Why do STRIKE temperatures change with heating vessel?

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Why do STRIKE temperatures change with heating vessel?

Postby billvelek » Thu Dec 21, 2006 2:58 pm

I've used BTP for a total of three brewing sessions (double batches each session for a total of 6 recipes); the mashing schedule has been off each time. :(

During both batches in the first session, the temperatures were way off target from the schedule; I later concluded it was because I had not calibrated my mash tun, which makes sense. So on a non-brewing day, I very carefully measured and calibrated my mash tun, and very carefully measured my kettle but did NOT calibrate it because I saw no sense in doing that; part of my heat source for my kettle is our natural gas stove, and when things get close to a boil I move it to my propane burner outside which has much higher BTUs. Also, I don't see what difference it makes to my mashing schedule, how long it takes to boil, considering variables that affect it outside like how high I have the burner set (hard to accurately duplicate), ambient temp, how windy it is, etc. However, I can see how it probably has a very minor effect on final volume, though, since there is more time for evaporation if it takes longer to reach a boil.

Anyway, to get back to my problem, after that session went wrong, I calibrated my mashtun the first time, but just used the bottom of the edit window for "Vessel" -- which seemed simple and direct enough -- so I didn't bother reading the User's Guide, and as a result did not know to use an infusion temp close to my mashing temp for accuracy. Instead I used boiling water. Well, during my next two batches (second session), actual temps were way off from target AGAIN. But then, while looking at what little there is in the User's Guide, I discovered the recommendation for calibrating at close to usual mash temp, so I figured that maybe that was the problem (although I couldn't imagine it making THAT much difference), so on another non-brewing day I RE-calibrated my mashtun very carefully using 150F for infusion temp.

Yesterday I brewed two more batches (third session using BTP), and my actual temps were AGAIN substantially different from target temps. Anyway, I was playing around with my recipe schedule this morning, trying to find the problem -- whether a BTP bug or user error -- and I discovered the likely cause, but one that doesn't make much sense to me. During "Mash In", BTP was directing me to use strike water that was more than 25F too hot, and as a consequence, every addition after that would result in a step that remained too hot. Why was it doing that? Well, without explicit instructions in the User's Guide, and being left to my own to intuitively figure things out, I figured I was supposed to fill in as much info as possible in the "Mash In" edit panel, including "Heating Vessel", so I indicated my "Turkey Fryer" kettle. I don't know what purpose that selection serves, but I figured that if it is there on the "Mash In" panel, it probably needed to be answered -- and I hope that Jeff will explain it -- but by selecting my kettle as a heat source rather than "None", my strike water temp jumped more than 25F -- even with the same target temp and same volume of infusion water. And by the way, "Heat Output" was set to .1% (lowest possible) and "Heat Duration" was set to zero minutes.

Also, it seems contrary to logic to me that if BTP somehow thought that my kettle was somehow adding heat to my mashtun, why wouldn't it LOWER the strike temp rather than raise it? So I don't know if that is a bug in the program, or a complete lack of understanding on my part WITHOUT A GOOD USER'S GUIDE. Anyway, I'm planning to brew again next week, between Christmas and New Years, so hopefully I'll have all of this ironed out so that I can FINALLY brew a recipe with some accuracy using BTP.

Cheers.

Bill Velek
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Postby bzwrxbz » Thu Dec 21, 2006 6:11 pm

Well, I agree that there should be radio buttons so the user can select what he/she wants, instead of potentially making mistakes.

It is my belief that instructions should not be needed for things like this, the GUI should be as obvious as possible, and in this case... it does not seem to be.

These are the types of things that get ironed out with time... another thing i would like to see is instant calculation, for I never feel at ease with the numbers unless I press "Ok" or something.

BTP is a great product... and I am happy despite the small growing pains :)
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Postby slothrob » Fri Dec 22, 2006 10:33 am

As I use a cooler mash tun, I chose "none" as the Heating Vessel, since I do not apply direct heat to the plastic mash tun. I also did not do the calibration steps, yet, since a put my water into my tun a few degrees higher than my Strike Temperature, then wait 10-15 minutes for the temperature to drop to my Strike Temperature. I then lose very little heat during the mash (1-2
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Postby billvelek » Mon Dec 25, 2006 12:57 am

[quote="slothrob"]As I use a cooler mash tun, I chose "none" as the Heating Vessel, since I do not apply direct heat to the plastic mash tun. I also did not do the calibration steps, yet, since a put my water into my tun a few degrees higher than my Strike Temperature, then wait 10-15 minutes for the temperature to drop to my Strike Temperature. I then lose very little heat during the mash (1-2
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Postby slothrob » Tue Dec 26, 2006 1:22 pm

I just posted that to let you know the method I use and how it works for me, I can only comment on the real world effect of the calculations on my system. I feel like I'm not understanding something about the way the direct heated systems work, because I don't know why the strike temperature would be different. Does it have something to do with heat loss vs. heat addition, so that the heat addition rate is so low that you need to start higher to keep your mash temp? Frankly, I don't have a clue, maybe someone that knows something about these systems can chime in.

I meant strike temperature in every occasion but the last sentance, when I should have said Target or Mash Temp. I add the water, without grain, to the tun, Then let it reach Strike Temperature, then add grain. This is a workaround for not having calibrated my tun, yet. It does work great, though. I gave the details of my method to show that the calculations are effective for setting strike temperature as it relates to grain mass and temperature. I can't personally comment on the effectiveness of accounting for mash tun heat mass, etc. I'd like to get this feature to work, but haven't had the time to do the calibration yet.

I suspect that the biggest variables are in making an accurate calibration. Accurate temperatures will be crucial to this. Assuming that the mash tun is at air temp is a potential source of error if it hasn't settled at this temperature, yet. One way to get a good measure of the tun temperature might be to leave a gallon of water in it overnight then measure the temperature of the water. My tun is probably 10-20
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