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Old 05-03-2009, 04:14 AM   #1
schristian619
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Default efficiency calculation question-BeerAlchemy?

So today I brewed up a porter. it was a 5 gallon batch. I just got a new kettle so I'm still working on figuring out my evaporation rate. I started with 7 gals pre boil and ended with 4.75 gals in the carboy (intended on 5.5 gals). I over shot my OG by 11! BeerAlchemy says my efficiency was 103%! isn't that impossible? I don't have another program to double check the numbers and don't know how to calculate by hand. Can anyone help me figure out what my real efficiency was? grain bill and #'s are as follow:

planned:
pre-boil-1.048
post boil-1.061
7 gals pre boil
5.5 gals to fermenter
75% eff

actual:
pre-boil-1.066
post boil-1.072
7 gals pre boil
4.75 gals to fermenter

grain bill:
8lb 2 row
2 lb munich 10L
1 lb crystal 60L
.5lb crystal 80L
.5lb black malt
.5lb chocolate malt


Any help is greatly appreciated

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Old 05-03-2009, 10:50 AM   #2
HomebrewJeff
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Originally Posted by schristian619 View Post
So today I brewed up a porter. it was a 5 gallon batch. I just got a new kettle so I'm still working on figuring out my evaporation rate. I started with 7 gals pre boil and ended with 4.75 gals in the carboy (intended on 5.5 gals). I over shot my OG by 11! BeerAlchemy says my efficiency was 103%! isn't that impossible? I don't have another program to double check the numbers and don't know how to calculate by hand. Can anyone help me figure out what my real efficiency was? grain bill and #'s are as follow:

planned:
pre-boil-1.048
post boil-1.061
7 gals pre boil
5.5 gals to fermenter
75% eff

actual:
pre-boil-1.066
post boil-1.072
7 gals pre boil
4.75 gals to fermenter

grain bill:
8lb 2 row
2 lb munich 10L
1 lb crystal 60L
.5lb crystal 80L
.5lb black malt
.5lb chocolate malt


Any help is greatly appreciated
Hmm... something isn't adding up right with your pre-post boil readings.

If you have 7 gallons at 1.066 you have 462 "gravity points". If you boil that down to 4.75 gallons, you still have 462 gravity points, and divided by 4.75 should give you 1.097.
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Old 05-03-2009, 01:03 PM   #3
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Did you stir up your pre-boil wort really well before taking a reading? It looks really high and I'd be willing to guess you took a sample from one of the "heavier" parts of the wort.

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Old 05-03-2009, 06:46 PM   #4
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Your probably right that I didn't stir the wort very well before taking the pre boil reading. Is there a way to estimate it based on volume and post boil SG? I played with the volumes in beeralchemy and it says for a pre boil volume of 7 gals and a post boil volume of 4.75 gal, I should have a pre boil SG of 1.048 and a post boil of 1.071. My actual post boil SG was 1.072. Should I assume my pre boil SG was close to my projected value?

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Old 05-03-2009, 07:37 PM   #5
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Also that's a LOT of water to lose to evaporation, usually in a 60 min boil I lose maybe 1 gallon, that could explain the High OG, the pre boil def seems like its a bit off too. That can be easily if you don't stir the mixed first and second runnings for a while and make sure you're not grabbing a sample from the thicker or thinner areas of the unmixed wort. I would say that in theory, if you had a great mash, and got say 90% efficiency, and boiled off 2 1/4 gallons instaed of just 1, then yes, you could get over 100% easily... but you've gotten too little water too, and may want to top off w/ a gallon and then stir well, and then check gravity again. At any rate, it will make beer, but not sure what effect overboiling may have. (or over-evaporation... either way)

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