Recirculation Mashing

Hey Guys  I have built a little heat exchange recirculation mashing  for my stove top to use as I build the brewery in the basement.  I have run 2, 6 gallon batches thru it.  First on the OG was ten points higher second one 15 points higher.  Both finished at their FG's one a point higher (15 over) & 4 Points lower (10 over)  My question is what adjustments do I need to make?  Is this an issue with my equipment, software settings or both?  Any advice on this technique will be greatly appreciated!!

Thanks Much
BobH

The basic variables are how long you sat at each rest temperature and what the mash pH was. But there is a whole laundry list of variables that you could have between two batches, from grain age and crush to fermentation conditions and yeast health.

When you're equipment setup is new, it will tell you how it will make beer. Document the batches and look for trends across each batch. Tailor the equipment and mash profiles to fit what your equipment will actually do. That will make BS a lot more accurate in its predictions.

Thanks!!  I use well water to brew with, and my mash water PH is adjusted to 5.2  I am wonder if my efficiency has gone up because of the new rig.  I drain, batch sparge but recirculate for 10 mins before pumping the remainder of the wort to the kettle.

--BobH

My notes show that when I use my heat exchanger to raise my mash from strike water temperature through mash-out, my mash spends about 20 minutes within the Beta amylase active temperature range. When I'm targeting heavy-bodied beers - emphasizing Alpha amylase activity - the time within the Beta amylase range lightens them noticeably and seems to increase overall efficiency.

If I want to reduce the Beta amylase contribution (and emphasize Alpha amylase activity) I shut down my pump, heat the heat exchanger bath to 200 F, add water from the bath to my mash to hit rest temperature, then add tap water to the bath to return it to the desired rest temperature plus 3 - 5 F to hold the rest temperature.

I generally hold my heat exchanger bath at 160 F while recirculating to avoid denaturing enzymes. That may be overly cautious. I'd like to get others' opinions.