The heat loss is minimal but the grain bed has a large mass that takes a lot of energy to change. So the recirculating liquor temperature is read and heat is added accordingly. While the temperature of the liquor in the bottom kettle or the hose is not the same as the mash bed it will be very close and the small additions and losses during the mash translates to an average mash temperature that is approximately 0.5 degrees within the set point. I hope this answers your question. Please feel free to contact me if you have further questions. Have a great day.
