I installed a new Carrier 48HC-D high-efficiency rooftop unit today. First, I secured the 20-ton unit to the commercial building's roof curb per specifications. The thermostat control wiring was connected, and refrigerant linesets were carefully evacuated using a Yellowjacket recovery machine. With a tight vacuum achieved, I charged the system with R-410A refrigerant following Carrier's subcooling targets. The economizer was adjusted for proper ventilation operation.