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Sous vide cooking, on the cheap

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  • #16
    Originally posted by Jonathon View Post
    How quickly it gets back to your desired temp but not above it is very important, too long at even 1 degree above your desired temp can overcook the food.

    A well-programmed PID will do this reasonably well, but I don't know anything about home brew heaters, .
    I think you may have mis understood my point about PID vs Electronic controllers.
    I am only refering to the temp CONTROL ..not the type or size of heaters used..that is a separate issue.
    No controller can prevent the system temp drop when you add cold food. As you say, that is down to the "Thermal Mass".
    how quickly the temp recovers is a function of the heater size (power) and the thermal mass.
    Control sensitivity is down to the controller system.
    PID's are designed to carefully control to fractions of a degree. Electronic controllers will control temp within 1 or 2 degrees.

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    • #17
      Originally posted by Jonathon View Post
      Looks very well done, great job.

      Is the element home brew-specific or a general heating element? How does it go at holding a set temperature?

      Is the controller a PID with some kind of intelligent control or a simple on/off thermostat?

      Would be keen to see a parts list, my current setup is too small for large chunks of meat but your setup would be perfect.
      Hi Jonathon,

      The element is a basic kettle style element (1500w). Brewing elements used for the boil are usually higher wattage as the goal is to allow rapid boil / evaporation of large volumes of wort. I had contemplated using a 2200 w unit however I wanted lower output to allow for slow / lower heating bursts. The thing with sous vide is that the meats internal temp will mostly be below the water bath temp drawing temp / energy inwards within the meat as once meat temperature is equal to the water bath the cooking is complete apart from secondary benefits of tenderness etc. The controller is just an on/off type rated to +/- 1 C. Blend is correct re the tighter control of a PID type however considering that there is a 6 degree c difference in the finished temperature of meat cooked to medium versus medium well meat I'm not too concerned with 1 degree variations in water temp and hence finished meat temp. Where I would / should have run a PID is with eggs where there is a marked difference in the finished product with 1 degree variations.
      As for "temp control" I am going to run a test to track stability and temp variations and will let you know. I am still not convinced that I shouldn't have used the 2200 w element and if there is a lag in reheating times I will probably use one for the next build, likewise a PID if target temps aren't maintained within reasonable limits.

      Cheers Yabba

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      • #18
        OK I have run a batch of water through it and mapped the temp control. From a start temp of 30.2 from the tap it took 20 minutes (19min 19 sec) to reach the 63 degrees set. With the momentum it over shot to 63.7. I dropped a 600 gram cooler block in to mimic meat insertion. The temperature dropped to 62.7 (it has a .3 variance for switching) triggering heating. Temp dropped to 62.5 before increasing and rotated between 63.3 and 62.7.

        I'm very happy with the control. I am a little suspicious to the true zero of it so I may need to calibrate it or allow for temp variances. I think it maybe 1 degree low.

        Cheers Yabba

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        • #19
          Sous vide cooking, on the cheap

          That control is excellent, up there with a $1,000 polyscience machine.

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          • #20
            Re: Sous vide cooking, on the cheap

            If you are able to stir you may find you get less overshoot (as the measured temperature will be closer to the mean bulk temperature.

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            • #21
              Sous vide cooking, on the cheap

              Originally posted by MrJack View Post
              If you are able to stir you may find you get less overshoot (as the measured temperature will be closer to the mean bulk temperature.
              I think he had a water pump running, which would have stirred the water fairly vigorously.

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              • #22
                Re: Sous vide cooking, on the cheap

                No worries then. Didnt notice that in the pic.

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                • #23
                  Originally posted by MrJack View Post
                  If you are able to stir you may find you get less overshoot (as the measured temperature will be closer to the mean bulk temperature.
                  Hi Mr Jack, Although there is a pump I think what your saying is still correct. What I'm getting at is that I have a 200 LPH pump which I thought would be quite turbulent however it is actually quite calm and slow moving. I think that a larger volume pump may help as you mentioned especially when water flow is restricted by bags of food.


                  Cheers Yabba

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                  • #24
                    Sous vide cooking, on the cheap

                    I wonder if you introduce too much air, through a more vigorous pump, would that affect the temperature?

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                    • #25
                      Re: Sous vide cooking, on the cheap

                      Is the pump outlet aimed at the heating element?

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                      • #26
                        Originally posted by MrJack View Post
                        Is the pump outlet aimed at the heating element?
                        yes.

                        Cheers Yabba

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                        • #27
                          I've just picked up a sous vide circulator from Anova, a US company. They do a 220v version for $200, with shipping and forex it cost me A$300 all up.

                          www.sousvides.com

                          It arrived about a week after ordering. It looks great (much better than my rice cooker PID setup) and works a treat.

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                          • #28
                            Stupid question....do you need to vacuum seal the food portions prior to immersing, or can they just go in something like a plastic sandwich bag?

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                            • #29
                              Best to vacuum seal... air pockets are insulators and not great from a food safety perspective. However, one can apparently do a decent job with a zip lock bag by putting food in, slowly lowering the bag into a bowl of water displacing air until you reach the zip lock level, then lock the bag up.

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                              • #30
                                Thanks kwantfm. This sounds like my next cooking experiment.

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