When heating, how much temperature drop do you usually see in a few hours? For example, say ground water is 50°F and it takes 15 minutes for water to cycle through the loop once. For the first 15 minutes, source EWT would be 50°. The next 15 minutes, it would be less that 50°. The next 15 minutes, it would be less that that. Etc... The longer the heatpump runs, the colder it will get until the field reaches an equilibrium. The bigger/better the loop design, the more efficient the heat transfer -- 'efficient' meaning as high an EWT as reasonable. With my system, the first hour it drops 4°F. The next hour another 2°. Then progressively less as time goes by. When running continuously for a month, its down ~12°F. The original computer design shows it dropping as much as 20° from original temp near the end of winter. I've heard technicians say, it should never be as low as 40°. If that is the case, then the field needs to be expanded. Yet less than 40 seems to be common from what many report on forum. Any thoughts or comments?