Installed Carrier 5 ton straight electric heat pump system. Installed Ecobee pro thermostat. Laid down new plywood in the attic for the system to sit on. Installed new secondary drain pan. Built and installed new trunk line supply plenum. Built and installed new return plenum with offset to match up with system. Installed new 12x12 return filter grill in the library, with new 8 inch flex running to the return plenum. Rebuilt primary condensation drain, installed new SS2 and SS3 safety switches. Cleared primary drain with CO2 and primed trap with water. Sealed all ductwork connections with mastic/hardcast. Pressure tested system with nitrogen and pulled vacuum. Installed new disconnect box and wiring for the condenser. Charged AC with R-454B refrigerant. Tested heating and cooling operation. Everything is working at completion of install.