Sweet -- sounds like a great first session on the new system!
Originally Posted by garbageman
I control RIMS element by probe at end of RIMS tube. Add 7 degrees to set point to equalize temp in Mash Tun. IE: RIMS exit temp 158 = 151 in grain bed.
The general wisdom is to use the hottest point in the loop as your mash temp rather than the grain bed (although you can stir the mash and/or tweak your system to try to get the gap down.)
The rationale is that since the wort is at 158 as it goes through the tube, this is denaturing the beta amylase (giving you a sweeter wort), regardless of the grain bed temperature. A few degrees higher and you'll start to denature the alpha amylase too, slowing or stopping the conversion.