A straightforward single-system replacement typically takes a two-person crew a full day, six to ten hours, sometimes two days for a more complex retrofit involving new ductwork or an electrical panel upgrade. Anything finished dramatically faster than that on a whole-system replacement is worth asking specific questions about.
1. Old equipment removal and refrigerant recovery
The outdoor and indoor units come out, and any remaining refrigerant in the old system is legally required to be recovered into a certified tank, not vented. This step alone can take an hour or two on an older system.
2. Line set and electrical prep
Whether the existing line set is reused or replaced (increasingly it's replaced outright, especially with the A2L refrigerant transition), and any new electrical circuit or disconnect is run.
3. New equipment set and connection
Outdoor condenser placed and leveled, indoor air handler or coil installed, line set connected and brazed.
4. Evacuation and refrigerant charge
The line set is vacuumed down to remove air and moisture, then charged with refrigerant to the manufacturer's specification, weighed in, not eyeballed.
5. Startup, commissioning, and airflow check
The system is run through both heating and cooling, static pressure and airflow are checked against the equipment's rated specs, and the thermostat and any zoning controls are configured.
The two moments worth asking about directly
Ask to see the refrigerant charge weighed in, not just "topped off," and ask what static pressure reading they got on startup. A contractor doing careful work will have both numbers on hand without hesitation; a rushed job skips the measurement and eyeballs both.
The best time to catch a corner-cutting installer is before they're on your roof, not after. A Manual J in writing, a specific AHRI-matched equipment pairing, and a clear scope of work for the ductwork are the three things worth confirming at the quote stage, all covered in more detail in how to read a heat pump quote and how to read a Manual J report. A contractor who answers those clearly at the quote stage is the same contractor likely to do the careful version of installation day described above.
