Single Vessel Brewing System Temperature Stability

[Bobby_M]

I put this guide together to provide additional context for some of my recommendations when people contact me and ask advice on their single vessel brewing systems. I sell a custom system that employs these recommendations but the advice is just as relevant to owners of other brand name systems. I have run extensive trials with remote probe thermometers placed in various positions within the test brewing systems to back up the claims made about stratification and heat loss.

Questions and debate welcomed...

I'm just pasting all the text here to make it easier to search and quote since the above slides are pictures.

Single Vessel Brewing Systems
mash temp stability and homogeneity


Heat Movement in Single Vessel Systems
Heat is lost:

•Through the sides of the vessel through the metal, then convection into the air.
•Into the head space, then through the lid.
•Out of the hoses and pumps into the air.

Heat is gained:

•On the surface of an electric immersion heating element
•Through the bottom of the kettle via induction or flame burners.
•Through water infusions or decoction (not relevant to this topic)

Does it matter?
§Pockets of colder mash convert slower and make a different sugar than the recipe intended.
§You may never know what your effective or average mash temperature was, which makes recipe communication and repeatability difficult.
§Step mashing via direct heat input will require that heat to be distributed to make the step schedule effective and repeatable.
§Whether any of this matters is based on your desired level of precision and consistency in your own brewing. That is to say, a mash with wide variation in temperatures and lack of precision will almost always make wort for better or worse.
Combating Heat Instability
§Insulation (helps in cold ambient brewing environments)
§Active heating while the mash progresses
§Distributing newly heated wort to areas where heat is lost via:
◦Occasional stirring, or
◦Constant recirculation from the heated area to the top of the mash
◦Whirlpooling (stirring) Deadspace Wort
◦A combination of the aboveam Jacketing is typically done on larger commercial systems to add heat to a large surface area but is impractical on a homebrew scale.
The Recirculation Approach (RIMS)
§The flow rate of the recirculation must be HIGH enough that heat gets replenished as fast as it is lost or as fast as the step mash schedule demands.
§The flow rate must be LOW enough that wort can drain into the dead space as fast as it is being removed from that area. Failure results in scorched wort and/or element dry firing.
§The delicate equilibrium between the above two requirements makes for a anxious brewer that cannot walk away from the brew system.
Constant Stirring
§An overhead view shows the stratification between the heat input (element) and the sensor location if the area below the mash is left static.
§Some Heat will migrate towards the drain if a pump is drawing.
§Without stirring this lower area:
§The sensor (and controller) will never know the true average temperature of the wort due to the stratification.
§During longer heating cycles, such as step mashing, the wort nearest the element will be overheated contributing to enzyme denaturing and unnecessary caramelization (potentially even scorching).
Basket Systems Are Especially Affected
The solid tapered side walls of the mash basket changes some parameters:
◦There is an increased amount of dead space (static wort) on the sides of the basket.
◦Any heated wort recirculated to the top of the basket bypasses that dead space.
◦The dead space on the sides of the basket is the coldest liquid of the system due to side wall heat loss. This in turn pulls heat out of the sides of the basket.
◦
The Recommended Solution
Splitting the pump output and sending heated wort to both the whirlpool port and the top of the mash fixes several problems.
◦The flow to the whirlpool stirs the entire dead space and if the arm is tilted up it will exchange the wort trapped on the sides of the basket. The result is better temp stability overall. The reduces the need for a very fast mash recirculation flow.
◦The flow to the whirlpool port acts as a pump bypass and allows for a much finer control of the mash recirculation flow rate, which should be 1 to 2 liters per minute to avoid dry firing the element upon a stuck mash drainage.
How the split is physically achieved is very system dependent but the main requirement is that each of the flows can be completely shut off or throttled to any flow rate. The whirlpool port will usually already have a valve in place.

 

[jwill911]

That's a good explanation and illustrates how to equalize temperature in the kettle. I'm already a fan of your recirculating eBIAB system. Working on 240v GFCI circuit in my garage/brew space. When the holidays are behind us I will pull the trigger.

 

[RufusBrewer]

Just today, I did my first batch using this approach. 1 part recirculation through the BIAB bag 1 part whirlpool under the bag. Employing a brewhardware spin cycle - of course.

I did the 1-2 liters through the bag

Worked very well. I am glad I made the investment in camlock fittings, valves and 1/2" SS parts.

 

[Jhedrick83]

Bobby-

Great write up. As someone who single vessel BIABs with an induction plate and small volumes (3-3.5 gallons in the fermentor), do you have or can suggest a way to set up a recirculating system like you suggest? I just finished a brew and have been considering adding in whirlpooling to both aid the speed of my IC but also to aid in forming a Trub cone for a cleaner transfer. Current BK is a SSBT 5.5 gallon kettle of it matter.

 

[Miraculix]

Thanks! You've put a lot of thought into this one. I didn't even put a fraction of that effort into it, so my method is simply a result of frustration and trial and error, but it works like a charm.

Make sure the pot is insulated against the floor. Either leave it on the hob (these gas hobs have the spikes the pot stands on, just perfect!), Or place the pot on a cushion or similar insulating material. Wrap a sleeping bag around it, covering everything, the lid, the bottom, the sides. Job done!

One hour means about two degrees loss in temperature this way, that's okay for me.

 

[SaltNeck]

When I first started, I'd mix the crushed malt with water - in a pot on the stove and slowly stir and heat it until it boiled, stopping as best I could at the rest temperatures of interest. I would then strain it through a bucket with holes drilled on the bottom into another bucket. Rinse the kettle and poor the wort back into the kettle to boil.

Made perfectly fine, if not excellent beer.

I still do that every now and then because I find it relaxing.

When using a BIAB, I simply stick the (mash) kettle in my oven (set at 150F-170F) and I might stir the mash once or twice during the mashing period.

I guess my point is I'm not sure how much difference total elimination of stratification and perfectly even mash heating makes in the end product.

Is there an objective measurement that can be used?

 

[sibelman]

Regarding the question @SaltNeck raises, I'm kinda long-winded.

On the one hand, I too wish that data -- carefully or objectively measured effects such as efficiency, dissolved oxygen or beer quality -- supports changes in my brewing setup and methods. (@Bobby_M says he measured a bunch -- thank you Bobby for this detailed presentation!) On the other hand, even without solid data, it seems intuitively obvious that cold or hot spots in the mash are a Bad Thing, a bit like unbroken dough balls. After all, we aim to achieve particular temperatures for...many reasons, not just intuition or tradition. Also obvious: mashtuns with substantial temperature gradients can make great beer.

For me, this tension between science and intuition comes down to how obviously beneficial a change seems vs. how hard it is to make that improvement, given that I'll have limited ability to measure the effect of the change. If it's gonna cost a ton or make my process burdensome, it doesn't matter how beneficial it seems. But if it's cheap and easy, why not do it? 'course, the rub comes when it's somewhat costly and difficult, and when the benefit (mash temp uniformity) feels only somewhat important.

Cheers!

 

[Bobby_M]

I want to backtrack just a bit here and just make it clear that the point of this "talk" is not to suggest that you can't make very good beer with a much more lo-fi configuration. In fact, your temps would have to be wildly out of whack for it to fail to make wort. Where the "close enough" control starts to break down is when your wort is not hitting your desired FG either high or low, troubleshooting is impossible because you can't answer the question "what was your mash temp?" with precision.

That said, many people are happy with making good beer and consistency, repeatability and recipe communication is not all that important. I cover this caveat in the "Does It Matter" slide.

Another approach is to say: IF you use an electric kettle AND you use a pump, this is the best way to get the most out of that system.

If you're running a lo-fi BIAB wrapped in a blanket or whatever it means to you and the beer is good, this is not for you. It's especially not for you if you're still not controlling your fermentation temps or using closed transfers to kegs. There are a lot bigger fish to fry.

 

[SaltNeck]

I want to backtrack just a bit here and just make it clear that the point of this "talk" is not to suggest that you can't make very good beer with a much more lo-fi configuration but instead the point of this talk is to ***fill in the blank***.

 

[Bobby_M]

I'm sorry, I don't think I can be any more clear. Am I missing something? The intent is explained pretty well right after the part you quoted.

 

[SaltNeck]

the point of this "talk" is not to suggest that you can't make very good beer with a much more lo-fi configuration

The point of your OP is *not* to suggest that good beer can't be made with a "lo-fi" config.

In fact, your temps would have to be wildly out of whack for it to fail to make wort. Where the "close enough" control starts to break down is when your wort is not hitting your desired FG either high or low, troubleshooting is impossible because you can't answer the question "what was your mash temp?" with precision.

That said, many people are happy with making good beer and consistency, repeatability and recipe communication is not all that important. I cover this caveat in the "Does It Matter" slide.

Another approach is to say: IF you use an electric kettle AND you use a pump, this is the best way to get the most out of that system.

If you're running a lo-fi BIAB wrapped in a blanket or whatever it means to you and the beer is good, this is not for you. It's especially not for you if you're still not controlling your fermentation temps or using closed transfers to kegs. There are a lot bigger fish to fry.

Like you said, these statements support that and say that it is possible to make good beer with a "lo-fi" configuration.

But what is the point or purpose of the OP then? To simply point out your solution for single vessel eBIAB? There must be a belief that it is better than something or else what is the point?

 

[sibelman]

At various points, my wife has asked about a brewery upgrade, "Yes, but will it make your beer better? " Sometimes my answer has been, "No, but it will make the process better for me." Mostly, of late, it's been, "No, but it will make the beer 's quality last longer (i.e. anti-oxygen measures).

Here, we're talking about improving a feeling of control. I want to control my mash temperature. I feel I'm doing that better if the temperature in my tun is more nearly uniform.
There's no mystery about what Bobby is about with this.

 

[RM-MN]

Here, we're talking about improving a feeling of control. I want to control my mash temperature. I feel I'm doing that better if the temperature in my tun is more nearly uniform.

I make sure my mash temp is uniform by stirring the grains into the water. Then I try to control the mash temp until full conversion is complete. Unless you know how long it takes for full conversion, you can try to maintain the temperature for a long time, hoping it will be sufficient. Now, how long does it take you to get full conversion?

Once all the possible starches are converted to sugars the temperature doesn't really matter. At that point you are just steeping the grains for color and flavor which can be done over a wide range of temperatures.

 

[dtashmore547]

I personally have a different approach to getting my temperatures consistent, I get good repeatability and excellent efficiency generally over 90 percent, my system which I have used since the late 70's involves spinning a basket of malt in a full volume mash, to stir the water in an electric kettle with temperature control via an SSD. there is probably a little bit of thermal gradient within the basket but it is the same every time. to finish the mash I can suspend the basket on a frame work hooked on the top of my kettle and use a pump to Lauter then sparge. it takes very little manual intervention during the mash but the Lauter and sparge it's totally manual. the basket hooks on a rotating frame pin the lid and the motor is a little 220v geared shaded pole motor (my first attempt used a windscreen wiper motor but needed a large 12v supply)

 

[micraftbeer]

But what is the point or purpose of the OP then?

Reading through Bobby's presentation, I'd summarize the point as "How to improve (minimize) temperature stratification in your single vessel brewing system."

And if you ask yourself, "OK, but why would I care about that?", he explains that as well:

Does it matter?
§Pockets of colder mash convert slower and make a different sugar than the recipe intended.
§You may never know what your effective or average mash temperature was, which makes recipe communication and repeatability difficult.
§Step mashing via direct heat input will require that heat to be distributed to make the step schedule effective and repeatable.

If you find yourself saying, "I don't step mash, so I don't really care about that. And I'm perfectly fine with the consistency and repeatability of my brews, and don't have concerns about sharing my recipes with others and their ability to replicate my results."- Then this post doesn't matter to you.

I personally skip over every post that at first sounds interesting, but is posted in the Mead Making or Cider Making forum. I don't care about those, because I don't brew cider or mead. So likewise, if this post about temperature stratification in single vessel brewing systems doesn't matter to you, you can just go read the next post and leave this one in your rearview mirror.

 

[SaltNeck]

There's no mystery about what Bobby is about with this.

Well sure, he's trying to sell his eBIAB systems. I'm just not convinced there's enough evidence of superiority. It's kind of like a false sense of security.

 

[micraftbeer]

There's no BrewHardware-proprietary hardware here. I could go list all the vendors and homebrew shops that sell kettles with whirlpool ports. His recommendation slide was an interesting concept (that I found non-intuitive) that said to not just recirculate wort to your top recirculation port, but also split that flow so some goes into a whirlpool port that's mounted lower down on the kettle.

BrewHardware is not the only place you can buy kettles with a whirlpool port (he even used a picture of a Spike kettle on that recommendation slide). BrewHardware is also not the only place you can buy 1/2" hose Tee fittings.

https://spikebrewing.com/pages/spike-dealers

 

[PINbeer]

Thanks OP for raising this in a dedicated thread. In my Spike Solo, I've noticed a 2-3 degree difference between sticking a thermapen into the grains during the mash and the temp as measured by the controller underneath the basket. I stir periodically and also try to ramp up the amount of recirculating wort, but there's a limit before I'm at risk of uncovering the element. I've typically gotten lower than FG predicted by Brewfather which I'm starting to believe is the result of a lower than desired actual mash temp. I have considered just raising the temperature a couple of degrees to compensate. However, that will just raise the temp of the grain bed to the target temp. The liquid under the basket will be higher than desired, and perhaps the area around the basket will be lower than desired (?). I'm not smart enough to know all the locations where and degree to which conversion actually takes place during the mash. Is it only in the grains? Or, as I suspect, does it happen to a meaningful level under the basket and on the sides also? If so, I think recirculating to the whirlpool port also would help get a more consistent (even if not perfectly consistent) temperature. I would love to hear from Spike or other single vessel system vendors on this directly. But I don't think I've seen them weigh in yet to either say that this is an opportunity for aftermarket improvement or that we should stop worrying and explain why. Regardless, I'll look to get a good setup to split the recirc at some point. Just need to give it some thought about the best hardware to make this work.

 

[PINbeer]

Relevant to my post immediately above about "hear[ing] from Spike" and also raising your target temperature ... I just went back to Spike's FAQs and read through them even if not related to the temperature directly. Found this comment below under the topic of "How to Improve Efficiency" and the sub heading of "Manage Mash Temperature Accurately". Seems like they do expect that the grains will be a couple of degrees lower than the rest and suggest my approach mentioned above to address the concern.

"For the most accurate Solo mash temperature, we recommend measuring your grain bed after a few minutes of recirculation with a thermometer. Due to the design of the system, the liquid in the kettle is made by reading at a higher temperature than the liquid within the grain itself. If your grain temperature is below expectation, simply raise your PID a few degrees until the internal mash temperature reaches your desired mash temperature. We also recommend stirring the mash 1-2 times during the one hour mash to ensure consistent temperatures. Be sure to turn off the pump when stirring."

 

[Sammy86]

Hey @Bobby_M great post! Very informative! Working with a AIO myself this provided a lot of good information. Thanks!

 

[Bobby_M]

Well sure, he's trying to sell his eBIAB systems. I'm just not convinced there's enough evidence of superiority. It's kind of like a false sense of security.

Good. You have a very skeptical approach. Me too. Personally I think everything is a scam until proven otherwise because almost everything on the internet is a scam these days.

I have 26,000 posts here and it's all an elaborate shill to sell stuff to you that you don't need.

I get it, I'm an equipment vendor so it is the only explanation and motive for anything I would ever say again. It's certainly not that I like helping my fellow homebrewers. I personally brew on a system like this and built it before I ever thought of selling ones just like it. Recipe and future batch consistency is important to me because when I come up with a recipe I really like, I want to be able to make it again as closely as possible. For example, when this happens... I want it to happen again.

You may have a problem with reading comprehension so try it again. Follow them in order

1. Some people care about very accurate and consistent mash temperatures.
2. HERE'S the really important part. IF you DON'T care, stop right here and have a nice day


Again, before you read on.... make sure you've decided that you care about accurate and consistent mash temperatures.

3. If you care, I have summarized the ways to achieve that goal.
4. If you believe my rationale to be true, use my information how you wish.
5. Buy a system that does what I suggest, from anywhere, modify a system you already have with parts you can buy anywhere, or build it yourself.

 

[Bobby_M]

Relevant to my post immediately above about "hear[ing] from Spike" and also raising your target temperature ... I just went back to Spike's FAQs and read through them even if not related to the temperature directly. Found this comment below under the topic of "How to Improve Efficiency" and the sub heading of "Manage Mash Temperature Accurately". Seems like they do expect that the grains will be a couple of degrees lower than the rest and suggest my approach mentioned above to address the concern.

"For the most accurate Solo mash temperature, we recommend measuring your grain bed after a few minutes of recirculation with a thermometer. Due to the design of the system, the liquid in the kettle is made by reading at a higher temperature than the liquid within the grain itself. If your grain temperature is below expectation, simply raise your PID a few degrees until the internal mash temperature reaches your desired mash temperature. We also recommend stirring the mash 1-2 times during the one hour mash to ensure consistent temperatures. Be sure to turn off the pump when stirring."

And my recommendation is that it's better to implement my dual flow solution, even on other vendor systems that are already very close to the design I suggest. The issue I have with just accepting the zoned temperature delta is that you don't have to and it's not very expensive or complicated to take the design to the final step.

 

[sibelman]

Re @SaltNeck's complaint: Bobby's track record as a contributor to HBT forums is unequaled among vendors who participate. I can't really see his presentation as a sales pitch, even though one could buy relevant widgets from his business. Full disclosure: I've bought a bunch of stuff from him over the years - much innovation, excellent selection, fair prices, and fine customer service. Oh, and there's his many cogent contributions to HBT.

 

[The_Antikveik]

To be fair, it's a little bit like recommending an umbrella to help keep a raincoat dry. A bit obvious and, strictly, not really necessary. It ignores the inevitable reality (biochemistry) of there being a temperature range about an optimum for reactions promoted by mash enzymes. Even with the most basic set-up (e.g. non-recirculated pot on a hop) a home brewer can hone in on an 'optimal' temperature to get a perfectly acceptable result regardless. It's very easy to hone in on what works best within a given brewing set-up by using simple surrogate measurements. It's sometimes referred to as empirical testing. Just thought I'd point that out. Nor is temperature stratification unique to a single vessel brewing system, of course.

 

[sibelman]

...perfectly acceptable result...

Yes, some "improvements" may not be worthwhile, maybe even counterproductive. Take stirring mid-mash: some think it causes problems.

If one is already recirculating, Bobby's refinement seems worth considering. My 3V system wouldn't benefit because there's very little liquid below my mashtun's false bottom. But I do like the idea of reducing mash temperature variation.

 

[SaltNeck]

Well now that everyone has attempted to justify themselves and others...

Stratification is easy to measure but the results of that stratification, *which is a much more useful measurement indeed*, is difficult to measure.

How could one quantitatively or objectively measure the results of stratification?

 

[sibelman]

How? The same way one could measure the results of mashing at one or another temperature, of step mashing, etc. With, er, science. A spectrophotometer would help determine changes in the mix of more- and less-fermentable sugars and such in the resulting wort. (Even the lowly hydrometer might shed some light on the effects of various mash techniques.) Difficult for me to measure, but not for a well-equipped brewing science lab.

It's not, in my view, unreasonable to consider such changes even if based more on intuition and less on measurement. Even when presented by a merchant of brewing equipment. But, as I led with in response to @SaltNeck 's first post, I do prefer to make changes based on data.

I also prefer interactions that steer away from ad hominem snarkiness.

 

[SaltNeck]

A spectrophotometer would help determine changes in the mix of more- and less-fermentable sugars and such in the resulting wort. (Even the lowly hydrometer might shed some light on the effects of various mash techniques.)

Interesting. So various types of sugar and starch have spectral signatures that can be compared against? Is that what you're insinuating? How would the volume of each type be determined in a wort?

A hydrometer... How do you believe that would help reveal stratification differences?

 

[doug293cz]

Interesting. So various types of sugar and starch have spectral signatures that can be compared against? Is that what you're insinuating? How would the volume of each type be determined in a wort?

A hydrometer... How do you believe that would help reveal stratification differences?

The primary thing you want to know about wort make up (w.r.t. fermentabiity) is the molecular weight distribution of the various carbohydrate molecules. Mono-, di-, and tri-saccharides (the fermentable sugars) have specific molecular weights, and the unfermentable carbohydrates (dextrine, soluble starch) have a variety of molecular weights, all higher than that of tri-saccharides. So, a molecular weight determining instrument is what you want - something like HPLC (High-performance liquid chromatography) [1, 2}

Brew on

 

[Jhedrick83]

As neither a scientist or a pedant, I may not bring much to the table here, but from my limited brewing experience, it seems that mash temps do matter. As for the experiment to quantify it, seems like this graph that most of us have probably see is a good starting point:

John Palmer may be able to provide hard data if you request it. The differences at different temps I'm sure go much deeper than that simplistic graph. So, stratification would lead to different molecular make ups within fractions of your total volume leading to a combined make up that may or may not be your target.

As for the difference in outcome, you could mash the same grain bill at two different temps and like one more than the other but that's just personal taste isn't it? Not really quantifiable.

 

[Bobby_M]

It's one thing to argue that an actively heated mashing vessel or that constant recirculation is not needed or that any benefits gained from such a system are too minimal for your personal adoption. I'm not trying to convince anyone that they NEED a system like this. I'm suggesting that if you're already buying or building a system that has recirculation and active heating, there is an optimal plumbing configuration to maximize the purported benefits of such a system. I'm amazed at the fact that this message has been interpreted so many different ways.

Maybe systems like this are complete BS. I mean everyone that has purchased the Spike Solo, Blichmann Breweasy Compact, Brausupply, Clawhammer, High Gravity Worthog, etc must be gullible morons.

 

[wepeeler]

I want to backtrack just a bit here and just make it clear that the point of this "talk" is not to suggest that you can't make very good beer with a much more lo-fi configuration but instead the point of this talk is to ***fill in the blank***.

Slap me in the face and call me Suzy

...possibly to improve our beer?


Bobby did a good job of laying out data. Key points, diagrams and explanations. Like he said, you can brew great beer without this knowledge, but even if recirculating or stirring or adding heat during the mash to ensure even heat distribution makes a little difference, then someone will benefit from it.

Heck, I'm not even going to employ these techniques, but I can clearly see the benefit.

 

[RufusBrewer]

Seems to me Bobby's message is simple and clear.

If you a) do single vessel mash & boil and b) recirculate your wort and c) wish to actively maintain consistent & accurate mash temps, consider the following hardware setup.

If you do not qualify on the propositions, stop reading this topic and move into the next topic.

 

[Brew_Dude41]

@Bobby_M I for one have always appreciated your insights, advice, and videos (not to mention your support of this site). I thought your presentation was was clear, concise, and to the point: stratification of mash temps can lead inefficiencies, here is how they can happen, here is how you can try to avoid temp stratification.
Thanks for the write up as it gives me a little food for thought...

 

[doug293cz]

There is another benefit to the recirculation arrangement that Bobby describes in the OP, and it relates to mash efficiency (specifically lauter efficiency.)

In systems with fully, or partially, solid wall grain baskets or malt pipes, the liquid between the pipe wall and the vessel wall is isolated from the grain during the mash. Since recirc into the top of the malt pipe only does not move this liquid, it remains as very dilute wort. And the most concentrated (highest SG) wort will be inside and underneath the malt pipe. When you lift the malt pipe to drain the wort (lauter) some of the wort will be retained in the grain due to absorption, and this absorbed wort will be the most concentrated wort in the system.

If the recirc also mixes up the wort between the pipe and vessel wall, this wort will become more concentrated, and the wort in the malt pipe will be lower concentration than if gap wort mixing had not occurred. Now when you lift the pipe, the absorbed wort will be lower in concentration than for the case of unmixed wort.

The higher the sugar concentration of the absorbed wort, the more sugar gets left behind in the grains, and the lower the lauter efficiency.

This also carries thru if you do a sparge. For any given sparge process and volume, the higher the sugar concentration in the grain bed at the beginning, the higher the sugar concentration will be in the grain bed after sparging. For example, if yourer sparge removes 60% of the sugar absorbed after the initial run off (a typical number for batch sparging), and you start with 6 lbs of sugar in the absorbed wort, then after sparging the grain still contains 6 * (1 - 0.60) = 2.4 lb of sugar. If on the other hand you homogenize the wort better throughout your total volume, and only have 4 lb of sugar in the absorbed wort, then after sparging you will only have 1.6 lb of sugar left in the grain bed.

How big an issue this might be will depend on what fraction of the total wort volume is held between the malt pipe and the vessel wall, which will depend on the specific geometry of your system.

Brew on

 

[hopjuice_71]

This is an interesting thread. I have a question for anyone who can answer it. So, the flow of the recirculation is split and some portion is returned to the top of the mash. For the remaining portion, does it matter how high up in the outer vessel (the kettle) the remaining portions is returned?

 

[Bobby_M]

This is an interesting thread. I have a question for anyone who can answer it. So, the flow of the recirculation is split and some portion is returned to the top of the mash. For the remaining portion, does it matter how high up in the outer vessel (the kettle) the remaining portions is returned?

The goal is to stir any liquid that is below or on the side of a basket or under a bag. As long as the return port/whirlpool is in a location that will do that will be good. .

 

[matt_m]

Since switching to a split recirc as @Bobby_M recommends as well as using line-loc to put the upper recirc just below the wort line instead of spraying, I've seen much more consistent efficiency numbers with my eBIAB system.

 

[The_Antikveik]

The graph for enzyme activity and temperature (Palmer et al.) posted above at #30, and similar graphs published in the literature, illustrate the point I made earlier about there being a temperature range (a "brewer's window" as it's described here) for activity of mash enzymes. I don’t think anyone here is saying temperature isn’t important during a mash procedure, but if an off-the-shelf single vessel brewing system fails out of the box, in terms of suffering with significant temperature stratification that translates into a noticeable impact on the end product, the beer, then that says something about the manufacturer and their claims. I certainly wouldn’t be critical of duped buyers. Having a vendor fix a perceived issue wouldn’t be on my list of solutions either, not just because of blatant conflicts of interest and the fact it isn't his responsibility. I’d expect the manufacturer to have done sufficient R&D to develop a prototype to a functional system that actually does what’s claimed on the box, before releasing it to market. Although it’s not clear to me how much temperature stratification we’re actually talking about here. Sorry if I’ve overlooked any actual data offered by the OP. All I see is a list of anecdotes and opinions, to be honest. I’m very happy with my single vessel system, which recirculates mash liquor effectively by its default design and has very little (<1℃) stratification between bottom and top of the mash, as assessed with a thermometer calibrated to the system’s temperature sensor directly under the mash. However, I can achieve comparable results (worts) in an uncirculated pot on the stove top/hob. How is this possible? I maintain consistent water treatment (ions/enzyme cofactors/pH), grist, liquor-to-grist ratio and temperature. I might increase time by 15 minutes, if I need to. Time being another relevant factor for the desired end point of enzymic reactions, of course.

As far as I can tell, it's yet to be demonstrated that small localised deviations from the average (set) temperature of a home brew mash matter enough to warrant procedure changes.

In my experience, the bigger a vessel the more potential for meaningful stratification to occur, until a point is reached where an optimised mixing/recirculation procedure becomes necessary. It’s debatable at the scales most home brewers mash, though. It might be important to note here that malted barley wort isn’t a pharma grade medium and there are very few benefits to treating it as though it were. Unless our minds are telling us otherwise and ignoring the diminishing returns, of course. If a home brewer isn’t able to brew consistently across batches, regardless of his brewing set-up, he’s not paying enough attention to his own procedures in his brewing process.

 

[Bobby_M]

You're right about some things that make it impractical for me to publish my stratification data. That's all I'll say about that and you can either trust me or don't. I'm fine with either.