In winter, ground-source heat pumps draw 55-degree to 60-degree water from four 1,500-foot-deep wells in Sachem’s Wood. The heat is removed from the groundwater by the heat pumps and is transferred to a separate water loop through the radiators. Then the groundwater is pumped back into the wells and absorbs heat from the Earth, ready to begin the cycle again. In summer, the process is reversed. The heat pumps take the cool from groundwater to cool the air, and then the water is pumped back into the wells.