Beersmith defines "Batch Volume" as "volume of beer as measured into the fermenter"
Soooooo, what am I’m missing here? Or am I missing something? I suck at math, my head hurts and at this point I don’t know up from down.
Your system sounds a lot like mine, a Bohemian Monobloc. Mine is 15bbl. What kind of recipe are you calibrating to? If it's a 20P over hopped wort, all bets are off. If it's around 13-15P and 45 IBU, you're in the sweet spot for most brew houses.
If you zero out shrinkage and trub loss, you're calibrating to the kettle, which is what Promash does. that leaves you with +/- 12 gallons of variance.
Question: Do you have accurate yield estimates from the
pale grain? +/- 1 point makes a big difference at this scale.
Relying on the stock numbers from any program is a source of error. Unless you're over 15% specialty malt(s), you can stick with the target estimates. The pale portion of the grist is the most impact and cost.
In commercial brewing, it matters where and when you measure. In my system, we follow this procedure:
- Preboil volume at 208-210F
- Preboil gravity and start timer after 10 min of boil
- Postboil gravity and volume taken after whirlpool and stand (just before knockout)
The volume difference between the pre and post measuring points is the boil off number for the profile. I use the full volume as the number, not an hourly estimate. This is because the boil off numbers don't change based on kettle volume, for me.
When the stand is done, the kettle is about 200F. I've found a shrinkage number of 3.4% to work to account for what the Hx gives me. I now have a pretty accurate fermentation temperature volume estimate
My loss to Trub and Chiller is 1.3 bbl. I lose 0.9 bbl to the trub cone and the rest to how we transfer. We bypass the fermenter until we get clear wort to start, then follow with chase water and bypass when the wort changes at the end. That is about 10 to 12 gallons.
To set a working brewhouse efficiency, you need accurate malt specs. Use the Fine Grind-As Is number for BeerSmith, then the Coarse/fine difference. Both are usually found in lot analysis sheets. Sometimes you have to ask your supplier or the maltster for more detail.
Armed with accurate numbers, you can use this formula to analyze your measurements:
BHE = (Sg x BV) / (Pg x GW)
BHE: Brew House Efficiency
Sg: Wort Specific Gravity, post chill (or post boil)
BV: Batch Volume, as measured in the fermenter
Pg: Potential gravity of grain
GW: Grain Weight
This formula simply divides the gravity points yielded into the fermenter by the total gravity point potential of grain (or extract or sugars) used.