Pre-day — the week before changeout
The real work starts before the crane shows up. Pre-day items include:
- Equipment delivery staged nearby — rooftop unit, curb adapter if needed, controls, consumables
- Permit confirmed and pulled; inspection schedule understood
- Crane scheduled with the lift company, pick-and-set times confirmed
- Property manager notified of lift day; tenants notified of HVAC outage window
- Roof-protection materials ready — mats, boards, or decking to protect the roof membrane during the walk and lift
- Isolation plan agreed — gas, electric, and controls disconnection sequence
Lift day — the sequence that actually happens
The project day typically runs in this order:
- Early morning — crew on site, roof safety brief, old unit isolated (power off, gas off if applicable, condensate drained, controls disconnected)
- Mid-morning — crane arrives, old unit disconnected from curb and rigged for the pick
- Lift 1 — old unit comes off the roof to the ground
- Curb inspection — exposed curb cleaned, flashing checked, curb adapter set if the new unit has a different footprint
- Lift 2 — new unit comes off the ground to the roof
- Set — unit placed on curb or adapter, flashed and sealed to the roof membrane, bolted or clipped per manufacturer
- Afternoon — electrical connections, gas (if applicable), condensate termination, controls wiring
- Late afternoon — startup checklist, refrigerant charge verification, airflow verification, control-sequence test
Post-day — commissioning and paperwork
After the lift day the project isn't done. Post-day work includes a return visit (sometimes same-week) to verify the unit is holding charge, cycle counts look right in the controls, and no condensate or airflow issues have appeared. The HERS rater or Title 24 verifier (where required for commercial work) does their test and files their report. Permit inspection by the building department closes the permit.
The property manager gets a project close-out package — equipment nameplate photos, warranty registration confirmation (where applicable), Title 24 forms, HERS or commissioning reports, and a written summary of what was installed with the as-left settings. That package becomes part of the building record.
What delays a project — the honest list
Projects slip from the planned schedule most often because of: a mismatch between the ordered curb adapter and the actual curb (measure twice, order once — but field conditions sometimes surprise); electrical findings that require a service upgrade not scoped in advance; roof-membrane damage discovered when the old unit comes off and requiring repair before the new unit lands; and weather, particularly wind beyond crane-safe limits on lift day.
A good installer walks through these risks at quote so the property manager knows what could extend the timeline and what the alternate plan is if it does.
Common questions
How long is the space without HVAC on changeout day?
On a straightforward single-RTU changeout, the space is typically without HVAC for the working day — isolation in the morning, startup late afternoon. For temperature-sensitive tenants (data closets, retail with freezer loads elsewhere) we schedule for off-hours or weekend changeouts; those projects often finish faster because there's no occupied-hours constraint on the work.
Why does a curb adapter cost significant money?
A curb adapter is a custom-fabricated transition piece that matches the roof curb footprint (fixed by the original install) to the new unit's base footprint (fixed by current equipment design). Each one is sized to a specific curb-and-unit pair, which means it's shop-fabricated to measurement. It's steel work, not a stock item.
What if the roof membrane is damaged during the lift?
Damage caught during the project is repaired by the roofer and documented. We work with the property's existing roofing contractor when possible so the roof warranty isn't affected by an unfamiliar crew. The lift crew uses protection mats and pre-briefs the lift sequence to minimize risk, but on an older roof you have to be ready for a repair.
Can two RTUs be replaced on the same crane day?
Often yes — one crane set-up can handle multiple lifts if the units are close enough together. The savings is real on crane time. The constraint is usually crew capacity to work two units in parallel after the lifts; we scope that case specifically rather than assuming it works.