Poor efficiency from Braumeister 50L

[Ckilner]

I consistently have mash efficiency problems with my Braumeister brews. I've just upgraded to a 50L after using a 20L for about 4 years but I've always struggled with the efficiency of the mash.
I've just done a brew which was supposed to come out at 5% but I'll be lucky if it hits 4%. I crush the grain myself at 1.6mm and used 12kg Maris Otter with 55L water but it missed the target (yet again).
I use a 5 stage mash

Mash In Add 55.00 l of water and heat to 40.0 C over 25 min 40.0 C 0 min
Protein Heat to 52.0 C over 12 min 52.0 C 20 min
Maltose Heat to 69.0 C over 17 min 69.0 C 20 min
Saccharification Heat to 73.0 C over 4 min 73.0 C 35 min
Mash Out Heat to 78.0 C over 5 min 78.0 C 20 min

I use Beersmith to calculate the recipes and I've set that to 75% efficiency but still it misses. I'm doing something wrong here but I can't see what.

 

[MHB]

90% chance its your crush. When you do a brew have you ever looked through your expended grain?
In a big handful of grist there shouldn't be more than 1-2 uncracked grains, they are pretty easy to spot they will have swollen up and look like pearls.

The other 10% is covered by everything else -
Are the any dough balls, dry clumps caused dumping the grist in too quickly and not stirring properly.
Is there a lot of flour, some mills especially ones with very small rollers make a lot of very fine flour. This can gum up the works preventing a good even flow of water through the grain bed.
Really off water chemistry, like very alkaline (pH over 6) after mashing in could contribute
Temperature being other than what the BM is saying, good machine but its still a good idea to check against a reference thermometer occasionally.
Mark

 

[Coalminer]

Must agree with Mark about temperature
My 20L BM consistently reads 3C above the real temperature over the full range 20 > 100C

 

[Ckilner]

Thanks. Interesting point re. uncrushed grains in the expended grains - one thing I've never looked at. I'll take a look at that. Until today's brew I crushed my grain to 1.2mm rather than 1.6mm which I did today. I found a Braumeister article which I thought was the answer to all my problems (https://www.speidels-braumeister.de/en/beer-brewing/tips-and-tricks.html). I compared my grist to the 1.6mm picture and they looked very similar.

However, I think I'm guilty of one point you raised. I tend to dump all the grist in at once and then give it a stir, then leave it soaking for 20 mins then give it another stir and then off we go. Perhaps there are dry dough balls.
I think i'm not far off with the water chemistry. I use the Bru'nWater spreadsheet (https://sites.google.com/site/brunwater/) to calculate the additions and adjust the pH with lactic acid to bring it to around 5.2 or slightly above.

 

[Ckilner]

Looking at this further I'm beginning to suspect Beersmith (or my understanding of it).
I have a Braumeister 50 and I want to produce a 56L batch at 1.050 so using the Vol tab in Beersmith I have configured water additions at pre-boil and pre-ferment.
I mash with 55L water and 11.9Kg grain. At the end of the mash I add 5L water to achieve 1.053 and according to Beersmith, that will give me 1.053.
I then boil for 60 mins and during this time, 8L wort will boil off. Beersmith says that the gravity will reduce to 1.050 which puzzles me because if I boil off 8L of water I would expect the gravity to increase.
Beersmith says that my post boil gravity is 1.050 which is what I want my final value to be but I've still got 12.56 water to add so that's going to cause the gravity to plummet.
Am I missing the point with Beersmith?

 

[cliffo]

It will definitely be all that top up water (kettle and fermentation) as it will be diluting your wort.

Are you running the water through the grain bed at the end of the mash or just pouring it straight in?

The 12.56l would be better used as sparge water through the grain bed after the mash too (if it all fits into the BM?).

 

[gilmoreous]

Doing a sparge helped my efficiency heaps. Using over 11kg of malt gave diminishing returns. My best efficiency is between 8-11kg malt. 60L mash in and 10L sparge.