Anova Sous Vide Circulator (Part 2)

[Martin Fisher]

FWIW, PedroG's post (No. 17) in the following thread shows what kind of difference an insulated cover, etc., can make in terms energy consumption when sous-viding....

 

http://forums.egullet.org/topic/139754-the-electrical-cost-of-doing-sous-vide/

[Chimo]

FWIW, PedroG's post (No. 17) in the following thread shows what kind of difference an insulated cover, etc., can make in terms energy consumption when sous-viding....

http://forums.egullet.org/topic/139754-the-electrical-cost-of-doing-sous-vide/

Thanks for the link. There was also some interesting tidbits on the kill-a-watt meter in there. It may not be fully up to the task with respect to getting the steady state power requirements of the SV due to its relatively slow data sampling frequency. During warm up I would expect the SV's heating element to be on at 100% duty cycle.

Two key factors in designing a battery-based backup would be the maximum demand (known) as well as the energy required for the desired hold time. As discussed here, that energy requirement will be a function of many variables. Sounds like a fun problem to ball-park!

[Chimo]

...

Inverters invert by switching (pulsing, chopping) DC to transform to higher voltage, switching means on and off. on and off means square wave. Pure square wave can do damage to some electrical devices. So they have to reshape square waves to more like sine waves.

 

dcarch

That's correct.  I have also seen and built other inverter circuits that have varying output waveforms.  Devices with motors are particularly sensitive to UPS output waveform.  A corded drill is a handy, if simple, check of how well the output has been smoothed to a sine wave's energy.

 

I noticed that there are a lot of other engineers/techs in this forum.  Good to see!

[Chimo]

I did a batch of 63.5C eggs and then some 78.4C asparagus tonight and had the Kill-A-Watt (k-a-w) plugged in. The container was a small Coleman cooler with a top opening approx 10"x12".  As predicted the start-up draw was about 1050W.  Once temperature was reached, the k-a-w readings fluctuated from ~30W to 500W with greatly varying KVA readings as well as the power factor varied as well and dipped to as low as 0.48. The power factor still read low when the k-a-w was drawing a few hundred watts.  I would not trust this device to provide an accurate tally of kWH for a cook.

 

As a side note, once the bath reached a steady state temperature, I removed the reflectex lid I had covering the cooler. The k-a-w indicated that the power demand went from ~30W to over 200W to cope with the evaporative losses.  Once I replaced the cover, the k-a-w soon settled back down to the lower power demand numbers.

[pbear]

Yes, but the question is how much. You can calculate the R-value of insulation by measuring the surface temperature of the vessel relative to the ambient air temperature, and comparing to the temperature differential between inside and outside the vessel.

 

The higher the R-value, and the lower the temp. variation between in and out, the less warm you'd find the outside of the vessel. If the cooler were filled with 1/2" closed cell foam, which has very high r-value, I'd expect the warmth of the cooler on the outside to barely perceptibly warm to the touch. At least with a 140F cook, which is only about 70F warmer than the air in the room.

 

I haven't done the math, so I could be wrong about it. Maybe it's well insulated and I should expect it to get as warm as it does. If that's the case, though, a 30 quart cooler with that much warm surface area makes for a pretty big radiator. It's definitely burning up some watts. Imagine the light bulb it would take to warm up a big cooler that much.

 

I'm pretty sure we're using the same assumptions regarding the science.  Where we differ, I think, is over expectation.  So, yes, R-value will tell us how effective the insulation.  It's a gradient.  Say the inside temp of whatever is being insulated - whether a sous vide bath or a house - is X and the ambient temp is Y.  How fast Y will "wick" heat from the box is a function of the heat coefficient of air.  How fast X will pump heat into the insulation is a function of the heat coefficient of the medium inside the box.  The important difference between a sous vide bath and a house is that water is much more efficient at transferring heat than air.  That's why we're using it.  Sauce for the goose is sauce for the gander.  Just as a sous vide bath efficiently heats the pouches, so too does it efficiently heat the insulation.  Which is why I say I'm not surprised the insulated box gets warm on the outside.

 

Relating back to the OP, what I think this means is that it's not realistic to expect a UPS to maintain a sous vide bath for long.  For a flicker, sure.  Even for several minutes.  More than this, though, not so much.

 

[dcarch]

I don't know if many "beer coolers" are insulated.

 

Mostly they are "Isolated" by using double layer construction. No insulation, just air space, between the layers.

 

An "isolated" vessel, if with vacuum in the space is extremely effective in not loosing heat, such as in a thermos bottle.

 

dcarch

[paulraphael]

I don't know if many "beer coolers" are insulated.

 

Mostly they are "Isolated" by using double layer construction. No insulation, just air space, between the layers.

I was wondering about this. I looked up my cooler on the Coleman site. All it says is "insulated case for longer ice retention." It does not say "insulated lid," and indeed the lid had nothing in it. 

 

Some of their other coolers are fancier, and the site goes into more detail about what's in there. I don't feel quite curious enough to drill a hole and take a look.

[Martin Fisher]

Most (if not all) poly cooler lids are not insulated.

[rotuts]

correct.  they are after all 'coolers'  and do not need an insulated top

 

if they were meat to keep food warm also, then the tops would be insulated.

 

the coleman's I have do indeed have foam insulation in the 'body'  nada in the top.

[Martin Fisher]

Good coolers, back in the day, had insulated tops and they worked much better.

Coolers are often used out in the sun where an insulated top is a good idea.

Edited June 21, 2014 by DiggingDogFarm (log)

[dcarch]

correct.  they are after all 'coolers'  and do not need an insulated top

 

if they were meat to keep food warm also, then the tops would be insulated.

 

the coleman's I have do indeed have foam insulation in the 'body'  nada in the top.

 

Cut a 1/2 hole, fill it with Styrofoam beads, or Perlite. Duct tape the hole.

Will work much better.

 

I have not had a chance to try this out: A few drops of oil on the water will prevent evaporation.

 

dcarch

[paulraphael]

These Coleman "xtreme" coolers have insulated lids. I'd have gotten one if I'd known about them. A lot cheaper and easier than my questionable project of insulating the lid with foam.  Some people have questioned the value of the lid insulation, but I'm betting it's worth at least a little. I also use reflectix.

[paulraphael]

Just announced today, in case we were suffering a shortage of Anova threads.

 

Looks like they're going for Poly Science's jugular.

 

I'm not sure why the 120v model doesn't got 18KW ... other brands do. Otherwise looks like a killer for $400.

[dcarch]

"----------I'm not sure why the 120v model doesn't got 18KW ... other brands do. Otherwise looks like a killer for $400.---"

 

Number one, You don't need more then 1000 watts to maintain temperature. I prefer a lower wattage heater. They last longer.

 

In a small confined space, the higher wattage will have to burn the heating element at a higher temperature.

 

dcarch

[nickrey]

Sad that the international model (220V) is 50% more in cost at $600.

[paulraphael]

"----------I'm not sure why the 120v model doesn't got 18KW ... other brands do. Otherwise looks like a killer for $400.---"

 

Number one, You don't need more then 1000 watts to maintain temperature. I prefer a lower wattage heater. They last longer.

 

In a small confined space, the higher wattage will have to burn the heating element at a higher temperature.

 

dcarch

I don't personally want more than 1kw, but I can see how it would be useful in a commercial kitchen where big, uninsulated cambros are typical. 

 

Is there really a history of professional lab circulators with 1.8kw heaters crapping out?

[Hassouni]

Grumble, and it ships 2 months before the ones we crowd-funded.

[Martin Fisher]

I didn't see warranty length noted anywhere so I fired off an email to ask.

[JoNorvelleWalker]

Grumble, and it ships 2 months before the ones we crowd-funded.

 

"What you mean we?"

[Hassouni]

Myself, rotuts (I think?) FrogPrincesse, many others here.

[JoNorvelleWalker]

I think it is an old Lone Ranger joke, but I am fond of my Anova.

[pmilas]

I must say that it's the best looking SV circulatorso far. And the data for HACCP is a great thing, does the polyscience have that?

[paulraphael]

Grumble, and it ships 2 months before the ones we crowd-funded.

It looks a lot like one of their existing lab circulators. Which could explain its quick arrival. I don't know what they changed besides the price (listed at $895 on the lab site). 

[Martin Fisher]

It's a 1 year warranty.

[chris_s]

I happened to have my Kill-a-watt device handy when setting up my sous vide rig yesterday so I did a little test. 

 

setup was a 3 gallon pressure cooker, with the lid propped half on with the anova sticking out. running at mostly 135f (turned up for a couple of hours to 140. 

 

over 22 hours it used 6.1 kilowatts, which at my local rate is 42c. So if anyone is concerned that doing super long cooks is eating up a ton of electricity, you can now sleep soundly