Installed 5 ton R-454B Carrier Infinity system. Horizontal furnace and evaporator coil in attic. Installed Carrier Infinity thermostat. Built and installed new extended supply plenum. Built and installed new return plenums with 2 media cleaners. Installed new secondary drain pan. New pad, disconnect box and wiring for the condenser. New flue pipe and gas pipe connections for the furnace. Rebuilt primary condensation drain, added SS2 and SS3 safety switches. Cleared primary drain with CO2 and primed trap with water. Removed a 12x9x9 wye, made the 9s home run to the plenum with 10 inch flex and reducer. Sealed all duct work connections with mastic/hardcast. Pressure tested system with nitrogen and pulled vacuum. Charged AC with R-454B refrigerant. Tested heating and cooling operation. Everything is working at completion of install.