DCM2: A/C complete, replaced (2) 16x25x1 and (1) 16x25x4 filters. Both systems are fully functional and operating within manufacturer specifications at this time. Refrigerant pressures and temperatures are appropriate for indoor and outdoor weather conditions. Temp split 17* main floor and 16* upstairs. Noticed flue vent rusted out recommend replacing both flue vents due to hole in one and other starting to form rust. Recommend replacing with double wall instead of single wall to better insulate flue.