
I want to try it myself. Doubt it would ever hit mass production for obvious reasons, but the simplicity is kind of seducing for me. Its a good way to learn thermodynamics in person.

LowEfficeny- your post was very helpful to me. You touched on several issues I need to consider like thermal inertia trade offs.

At least the cooktop idea would work.

If you guys were to try this- what wattages would you choose for preheating and baking? Say you had an off the shelf Whirlpool or GE oven and could pick any wattage.
 
Well some good news to make folks happy... I am less enthusiastic about trying this now. Multiple door openings will lower the temperature to much, and to avoid it getting to low a temp a higher wattage element would be needed which would result in significant over shoot during long bake periods.

But the idea is still giving me a thrill.

Basically I was imagining a GE range with a knob like this:

https://www.ebay.com/p/WB3K5254-GE-Range-Oven-Selector-Knob-KN-7d/2080218455

https://www.ebay.com/itm/WB3X5678-WB3K5254-GE-Oven-Selector-Knob-KN-7e1-/331763942293

With something like "preheat" "roast" "bake" "warm"

or

"preheat" "bake hi" bake med" "bake low"

Loved the feeling of the oven selector knob turning when I had the GE range years ago. It was several steps up from this:

 
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Hi All,

Here is an Australian General Electric (AGE) Hotpoint stove I own that has no thermostat control for the oven; only a thermometer built into the oven door.

The upper and lower elements each comprise two banks of nichrome wire coils in ceramic holders. Each element has a 3-heat switch that switches the two banks in series (Low), one bank on full heat (Med.) and both banks in parallel on full heat (High).

It is the same model of stove my grandmother used from when her house was built in 1948 up until the late 1990s. She used to bake, broil and roast in it daily. To preheat it she would put both elements on High. Once the thermometer showed approximately the right temperature, she would switch the top element to Low, and leave the bottom element on High or switch it to Med. She never needed to adjust the switches again while cooking to regulate the temperature.

The oven interior is very small, has a very thick layer of asbestos insulation around it, and the outer shell is thick cast iron. I believe all of that combined makes the heat regulation very stable despite having no thermostat.

Regards, Tim

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mit634-2019080204190208650_3.jpg

mit634-2019080204190208650_4.jpg

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Thank you to both! These posts are immensely inspirational. Its comforting to know that oven was able to bake and broil without major performance issues.

By any change, do you know the wattage of each element in the Australian Hotpoint?
 

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