I have been having some issues on the last 5 brews I have done (since getting a new system) with low apparent attenuation of the yeast or high final gravity. All brews seem to be consistently coming out 5-6 points above the estimated FG.
3 Vessel electric HERMS 5gal (batch size) system. Mash efficiency 78% Brewhouse efficiency 66%.
SS Brewtech Brewbucket fermenters inside a temp controlled fridge with an accuracy of +-0.1 deg Celsius.
Yeast Starter temperature controlled chamber with a stir plate.
Beersmith 3 for all recipes.
After stirring my grains in to the strike water (calculated temps in Beersmith 3) the mash temp stabilizes within a couple of mins and stays constant for the entire mash. The mash temp at the top of the Mash tun is approximately 1 deg different to the bottom and remains very consistent.
My water has been tested and I treat it accordingly for each brew. Mash PH is always between 5.2 and 5.3.
I have tried different ways of pitching yeasts and different yeasts - dry yeast rehydrate, dry yeast not rehydrated, liquid yeast large starter, decanted starter and liquid yeast straight from the pouch. Yeasts have been Safale US05, Mangrove Jacks M44, WLP001, WLP090. Yeast is always pitched in to well aerated wort.
I check the gravity with a hydrometer and then recheck with a different hydrometer. For FG lately I have been checking straight out of the fermenter at fermentation temps then checking again once the beer is cooled and fined (with gelatin) then warmed back up to 20deg (hydrometer calibration temperature).
My previous system was a Robobrew and I never didn't hit my estimated FG over 15 batches, the only thing that has changed in the process is going to a 3 Vessel system.
Here is a link to some of the sample recipes I have done - http://beersmithrecipes.com/listrecipes/143366/lasersnake
I just pulled two beers out of the fermenters and here are the numbers for them;
6Foot5 IPA - 23l Batch
6.35kg Pale Malt (93%)
0.16kg Cara-Pils (2.3%)
0.16kg Medium Crystal (2.3%)
0.16kg Vienna (2.3%)
3 Packs of Mangrove Jacks M44 rehydrated. Fermented at 19.5deg for 7 days then slow rise to 21 for 5 days.
Estimated OG = 1.062
Actual OG = 1.061
Estimated FG = 1.011
Actual FG = 1.016
And the other batch;
S Bomb IPA - 23l Batch
6.60kg Pale Malt (89.6%)
0.77kg Medium Crystal (10.4%)
2l Starter with WLP001. Fermented at 19.5deg for 7 days then slow rise to 21 for 5 days.
Estimated OG = 1.066
Actual OG = 1.065
Estimated FG = 1.013
Actual FG = 1.019
My yeast attenuation for these is around 70% which is lower than the low side of both yeasts used.
I think it is very strange that all batches are consistently 5-6 points above estimated FG. If anyone has any ideas I would be really grateful.