I doughed in at around 155. Target mash temp is 148. I stirred till I got it down to around 149 and closed the lid. Set a timer and started doing other things. 20 minutes into my 90 min mash and it’s 145. Is that too low? I still have an hour left in the mash. Should I try to increase the temp or just leave it?
Decided to bump it up. Got 1gal of water to about 158 and dumped it in. Back on track. Also added about .3ml of lactic to keep the pH where it needs to be
Your target mash was on the lower side at 148, so a small drop to 145 won’t change much. Your wort was going to be very fermentable; still the case. I’m sure everything converted over the course of an hour, all other things equal.
You did get a chance to learn something about how the temperature works in your system. All data is a good data.
I didn’t build a RIMS to improve my beer, I built it because I’m lazy and it evens the mash out in the situation you describe.
Edit: You mention adding lactic. I add a little to every mash. What was your target ph?
Does mashing in at +7 typically work for your system? I’ve found what works best for me is to deselect adjust temp for equipment in beersmith add water 20 degrees above my target temp to pre heat, there with be a drastic initial temp loss, then add the grain when its +10 above my target mash temp. I keep my water to grain ratio a constant at 1.5 Qt per pound. Works every time and after 60 minutes its always where I left it.
I’m thinking you may have lost the other 3 degrees soon after shutting the lid? Do you usually lose more than a degree or two after 60 minute mash?
I really don’t think a three degree difference means squat. You could add the water but it probably won’t change much. Next time leave the lid shut and go have a beer.