Installed 2 ton Carrier 2 stage R-454B system. Horizontal gas furnace in attic. Installed Ecobee pro thermostat. Installed new disconnect box and high voltage wiring for the condenser. Built and installed new extended supply plenum. Built and installed new return plenum with 20x25 Aprilaire media filter. Installed new secondary drain pan. Rebuilt primary condensation drain, added SS2 and SS3 safety switches. New gas pipe and flue pipe connections for the furnace. Sealed all ductwork connections with mastic/hardcast. Cleared primary drain with CO2 and primed trap with water. Weighed in 12 oz R-454B refrigerant. Tested heating and cooling operation of new system. Everything is working at completion of install.