I love love this post!

dcarch
Great information. Thanks for the explanation. A visit to Harbor Freight is on my list anyway. I'll add another item to look at.

I hope you can help me with a quandary regarding low cooking temps.

I have a Nesco roaster oven.
I no longer have a crockpot--I pitched my not so old one because it never cooked below a fairly rapid boil.

If I want to use 'Crockpot'' recipes in the Nesco, what temperature settings are equivalent to low, medium, and high in a crockpot?

And, by the way, thanks to you and others here, I bought a Sous Vide Supreme (In a super deal with the cooker and vacuum sealer and cookbook--their big package--for only $350.) I have loved using it. Thank you SO much for the inspiration that led to that purchase. Since I am not handy with electrical stuff and didn't want to build my own, it has been worth every penny.

Sandra

Sandra - I did a Google search and found these posts on "what temperature settings are equivalent to low, medium, and high in a crockpot?" Maybe dcarch can weigh in on how accurate they are.
Clare

How to Convert a Slow Cooker Recipe to Baking in a Roaster.

Sandra, a Nesco typically has a dial thermostat which set's the temperature, supposedly goes from 200F to 450F. At 200F, I guess that qualifies as a slow cooker because that is not the boiling point of water. A Crockpot's heating element is from the bottom, and the Nesco is typically around the sides, that may mean you will need a slightly longer cooking time because the heat gets to the center of the food will take longer due to the lack of vertical convection of the liquid.
As I said, a bi-metal thermostat can be highly inaccurate. There are not calibrated in the factory, and after a while using the cooker, metal fatigue can also occur. The best thing really is to use your thermometer to check the cooking temperature. If you have the router speed controller, you can set the temperature to as low as you want, say 165F.

Congratulations on the sous vide cooker. It will expand your cooking experience vastly. The other day I pasteurized egg yolks for ice cream, pasteurized raw milk also. I don't spend good money for expensive cuts of meat much anymore. Why spend $16.00 a lb for rack of lamb when I can buy Lamb loin chops at $7.00 a lb with twice the meat, just as tender and tasty done with the sous vide cooker? A $100's worth of prime rib will never be overcooked or undercooked.

Clare, thanks for the links. I am glad that you posted the links. This is a very good example that if you are Googling for any information, you must check multiple sources, never trust one single source (Don't trust me either Haha!). The information in the second link are completely wrong!

"---Every time that you remove the cover, add an additional 20 minutes to the cooking time.---"

No true. You know from your own experience this is not true.

"---If your food isn't done after 8 hours when the recipe calls for 8 to 10 hours, this could be due to voltage variations---"

Wrong! Variations in voltage have no effects on the thermostat setting.

"---due to altitude or even extreme humidity.---"

Wrong! If you are cooking below boiling point.

dcarch

HA! dcarch - One look at that link I knew you were going to tear it apart!

Since you offered us not to trust you, either, I'll point out that a Crockpot heats from the sides as well. At least my Rival (a genuine "Crockpot") does.

But here's a question that I'm not clear on from your above posts: "Variations in voltage have no effects on the thermostat setting." This implies that a Crockpot has a thermostat, not just a timed, cycling on/off as you describe elsewhere above. If that's the case, then how would a router speed controller help adjust the cooking temperature? Wouldn't it just end up providing lower heat for longer cycles to achieve the same temperature? And, if thermostatically controlled, how would external factors such as room temperature affect the Crockpot's temperature.

To a layman like me, these factors would sound like they are timed/cycling units rather than thermostatically controlled.

Dcarch

The sous vide has already changed my cooking. I probably use it once every two weeks at least, and often share the wealth with friends. I have mostly used it for red meats so far, but next plan to explore seafoods. Tonight I fixed jasmine rice, seared shrimp and baby bok choy and stewed the shrimp heads and shells to make a sauce (don't know if that is what one does, but it worked--the liquid, reduced, butter and wine added, was great over the shrimp and rice, and I just couldn't stand the thought of not using all that flavor). I had hoped to also have some scallops, but the Asian market I went to no longer carries them. If I had found nice big scallops, I was playing with trying your trick of sous vide-ing them first, then searing them VERY fast. But no luck. That's for another day.

In regard to the slow cooker temps-do you think 200 for low and 300 for high are roughly right for target temps if I want to use slow cooker recipes in my Nesco? That seems high to me. Maybe because I have become used to sous vide temps that are MUCH lower?

Once I know the target temps, I can check the accuracy of the settings and play with additional regulators if necessary. I just don't know what the heck ''low'' and ''high'' temps MEAN.

FOAS, very good questions.

There are many makers and models of slow cooker, I am sure there will be some with side heating. But it makes no manufacturing sense to have side heating for a cooker that is 6 to 8 quart capacity. To install a surround heating element , to manufacture a round heating element, and to store and ship a surround heating element instead of a flat round one is very expensive. A slow cooker is about 200 watts to 300 watts. If you use Nichrome wire as the heating resistive wire to go around the pot, it can get very thin and may be easier to get burnt out.

Regarding a bi-metal thermostat, it senses the set temperature and thru differential expansion force, it trips a flip-flop on/off contact to send electric power to the heating element. The duration and frequency of the on/off cycle and the thermostat setting determines the heating temperature, not the voltage variations.

A router speed controller is also known as a PWM (Pulsed Width Modulated) controller. What it does is to electronically chops (Pulses) the on/off cycle(width) of the voltage, but not the amplitude of the voltage, to increase or reduce the effective power going to the heating element. It does not tell you the temperature. You have to measure the temperature if you are at full power or 0 power. You need to set the cooker's temperature at the highest setting and allow the controller to meter how much power(heat) to go to the cooker.

A cooker achieves high/low settings mostly by using two heating coils switched either in series or in parallel.

Room temperature has an effect on a mechanical thermostat because the thermostat is generally not well insulated.

dcarch

Sandra, sounds like you have some great meals going.

Regarding slow cooker temperature, my preference is to go as low as possible based on food safety charts' recommendations. For many meats and recipes, I prefer temperature much lower than 200 F, that's why I use sous vide. But with the roaster oven's lowest setting is 200F, there is no way you can go lower than 200F, unless you bypass the thermostat and use a controller. With a controller, you can get the temperature low enough to use the roaster as a warmer.

A word of caution; If you are going to go low temperature, you may have to heat up the food on high heat first to get the food pass the danger zone as quickly as possible.

dcarch

Thanks, dcarch. Unfortunately my Crockpot is made such that I can't take it apart to see what the elements look like without potentially permanently ruining the unit. Based on the inside shape of it, plus how it "felt" like while it was heating up, there are two thin heating elements around the outside, and one on the bottom.

I'm definitely interested in trying to bump down the heat a bit. Even the low setting achieves a pretty rapid boil after a few hours. On the other hand, you bring up an important point re food safety, which is the common explanation for why modern Crockpots cook higher than their vintage counterparts.

In the last year or so I got a new Harbor Freight around the corner (for better or for worse - it didn't take me long to realize why their crap stuff is so cheap) so I might have to fork out $20 for a controller and play around a bit.

Aptosca,
Thank you for the links. The first one gave useful info on several links and helped clarify my ideas on how to use the roaster as a slow cooker.
My oven goes down to 170, but I don't even want to think of a gas oven on for 8 hours, even at the lowest temp. I'd have to have the exhaust fan on or the door open, and it's below freezing outside! I think the roaster can go as low as 180, but I'll have to check it.

Dcarch, thanks for the heads up about higher temp first, then lower.

Question: why can I sous vide meat safely at 125 or 130, but possibly need to cook at 200 or so in a slow cooker, at least for a while. Will searing eliminate the need for that initial higher temp?

What I meant is this:

The slow cooker has about 200 watts to 300 watts of cooking power, v,s, a roaster oven, which has about 1,500 watts or more of cooking power.

If you put a lot of cold food in a slow cooker, it may take many hours for the food to go thru the danger zone.

Sous vided food is different even you cook at 120 F, you would sear the food at high temperature to sanitize the food after the water bath.

dcarch.

This post was edited by dcarch on Fri, Jan 18, 13 at 22:48

This is great information. I don't know where it could be found other than here on CF. It will not be a thread for everyone because it requires some knowledge of physics and electronics. But, as the replies show, there are those among us who have that knowledge and are ready for what dcarch has to offer.

Thanks, dcarch.

Jim

You are welcome Jim, and thanks.

It was not easy to learn what I know. :-)

I was spanked, ground and made to face the corner of a room too many times when I was a little kid.

I had these compulsions that if it moved, it needed to be taken apart and if it was not broken, it still needed fixing.

dcarch

"I had these compulsions that if it moved, it needed to be taken apart and if it was not broken, it still needed fixing."

My brother was exactly like that. Whenever he bought anything, the first thing he did was take it apart. His degree was in photography but he worked as a laser equipment technician. He was self taught in electronics and optics.

Jim