Installed 3 ton Carrier 2 stage R-454B heat pump condenser. Installed Carrier air handler with heat kit. Secured new plywood down for the secondary drain pan and air handler to sit on. Rebuilt primary condensation drain and installed new secondary drain pan with SS2/SS3 safety switches. Built and installed new supply and return plenums. Reusing media filter and UV light in the new plenums. Increased size of return to 18 inch with new plenums and return grill. Upsized return plenum in hallway. Installed dampers at the supply ducts. Sealed all connections with mastic and hardcast. Installed new disconnect box and new pad for the condenser. Installed Ecobee pro thermostat. Tested condensate drain operation. Charged AC with R-454B refrigerant. Tested heating and cooling operation. Everything is working at completion of service.