Temp jump during recirc

Discussion in 'General Brewing Discussions' started by nununene, Aug 29, 2019.

  1. nununene

    nununene New Member

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    I have a weird occurrence when recircurlating my mash. I don't start the recirculation until after 15 min or so. During that time the temp stays solidly at 150. When I start the recircualtion after about 10 minutes the temp, on the kettle gauge, jumps to ~168 and comes back down after about 15 minutes to low 150s. Any thoughts? I know the temp of the 40 lbs of h2o, 16 lbs grain, and 15 lbs of kettle wouldn't be able to jump 20 degrees instantly. After all I am on earth and are bound by the physics of earth so waddup?
     
  2. 4Bentley

    4Bentley Member

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    Yes, the same thing happens to me, but not to that extent. I believe the wort is hotter on the bottom where the heating element is. When you start to recirculate it moves hotter wort to the top. After a few minutes it is all the same from the movement. If you take measurements at the top, middle, and bottom you can see the difference.
     
  3. Drewfus1

    Drewfus1 Member

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    How much volume do you have under your false bottom? In my system there is a full two gallons below it. I calculate mash thickness for the volume of water above the false bottom and temperature drop from mash-in based on the full volume of water in the kettle. I circulate well before mash-in and then start up circulation again immediately after. Do you have a thermometer on your recirculation line? If not, get one. The thermometer on your kettle isn't enough to do an accurate recirculation mash. The liquid below your false bottom can be much warmer than the water above it.
     
  4. Nosybear

    Nosybear Well-Known Member

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    For the win... Same thing happens with my rig.
     
  5. J A

    J A Well-Known Member

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    The simple answer is that your temp probe is reading a temp at only one point in your grain bed. The grain isn't all going to heat up evenly so wherever the hot liquor is most concentrated, the temp is much hotter. When you start moving the wort around, it's going to course through the layer where your probe sits and bump it way up until the grain absorbs the heat.
    I'd circulate right away to avoid the hot spots and then let it sit when it settles.
     
  6. nununene

    nununene New Member

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    I used to calculate the L:G based on 1.25 qt/lb and then add 8 qt to accommodate the space below my false bottom but I bought a kit from Bell's brewery and I asked that question and they said to include the liquor below false bottom in the 1/25 and not to add the 8 qts. I like the idea of recirculating before mash-in and starting right away. Thanks for your help.
     
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  7. J A

    J A Well-Known Member

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    Your wort temp is what's important, not the grain bed. The starch and enzymes have to interact in order to convert to sugars. the enzymes are in solution in the wort and if you're getting the wort too hot in order to heat up the grain bed, you risk going above the temperature at which the enzymes can operate. If your wort is 168 or higher for very long, conversion will stop, regardless of the temperature of the grain itself.
    If you're recirculating and controlling temp, the grain will eventually be as warm as the wort but it won't matter much during the conversion process. My system allows me to measure and control the wort temp within a little over a degree of the desired mash temp. I've found that I've gotten the best efficiency and the best wort quality by not worrying at all about what the grain bed is doing and keeping the wort just so and raising it as needed to the next step temp, letting the grain bed catch up or not.
    I start the recirc before I add the grain. By getting the strike water to the proper temp, or just slightly higher and milling directly into the tun while the strike water circulates, the grain picks up heat a little at a time and the RIMS tube keeps adding heat as necessary to hold the exact temp until all the grain is in the tun. From there I usually let it settle in and then rest a little with recirc off while the malt absorbs some liquid. Then I can restart the recirc and start raising to the next temp and adding more liquor ( I almost always dough-in very thick at around 122 or so and then raise to the main conversion temperature).
     
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  8. HighVoltageMan!

    HighVoltageMan! Well-Known Member

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    I recirculate from the beginning to the end and I measure temp in the grain bed, I’ve seen where some people say that is not the best place to measure, but my temperature is constant throughout the bed and wort. JA is correct to recirculate right away, I would add to recirculate from the start to the finish. What your seeing is temperature stratification, top is hotter than bottom, which is very common in a static mash.

    Recirculate, recirculate and recirculate some more. It works great.
     
  9. HighVoltageMan!

    HighVoltageMan! Well-Known Member

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    I recirculate from the beginning to the end and I measure temp in the grain bed, I’ve seen where some people say that is not the best place to measure, but my temperature is constant throughout the bed and wort. JA is correct to recirculate right away, I would add to recirculate from the start to the finish. What your seeing is temperature stratification, top is hotter than bottom, which is very common in a static mash.

    Recirculate, recirculate and recirculate some more. It works great.
     
  10. nununene

    nununene New Member

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    Thanks, everybody. I'm going to recirc during strike heat-up, the entire mash, and I'm going to add a thermometer to recirc line. I'll let you know how that works.
     
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