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jackal10

Crock pot with accurate temperature control

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Does anyone make a crock pot or slow cooker with an accurate temperature controller, such as a PID controller?

It may increase the price, but a lot cheaper than a water bath.

As its not stirred it won't be quite as accurate, but it should be more then accurate for domestic use

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Boy, despite their shared interests in "set it and forget it" cooking, a few different internet searches suggests that there's not a lot out there to bridge the wide gap between the crock-pot traditionalist and molecular gastronomist.

Does anyone have experience with crock pots that maintain steady temperatures within, say, +/- 5 degrees (as checked by a probe thermometer)?


Chris Amirault

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What about an electric frying pan? Don't know if it's deep enough or goes low enought for you purpose.

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The problem I find with both slow cookers and electric fry pans is that they maintain their heat by cycling - this means that the temperature fluctuates and overshoots or undershoots the target temperature for much of the time.


Anna Nielsen aka "Anna N"

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The Russell Hobbs is the most accurate slow cooker that I have, however it is quite expensive.

Oddly enough, I have some vintage appliances that maintain much better temperature control than any of the newer ones I have tried.

They relied on a combination of rheostats and similar combinations of direct current controls integrated with a thermostat. Anyone who has used one of the old type electric roasters, prior to the introduction of the newer (and cheaper) controls, will understand what I mean.

I have deep fryers (Sunbeam) that can double as "deep-well" cookers, i.e., slow cookers, that will maintain the correct temperature exactly. It senses when the temperature drops, as when an addition to a soup or stew or even removing the lid for a time for stirring, etc., and will increase the power just long enough to match the thermostat setting. They have controls that are set by increments of temperature (Fahrenheit) not just "Low, Medium or Hot" which seem to mean different things to different modern manufacturers.

The only reason I know this so well is that back in the early '70s, my stepson had to do a project for school and chose something to do with electrical controls. Various appliances were plugged into volt meters (borrowed from his teacher) that indicated how much wattage was used by the appliance at various settings during use. I recall that some of the appliance were the Sunbeam fryer/cooker, a frying pan, a coffeemaker, vacuum type, also Sunbeam, a toaster and a toaster oven. He also tested some electrical tools but I wasn't paying as much attention to that. Mainly I didn't want my appliances damaged.

I have a 50-year-old milk pasteurizer that will take the milk temperature to 162 degrees, hold it at that temperature for fifteen minutes and shut itself off and signal with a chime.

I have tested the milk with various thermometers, before "instant" ones I used a floating glass thermometer made for this specific task, and never found a problem.

I have embraced the digital age with enthusiasm but have found that some of the old, really old, things still work better than some new ones.


"There are, it has been said, two types of people in the world. There are those who say: this glass is half full. And then there are those who say: this glass is half empty. The world belongs, however, to those who can look at the glass and say: What's up with this glass? Excuse me? Excuse me? This is my glass? I don't think so. My glass was full! And it was a bigger glass!" Terry Pratchett

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There are induction plates with digital temperature control, quite inexpensive ones too (USD 100-200). I've no idea how accurate they are and if they work by adjusting the effect or cycling on/off, but I would really like to know.

I've also been unable to find one that goes below 60 C/140 F (probably for safety/food poisoning reasons) so no sous vide-ing your steak or fish. But they could still be pretty useful for slow braising and confits.

There is also a fabled-mentioned-in-passing induction plate from Phillips that supposedly has a separate temperature probe. No amount of Googling has worked though.

Example:

http://www.amazon.co.uk/Micromark-Glass-Pl..._sbs_kh_title_3

(although this one only goes down to 80C)

I want to know more! And I want one that goes down to at least 55 C, dammit!

Edit: This one at least goes down to 60 C. The link show the twin plate version, but there is a cheaper single plate version too

http://www.redumbrella.co.uk/product_detailpage.php?id=1070


Edited by TheSwede (log)

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Has anyone ever considered using one of these warming trays which maintain foods at serving temp but not high enough to cook them further.

I've never tested mine to see the exact temps and I've never used them for poultry or meat dishes (except for platters of chicken wings) but I have kept them full of various types of hot canapes for extended periods.

Cocktail meatballs in spicy sauce, etc., etc.

(I've also used them for fusing colored foil on paper, melting wax and various other tasks for which they were never intended.)

I have several sizes from one with a 6 inch square plate surrounded by a wood frame, all the way up to a "commercial" one that holds a full sheet pan. They all have textured glass tops which are easy to clean.


"There are, it has been said, two types of people in the world. There are those who say: this glass is half full. And then there are those who say: this glass is half empty. The world belongs, however, to those who can look at the glass and say: What's up with this glass? Excuse me? Excuse me? This is my glass? I don't think so. My glass was full! And it was a bigger glass!" Terry Pratchett

My blog:Books,Cooks,Gadgets&Gardening

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I have a remote probe digital temperature controller which I have hooked up to an AC extension cord. Several manufacturers make them, they're available from HVAC or process control supply houses. Maybe $100 or so. They're pretty accurate - more so than most kitchen thermometers around our house.

Since the controller is external, it is easy to re-purpose it - one week it might be controlling an old refrigerator to give a controlled fermentation chamber, another might see it switching fans and heaters in a DIY bulk dehydrator. As long as the device controlled can achieve the temperature sought, then the controller has only to switch the power to suit.

The hysteresis is [if memory serves] adjustable, but in any case is sufficiently short that temperature cycling would not be an issue.

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Does anyone make a crock pot or slow cooker with an accurate temperature controller, such as a PID controller?

It may increase the price, but a lot cheaper than a water bath.

As its not stirred it won't be quite as accurate, but it should be more then accurate for domestic use

PID controllers are pretty cheap on this website. Along with a solid state relay and a probe (also available on the website) you can easily connect one to your existing cooker.

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This handy device:

http://auberins.com/index.php?main_page=pr...&products_id=44

(same firm as ChefCrash linked to above)

..together with a rice cooker will give you your own sous-vide water bath.

Edit: Just ordered the controller I linked above. Will probably take some time to arrive (US -> Europe) but I will report back here once I get it.


Edited by TheSwede (log)

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So, combining the above ideas... Would an ordinary large home slow-cooker with one of the Auber Ins. controllers above get a level of control adequate for sous vide for all of about $120 combined??? That seems to be what Auber is claiming one can do... If so, well, that'd be pretty cool...

I've been playing with getting set up to do this, but the cost and size, etc., have put me off... This seems to bring it into the 'sane' range!

jk

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So, combining the above ideas...  Would an ordinary large home slow-cooker with one of the Auber Ins. controllers above get a level of control adequate for sous vide for all of about $120 combined???  That seems to be what Auber is claiming one can do...  If so, well, that'd be pretty cool...

I've been playing with getting set up to do this, but the cost and size, etc., have put me off...  This seems to bring it into the 'sane' range!

jk

It should be able to maintain a fairly constant temperature. I suppose there is a question as to whether the temperature will be uniform enough without a circulator for items that cook for a long time. (One could probably use a cheap aquarium bubbler to keep the water moving enough to keep the water temp fairly uniform).

There are a fair number of positive mentions of his PID kit for espresso machines that lead me to believe his unit probably does what it says. The 'home' model would be underpowered for me. My electric cooker (which is only 6 qts) is 1300 watts.

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Looks like there's a market here!

I have been looking closely at various electric crock pots that are out in time for the holidays. Big, small, digital, analog, expensive, affordable, shiny, colourful, etc. but none that I have seen include any kind of precision temperature control. One model even has a digital display that says HI, MED or LOW.

The Auber Plug-n-Play Temp Controller looks like a winner to me - the 800 Watt model is only $60. I had wondered about home aquarium equipment and I see they make one of those too.


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Note that the cheaper one can only handle 800 W. I bought the more expensive one to have some flexibility in what appliance I connect.

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There has already been quite a bit of discussion about the possible use of PID and other kinds of temperature-controlled Crock-Pots in the main sous vide thread.

The general consensus was that an actual Crock Pot is probably too small for any meaningful temperature equalization throughout the water bath. This is especially true due to the way slow cookers work: by heating a large, thick ceramic insert that lines the entire inside of the slow cooker. It's hard to believe that there won't be significant overshooting of temperature due to this design, and it also seems likely that there will be dead spots, etc. unless the PIDed crock pot is loaded very lightly.

Since a big part of what makes sous vide cooking so interesting is the effects one can create with very precise temperature control, especially at lower temperatures, it seems to me that a PIDed crock pot would be a lot of trouble and expense for not so much payoff. You could do some things, but certainly couldn't explore anywhere near the full range of this technique. If one is interested in doing non-circulating PID-controlled water bath, I would suggest that a very large stock pot on top of a PIDed heating plate would provide the best performance and the most bang for the buck, since both the heating plate and the stock pot could be used in the more traditional way as well.

Here's a post from the main sous vide thread that touches on some of these issues:

I'm not sure that I buy the "spatially uniform" bit.  The reason lab heaters circulate the water is to maintain all the water at the same temperature.  For something like a crock pot, I have my doubts as to whether it could maintain the temperature with any precision and uniformity.  For one, I think the very nature of the way the heating element works would likely cause the temperature to overshoot with some frequency, and the temperature would likely swing with a range of several degrees.  Now, your friend may not think that temperature accuracy of +/- 5C is a big deal, but it can make a really big deal on what you're cooking when you're trying to take advantage of the technology's full power.

I'd also be curious if you could ask your friend what features, exactly, a recirculating water bath heater would have that would not be used in sous-vide cooking.  My Lauda has settings for temperature and fail-safe cutoff temperature, and it recirculates the water (mine is a stand-alone heater that I can clip on to any water vessel, rather than an all-in-one water bath).  That's pretty much all it does, and it's accurate to 0.1 degrees C.  All of these features I'd say are used in sous-vide cooking.

I agree with the above quotes quite strongly.

Baths without circulation pumps do work, but they are prone to temperature stratification, and even worse, dead space between food items.

One way to get a non-circulating pump is take a crock pot, rice cooker or hot-plate with a pot and add thermostatic control (PID or On-Off) such as Ranco, or the new sous vide conversion unit that was briefly posted to this thread, then disappeared.

However, there are also laboratory water baths that lack a circulating pump - the most common brand is Precision (but other brands make them). They are a bit cheaper than a circulating pump water bath. They are sometimes called "utility water baths". In a lab they are NOT used for precise temperture control.

If you have one bag of product is the middle of a large crock-pot or non-pumped lab water bath it is probably going to be OK. This is particularly true if you are cooking at 170F or above because at those tempertatures there is substantial convection in the water (i.e. what we normally call simmering).

But if you are cooking at lower temp (rare beef, barely cooked salmon) or if you put a bunch of bags in at the same time the circulation can be a BIG help. If you are working in a restaurant, or you cook in quantity, then a circulating water bath is cheaper than a non-circulating one when you consider how much more you can load it. It may look big but you can't really pack it as full as you could with a circulator.

If on the other hand you are experimenting at home, are on a budget, or are doing just one or two bags at at a time, then a modified crock pot / rice cooker or non-circulating water bath may work out just fine.


Samuel Lloyd Kinsey

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Note that the cheaper one can only handle 800 W. I bought the more expensive one to have some flexibility in what appliance I connect.

Indeed - but, being in Europe on 220/240 volt mains, you've got more flexibility than you might have thought.

The switching capability (and heat dissipation) is based on the electric current flowing. So the wattage that can be switched depends on the mains voltage.

So for the cheaper model -

The controller can handle 7 ampere of current. For US and other countries that use 120 VAC, it can control up to an 800 watts heater (1500 watts for 220 VAC).

The slightly more expensive one will switch double the current - so 3kw on European mains.

Taking international delivery cost (and maybe import taxes) into consideration, there's not going to be much total cost difference for a big change in capability (which might carry over to durability).


"If you wish to make an apple pie from scratch ... you must first invent the universe." - Carl Sagan

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There has already been quite a bit of discussion about the possible use of PID and other kinds of temperature-controlled Crock-Pots in the main sous vide thread.

The general consensus was that an actual Crock Pot is probably too small for any meaningful temperature equalization throughout the water bath. 

I have read the entire Sous-Vide thread and don't believe that the conjecture in that thread is worth treating as if it were THE TRUTH -- the issues raised are all worth thinking about but I wouldn't treat that consensus as being truth-defining -- the general consensus mentioned was based on next to 0 empirical data. The parameter space is so large that I think actual experience is needed in order to make a determination. Without actual testing, I don't give a lot of credence to some of the conjecture. The biggest issue with a PIDed crockpot would NOT be overshoot. A decently calibrated PID will keep things within a degree which for most sous vide applications is plenty stable. Once the crockpot is at temperature, I don't see any reason why it would be more likely to have overshoot than a hot plate (which one could also use with the Auberins set-up).

It is a reasonable question to ask whether the temperature will be uniform enough without a circulator of some sort -- but, again, someone needs to actually test. A lot will depend on the volume of water AND the volume of the item being cooked. And, I'd be willing to bet that a cheap aquarium pump would provide more than enough circulation to keep things uniform enough for the vast majority of sous-vide applications.

With ANY setup (even laboratory equipment), one does need to have an appropriate volume of water in relation to what is being heated. With an 'on-the cheap' setup like we are talking about, there is probably a smaller range of what the setup can handle than with expensive lab equipment, but for some of us that is a reasonable tradeoff. It will be interesting to see what range of sizes a crockpot will be able to handle.

It isn't obvious that the 0.1 degree precision of laboratory circulators is required for good results for most applications. It might be the case that the perfect egg isn't attainable without 0.1 degree accuracy -- but I think 1 degree of accuracy is more than adequate for most cuts of meat.

I would be curious to see how one of these units would work with an electric turkey fryer which might be a better fit for doing larger pieces of meat than a crockpot.

Anyway that is my semi-educated opinion.

--E

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E: Think about the way a crock pot heats. Now think about the volume of water we're talking about in a crock pot. As it so happens, I have a couple of them myself. The largest crock pot available on crock-pot.com is 6.5 quarts. That's only 1.625 gallons, 375 cubic inches. Now, this is probably plenty of room if you're cooking 4 lamb chops or a few fish fillets. But what about cooking, say, six double-cut pork chops? I trust you don't think this is an exorbitant amount of food to cook at one time. Those pork chops will take up around 130 cubic inches. So now you have only 245 cubic inches of volume in your slow cooker available for water -- less than one gallon. That strikes me as too little so reasonably and accurately maintain an even temperature throughout the crock pot to, say, +/- 1C (and, yes, in many applications a single degree C can make a difference) and I think it's likely that the food would come quite close to the ceramic lining that is heating the water. Do you think that the ceramic at the bottom of the pot won't be warmer than the water at the top of the pot? Especially if there are several bags of food in between? As for temperature swings, keep in mind that, even after the PID establishes and maintains the temperature evenly when there is nothing in the pot but water, there will be an immediate disequilibrium once the food is introduced to the water bath. If there is a relatively small volume of water relative to the food (which there often would be in a crock pot) how well is the PID controller going to respond to that?

As for doing "testing" on this method. . . unfortunately there's nothing I have seen here yet that suggests that the people seeking to do such evaluations are interested in taking the time, trouble and (especially) expense of doing any meaningful testing. What are they going to do -- drop 20 lamb chops into a PIDed crock pot with a temperature probe sticking into each one? Most of what I have seen are things along the lines of "I measured the water and, after 2 hours it stayed between 130 and 134." That doesn't mean much to me.

So.. absent of any such testing, I am likely to trust the evaluations of the scientists who use this equipment. And, as nathanm brought up, water baths that do not have a circulator are not considered accurate for work requiring temperature precision.

For short-time sous vide cooking of small amounts of food, such as a couple of fish fillets or relatively thin pieces of meat, it strikes me that anyone who is interested in saving a lot of money is well served with a large stock pot, a stove and a fast-acting thermometer. Why go to all the time and expense to PID a crock pot for this, right? For long-term cooking when temperature precision is important (e.g., 48 hour medium-rare beef short ribs) it's not clear that a PIDed crock pot can offer enough precision and stability throughout the water bath, except perhaps in the case where one would like to cook two short ribs in the very middle of the crock pot. Again, I would question whether it's worth going to this kind of trouble and expense to be able to cook 2 short ribs at a time. If you pack the largest crock pot with short ribs and there's maybe 1/2 or 1/3 gallon of water for temperature regulation with no circulation, I can't believe there wouldn't be problems. For long-term cooking where temperature precision is less important (e.g., sous vide "confit"), it would probably work just fine. Now... you throw in a circulator, and that's a different story.

But, you know... why fantasize about all the great things you can do by PIDing a crock pot and chuckle about how you won't have to pay 400 bucks for a circulator on eBay? Make one. Test it thoroughly. Come back and post the results. Personally, if I were going to do such a thing, I'd be looking at minimum requirements of temperature accuracy within 0.25C and stability within 0.5C with less than 0.25C variability within the bath, all when there is enough food in the bath to make dinner for 8. Those strike me as reasonable specifications for anyone who wants to do sous vide cooking enough to invest in such a thing.


Samuel Lloyd Kinsey

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But, you know... why fantasize about all the great things you can do by PIDing a crock pot and chuckle about how you won't have to pay 400 bucks for a circulator on eBay? Make one. Test it thoroughly. Come back and post the results. Personally, if I were going to do such a thing, I'd be looking at minimum requirements of temperature accuracy within 0.25C and stability within 0.5C with less than 0.25C variability within the bath, all when there is enough food in the bath to make dinner for 8. Those strike me as reasonable specifications for anyone who wants to do sous vide cooking enough to invest in such a thing.

Obviously a crockpot is not going to be adequate for cooking for 8. Many of us are cooking for 2. I mentioned in my post that water volume might be an issue with regards to large pieces of meat.

Why use a PID rather than a stockpot? Because with a stockpot (which I happen to use for sous vide) one has to be quite vigilant if one wants to keep the temperature stable at all. And keeping it stable within a degree or so is a big chore.

I don't understand the nature of the conjecture that there being less than a gallon of water should prevent a PID from maintaining a stable temperature (assuming that the circulation issue is dealt with). Unless the crockpot behaves unpredictably, a PID -- IF CORRECTLY SET UP -- should be able to work fine as long as it isn't overloaded. A PID is a pretty sophisticated processor that takes into account the on/off latency (which is why they don't have the same overshoot/undershoot that simple on/off thermostats have). A PID does require that the heat source behave predictably.

The requirement of 0.25C stability sounds quite arbitrary. For the vast majority of applications. Again, for cooking the perfect egg that might be required. I have not seen a posting by a scientist that indicates that 0.25C stability is a requirement for most sous vide applications.

Hopefully, some of the people that have ordered the units will report back before too long. If the initial reports are good, I'll probably dive in (although I won't be using a crockpot but another type of electric pot since that is what I have).

Best,

E

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I don't understand the nature of the conjecture that there being less than a gallon of water should prevent a PID from maintaining a stable temperature (assuming that the circulation issue is dealt with).

But that's the rub! Assuming the circulation issue is dealt with. There are plenty of less-expensive applications that might work asuming the circulation issue is dealt with. I'm talking about when the circulation issue isn't dealt with and one is relying upon convection. I thought that was pretty clear from what I wrote above, but my apologies if it was not.

The requirement of 0.25C stability sounds quite arbitrary. For the vast majority of applications. Again, for cooking the perfect egg that might be required. I have not seen a posting by a scientist that indicates that 0.25C stability is a requirement for most sous vide applications.

I didn't say stability within 0.25C. I said accuracy within 0.25C and stability within 0.5C. Since there are many applications -- and many of the most interesting applications -- that have tolerances within 1 degree C, this seems like a reasonable requirement and not arbitrary at all. As for 0.25 variability within the bath, perhaps this is being a little too precise. But, if our tolerances are accuracy within 0.25C, stability within 0.5 and no more than 0.25 variability in the bath, it's still possible that one part of the bath could be a full degree warmer than another part of the bath. 1 degree C certainly has a notable effect on many sous vide applications.


Samuel Lloyd Kinsey

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