Calculating maximum amount of grain in a Braumeister clone

[b_thomas]

After nearly a year of collecting a building my (ghetto) Braumeister clone I finally brewed my first batch on it yesterday. Whilst I was pleased with the end result my effeciency (50.2%) was no where near what I had expected. I have a feeling that I mashed too thick - 6.85kg of grain in a 20L "mash-pipe" in a 40L pot was a bit of a squeeze - however I would have thought the constant recirculation during the mash and a Mash-Out temperature step would have offset the mash thickness.

I guess my question is how do I calculate how big a grain bill can I sensitbly mash?

- My setup is a "reverse" of the Braumeister in that wort gets sucked out of the bottom and then passed over the top.
- The Mash-Pipe is a 20L pot on legs which sits it above the heating element and temperature probe.
- This results in 11L of space between the bottom of the main 40L pot and the base of the Mash-Pipe.
- The rims of the 20L and 40L are both flush so there should theoretically be 9L of "edge space".

I had assumed that my Mash Tun volume would be the 40L pot, but should I be thinking of the Mash-Pipe as my Mash-Tun and the volume around it that it displaces as "dead space"?

Anyways - hoping someone out there who has a bit more experience with brewing on these systems has some insight in to what I'm doing wrong.

 

[lael]

There is a post I did in the Mathos controller for $30 that has a link to an excel spreadsheet that will help you calculate exactly.

Buuut... The short answer is divide your malt pipe capacity by 2.8 and that will tell you. Below that your fluidisation in the pipe is too low. Reverse flow seems to result in better efficiencies. Ideal fluidisation is 3.6, but anything down to 2.8 works in practice. 2.7 and you are starting to push limits.

 

[MastersBrewery]

also note your grain crush, and water balance will influence efficiency also

 

[b_thomas]

Cheers! I will check out that spreadsheet and get calculating.

Grain crush isn't something I have too much control over - I purchase mine freshly milled from my LHBS