Installed 3.5-ton R-454B Payne heat pump condenser and Carrier air handler with electric heat kit. Installed new disconnect box for the condenser. Installed Ecobee Lite thermostat. Built and installed new supply and return plenums. Sealed all connections with mastic and hard cast. Installed new secondary drain pan. Rebuilt primary condensation drain and installed SS2 +SS3 safety switches. Cleared drain with CO2 and primed trap with water. Pressure tested system with nitrogen and pulled vacuum. Charged AC with R-454B refrigerant. Tested heating and cooling operation. All is working at this time.