Author Topic: Mash Tun temperature drops  (Read 15046 times)

Offline markok

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Mash Tun temperature drops
« on: November 09, 2012, 04:42:44 PM »
I have a 10 gal. home depot cooler (mash tun). Even though I preheat tun and cover with blankets, the temp still drops about 10 degrees over one hour. I don't open it at all during the hour. I hear people claiming they manage their temps within a degree without any other means. Any suggestions?

KernelCrush

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Re: Mash Tun temperature drops
« Reply #1 on: November 09, 2012, 04:51:13 PM »
What is your mashtun volume and what is the volume of your mash?

Offline markok

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Re: Mash Tun temperature drops
« Reply #2 on: November 10, 2012, 06:23:38 AM »
The tun is a 10 gallon cooler and the last mash I performed was 4 gallons of 172 degree water with 12 lbs. of grain. I used the Beersmith mash in schedule and even added two degrees more to my strike water. The grain was about 68 degrees. All in all I achieved the proper starting temperature of 156. I know that most use blankets but this did little for me.

I saw a suggestion a few months back that a forum user placed an insulator board on top of the mash to avoid heating head space above. This is something I will try. I am also considering looking for a second hand electric blanket at a Goodwill type store. I would think this would do better than any insulation that is not heated.

I also realize that about 80 percent or more of the saccharification has  taken place within the first 10 to 15 minutes and the heat loss in this time is only about 3 degrees therefore this is merely academic as I strive to achieve  perfection.

Offline rblagg

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Re: Mash Tun temperature drops
« Reply #3 on: November 10, 2012, 01:29:20 PM »
I am having similar problems.  A more experienced brewer helped me out.  It ended up being my thermometers.  They were inaccurate and incorrectly measuring the temps.  I thought I was losing 7 to 10 degrees over the hour.  In reality, I was losing about 2 to 3 degree over the hour.  I am not saying you are having the same problem, but it is something to think about if you have not checked them. 

Offline ghwren

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Re: Mash Tun temperature drops
« Reply #4 on: November 11, 2012, 06:23:10 AM »
Here's a great video on the proper way to do an ice bath check for your thermometers from the makers of the Thermapen: http://www.thermoworks.com/blog/2010/10/making-a-proper-ice-bath/. While three points of calibration are important, this is an easy one to get wrong. My two NIST-traceble lab thermometers were 5 deg high at freezing and 10 and 13 deg high at boiling. No idea where they were at mash until I finally purchased a thermapen ( 6 deg high.)

Offline markok

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Re: Mash Tun temperature drops
« Reply #5 on: November 11, 2012, 04:14:07 PM »
I have a Thermoworks probe thermometer that I just purchased. I have not calibrated it however I did place it and a glass therm. in my mash. They were both reading 156 at start and 143 an hour later. I stirred and the temp actually rose to 146 for a 10 degree total loss over one hour. I know there has got to be a way control this better but I just haven't figured out how short of buying a recirc heating system.

Offline Maine Homebrewer

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Re: Mash Tun temperature drops
« Reply #6 on: November 11, 2012, 05:32:13 PM »
Quote
I stirred and the temp actually rose to 146

Looks to me like the temperature wasn't evenly distributed.   
"To alcohol! The cause of - and solution to - all of life's problems!" -Homer Simpson

Offline rblagg

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Re: Mash Tun temperature drops
« Reply #7 on: November 11, 2012, 08:05:51 PM »
My calibration method was to take several different thermometers, two floating, Infrared instant read, instant read probe and electronic instant read probe normally used for cooking and test all of them both freezing, boiling and mashtun temps.  Interestingly, I found that the infrared was most accurate at lower temps usually under 100 degrees.  It makes sense since it is normally used for HVAC.  The electronic probe for cooking was accurate at mashtemps and boiling, but not at lower temps.  The floating thermometers from the brewstore and probe were overall most accurate at all temps. 

Offline GoodisBeer

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Re: Mash Tun temperature drops
« Reply #8 on: November 12, 2012, 03:12:00 PM »
Where are you measuring the mash temp? Do you use a hand held thermometer and measure the water temperature at the top of mash, instead of middle of mash? Do you stir and let rest for 2-3 minutes before measuring temp and make corrections? I have a through wall thermometer just above the ball valve at center of grain bed. Pre-warm mush tun with boiling water for 5-10 minutes, dump, add room temp grain, then add strike water according to BS calculations. Stir and rest. Measure temp and make adjustments (rarely needed). Secure lid tightly and I loose maybe 1-2° F over an hour. Do you have similar set up? Sorry if this is redundant .

Offline markok

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Re: Mash Tun temperature drops
« Reply #9 on: November 15, 2012, 12:18:04 PM »
I appreciate your questions. I have a probe that goes through a hole a top of thermos. It sits a few inches below the mash surface. I do not disturb it after my mash begins and over the course of an hour I can see the temp drop about 9 to 10 degrees.

KernelCrush

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Re: Mash Tun temperature drops
« Reply #10 on: November 15, 2012, 01:47:03 PM »
My cooler used to hold temps bang on over an hour or so, but now after about 200 gallons of mashing, it is starting to lose a bit but not like you are seeing.    What brand of cooler is it?  How old is it and how long has it served as a mashtun? 

Offline oud272

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Re: Mash Tun temperature drops
« Reply #11 on: November 15, 2012, 06:45:56 PM »
Hope this helps. Just did a mash using 10gal Homedepot Rubbermaid and lost 1F over an hour.
Details:
7lb 4 oz of grain.
9qt water into MLT at 173F, water temp after 5min = 164F
Mash temp with grain (grain was at 68F) = 151.5F (target temp was 152F)
Mash temp after 60min = 150.5F

Offline markok

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Re: Mash Tun temperature drops
« Reply #12 on: November 19, 2012, 08:01:10 AM »
Ok I used a piece of Home Depot pink polystyrene insulation. I cut out a circle that fits perfectly in the home depot 10 gallon mash tun. I pushed it down to an inch or two above the mash level with my probe thermometer already in place. I was amazed that I now lost only about 2 degrees in an hour and this included opening and stirring the mash at the 10 minute mark. This is a great solution to anyone having the same probem I was having. Cheers

Offline marcuskillion

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Re: Mash Tun temperature drops
« Reply #13 on: December 25, 2012, 08:59:23 AM »
My tun is the same one . I mash for one hour about 13 pounds grain and never lose more than a degree or two and I always open it up every 15 minutes or so and stir it around .

 I am going to guess that your thermometer sucks . I bought several and had this exact problem . they read different all the time . I now have a Acurite  http://www.walmart.com/ip/Mainstays-Digital-Meat-Thermometer-with-Removable-Stand-00994W/14913173  it works great and I tested it against 3 regular mercury thermometers .

 

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