Quick answer
- Measure the existing curb and economizer path before you solicit bids.
- Treat crane access, roof protection, and after-hours logistics as schedule drivers, not add-ons.
- Require a documented commissioning path so the new unit actually delivers design CFM and temps.
When this applies
The RTU is end-of-life or chronically failing
Compressor shorts, cracked heat exchangers, obsolete controls, or parts lead times that make another repair season a gamble. Use this when replacement is likely within 12–24 months and you need a plan, not a panic bid.
A TI or remodel will touch the roof system
Tenant improvement, kitchen expansion, or office densification changes load or duct takeoffs. Changeout planning should land in the same work window as curb, duct, and controls work.
You are bundling multiple units
Portfolio or multi-RTU roofs benefit from one crane mobilization, one Title 24 package, and one commissioning plan — planning early is where the savings live.
How it works
Survey the roof as a system
Document unit model/serial, curb size, gas and electrical service, condensate routing, economizer and outdoor-air path, smoke-detector interlocks, and structural notes. Photograph curb corners and flashing. Note crane approach, setback from parapets, and any solar or antenna conflicts.
Decide curb strategy before you bid equipment
Like-for-like footprint often still needs an adapter curb. Different tonnage or brand almost always does. Adapter lead time and roofing tie-in drive schedule; price them in the base bid with clear exclusions for unforeseen deck or curb rot.
Sequence shutdown, lift, start-up, and documentation
Lock after-hours windows with the tenant, gas/electric shutoffs, roof protection, and a start-up checklist (refrigerant charge, gas pressure, economizer calibration, thermostat/BAS points). Deliver Title 24 forms, equipment submittals, and O&M before final payment.
Failure modes to avoid
Bidding tonnage without a curb and structural check
The cheap number that assumes a drop-in fit becomes a change order when the curb is wrong or the deck needs reinforcement. Require field verification in every competitive bid.
Ignoring economizer and outdoor-air requirements
A new high-efficiency RTU with a wrong or disabled economizer fails comfort, energy, and Title 24 expectations. Spec the OA strategy and who commissions it.
Crane day without a logistics plan
Street permits, HOA/property rules, tenant ops, and weather windows kill schedules. Confirm access and lift plan in writing before equipment ships.
Proof & local context
- • Precision Heating & Cooling (CSLB #1056688) plans and installs light-to-mid commercial RTU changeouts across San Jose / South Bay and Central Valley sites — Bryant-authorized, bilingual crews, Perfection Guaranteed.
- • Our commercial bids spell out curb adapters, crane assumptions, Title 24 documentation, and start-up scope so the changeout is scheduled work, not a discovery process on the roof.
- • Serving commercial and light industrial clients since 2000 with the same field discipline we apply to residential Bryant systems.
Next step
Guidance reflects light-to-mid commercial HVAC, refrigeration, and server/edge cooling practice across San Jose / South Bay and Central Valley (Hanford, Clovis) jobs. Not for hospitals or hyperscale data centers. Confirm site conditions, Title 24 path, and manufacturer data before bidding.
FAQs
How far ahead should we plan an RTU changeout?
Eight to twelve weeks is realistic for survey, submittals, curb adapters, crane booking, and permits on a typical South Bay or Central Valley light-commercial roof. Complex curb or structural work needs more lead time.
Do we need a structural engineer?
Often yes when tonnage, footprint, or curb height changes, or when the roof shows distress. A lightweight like-for-like swap may not — but the bid should say who decides and who pays for engineering if required.
Can we reuse the existing curb?
Sometimes, if dimensions, condition, and flashing are sound. Many changeouts still need an adapter curb for brand or capacity changes. Field measurement beats catalog assumptions.
What should be in the start-up package?
Charge verification, airflow/economizer checks, gas manifold pressure (if applicable), thermostat/BAS point-to-point, safety switches, and as-left setpoints — plus Title 24 forms and equipment O&M.