nstalled 4 ton 2 Stage R-454B Carrier heat pump system. Installed vertical air handler with electric heat kit. Installed new plywood overlay for air handler to sit on. Built and installed new supply plenum. Sealed all connections with mastic and hardcast. Installed new disconnect box and wiring for the condenser. Rebuilt primary condensation drain and added SS2 safety switch. Pressure tested system with nitrogen and pulled vacuum. Installed Ecobee pro thermostat. Cleaned out return chase under the air handler. Cleared primary drain with CO2 and primed trap with water. Charged the system with R-454B refrigerant. Tested heating and cooling operation. Everything is working at completion of install.