(RESOLVED) Conversion efficiency

Discussion in 'Brew Sessions' started by troyh, Mar 1, 2013.

  1. troyh

    troyh New Member

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    I'm really stuck on this conversion efficiency calculator. I have a recipe with an OG of 1.057 and it expects my pre-boil gravity to be 1.042. If I enter the expected value of 31L into the volume and 1.042 in the gravity field, it gives me 75% conversion efficiency. Is that correct? According to Braukaiser, if I'm getting under 95% conversion efficiency, I've got a problem. Correct?

    I just don't get the Mash Water Volume I'm supposed to enter into the calculator. The FAQ says:

    What exactly does this mean? In this session, for a 3L/kg mash thickness I need 18L of water. The Expected Value is 31L, so where does this extra 13L come from? Sparge water, right? And that's what the Mash Calculator calls "Mash Remaining". Ok, but again, if I enter 31L and my expected gravity in the kettle of 1.042, my efficiency is 75%. Is that what you expect my efficiency to be?

    I have to enter a gravity of 1.052 to get a 95% conversion efficiency. But if I start the boil with 1.052, I'll way overshoot my target OG of 1.057.

    I know all about the consistency is more important than efficiency. I'm just trying to understand these calculators. I've used Brewer's Friend for 5 batches now and am ending up with 66% brewhouse efficiencies but I look at recipes on Brewer's Friend and no recipe is showing a brewhouse efficiency that low. I used to do my own math for brewhouse efficiency and I was averaging 74% brewhouse efficiencies. My math and your math don't agree and I'm trying to figure out what is correct.

    What am I misunderstanding?
     
  2. LarryBrewer

    LarryBrewer Active Member

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    Re: Conversion efficiency

    Share the recipe (or post the grain bill, boil size, batch size, batch size target mode, and effficiency) and I'll give it a shot. Also need to see the contents of the water requirements calculation so all the assumptions match.

    75% sounds low. If you are getting 75% conversion, and 66% brew house, something is off.

    You want to enter the TOTAL amount of water that you poured into the mash tun (strike and sparge water).

    I got 58% brew house efficiency from an IIPA I did with 16 pounds of grain - BHE does vary with grain weight. 66% sound fine. I only get +70% when I do really light beers. Then again I batch sparge, and I leave behind 2 quarts of trub in the kettle. I routinely get 100% conversion efficiency since I tuned the gap on my mill and calibrated my thermometers.

    Thanks for letting us look into this, we'll get to the bottom of it. We can use this as an opportunity to clear up some terminology. Also, if you want to show how you arrived at 74%, that would be helpful.
     
  3. Kaiser

    Kaiser Member

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    Re: Conversion efficiency

    I'm having a dejavu since I thought I already replied to this.

    The conversion efficiency is only for the mash. You need to use the gravity reading from a well mixed mash and the water volume that is in that mash. If you are taking a preboil gravity you are not testing for conversion efficiency.

    Kai
     
  4. troyh

    troyh New Member

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    Re: Conversion efficiency

    Kaiser, I am doing that. The other thread involved sugar, a different recipe than the one I am doing now.

    My gravity reading is 1.048 and I used 31L of water, just as the mash calculator told me to do. That results in an 88% conversion efficiency.
     
  5. LarryBrewer

    LarryBrewer Active Member

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    Re: Conversion efficiency

    Okay, 88% sounds more reasonable. Check your mill's gap is 0.040" (corrected) (which works great for me, others may have different gaps that work for them). Also make sure your thermometers are calibrated. Could also be a mash pH issue depending on recipe and water.

    How long are you mashing for? I've been doing 90 minutes for the primary rest. I did have a 90% conversion several batches ago, but I did everything I just mentioned and got it up to 100% again. My digital thermometer goes out of whack pretty easy, which is annoying.

    I know it is frustrating, but you are still brewing what is way better than store bought beer, so don't stress over the numbers too much.
     
  6. troyh

    troyh New Member

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    Re: Conversion efficiency

    My mill's gap is 0.035" (I assume you meant 0.040", not 0.4"! :eek: ), which is the factory setting and I just checked it again last night trying to diagnose this. My thermometers are calibrated against a Thermapen. I'm mashing for 60 minutes but this batch was a 90-minute mash but I don't think it changed much. My mash pH was 5.34 on this batch.

    It's not frustrating, I'm just trying to understand. I just built out a new brewery (HERMS, all electric, PID-controlled) so all my equipment is different so I'm trying to figure out if I've got my process and equipment down. My efficiencies with my old Rubbermaid cooler mash tun were higher than it is with all this expensive equipment.

    For what it's worth, my setup is the Electric Brewery setup, an exact match and he claims he gets 95% conversion efficiency and 90% brewhouse efficiency. I'm way off those numbers even though I have the same equipment and our processes are the same.
     
  7. LarryBrewer

    LarryBrewer Active Member

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    Re: Conversion efficiency

    His definition of 'efficiency' must be very different, and probably doesn't count grain absorption losses like we do. It may also be ending kettle efficiency, not efficiency to the fermentor. I'd be open to reading about it, just to see how it works, higher numbers do make people feel better, but I'd have to check the math to make sure it makes sense.

    10 pounds of grain at an absorption rate of 0.5 qt/lb means 5 quarts is kept back in grain absorption alone. Let's say a typical batch of mine calls for 37 quarts. 5/37 = 13%, and that is coming directly off the top of conversion efficiency as soon as I drain to the kettle. It is more complex than that because the sugar in the mash adds to the total volume of the solution, grain absorption then reduces it, and it is a net loss.

    So, assuming there are zero losses elsewhere in the brewing process, somewhere in the mid 80's would be my theoretical max. I don't want trub in the primary, nor do I want to do extra work to save $0.75 on grain. Hops absorption works similarly, and I don't squeeze out my hops bags.
     
  8. troyh

    troyh New Member

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    Re: Conversion efficiency

    Here's the recipe: http://www.brewersfriend.com/homebrew/r ... n-pale-ale

    I'm still confused about the mash volume for conversion efficiency. I have a HERMS system, so here's what I do:

    I fill the HLT with enough water to cover the HERMS coil inside it. Then I heat that water. When it reaches strike temp, I move some of it (the amount the mash calculator tells me) to the MLT, and begin circulating it through the HERMS coil until it reaches the strike temp (it got colder when it moved to the cold MLT and I add more water to the HLT to cover the HERMS coil again). Once it's at the strike temp, I dough-in and mash. To sparge, I pump the wort into the BK and pump more of the HLT water into the MLT (at the same rate). I do this until I hit the boil volume in the BK.

    So to use numbers from this session, I put 18L into the MLT (a 3L/kg mash thickness) to mash. I used about 11L to sparge (the HLT volume dropped 11L). I stopped when I hit my boil volume of 28.8L.

    For the "Mash Water Used" field in the conversion calculator, what should I enter? The "Expected Value" is 31L, but why don't I enter 29L (18L for mash + 11L for sparge)?

    And if I tinker with the value, higher values make my efficiency go up. I would think it was the opposite, i.e., that using less water means I'm more efficient.
     
  9. LarryBrewer

    LarryBrewer Active Member

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    Re: Conversion efficiency

    Yes you should enter the 29L value, not the 31, since you actually used 18 + 11. However, I'm confused how you are adding 29L of water to grain, then draining that and getting 28.8L in the kettle - grain absorption does not appear to be happening. The extra 3L the calculator estimates must be the grain absorption. Look under your equipment profile for grain absorption, and the water requirements tab (or quick water requirements feature under the recipe).

    How much water is in the line to begin with, and is there a false bottom that is not being accounted for?

    This may help - let's say you brewed a 5 gallon batch at 1.050. Now, let's say with the same grain bill, you brewed a 6 gallon batch and got the same OG - that means efficiency was roughly 20% higher on the 6 gallon batch. The higher the volume, the more dilute the solution. But in this case, the wort gravity is the same, so more volume at the same gravity means higher efficiency.
     
  10. troyh

    troyh New Member

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    Re: Conversion efficiency

    Yes, the 3L is in grain absorption. It estimates 3.2L of water in grain absorption and MLT dead space. The reason it "disappears" in my math is because I'm adding the amount of water put into the BK (18L) and the water taken out of the HLT (11L). The MLT, in the middle, still has the grain and water in it that never made it into the BK (because I stopped it when I hit my boil volume). Make sense? It makes sense to me since your FAQ says not to count the grain absorption loss or dead space loss.

    What I don't get, then, is the difference between the conversion efficiency calculator and the pre-boil efficiency calculator. Shouldn't they always have the same gravity and volume values? Yet they are calculating something differently.

    Before I started using Brewer's Friend, I'd calculate my mash efficiency by calculating the weighted PPG of the grains, multiplying that by the number of gallons for the batch size. That would give me the maximum gravity points I could get. Then I'd divide that by what I got in the boil kettle (gravity points * gallons) and that would give me what I thought of as my "mash efficiency".

    For example, if the 10lb grain bill had a weighted average PPG of 34, 100% efficiency would give me 340 total gravity points. If my pre-boil gravity was 1.045 and I collected 6.5 gallons, I'd calculate my mash efficiency to be 86% (from 45*6.5/340). How is this different from "conversion efficiency"?

    I understand what you're saying about the increased efficiency. That makes sense. The terminology threw me off.
     
  11. LarryBrewer

    LarryBrewer Active Member

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    Re: Conversion efficiency

    In your case, the gravity would be the same for the 'mash complete', and 'pre-boil efficiency' log entries.

    The conversion efficiency logic also accepts the gravity of the first runnings and the strike water volume. In that case the gravity of the first runnings, and the overall pre-boil gravity would be different.

    Some definitions:
    * Conversion efficiency is how well the grains converted to sugar. For this we need to know the total volume of water that touched the grain at the point the gravity reading was taken - that total volume is what the system calls 'mash water'.
    * Pre-boil efficiency is how efficiently the sugars were separated from the grains on their way to the kettle.

    Depending on how much water is still in the MLT - you are holding back some sugar there, so that could be part of the low efficiency on your new system. For mash water used on the 'mash complete' entry, it would be the amount in the kettle, plus the amount left behind in the MLT (grain absorption, dead space, and in your case some extra standing water that did not get drained).

    We need to clean up the terminology here so it is clearer and works with this sparging approach. Either label changes, or more info in the FAQ will be coming soon.
     
  12. troyh

    troyh New Member

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    Re: Conversion efficiency

    Ah! This is what I was originally doing on my first brew sessions and I was getting 98-99% efficiencies and I thought that couldn't be right. :shock: So I kept using the Expected Value hint value. If I put my first running gravity (1.087) in with the amount of mash water I used (18L), I get 99.4%. That makes me feel better, but then you say...

    And then I'm back to low 80% efficiency. If I did what you said just there, I'd have a higher volume of water for the 'mash complete' entry than I would for the pre-boil gravity.

    I don't understand why I'd count the amount of water left in the MLT. It wasn't needed and essentially played no part in my conversion since it's didn't wash the grains at all yet. And it's my understanding that I could put a very high amount of water on top of the grain bed and it shouldn't affect efficiencies. You want 1-2" of water above the grain bed, right? Why should that amount of water factor in my efficiency? The amount of water I put through the grain bed to lauter the grain makes sense to include but only if I specify the gravity for all the runnings, not just the first runnings.

    IOW, for the 'mash complete' entry, if I enter first runnings (a high gravity) and the mash water used (a low volume) I get a great efficiency, 99.4%. But if I enter the gravity of the blended runnings in the boil kettle and all the water in the system, I get really low efficiency numbers.
     
  13. Mashhound

    Mashhound New Member

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    Re: Conversion efficiency

    Hi I have just read this post and found it timely as I have built very much the same system (electric brewery) as you Troyh and have been confused on what figures to enter in the 'mash complete' section.
    If seems to make sense to use the gravity of the first runnings (ie in your case the 18l) and use the bk volume which is fully blended for the pre boil gravity. As I too discard excess once I have the desired boil volume.
    The figures do look good......but are they correct??
     
  14. troyh

    troyh New Member

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    Re: Conversion efficiency

    I don't understand the difference between the conversion efficiency and pre-boil efficiency. After reading the first half of LarryBrewer's post, it all made sense to me, but the 2nd half confused me again. When it made sense to me, the conversion efficiency is what I'd call "mash efficiency" and the pre-boil efficiency is what I'd call "lauter efficiency":

    Mash Efficiency is a measure of how well you mashed, i.e., you had the right temperature, the right pH, the right thickness, a good crush, etc. So it makes sense to measure the first runnings for that because that is a sample and the best of the mash results and shows how good your wort will be if your lauter efficiency is perfect.

    Lauter Efficiency is how well you washed the sugar out of the grains, i.e, how evenly the fluid flowed through the grain bed, the speed of the sparge/lauter, the process (batch sparge vs fly sparge), etc.

    That all makes perfect sense to me, but I'm not sure if it's correct. :?

    And what is the End of Kettle efficiency? Shouldn't it always equal the pre-boil efficiency (unless you spilled water into the kettle and diluted the wort)?

    Braukaiser's post (http://www.braukaiser.com/wiki/index.ph ... Efficiency) is related but I don't quite understand it all and need to keep reading it.
     
  15. LarryBrewer

    LarryBrewer Active Member

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    Re: Conversion efficiency

    You have it right, and it sounds like you are getting good conversion efficiency after all - whew!

    Pre-boil efficiency (very similar to lauter efficiency as you point out), is a measure of how well the sugars were separated from the MLT (so we are on the same page there). If you take a gravity reading of the water left behind in the MLT, you will find it has some sugar - and that is hurting efficiency. Other sugars are simply trapped in the grain. That's why its is telling you ~75%, and it is correct. You could also fiddle with Braukaiser's spreadsheet: http://braukaiser.com/documents/efficie ... ulator.xls if you want to double check it with an additional tool.


    We almost called Pre-Boil efficiency lauter efficiency, and maybe we need to reconsider that. The math on Braukaiser's post has a slightly different definition of lauter efficiency though and we didn't want to divert from what is there.

    We'll work on clarifying some of this in a way that a) works for an approach like yours, and b) doesn't confuse existing users, c) fits with Braukaiser.

    Correct - ending kettle efficiency should be the same as pre-boil efficiency. Some recipes target 'kettle' batch size. Some recipes also have sugars added to the boil, and the ending kettle efficiency expects those sugars to be present (while the pre-boil efficiency does not). Pretty technical reason for adding the extra category, but it does help in those cases.
     
  16. LarryBrewer

    LarryBrewer Active Member

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    Re: Conversion efficiency

    Just to follow up:

    In that case, using our expanded terminology, 86% was your pre-boil efficiency (aka lauter efficiency). I just plugged in a recipe as you described, brewed it, and entered a pre-boil gravity log at 1.045, 6.5 gallons. The system calculated 86% pre-boil efficiency, so the math is the same. That's good! Now, why is is not 100%? Because 14% of the potential sugar is still in the MLT (either unconverted if conversion efficiency is below 100%, in solution in the water / deadspace, or trapped in the grain itself and not rinsed out).

    Conversion efficiency only looks at what happened inside the mash tun, and should be close to 100% every brew. For your mash complete logs - if you take the gravity of your first runnings, and use the strike water volume in place of 'mash water', you'll be golden.

    The whole point of breaking down 'mash efficiency' into several variables is to tease out these differences and show the brewer where efficiency losses occur. In your case, it sounds like you have close to 100% conversion efficiency - so you are doing great up to the point you start to drain to the kettle. What could be happening is a channeling effect going on with the rinse, and that is causing a drop in pre-boil efficiency.

    I should have posted this at the start of the thread.
    http://www.brewersfriend.com/2012/11/30 ... finitions/

    This picture should be helpful in showing the overlapping definitions:
    http://cdn.brewersfriend.com/understand ... _large.png
     
  17. troyh

    troyh New Member

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    Re: Conversion efficiency

    Ok, this is all so much more clear to me now. Thank you! And the difference between pre-boil and end of kettle efficiency because of the sugars even bit me on my previous batch (I'm so used to measuring gravity only after adding sugars since I care about OG at the end). I like the distinction.

    More measurements is better for an engineering-type like me. I wouldn't mind if you added a 5th for measuring the losses from the fermenter to the keg.

    Another question: the profile has a heat expansion setting of 4%. Is that automatically included in all the calculators (I assume it is, or it wouldn't be there)? IOW, my entries should always be what I see on the kettle sight glass and you'll reduce that by 4% for the end-of-kettle efficiency calculation?
     
  18. LarryBrewer

    LarryBrewer Active Member

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    Re: Conversion efficiency

    Great! We'll update the FAQ and the fields on the brew log so it is clearer.

    Lauter efficiency is technically independent of conversion efficiency, and that is why we didn't go with that term. We set it up so the efficiencies are cumulative and in order of the brewing process.

    You could start a new thread in the feature request forum and we'll see who else wants it. Pretty much it is the yeast cake and any samples taken - that's why I always brew 5.3 - 5.5 gallons to end up safely filling a keg after all is said and done.

    Yes this comes into play on the brew log entry dialog, for any volume entry, but you have to activate it. If you check the 'Temperature Correction' checkbox, a new field appears where you can enter the actual temperature, and it will then tell you the adjusted value. The adjustment factor is based on your profile setting. The adjusted value will be saved and used in the batch performance calculations.

    The question is, what temperature is your kettle's sight gauge calibrated to?
     
  19. LarryBrewer

    LarryBrewer Active Member

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    Just added a bunch of helpful info to the FAQ section related to this thread. Should make it a lot clearer for future brewers, especially fly spargers. Thanks for having this discussion and glad it was resolved!
     

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