I've got a 10 Gal Herms set up. I heat my HLT up 10-15 deg over my target mash step temp and recirculate the mash wort through the herms coil in my HLT. I get to the 168 deg mash out temp by having my HLT around 180 - 185 deg. then I have to cool my HLT down to 168 to use the water for sparging.
Question, do I really need to cool the HLT down, or can I batch sparge 2nd and third runnings with 180 deg water? I mean hell, I'm about to heat it all up in the boil kettle anyway... or am I looking at serious astringency or tannin problems?