efficiency calculation question-BeerAlchemy?

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schristian619

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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
 
schristian619 said:
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
Click to expand...

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.
 
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.
 
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?
 
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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