Recipe editor batch target = fermentor predicts to high OG

Discussion in 'Recipe Editor' started by DonY, Jan 13, 2015.

  1. DonY

    DonY New Member

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    I'm not confident the recipe editor is predicting OG properly when batch target is set to fermentor for BIAB brew method.

    I did my first brew using a recipe I scaled in Brewsfriend with batch target set to fermentor. It predicted a pre-boil gravity of 1.027 with 1.068 OG post boil (that should have been a red flag that I wasn't going to gain 21 points due to evap). My actual OG was 1.047! I'm a BIAB brewer and have 10+ batches under my belt with detailed brew records to measure efficiency into kettle and efficiency into fermentor along with volume losses due to grain absorption, boil off and trub loss.

    When I reviewed the recipe and my equipment profile to try and figure what went amiss I experimented changing batch target to kettle and setting batch volume to measured volume into kettle. Viola, predicted OG was correctly predicted at 1.048.

    Not to trust a single recipe I entered my previous beer recipe I brewed and used my brew house measurements to set batch volume and efficiencies for Brewersfriend's calculation. With batch target set to fermentor the predicted OG was over 20 points to high vs my measured OG from my brew records. If I set batch target to kettle and changed efficiency to my measured eff into kettle the predicted OG is with in a point of my actual OG measured.

    It appears with brew method set to BIAB and batch target set to fermentor the OG prediction is approx 20 points to high.

    At this point I'm not going to use batch target of fermentor until I can figure out what's causing the high OG prediction.

    Has anyone else had this experience?
     
  2. McKnuckle

    McKnuckle Member

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    Re: Recipe editor batch target = fermentor predicts to high

    I can't say I've had the identical experience, but I don't use target = fermenter because the trub loss in my kettle is so variable, and that is a factor in the equation. Sometimes I pour it all in; other times I strain it mercilessly. So I'd much rather just stop the calculations at the ending-kettle step.

    This way I'm using the ending-kettle efficiency to gauge my recipes, rather than brewhouse - because brewhouse takes the kettle-to-fermenter transfer step into account. Also, what I care about more is the OG, not the fermenter volume (at least not super precise).

    All this being said, I still sit around and rack my brain painfully after each brew session to figure out how things ended up the way they did! :)
     
  3. DonY

    DonY New Member

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    Re: Recipe editor batch target = fermentor predicts to high

    It would help my mental process on this if I knew the equation the recipe editor uses to predict OG for the batch target type of "fermenter". My equipment profile had Kettle Deadspace set to 1.3G based on my experience from other DIPAs I've brewed with my equipment. My actual trub loss on this brew session was just north of 1G. Something else is at play. If I plug the numbers into the Dilution and Boiloff calculator from what I used in the recipe editor it correctly predicts the target OG.
     
  4. DonY

    DonY New Member

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    Re: Recipe editor batch target = fermentor predicts to high

    I might have stumbled upon what's going on. My assumption in the Recipe editor was to set target batch size for the target batch type selected. My recipe target was for 2.5G into fermentor which predicted the OG to high. If I change the target size to my post boil volume (fermentor volume plus expected trub loss) leaving batch type as "fermentor" the recipe editor predicts the correct OG. Based on this behavior the batch type selected has no bearing on predicted OG and batch size should be set to the expected post boil volume. Wow, what a "red herring" batch type is during recipe design.
     

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