Using a PID to control a pump in a HERMS setup? A no-no?

[The Pol]

I don't care where the heat is being applied. I think what you mean by "not overshooting" is not having the total mash go further than you wanted. However, the only way to get a 10 minute ramp from protein to sac rest is to have the output of the hex WAY higher than the target temp. The problem is that you're denaturing the hell out of your enzymes and running the whole mash through the hex several times makes it worse. Decoction mashes don't have this problem because you're only pulling a small portion out and it later acts just like a pure water infusion step.

Applying a well elevated temp to the mash inline like that is similar to heating the entire mash to that temp for a short time, then cooling it back down to your target temp.

Agreed Bobby... I dont see how you can possibly go from 122F to 152F in 10 minutes without returning wort to the mash that is ABOVE the target temp. That is 3F per MINUTE. That is like placing a 4500W element in the mash in fact, at full power.

If you are stepping from 122F to 152F... and you are using 152F wort returning to the MLT to do this warm up... I cannot fathom that it is even possible to do in 10 minutes.

If you place a 4500W element in 10 gallons of pure water, you will get 3F/minute increase in temp. I dont see how using 152F wort will do the exact same, in the same ammount of time.

 

[Seveneer]

All I can say is take a look at my web page and then try it for yourself.

/Phil.

 

[The Pol]

Bottom line, mathematically:

4500W applied DIRECTLY to 10 gallons of water (not as much thermal mass as a mash) will raise the temp at a rate of 3F/minute.

This is the same rate that you claim with your HERMS system, which is only using 152F wort to heat the mash.

Mathematically, I dont see it possible. 152F wort does not have the same heating capability of a 4500W element placed directly in the fluid at full power.

 

[Seveneer]

I'm not heating 10 gallons of water. I'm heating 10kg of grain and 25 litres of water.

/Phil.

 

[The Pol]

I'm not heating 10 gallons of water. I'm heating 10kg of grain and 25 litres of water.

/Phil.

Right...

SO you are heating 6 gallons of water

And 22 pounds of grain....

A total mash volume of....

7.8 gallons of VERY thick (1.1qt/lb) mash.

Which will have a much higher thermal mass than 8 gallons of water alone. The higher the thermal mass, the MORE energy it takes to change the temp of that volume. This was my point all along.

 

[eccsynd]

Here is an old chart datalog from my BCS-460 on a water test. I get about a 1.5-2deg rise / min, depending on the grain bill with 5gal batches and a 1500W element, herms w/ 1.5gal exchanger. I totally disagree that the HEX temperature has to be kept less than or equal to your desired temp. In the chart below, the PID temp probe is Trace1 (blue) which is placed in the wort flow on the output of the HEX, and the HEX temp is trace0 (gray). The output of the PID is the bottom blue, trace3, you can see it start switching as the temp approaches the setpoint, 154 in this case.

As you can see, the HEX temp is 20deg higher than the wort temp. And it rises linearly. If I had a bigger element, it would rise faster. I don't overshoot because my PID works as it should. As soon as the mash temp nears the setpoint, the hex temp starts trailing off. It keeps the HEX high enough to counteract any thermal losses, but not too high such that it creates an overshoot.

This specific log is a water test, but normal mashes behave similarly based on past experience, although the mash/hex differential is less because the pump doesn't run wide open.

 

[The Pol]

You know what, HERMS is well suited for step mashes. I just did some other calculations, and it checks. HERMS is excellent for step mashing.

 

[DonD13]

Well, not having brewed an AG yet, but considering building a HERMS and having a decent understanding of thermodynamics, this thread is really interesting to me.

Without any specific measurements (purely hypothetical HERMS setup), you could concievably have a big enough coil that the wort temp at the output of the HEX is very close to the HLT temp. In this case, you would get the entire mash up to temp in whatever amount of time it takes to recirc the entire mash. With a typical march pump (lets say 2.5GPM to account for the flow restriction of your HEX and valves, plumbing etc. and to make the calcs easy) you would recirc an entire 10gal mash in 4 minutes, which I would think is plenty fast step time.

The question is: how big of an HEX would one need to get the output temp almost to HLT temps? Has anyone done any experimentation to determine this? Like I said, I'm looking at building a HERMS, so this is fascinating discussion to me.

Later,
Don

 

[The Pol]

Well, not having brewed an AG yet, but considering building a HERMS and having a decent understanding of thermodynamics, this thread is really interesting to me.

Without any specific measurements (purely hypothetical HERMS setup), you could concievably have a big enough coil that the wort temp at the output of the HEX is very close to the HLT temp. In this case, you would get the entire mash up to temp in whatever amount of time it takes to recirc the entire mash. With a typical march pump (lets say 2.5GPM to account for the flow restriction of your HEX and valves, plumbing etc. and to make the calcs easy) you would recirc an entire 10gal mash in 4 minutes, which I would think is plenty fast step time.

The question is: how big of an HEX would one need to get the output temp almost to HLT temps? Has anyone done any experimentation to determine this? Like I said, I'm looking at building a HERMS, so this is fascinating discussion to me.

Later,
Don

A March 809 will pump about 2.5 gallons/min at FULL throttle, whether or not your filtering device, false bottom or braid will allow this without grain compaction, would be a question.

You left out one thing... the grain. You arent heating the grain in the coil... you are passively heating that with wort.

The temp at the output will depend on pumping rate, heat applied, coil length, coil ID etc.

 

[The Pol]

If you want to pump 2.5gal/minute through a coil and heat it in that coil from 122F to 152F, a 30F rise... you will need... wait for it.

The equivilent of 8000 WATTS of power applied directly to 2.5 gallons of water will bring it from 122F to 152F in ONE minute.

This is 27,300 BTU applied to that water. That is an incredible ammount of heat applied directly to the water.

So if you take the coil itself out of the picture, you still need A LOT of heat, even if directly heating, to make the 30F rise at 2.5gal/min that you are speaking of.

The assumption that circulating the 10 gallons through the HEX in 4 minutes will allow you to reach your step temp. is incorrect. In practice, this does not work, as the grains absorb A LOT of heat, and getting the output of the coil to your target temp in ONE pass will take incredible heat and transfer of heat through that coil.

But again, whatta I know.

 

[eccsynd]

Without any specific measurements (purely hypothetical HERMS setup), you could concievably have a big enough coil that the wort temp at the output of the HEX is very close to the HLT temp.

I wouldn't worry too much about the heat transfer differential, i.e., the difference in HEX temp and the wort temp. The graph that I posted above shows that the transfer characteristics of my HEX are TERRIBLE, 20deg difference. I could make it better by adding an agitator, and more copper coils.. But why? The only down side of a big differential is response time, but I think the time/money is better spent getting the HEX volume lower, which REALLY affects response time. Let your PID do the work.

 

[kladue]

What is so hard about raising wort temps 30+ degrees, here is a shot from the old (2003) system with 35 degree rise across the mixer chamber Picasa Web Albums - Kevin - Old Brewing S....

 

[The Pol]

What is so hard about raising wort temps 30+ degrees, here is a shot from the old (2003) system with 35 degree rise across the mixer chamber Picasa Web Albums - Kevin - Old Brewing S....

At .83GPM?

We are talking about 30F at 2.5 gal min.

There is a small difference, I would think, when you tripple the flow rate.

Sure sure... you can raise a 10 gallon mash 30F in 4 minutes with a HERMS, I give in... sure you can. Build it.

 

[DonD13]

If you want to pump 2.5gal/minute through a coil and heat it in that coil from 122F to 152F, a 30F rise... you will need... wait for it.

The equivilent of 8000 WATTS of power applied directly to 2.5 gallons of water will bring it from 122F to 152F in ONE minute.

This is 27,300 BTU applied to that water. That is an incredible ammount of heat applied directly to the water.

So if you take the coil itself out of the picture, you still need A LOT of heat, even if directly heating, to make the 30F rise at 2.5gal/min that you are speaking of.

The assumption that circulating the 10 gallons through the HEX in 4 minutes will allow you to reach your step temp. is incorrect. In practice, this does not work, as the grains absorb A LOT of heat, and getting the output of the coil to your target temp in ONE pass will take incredible heat and transfer of heat through that coil.

But again, whatta I know.

I wasn't suggesting that this hypothetical system would actually be buildable, and you're right, I totally ignored the mass of the grain, which would make a HUGE difference. 8000 watts in general doesn't scare me, since I'm looking at propane heat for the HLT, but actually transferring all that heat through the HEX without heating it to denaturing temperature would require an enormous HEX.

This is exactly why I come here. No matter what I think up, somebody here has already tried it and found the practical limits.

 

[Lil' Sparky]

I wonder if some BRUTUS users could chime in on their experience stepping (without overshooting) on their direct-fired system. They're running their pumps at full throttle and the burners are pid controlled so that the output from the MLT is at the target.

 

[The Pol]

Direct fire will be completely different.

You are dealing with A LOT more BTU potential, you are also firing right at the MLT, so you are heating EVERYTHING at one time, you arent heating a small stream.

Direct fire will be MUCH different than a HERMS. Direct fire heats everything with 2x-5x the BTU potential to do so.

 

[Bobby_M]

...but you still cannot apply too much heat in a direct fire RIMS because you can't really pump more than 1GPM without grain compaction (Yes, even with a FULL diameter false bottom). At best, the direct fire is helping to offset heat loss by warming the vessel itself, but the flame has to be low enough not to heat the 1 gallon under the FB to higher than your target temp. I have to agree with Pol that the hypotheticals being thrown around here might as well be talking about heating with pixie dust.

 

[kladue]

Well i will have to put the new system to the test and see what it can do, it has twice the boiler area of the old system. The only test data for the new boiler so far is is at 1 gpm Picasa Web Albums - Kevin - System Testin... and at .5 gpm water Picasa Web Albums - Kevin - Boiler Test.

 

[Lil' Sparky]

Yeah, I know direct-fire is different. I was just wondering, for sake of discussion, if we had any hard numbers by the brutus guys who use similar electronic control logic to ensure the wort doesn't exceed the target temp.

Bobby, how did you come up with the 1 gpm maximum on recirculation?

 

[conpewter]

...but you still cannot apply too much heat in a direct fire RIMS because you can't really pump more than 1GPM without grain compaction (Yes, even with a FULL diameter false bottom). At best, the direct fire is helping to offset heat loss by warming the vessel itself, but the flame has to be low enough not to heat the 1 gallon under the FB to higher than your target temp. I have to agree with Pol that the hypotheticals being thrown around here might as well be talking about heating with pixie dust.

Hey guys, why have all of these talks been about not heating the returning wort over the target temp? I know enzymes will denature at higher temps but this is not an instant thing (Heck even Alpha amylase will denature at 153 after 2 hours) So even if your wort hit 170 before being put back in the tun you'd not have damage the alpha amylase too much in that short amount of time, I'm not positive about beta.

Edit: This BYO article has some of the temperature dependence talk of the amylase enzymes at the bottom

 

[Bobby_M]

Yeah, I know direct-fire is different. I was just wondering, for sake of discussion, if we had any hard numbers by the brutus guys who use similar electronic control logic to ensure the wort doesn't exceed the target temp.

Bobby, how did you come up with the 1 gpm maximum on recirculation?

I pulled that out of my ass like all the other figures in the thread

I have to run the March output valve at less than half open and I still have to re-stir the mash about every 20 minutes or the siphon tube starts sucking air.

 

[The Pol]

I pulled that out of my ass like all the other figures in the thread

I have to run the March output valve at less than half open and I still have to re-stir the mash about every 20 minutes or the siphon tube starts sucking air.

What is YOUR crusher gap Bobby??

 

[Bobby_M]

I haven't checked it in a while because I lost my feeler gauge set.

 

[np0x]

Good stuff...so i have a herms, and i have done steps in it, although I choose to call them ramps for all the reasons listed above. All i can offer right now is the ability to offer some data at a later point.

I use a convolutus cfc for a heat exchanger and a very small volume of water in my 3000 watt heat tank. I recently got an insulated keggle(1/2 inch of rubber) and I am looking forward to doing a step mash or two to see what kind of temperature rise i can get. I have instrumentation on my input as well as my output side of my HEX, so I can give a graphical response to it all once completed.

Not delving into the physics of it too much of it, just doing it by mass, if i have a 20lb grain bill, that will contain an immovable mass of the 20lbs + 2.5 gallons of water(absorbed into the grain) getting me to about 32lbs of mass not moving through the HEX, Leaving the work to the remaining 7.5ish gallons of water(62.5)....I will do a step mash on my next brew and post the graph... assuming temp entering the HEX compared to exiting will offer any resolution to this conversation. Asymptotic approaches to temperatures be damned. All of which is to say we need to brew...weather is breaking on the northern virginia finally...

 

[Lil' Sparky]

I pulled that out of my ass like all the other figures in the thread

I have to run the March output valve at less than half open and I still have to re-stir the mash about every 20 minutes or the siphon tube starts sucking air.

I wasn't trying to be a smartass. I just wondered how you came up with that #. I don't recirculate continuously, so I've been able to run mine full-flow during the time I recirculate without any problems. That's with most grain bills - wheats seem to be a little more sticky. I've also kept my barley crusher at the factory setting, so that may play a role, too.

 

[Bobby_M]

No, the question was fair and I'm admitting that it's a rough estimate. I was really disappointed to find that I couldn't continuously recirculate more than a trickle without babysitting it. One batch got pretty badly scortched when I compacted. I didn't catch it for like 4 minutes. I'm sure a lot of this has to do with my burners and their inability to run at a "simmer" type flame. If they were more adjustable, I'd be able to run the pump nice a slow without worrying about spot overheating.

 

[np0x]

I was really disappointed to find that I couldn't continuously recirculate more than a trickle without babysitting it.

I don't know what your details are, but I was having some issues as well, but I made an effort on the last two brews to really start slow and get the grain bed floating before I started an aggressive circulation. I have a perforated false bottom(stainless steel with the little 3/16th" holes) and march pumps running through 1/2 inch tubing. I found that if I started really slow the grain would stay up top and as it settled (upwards if that's possible) i was able to start flowing faster and faster as it got all locked together. I also was having stuck mashes and stuff, so i feel your pain, start at a trickle and slowly work up...of course I probably will have a stuck mash next time because I post all this, but heh, take one for the team and all that. (I am doing 10 gallon batches in keggles).

 

[Bobby_M]

I'll try that next time I brew. I also plan to use 5% rice hulls from now on also.

 

[conpewter]

I'd still like to get the thoughts on why it is such a bad idea to heat the circulating wort to above your target temp to heat the rest of the wort/grain faster.
https://www.homebrewtalk.com/f11/us...rms-setup-no-no-95372/index2.html#post1263612

 

[Lil' Sparky]

I don't think it's such a bad thing, as long as the wort out of the HEX isn't WAY above (not sure how to quantify that) the target. The wort will only be higher than your target for a short time. This is expecially true when you begin the step. If your mash is at 122º and your wort out of the HEX is 160º, it'll be back down below 150 almost as soon as it's added back on top of the mash. I'm not a chemist, but it doesn't sound like you would severely denature the alpha/beta enzymes doing this.

Also, I don't think you'd want to continue doing this as your mash gets close to your target because you can overshoot it.

 

[np0x]

I'd still like to get the thoughts on why it is such a bad idea to heat the circulating wort to above your target temp to heat the rest of the wort/grain faster.

It's "bad" because the enzymes are in solution, you are denaturing(unintentionally) if you have a high return temp, in an extreme case you would be denaturing a lot of them. The number and impact of the denaturing would be something I cannot characterize and would impact different recipes differently depending on adjuncts and qty of excess enzymes. All mash temps are denaturing some enzymes, higher temps denature faster.

 

[Bobby_M]

I guess it really depends how much hotter. I don't have concrete resources handy, but the optimum temp range for each enzyme might be 10F wide or so, but it falls off sharply on both ends. Obviously the higher the temp is, the faster the denaturing process. If you're shooting for a 148F beta rest, I wouldn't want the wort hitting 175F. Now, I understand we're talking about short bursts of maybe 10 seconds so maybe you're onto something.

I keep reading that b-amylase denatures at 70c/158f. How much in how long though? I'd have to think even running the same bulk of it up to 170F even for two or three 10 second bursts would be bad.


Edit.. more data:
http://***********/stories/techniqu...ps/632-fermentability-a-mashing-out-mr-wizard

" If malt and water are mixed together at 158 ºF (70 ºC) several things begin to happen. Starch begins to gelatinize, beta amylase begins to denature and alpha amylase begins to cleave amylose and amylopectin in smaller molecules. This temperature is well above the optimum temperature for beta amylase, but that fact does not stop beta amylase activity and maltose production is seen. Over time, the population of beta amylase enzymes denatures and those molecules that are active keep working until they denature. The time period depends on environmental conditions and enzyme concentration.

The same thing happens with alpha-amylase during mash-off. The temperature increases, the last bits of ungelatinized starch gelatinize and alpha-amylase activity continues until the population of alpha amylase enzymes has been completely denatured. Everything has a time component and these reactions are not able to occur instantaneously.

So it is logical to conclude from such laboratory experiments (and the data is out there demonstrating these phenomena) that mashing at temperatures above the denaturation point of a particular enzyme does not instantly stop enzymatic activity."

More from homedistiller:

The more interesting factor is the denaturing of enzymes. When enzymes break their internal weak fold to fold bonds they lose their shape and so their effectiveness. In a few cases this denaturing is reversible - but this is rare. The major cause of denaturing in the mash is temperature. If enzymes are involved in collisions (or vibrations) too energetic then their internal structures change. They are still proteins, but they are no longer enzymes. Under a fixed set of conditions, the rate at which enzyme denature due to temperature is akin to the way radioactive material decays, or the charge on a capacitor bleeds off. It makes sense to describe it in terms of a half-life. A 1.25qt/lb 65C mash (and other conditions of pH etc), the half-life of beta-amylase was about 16 minutes. This means that the first 16 minute mash interval will have twice the activity of the second interval and four times the activity of the 3rd interval, and so on, assuming other conditions are constant (which they are usually not). The enzyme decay rate with increasing temperature is also exponential in nature, but is much greater than the activity increase and usually in the range of 6X to 36X per 10C increase !! This means the half-life time decreases markedly with temperature increase.

Another angle on this is to consider the time it takes to fully stir a hot step infusion or decoction infusion. If you're adding 210F water, there's a brief time where a portion of the mash is exposed to denaturing temps. By brief I mean, less than a minute while you're stirring and temps are equalizing. It's probably about the same as heating to 170F in short bursts.

 

[kladue]

FWIW the 1 gpm flow through the mash has been the upper practical limit with a 15.5" Dia. screen wire false bottom. Having a flowmeter in the wort circulating circuit enabled testing of higher and lower flows with various grain bills, crushes, and water ratios. From about 5 years of flow testing it appears you could circulate above 1 gpm for a short period of time but the grain bed compacted and flow rates fell well below .25 gpm until the pump was stopped and mash bed was stirred to loosen compaction. Would really like to see the system with 2.5 gpm recirculation rate and the method used to measure flow in operation while mashing.

 

[Lil' Sparky]

Slightly off topic from the original posts/questions, but it's relevant to the last page or two...

As I've said before, I've got a direct-fired MLT, but I've never really tried to monitor things very closely, so I had no idea how fast I could do steps, or how high the wort at the bottom of the MLT was really getting.

I brewed this weekend and thought I'd post some notes for comparison. I recently installed a temp probe at the pump so I can measure temps out of the MLT to ensure I'm not overheating the mash. I took some pics and video, but I haven't had a chance to load them up on my website yet.

We did two 10 gal wheat beers. I had forgotten to order rice hulls so we did a beta-glucan rest at 110º to break up the gums in the wheat to help avoid a stuck mash (worked very well, BTW). After that I wanted to step through the typical protein rest range (122-135) quickly to save some of the head producing proteins.

During the step, I kept the valve on the pump open about 1/2. Initially I was able to turn the burner up fairly high and got a temp differential of ~ 25º between the probe in the mash and the probe at the pump. Within just a few minutes the output at the pump was at my step target (153º), so I was able to adjust the burner down, and I ensured the output from the MLT stayed below 160º. The total +43º step took < 20 mins, but most of that time was spent going from the 140s to my target.

Once at my sacc rest temps, I continued to recirculate the mash and monitor the temps. I had to fire the burner briefly for the first mash after it had lost 1º, and the 2nd one never moved (but at that point I was boiling beer #1 right next to it, so it was probably getting a little heat from that burner).

Is it a set-it-and-forget it system? No, but it did make me question if automating the mash temps with a HERMS/RIMS is worth the trouble for me.

 

[kladue]

An approach to the herms setup would be to move the exchanger out of the HLT and use a CFC type exchanger with a pump and control valve in the water side. You should be able to match a voltage output PID to a low voltage HVAC zone valve with a voltage control input for automatic control of wort temps leaving exchanger. The main question would be is it worth the investment in what would be a simple monitor and adjust manual operation for step mashing with a CFC, pump, and ball valve.

 

[np0x]

So i did a somewhat chaotic brew day this sunday, but I still was able to gather some information in regards to HERMS and step mashes. All along the words asymptotic kept coming to mind, and I had had this thought before, but never captured the data...but we will get to that. Initially i got my strike water up to temp using my HEX only, this is a pair of 1500 watt elements, that got me a 50F rise in temp in about 20 minutes(reading the lighter of the two lines in the graph(the herms sending side)) about 2.5 F a minute.

This is what is to be expected, nice clean flow, no pesky grain, everything is circulating. I got up to a low temp of about 122 for a nice step mash experiment, for this board specifically, so appreciate this already, cause the day gets ugly...

Anyway, I dough in and then get weird flow issues, so bad in fact that end up taking all 20lbs of grain and 5 gallons of water OUT Of the mash tun trying to figure out why the whole thing is stuck. About the time my wife joins me for a cup of coffee and i sit down looking at the mess i have on my hands(and arms) i notice that the inlet to the pump has about 3 inches of grain in the hose, ok back on track everyone back into the pull back to the original experiment, what's an hour or two extra in the mash time(it's a saison, I expect some killer attenuation)...that's basically all the data points from 1500-900, now the part we were talking about...

It's all going swimmingly UNTIL we get close to our mash temp, the differential on the return temp(the same as my target 152) and the mash temp decreases until it gets to a point that it will take an infinite amount of time before I ever actually get to mash temp. Since the returning liquid is the same as my target it can't actually raise the temp significantly as it gets close. I feel the graph shows this rather well. Also running cool mashes with the herms might be dodgy, what with stuck mashes and all that, although i don't know if what I had would really count, it was really a clogged pump. What fun! Up to my elbows in starchy mash...i guess I should be thankful it was only about 115F, it was like a nice hot tub, instead of a scalding kitchen accident.

For those interested, the square graph at the bottom of the graph is the HEX cycling on/off...The highest line(if it wasn't already obvious) is the return from the HEX, and the slightly lower line is the exit from the mash tun going into the HEX.

Cheers.

(and I can't tell you how close I came to just saying hell with it and doing a decoction.)

 

[Lil' Sparky]

I'd like to see that graph on a "good" brew day when you don't have a stuck mash. I take it that's what all the erratic behavior between ~ 1300-900 was all about??

It looks like you can get a +30 deg differential with your HERMS, too. That seems like some pretty good heat transfer taking place in your HEX, and your elements seem to do the job.

BTW - What's the x axis scale? It looks like you ramp from 113 to 145 pretty fast (between 800-700). How much time does that represent?

 

[np0x]

My HEX is my convoluted wort chiller(and heater)...it puts some heat across, the x-axis is somewhat difficult to read in this context, each block is 200 seconds(20 10 second samples). The 1300-900 was when i had ALL the mash in buckets OUT OF THE BREWERY...so the temperature probes were reading ambient air or hot water from the hex-all of it meaningless, ignore that part, left in purely for your visual enjoyment...fun!

 

[The Pol]

I'd like to see that graph on a "good" brew day when you don't have a stuck mash. I take it that's what all the erratic behavior between ~ 1300-900 was all about??

It looks like you can get a +30 deg differential with your HERMS, too. That seems like some pretty good heat transfer taking place in your HEX, and your elements seem to do the job.

BTW - What's the x axis scale? It looks like you ramp from 113 to 145 pretty fast (between 800-700). How much time does that represent?

I think that he said each block is 200 seconds, so that would be 800 seconds, or about 13-14 minutes.

Is it showing that your mash never really reached 150F??? Was this due to the slowing of the MLT heating since you werent OVERSHOOTING the return wort temp??

My concern with overshooting the return wort temp. is this... stratification in the MLT. If you heat the wort to 160F in the HEX and return it to the MLT. The top of the mash will be nearing 160F when the bottom is much cooler. To me, this makes having a HERMS a moot point, because you have effectively lost temp. control and your mash is a hodgepodge of temperatures.

EDIT: It looks like you had 6 samples from the time that the HLT output started heating, til your mash reached its max. (nearly 900-600) That is 1200 seconds, 20 minutes... I am just personally not comfortalbe doing a 20 minute step, if I am reading it right.

 

[Lil' Sparky]

I still don't quite understand the x axis. I know you said 200 secs/block, but 5 blocks = 200 samples, which makes me think there are 40 samples/block, not 20.

Anyway, it looks like the HEX input climbs from 113-145º in 3 blocks (10 mins?), and is only in the 120-138º range for a block and a half (5 mins). That's about what I saw with my direct-fired system Sat and seems acceptable to me. The difference I had was I was able to reach my target temp faster from the 145º range because I DID overshoot my target, but never more than a few degrees.

POL - I get your issue w/ stratification during a rest, but I don't quite understand the problem w/ stratification during a step. In fact, I'd say in a way it's a good thing, because you're already eliminating some of the effect of the enzymes in the range between your rests from the very beginning because the higher temp at the top of your mash is denaturing those enzymes.

I think the bottom line is you have to decide for yourself if you can live with the hypothetical pros/cons of any system/process and go with what makes you a happy brewer. I haven't been disappointed in any of my beers because of the system I use and I'm sure you haven't either. It is fun to think about and talk about these different ideas, though.