Hot Sparge Question.

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?

You should be ok if your batch sparging. You may get some tannin extraction. Make sure you sparge water is neutral to slightly acidic and you should be good.

You can go hot sparge directly into a 155F mash, but you can't go hot into an already "mashed out" mash. You'll equilize somewhere well above 170F.

I think cooling down your sparge would only take a gallon of cold water. You can also compromise by heating the HLT to 175 and let the HERMs intially bring the mash up to 160ish just before first runnings. The 175 sparge will get you all the way up to the 170 limit.