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Vac-Star SousVideChef


Andreas
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Next instalment. This time, I cooked a pork fillet. Set the machine for 60C. Tested with Greisinger reference thermometer. Once again, the LCD readings oscillated, but not so the reference thermometer, which was rock steady on 60.2C. I then adjusted target temperature to 59.8C and it sat consistently on 60C. The controller kicks in about with the same regularity as the PID controller on my espresso machine. I'm very happy with the unit, particularly as I found a polycarbonate container that holds 20 liters of water and also fits the unit with the VacStar styrofoam packing in place.

Nick Reynolds, aka "nickrey"

"The Internet is full of false information." Plato
My eG Foodblog

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Nickrey, I looked on the Vac-Star site and could not find any mention of the polycarbonate container nor the thermal balls. Did you mean to reference some other site? I have the Polyscience circulator and am looking for a cooking vessel but find theirs to be expensive.

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Or alternatively, you could do what I did and go to a specialist storage shop and pick up a suitable container. Look for one that has a number 5 in the recycle symbol, which means it is polypropylene.

This is a folder storage box from which I cut out a piece of the lid so the circulator could go inside. It was $14.

IMGP4267a.jpg

It is also the ideal size for the unit to be stored inside using the original delivery packaging.

IMGP4268a.jpg

PedroG uses ping pong balls as an insulator. I'm going to get myself a piece of styrofoam, cut it to size, and glue it inside the lid.

Edited by nickrey (log)

Nick Reynolds, aka "nickrey"

"The Internet is full of false information." Plato
My eG Foodblog

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@nickrey, thanks very much for the review of this device. It looks to be as good as I'd hoped (though I'm a little surprised that they use a mechanical relay, as solid state relays are pretty cheap). I've now ordered one to replace my now-defunct homebrew one. The family are happy that we'll have confit duck legs again soon!

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PedroG uses ping pong balls as an insulator. I'm going to get myself a piece of styrofoam, cut it to size, and glue it inside the lid.

Floating Balls for Sous Vide Baths

r = radius

F = surface of cirmumscribed hexagon

F = r² * tg(30°) * 6

r = sqrt(F / 6 / tg(30°))

Polyscience:

400 balls à 20mm Ø (r=1cm) = $99

400 * 1 * tg(30°) * 6 = 1385 cm²

-> $0.07 / cm²

VacStar:

100 balls for GN ½ container = CHF 30 = $33.50

GN ½ = 26.5 * 32.5 cm = 861 cm²

Ball-Ø = 2 * sqrt(8.61/6/tg(30°)) = 3.15cm

-> $0.04 / cm²

Ping Pong Balls:

Ball-Ø 40mm (r=2cm) (before year 2000 38mm)

amazon.com: 144 balls = $12

144 * 2 * tg(30°) * 6 = 997.7 cm²

-> $0.012 / cm²

Peter F. Gruber aka Pedro

eG Ethics Signatory

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  • 4 weeks later...

Does anybody know the density of the Polyscience or VS balls?

Each ball could potentially remove an amount of water surface area equal to its max cross sectional area if the density is half that of water. Assuming dense packing, that would be 91%.

Ping pong balls are very light (2.7g, 40mm diameter), and only a small portion of the ball would penetrate the water, so a large portion of the original surface area of water remains. By my calcs, ping pong balls would only remove 52% of surface area, which might result in less efficient insulation relative to a heavier ball. On the other hand, the balls themselves might reduce the airflow at the water surface, and slow the evaporation that way. Without actually testing it, I obviously can't say how large an effect this would have, or if it would fully cancel out the effects of having a greater surface area.

I'm not saying anything definitive; I just wanted to bring up the possibility that the Polyscience/VS balls are optimized for the task, and perhaps this is the reason behind the exorbitant cost. I'm very curious why a bag of plastic balls would cost $100!

Caveat: It's late right now, so I don't fully trust my calculations to be perfect. And there are lots of effects that I am ignoring, such as surface tension and possible hydrophobic ball surfaces.

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@nickrey, thanks very much for the review of this device. It looks to be as good as I'd hoped (though I'm a little surprised that they use a mechanical relay, as solid state relays are pretty cheap). I've now ordered one to replace my now-defunct homebrew one. The family are happy that we'll have confit duck legs again soon!

The unit still hasn't turned up. I phone the manufacturer on Friday to see where it was (after around four weeks). They said they'd had a problem with a part for the cooker so have had to source new ones. They're expecting to be able to dispatch new cookers this Friday.

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  • 2 weeks later...

My Sous Vide Chef arrived a few days ago and is working fine. My opinion on the device is the same as @nickrey: it works well, the display shows rapid and random variation in temperature of ±0.2⁰C, and the heater seems to be controlled by a mechanical relay (at least, it clicks every time the heater switches). As best as I can judge, the water temperature is constant and even across the volume of the bath (I'm using a cool box/beer cooler). Food comes out lovely.

I'd recommend it as a mid-range sous vide cooker. It's less hassle than the Sous Vide Magic, more capable than the SideKik, and cheaper than the PolyScience units. Even my wife will tolerate it in the kitchen!

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  • 1 year later...

Vac-Star has put out the Sous-Vide Chef II which addresses some of the shortcomings of the first version (namely the mechanical relay has been replaced with a SSR). I questioned them about the temperature sensor and got a very quick and open response: They are using a DS18B20 (a semi-conductor with a resolution of 12 bits). Its internal accuracy is supposed to be +/- 0,0625 °C.

Could someone with the technical background verify that the sensor technology is good in the long run? I assume that there will be no way to calibrate the device outside the factory.

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Vac-Star has put out the Sous-Vide Chef II which addresses some of the shortcomings of the first version (namely the mechanical relay has been replaced with a SSR). I questioned them about the temperature sensor and got a very quick and open response: They are using a DS18B20 (a semi-conductor with a resolution of 12 bits). Its internal accuracy is supposed to be +/- 0,0625 °C.

Could someone with the technical background verify that the sensor technology is good in the long run? I assume that there will be no way to calibrate the device outside the factory.

Hi pep,

This semi conductor (the thermometer of sousvidechef II) has an operating temperature range of -55°C to +125°C and is accurate to ±0.5°C over the range of -10°C to +85°C (look at this datasheet ). As you can see this is not so inaccurate but not as accurate as mentionned by Vac-Star (+/- 0,0625 °C????). This mean that 2 sousvidechef II can have a difference of accuracy of 1°C which is not few for sous vide cooking...I think your contact at vac-star had no idea of what he was talking about.

In addition, as you mentionned it, because of the kind of "thermometer" choosen by sousvidechef II 's manufacturer nobody can calibrate that immersion circulator, not even the manufacturer...

Franz

Edited by FranzWagner (log)
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The manufacturer's datasheet referenced in the last post has the following statement:

"The resolution of the temperature sensor is user-configurable to 9, 10, 11, or 12 bits, corresponding to increments of 0.5°C, 0.25°C, 0.125°C, and 0.0625°C, respectively."

If they chose the 12 bit resolution, the Vac-star person would be correct when they said that the resolution was .0625.

Edited by nickrey (log)

Nick Reynolds, aka "nickrey"

"The Internet is full of false information." Plato
My eG Foodblog

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The manufacturer's datasheet referenced in the last post has the following statement:

"The resolution of the temperature sensor is user-configurable to 9, 10, 11, or 12 bits, corresponding to increments of 0.5°C, 0.25°C, 0.125°C, and 0.0625°C, respectively."

If they chose the 12 bit resolution, the Vac-star person would be correct when they said that the resolution was .0625.

Dear Nickrey,

Don't be offensed but "resolution" and "accuracy" are totally different things. There are 100 of pages available on internet explaining the difference. To sum up :

accuracy, resolution, and precision are easily confused parameters used to describe the performance a system is capable of.

Resolution is simply the smallest change that can be measured. In the case of Sousvidechef's temperature sensors, the resolution would be how small of an increment of temperature change can be detected by the sensor.

Vac-Star is misleading you mentioning resolution instead of accuracy, what is important to know for the end user is the accuracy, only.

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The manufacturer's datasheet referenced in the last post has the following statement:

"The resolution of the temperature sensor is user-configurable to 9, 10, 11, or 12 bits, corresponding to increments of 0.5°C, 0.25°C, 0.125°C, and 0.0625°C, respectively."

If they chose the 12 bit resolution, the Vac-star person would be correct when they said that the resolution was .0625.

Dear Nickrey,

Don't be offensed but "resolution" and "accuracy" are totally different things. There are 100 of pages available on internet explaining the difference. To sum up :

accuracy, resolution, and precision are easily confused parameters used to describe the performance a system is capable of.

Resolution is simply the smallest change that can be measured. In the case of Sousvidechef's temperature sensors, the resolution would be how small of an increment of temperature change can be detected by the sensor.

Vac-Star is misleading you mentioning resolution instead of accuracy, what is important to know for the end user is the accuracy, only.

I reread the mail I got from the Vac-Star contact and he did in fact say "internal resolution" ("interne Auflösung") when referring to the 0.0625 °C. The phrase "internal accuracy" was a mistranslation on my part, I actually switched his words around ("Genauigkeit von 12 bit", i.e. "accuracy of 12 bits", vs. "interne Auflösung von 0.0625 °C").

Thanks for the link to the datasheet, apparently I missed that when googling. I do think that their product description on the web is somewhat misleading, because they talk a lot about temperature stability (+/- 0.05 °C) and resolution (0.1 °C), insinuating that accuracy is in the same league.

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I bought the Sous Vide Chef 2 a few weeks ago and so far I'm quite happy. It survived both my short <2h attempts and one long 36h run.

I think the accuracy is quite good, at least as good as my previous self build rig which uses a PT100, so it's probably really in the +/- 0.5°C error range.

The build quality is ok, the plastic looks more cheap in reality than on the photos and the clearance between both plastic housing parts is ok, but I still have a few concerns about condensation.

I have not yet opened it to clean it, but I've read on other forums that it's too cramped in the casing to clean properly.

One thing which is more annoying than anything else is that it has a water outlet at the backside of the submerged part, which atleast in my container snuggles tightly with the container wall and this apparently can lead to vibration which is quite loud and annoying. I'll need to try a few other container to see if I can optimize that.

Currently my verdict is, that I would buy it again.

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I bought the Sous Vide Chef 2 a few weeks ago and so far I'm quite happy. It survived both my short <2h attempts and one long 36h run.

I think the accuracy is quite good, at least as good as my previous self build rig which uses a PT100, so it's probably really in the +/- 0.5°C error range.

The build quality is ok, the plastic looks more cheap in reality than on the photos and the clearance between both plastic housing parts is ok, but I still have a few concerns about condensation.

I have not yet opened it to clean it, but I've read on other forums that it's too cramped in the casing to clean properly.

One thing which is more annoying than anything else is that it has a water outlet at the backside of the submerged part, which atleast in my container snuggles tightly with the container wall and this apparently can lead to vibration which is quite loud and annoying. I'll need to try a few other container to see if I can optimize that.

Currently my verdict is, that I would buy it again.

Could you post some real-life photos, please?

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Hi Haldir,

What issue are you facing with condensation? I have heard the sousvidechef first version had problems with that and condensation was appearing on the display when using it at 85°C during several hours...

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I haven't faced any issues with condensation yet, as I haven't used it at high temperatures for more than 1h. For my short 1h 90°C run the display was wet, but apparently not in the display, just the outside. I'm just a bit wary, as I don't think that the casing is sealed.

Edited by Haldir (log)
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I cooked some duck confit with my Sous Vide Chef II at 82.2C for 8 hours with no condensation.

This time I've got myself a 22 liter polycarbonate container with a lid that has a square drilled out for the device to sit in. The container is rated for heat from -40C to +100C.

sous vide chef II.jpg

Edited by nickrey (log)

Nick Reynolds, aka "nickrey"

"The Internet is full of false information." Plato
My eG Foodblog

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Cooked two lots of duck confits contiguously. This picture was taken 2 hours before the end of the second lot of cooking (14 hours in).

duck confit.JPG

No liquid on device, no condensation. Think it's safe to say that it doesn't do this at high temperatures. Reason there is water around rim is that the container was filled to brim. No evaporation using this container either.

Nick Reynolds, aka "nickrey"

"The Internet is full of false information." Plato
My eG Foodblog

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  • 2 months later...

Hello all SousVideChef II owners.

What is the latest feedback regarding these units. How are they holding up after many months usage? I finally need to source a circulator and for the European market this one seems to be best value for money. Please advice.

Cheers..

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