I am trying to calculate grain bills for my new 20bbl brewhouse (which is used), and I have been using the MBAA calculations handbook, which I really love. However, i have been gettng numbers that are higher than I anticipated, especially after looking at what I was using for my 10 bbl set up. I am using 90% mash efficiency and a 70% overall brewhouse efficiency. I have been getting numbers around 1500# for a 14 plato beer.
To be honest I am not sure what the overall brewhouse efficiency is refering to.
Do these numbers sound right to anyone brewing on a 20 bbl brewhouse?
Short answer - yes. There are SO many other variables it's hard to know where to start with additional questions. When I was brewing on a 20bbl system, our grist bill would range from 1340 to 1550+ pounds for beers with a final abv of 4.5-5.5+. What volume are you planning to have @ boil? We'd runoff until we had 25.5 bbls and would "hopefully" have 20+ bbls (sometimes less...) in the brite when all was said and done. The best answer - take an educated guess and keep track of everything. It's really the only way to find out what the efficiencies of your system are with your brewing process (big duh there...).
Your figures sound about right. I think you could raise your efficiencies and still be ok. That depends (see lprevious poster) on what kind of brewing equipment you have.
Best is to brew, and quantify the barrels and gravity of the wort collected into your fermentor. Then you can adjust the next brew accordingly.
I brew on essentially a 20bbl brewhouse and for 14 degree plato beer use between 1000 and 1100 pounds. I suggest brewing a light beer first. Use 600 pounds and check your kettle gravity as you lauter and evaluate your efficency then. Another thing to keep in consideration is the depth of the grain bed, you will lose efficiency the deeper you go. Spin the rakes from time to time.