Installed 2.5 ton R-454B straight electric system for the guest house upstairs space. Air handler with heat kit in attic. Installed disconnect box for the condenser and new sealed wiring. Built and installed new extended supply plenum with elbows. Built and installed new return plenum. Installed new secondary drain pan. Installed Ecobee lite thermostat. Pressure tested system with nitrogen and pulled vacuum. Rebuilt primary condensation drain, installed SS2 and SS3 safety switches. Cleared primary drain with CO2 and primed trap with water. Attached existing flex duct and sealed all connections with mastic/hardcast. Charged system with R-454B refrigerant. Tested heating and cooling operation. Everything is working at completion of service.