ThermoKool 138

[November]

Bill,

I'm not sure I understand your question.  The ThermoKool MR-138 does not generate moisture or remove it through condensation (it cools based on the Peltier effect), so the relative humidity would depend on what temperature you selected.  If you select a colder temperature, the relative humidity will increase, as cold air can not hold as much moisture as warm air.  If you select a warmer temperature, the relative humidity will decrease.  Assuming the humidity in your house does not exceed the saturation point of the temperature you select, the absolute humidity will remain the same.

- red.november

[Bill/SFNM]

Thank you, November. I understand. I'm looking for a small, temperature-controlled chamber in which I can also have some degree of control over the humidity which will definitely mean adding humidity (target temp 50F-60F, humidity 60%-70%. Current ambient RH=24%). The application is for dry curing of meat and sausages. I have been using a  wine refrigerator for this purpose, but it is being used for the next few months for aging some cheeses.

If anyone has suggestions, please PM me. Thanks!

Bill/SFNM

[Bill/SFNM]

Once the dough was complete, I put it into a lightly covered container and then into my ThermoKool MR-138 unit, set at 75° F (for a typical photo of the unit, see http://www.focususa.com/showpage.asp?categoryid=14&category=personalcare&subcategoryid=275&subcategory=travel&itemid=2953&template=product_info.htm).

Thank you Peter and November for bringing this unit to my attention. As the ambient temp has been rising, I have been struggling to keep the dough from fermenting/proofing too fast. I've just ordered one! Thanks!

Bill/SFNM

[November]

Peter & Bill,

I'll post some MR-138 thermal performance numbers later today or tomorrow that you might find useful.

- red.november

[Pete-zza]

Bill,

I read at the PMQ Think Tank that the average ticket for pizzeria pizza is about $14-18, so the cost of the MR-138 unit is equivalent to about 7 or 8 delivery pizzas .

One of the challenges you will have with the MR-138 is in what type and sizes of containers you will need to use with the unit. I did a rough measurement this morning and it appears that the unit will handle a container that is about 7.5" from front to back and have the door shut. There is a rack that can be positioned at a few different heights, but one might be able to buy or fashion a rack arrangement that can hold several containers of dough at the same time. Or possibly the containers can be stacked one atop the other.

Containers have not been a problem for me because I almost never make more than a couple of dough balls at one time. The main value of the unit to me is its wide temperature range and being able to maintain consistent temperatures. That is why I used it to make the variant of the No Knead dough. Also, I got a more accurate figure for the time it is likely to take to make the dough again under the same circumstances. That should allow me to be able to plan my doughs better so, for example, they don't finish rising and have to be used at 3 AM.

Peter

[Bill/SFNM]

Thanks for the info Peter. The container I use for fermenting 6 balls of 300g dough is 7.25" in diameter by 8.5" high. I have a number of containers I use for proofing, but I'm having a feeling that 6 containers won't fit. I guess we're talking about 14-16 delivery pizzas. 

Bill/SFNM

[Pete-zza]

I guess we're talking about 14-16 delivery pizzas.

Bill,

As the spider on the mirror said: "That's another way of looking at it".

Peter

[Bill/SFNM]

 they don't finish rising and have to be used at 3 AM.

And the problem with that is ....?? 

[November]

Bill,

I didn't spend any time making the drawings to scale, but these dimensions (all in inches) should give you a pretty good idea of how you're going to be able to fit your items in it.  The 2.75" dimension is from the top surface of the rack in the bottom position to where the vent holes begin for the air outlet.  (The outlet vent is on top while the air inlet is on bottom.)  You should not run into a problem with placing an item right next to the vent because it also blows up as well as out, but I wanted to illustrate that anyway.  You will have a problem if you place something close enough to block the inlet air.  The 7.75" dimension is how much space you have between the door and the vents on top and bottom.  As you can see from the top profile, everything tapers toward the back, so the 9.625" dimension is the width at the narrowest point, but not deeper than the vents.

- red.november

[November]

The numbers seemed so clean that I decided to spend some extra time running more tests.  The average results are what I used to come up with this equation for determining how long it takes for the internal temperature of the MR-138 unit to reach another temperature approaching room temperature.  So if you have the MR-138 set at 50°F and you turn the unit off, this equation allows you to determine how long it will take to reach room temperature, or any other temperature in-between.  This is useful if you want to make use of the slow increase in temperature in the unit for bringing cold fermented doughs to room temperature before you bake, so you're not wasting energy and you know exactly when to open the door to pull the dough.

t = [delta]T² * log [delta]T
  where   t is the time in minutes,
       ...   [delta]T is the temperature difference in Fahrenheit.

Example (50°F -> 68°F):
t = 18² * log 18
t = 324 * 1.2552725051
t = 406.7082916535 or 6 h 46 m 42.5 s

All the tests were performed with 1.988 kg of mass (48.7% glass, 48.5% dough, 2.8% plastic) in the unit.  I haven't tested it, but I'm pretty sure the equation will work in the other direction for warm fermentation decreasing to room temperature.  The only thing I can think of that would prevent it from being accurate in the other direction is if the unit has seals that are either tighter or looser under warm temperatures.

- red.november

EDIT: An astute observer may notice that the time it takes to increase 1°F is 0 minutes.  That is due to one of the problems I had with testing really short times.  The unit seems to work on fuzzy logic, so several times when I turned off the the unit the temperature would change by as much as 3°F instantly.  Of course this isn't really possible, but I have no way of modeling what's going on in the first few seconds of being off.  It could just be the difference between the fan being on or off.

[Bill/SFNM]

Just received my MR-138. The size is perfect for bulk fermenting/proofing of individual balls for 6 pizzas with room to spare. I've set it to 65F with ambient temp of 77F to see how long it will take to cool and see how close the numbers are to November's.

If it can maintain accurate temps, it will see a lot of use here as summer rolls in.

Bill/SFNM

[November]

Bill,

That's good to hear.  How much mass are you using when testing the thermal acceleration?  One thing to remember is that it's designed to be ultra efficient, so if you have the unit in a region of your house that experiences "fast drafts" such as near central ventilation or a window, the temperature of the unit will drop by a few degrees and won't kick on the heat unless it's a large differential.  It will simply cut-off the cooling until the ambient heat warms the unit up again.  My advice is to place it nestled in a corner or between other large objects.  Next to your refrigerator is perfect because the warmth emanating from the back of the refrigerator will help force more active thermal regulation.  I'm actually going to build a mission style (for the other woodworkers out there) stand with pullout work surface and adjustable shelving for it to stand near my refrigerator and microwave.

- red.november

EDIT: By the way, it should take approximately 14 minutes to reach 65°F from 77°F if it's empty.

[Bryan S]

Red Nov, Bill, After some searching on the information highway, this seems to be the best price for this gizmo. Or i could be wrong, which would come as no suprise to me.    http://www.thebuzzelectronics.com/thermokool_mr138_thermokool_mr-138_deluxe_mini_cooler_and_w.htm

[November]

Red Nov, Bill, After some searching on the information highway, this seems to be the best price for this gizmo.

Bryan,

Yes, it was the cheapest I could find it too back when I was first looking at it.  Peter mentioned this merchant after I brought the unit to his attention:

http://www.pizzamaking.com/forum/index.php/topic,4686.msg39620.html#msg39620

- red.november

[Pete-zza]

Bryan,

Buzz Electronics is where I purchased my unit. Shortly thereafter, when I wanted to post a link to the product, their website no longer showed the unit as being available. Apparently they were out of stock.

I found the entire online purchasing process with Buzz to be first rate, from order placement to delivery, with timely shipment and tracking notifications, etc. Maybe I just got lucky but I wouldn't hesitate to do business with them again. Plus, their prices are better than most.

Peter

[Bill/SFNM]

November,

I grabbed 4 cans of room temp soda for the initial testing. Unfortunately, it took the unit a long time to stabilize, possibly because it had been in a hot UPS truck all day. The LED temperature was 7 or 8 degrees lower than that measured inside the unit and stayed that way for over an hour. Then within a matter of minutes, all of the temps came into sync. I was pretty busy with other things so I'm not really sure what was happening, but since then the temp has been steady at 65F.

I'll be making some bread today, so I'll give it a try.

Bill/SFNM

[November]

I grabbed 4 cans of room temp soda for the initial testing. Unfortunately, it took the unit a long time to stabilize

Bill,

What were you testing, the length of time to cool down, or the length of time to reach room temperature after already cool?  It sounds like you were testing the length of time to cool down with extra mass inside, which is something I haven't done.

- red.november

[Bill/SFNM]

November,

I guess the main thing I was trying to test was that unit wasn't DOA. Regardless, it seems to be working great. Even if it is an draft-free area, there is definitely a 5-degree drift on both sides of the set temp, but correction is quickly made. The photo below showing a 5-degree difference between the LED temp and ra emote temp sensor on the middle shelf is the exception. Most of the time they seem to be a degree or two apart at most. Of course, keeping the door closed is important.

For a device designed to keep your sodas and beers cold, it seems very well suited for pizza making. I do make a lot of baguettes which I can ferment in the MR-138, but not proof, so I'm trying a round loaf today.

My original intent was to use my current fermenting/retarding/proofing protocols and to simply fix the room-temp at around 68F even if the ambient temp is much higher. But it is clear I can use the MR-138 to create new protocols. The main direction I'm thinking of heading is lower temps and longer fermenting/proofing.

Bill/SFNM

[November]

Bill,

Like I said before in this thread, the unit appears to operate on fuzzy logic, since it doesn't have the luxury of keeping a sensor out there where food is supposed to go.  In fact, I would hope there is some difference between a sensor placed on the shelf and what it indicates, because it's supposed to be smart enough to determine the average temperature which is almost never the temperature of a single region of space, especially when you have a bulky object with thermal properties that differ from air.  This would be especially true with dough that generates its own heat.

What is the temperature differential when no objects other than the remote sensor are placed inside?

- red.november

[Bill/SFNM]

I continue to be extremely pleased with usefulness of the MR-138. It seems just the right size for the types of breads/pizzas I bake. By removing all of the shelves, I can fit a 4-quart and a 2-quart container. Here is a photo of pizza dough undergoing a 24-hour fermentation in the 2-quart container (for 6 balls @ 200g per ball) and a big 1800g gram loaf of rye bread in the 4-quart container undergoing a 48-hour fermentation. Ambient temp is expected near 80F today.

Bill/SFNM