Sorry I couldn't stick around long enough to listen to the whole show live (was a first for me). It was getting late and I had to put my daughter to bed (including reading several books; in German of couse )
But I head Daniela make the remark that the efficiency on your system is pretty random. This is a common problem with fly sparging. If you don't sparge perfectly, you can easily get channeling which will leave sugar in the grains. Thus an unpredictable efficiency.
This problem does not exist with batch sparging. You run off the first wort (the water you mashed with). Then you add new water and stir the mash to dissolve the sugars. While the mash is sitting for 10+ min, you can already bing your collected wort to a boil and create some hot break. This actually makes managing a boil-over easier and AG brewing in a 7gal turkey fryer pot much less messy . I usually need to reload the mash with water twice to get the 24L run-off that I collect.
Since there are no channeling problems in batch sparging, your efficiency will be more predictable. Sure batch sparging is slightly lower efficiency than fly sparging (when done right), but I usually get +/- 80% on my system (Igloo cooler) and grain is cheap. I can also sparge in 30min when I batch sparge since I can let it rip.
I'm just saying, give batch sparging a try. It's simpler. You don't do decotion masches either since they are more complicated
If you brew your first AG batches and have to learn the efficiency of your system, keep some DME and water at hand. Based on the OG and the boil-off you expect, you can determine the pre-boil gravity and volume. If your efficiency was off, use DME or water to compensate. This way you can still hit your OG if you didn't hit the expected gravity. I did this for my first few batches and it made me relax quite a bit. ProMash/BeerSmith can help you with that.
Currently I'm a little bit pressimistic on the efficiency when I design a recipe. This way I will have to dillute with water to adjust the OG and still keep it AG. But my efficiency is fairly predictable (+/- 2%) these days.
hope that is not a repeat of what was suggested during the show and that it helps.
Justin, brew-on
Daniela, Gut Sud
Kai