Homebrewing - Beer, Mead, Wine, Cider

Low brewhouse efficiency can be a bear to troubleshoot. Usually they're procedural problems. Tweaking the chemistry gets you a few points but if you're off 10% or more off your target efficiency, it's usually something else.

One of the things that can hit your efficiency numbers is a stuck sparge, or channeling in the mash tun. Sparge water finds the path of least resistance to the spigot, so if the grain bed is uneven, the sparge water will bypass the denser inclusions and leave sugar on the table, sort of like a stream cutting a channel in the mud.

Your grind might be contributing to that situation if it's too fine, and you have too much flour in the mix. You need to stir it really well after strike, and then let it settle. If you can adjust anything on your mill to reduce flour that will certainly help. Otherwise adding rice hulls to the mash help to even out the consistency of the grain bed.

One trick I used to use would be to give everything one last stir at the end of the mash, and then pull a couple liters of wort to gently pour back on top. Is repeat the process into the wort ran clear. This would help to even the grain bed and then help it settle.

Other contributing factors could be how fast you sparge. Too fast and you're not going to capture all the sugars. Slower is generally better, since it gives the fresh water time to dissolve any extra sugars left in the grain. It also helps to reduce channeling.

My typical efficiency was 75%, maybe 80% on a very good day, but I tried to remind myself that chasing efficiency only got you frustrated.

Hope any of this helps!

Did you sparge the grain when you were done mashing?

My FIL often has efficiency issues with his AiO system and a friend of mine had similar issues to the point where he built himself a cooler mash tun to use with his. I don't know what the issue is, but you can pretty easily solve it by purchasing an extra pound of base malt for a few bucks. At the homebrew scale this isn't breaking the bank (like it would be a commercial brewery making 100s of bbls).

Why are you heating your strike water to 71C? is it enough when adding room temp grain to cool down to your target mash (I wonder if you're not accidentally destroying some enzymes)? What about the age of the grain? Enzymatic activity drops the longer grain is stored. Maybe you got a very old batch?

Using and AIO system, it should have the ability to control temp during the mash. I use one myself and a general all rounder mash program would be this: add the grain at around 45-54 C, then let it ramp up to 63. Hold for about an hour, ramp to 72, hold 10-30 minutes and then mash out at 78. Sparge at 78. I'd rather start too cold than too hot. Plus, there's some other enzymes in there that work at low temps but get denatured at 63+ (like proteases and beta-glucanases).