Got the mash tun, how big does my Kettle need to be?

I love the sticky on how big my mash tun needs to be, but I'm working at it from the opposite end.

I currently have a 70 quart cooler mash tun that holds 42 lbs of grain max. I'm in the process of building a 55 Gallon mash tun that can hold up to 132 lbs of grain. I know theirs got to be some equation that looks something like:
X size Mash Tun * Initial Boil Gravity / Efficiency = Total Wort

I know I need to know my efficiency right? Or at least my final goal. Like say I want to know how much 1.080 wort I could get at the end of an hour boil, I know my efficiency is ~50% because I do parti-gyle mashes.

Or how many total gravity points are available in x lbs of grain.

I've confused myself now...good luck everybody else!

1 lb of 2-row has a potential for 36 points in one gallon.

42 lbs = 42 * 36 = 1512

At 50% efficiency that's 756 points

In 5 gallons that would be 756/5 = 1.152

To get 1.080 post boil you need 756/x = 1.080. Solving, x= 9.45 gallons.

I'm assuming you want 1.080 post boil. So, now you need to factor in loss to the break and evaporation during the boil. But you'll need to start around 13 or 14 gallons pre-boil. Maybe more if you boil 90 minutes.

So, you pot should be at least 15 gallons.

But do check my math And you can figure that for 132 lb of grain, you can scale accordingly. Your kettle will need to be almost the size of your mash tun...

As that came back really quickly I feel retarded. I must have been asking google my question all wonky.

G-Lover said:

As that came back really quickly I feel retarded. I must have been asking google my question all wonky.

Click to expand...

That happens! It is easy to over think things sometimes!