How long does a full commercial rooftop packaged unit replacement take from crane lift to startup?

A standard commercial rooftop packaged unit replacement typically takes 4 to 8 hours from crane setup and rigging to operational startup, provided the roof curb dimensions and utility connections match the existing footprint.

Commercial rooftop unit retrofits require tight scheduling to minimize tenant downtime, maintain building pressurization, and avoid costly crane overage charges on active job sites across Greater Pittsburgh. According to commercial mechanical contracting benchmarks, direct like-for-like packaged unit replacements without structural roof deck modifications consistently execute within a single 8-hour working shift.

If you only do one thing: Verify roof curb dimensions and supply-return duct drops prior to crane day to confirm whether a custom transition curb adapter is required.

1. Crane Rigging and Old Unit Removal (1 to 1.5 hours): The crane establishes outriggers and street barricades under local municipal permits. Riggers attach rated spreader bars and nylon slings to the factory lifting lugs, disconnect remaining utilities, and pick the decommissioned unit onto a flatbed trailer.
2. Curb Inspection and Gasketing (30 to 60 minutes): Technicians clean the structural roof curb, verify internal duct transitions, and apply continuous 1.5-inch closed-cell neoprene gasketing around the curb perimeter to establish a weather-tight and airtight seal.
3. New Unit Hoisting and Placement (30 to 45 minutes): The crane lifts the new packaged unit into place, seating the base rails onto the gasketed curb while crew members align the supply and return duct drops below.
4. Utility and Control Connections (1.5 to 3 hours): Technicians land the 208/230V or 460V three-phase electrical supply, wire the 24V thermostat or Building Automation System (BAS) communication bus, reconnect the natural gas line with a sediment trap, and install a pitched condensate P-trap drainage line.
5. Startup, Combustion, and Airflow Commissioning (1 to 2 hours): Technicians verify line voltage, check fan motor amperage against nameplate Full Load Amps (FLA), set gas manifold pressure (typically 3.5 in. w.g. for natural gas), verify economizer damper travel, and record total external static pressure (TESP) to ensure proper airflow delivery.

• Watch out for: Sustained wind speeds exceeding 20 mph, which halt crane picks under OSHA safety standards and force immediate rescheduling to prevent load control failure.
• Watch out for: Mismatched curb footprints discovered on crane day; installing an emergency adapter curb adds 2 to 4 hours of rigging delay and up to 500 lbs of unplanned dead load.
• Watch out for: Existing electrical disconnects or circuit breakers that do not match the Minimum Circuit Ampacity (MCA) and Maximum Overcurrent Protection (MOCP) ratings on the new unit nameplate.

Schedule an on-site mechanical and roof survey at least two weeks before the lift date to measure curb rails, confirm electrical disconnect sizing, and secure local right-of-way crane permits.