Author Topic: Brewhouse Efficiency Calculation  (Read 6916 times)

Offline Chopper

  • BeerSmith Apprentice Brewer
  • **
  • Posts: 3
  • BeerSmith 2 Rocks!
Brewhouse Efficiency Calculation
« on: May 01, 2012, 11:23:36 AM »
I can't seem to match my Brewhouse Efficiency from Beersmith with the one I calculate manually.  Does Beersmith only use the grain bill, measured OG, and batch volume (volume in the fermenter) to calculate Brewhouse Efficiency?  Or is there something else built into the equation?

Here is my grain bill (using information from http://www.beersmith.com/grain-list/):
5 lbs of US 2-Row (Potential SG: 1.036) = 180 points
0.3125 lbs of Caramel 60 (Potential SG: 1.034) = 10.625 points
0.3125 lbs of Amber Malt (Potential SG: 1.035) = 10.9375 points
0.25 lbs of US Chocolate Malt (Potential SG: 1.028) =7 points
0.0625 lbs of US Roasted Barely (Potential SG: 1.025) = 1.5625 points
0.25 lbs Dark Brown Sugar (Potential SG: 1.046) = 11.5 points

So there is a total of 221.625 potential points.  My batch volume of 2.4 Gallons had a measured OG of 1.064.
64 / (221.625/2.4) = 0.693

This gives me a calculated Brewhouse Efficiency of 69.3%.  Beersmith gives me a Brewhouse Efficiency of 67.2%.  I know it is only off by a couple percentage points, but I would like the math to work out.  Also, if Brewhouse Efficiency is what is used to back into a grain bill, I want to make sure I understand how it is calculated.

Cheers,

Chris

Offline tom_hampton

  • BeerSmith Grandmaster Brewer
  • *****
  • Posts: 929
  • BeerSmith 2 Rocks!
    • Tom's Miata Racing Blog
Re: Brewhouse Efficiency Calculation
« Reply #1 on: May 01, 2012, 02:03:07 PM »
Your formula has always been my understanding of how BS calculates brewhouse eff.

NOTE: that there is probably more than 2% error in your SG, Volume (particularly this one), and temperature measurements. 

2% error in your batch volume is 1/2 cup.
2% error in your SG = 2 pts.
Most standard thermometers are accurate ~1 deg.  which is about 1% of the range we work in.

Even if you only made a 1% (1/4c, 1pt, 1deg) measurement error in these three parameters, on average you would have a ~1.7% error in measured efficiency.  So, you are within the margin of error.
R.I.P.:Belgian Blonde
On Tap: Apfelwein, Kolsch(v2), Pumpkin Ale, Belgian Specialty 
Aging/Storing: Coffee Porter, Chocolate Porter, Flanders Red, English Barlywine
Fermenting: Maggie's Altbier
Next Up: PtE(1.1), Belgian Dubbel?

Working thru all BCS recipes

Offline Chopper

  • BeerSmith Apprentice Brewer
  • **
  • Posts: 3
  • BeerSmith 2 Rocks!
Re: Brewhouse Efficiency Calculation
« Reply #2 on: May 01, 2012, 02:33:46 PM »
Tom, thank you for your input.  I understand that each measurement has a tolerance, but for the simple Brewhouse Efficiency calculation, that shouldn't matter.  For my calculation and Beersmith's calculation, they are both using 2.4 for Batch Volume and 1.064 for OG.  Even if those numbers were actually 2.35 and 1.065, the numbers I entered into Beersmith and my formula were 2.4 and 1.064.  That made me think that some of the potential yields of the grains were slightly off or rounded up or down, but I would have needed another 7 potential points (which is pretty significant for my small grain bill) to meet Beersmith's Brewhouse Efficiency.  So I'm still pretty confused because it seems that Beersmith is using another variable in their calculation.  Do your numbers match when you calculate them?


Offline rdewsbury

  • BeerSmith Apprentice Brewer
  • **
  • Posts: 19
Re: Brewhouse Efficiency Calculation
« Reply #3 on: May 01, 2012, 05:18:36 PM »
Chris,

If there is a discrepancy in the formula,  the easiest way to check is to put in a really simple grainn bill (8 pounds on marries otter at a particular point value for instance) then work it by hand and by beer smith.  If there is still a problem, then brad should be able to shed light in it. 

I ssee where Tom is going with his reply, quite validly, but you are still on the recipe design, not the actual measurement.

Roger

Offline Chopper

  • BeerSmith Apprentice Brewer
  • **
  • Posts: 3
  • BeerSmith 2 Rocks!
Re: Brewhouse Efficiency Calculation
« Reply #4 on: May 01, 2012, 07:38:36 PM »
Thanks Roger, I was able to figure out what happened by looking at one grain at a time.  There were three reasons why my numbers didn't match:
1. Beersmith doesn't round the potential points, even though it appears that way.  For example, the potential for US 2 Row is listed as 1.036, but it uses 1.03634 for its calculations.  That number comes from 1 + (46*.79) where 79% is the yield.
2. Beersmith does round the grain weights.  5 oz is 0.3125 lbs, but it uses 0.31 lbs.
3. The biggest contributor was the brown sugar that I added to my recipe.  For some reason, you need to click on the sugar you add and change the "Type" to Grain.  Then, it properly calculates the sugar contribution.

After making those three changes, I was able to match my Brewhouse Efficiency to Beersmith's, which turned out to be 68.8%.  If I didn't add the sugar, my efficiency would have been 67.2%, which will be the number I will use to base my next recipe off of because it doesn't call for sugar.

Offline rdewsbury

  • BeerSmith Apprentice Brewer
  • **
  • Posts: 19
Re: Brewhouse Efficiency Calculation
« Reply #5 on: May 01, 2012, 08:42:26 PM »
Wow, Chris.

Great analysis of the problem.  It looks like this is less of a concern for ledger batches, so the 15 and 20 gal folk will get less error than the 1 and 2 gallon small batchers.

Your point about the sugar is an eye opener for me, as I always expect fermetables to be included without having to flag them.

Thanks for posting the solution.

Roger

 

modification