Commercial Rooftop Unit Installation & Replacement in Southern California and Arizona

When does a site need a rooftop unit installed or replaced?

Install a rooftop unit when a building gains load it was never designed for. Replace one when it has reached end of life, failed in a way not worth repairing, or no longer fits how the space is used.

A packaged rooftop unit holds the compressor, coils, supply fan, and usually a gas heat section in one cabinet. REE Mechanical Inc. installs and replaces them up to 100 tons. New installs typically follow a store fit-out, a remodel that adds sales floor or fitting rooms, a change of use that brings more people and lighting, or a zone that has always run hot and needs its own unit. Size a new unit from a load review, not from the old nameplate; see how retail sales floors are sized for RTU tonnage. For a refresher on the equipment itself, read how a commercial rooftop unit works.

Should this rooftop unit be repaired or replaced?

Weigh age, the part that failed, the refrigerant, and the unit’s history. A failed capacitor on a mid-life unit is a repair. A failed compressor on a unit approaching the mid-teens of years usually is not.

Signal	Leans repair	Leans replace
Age	Early or middle of its service life	Approaching or past the mid-teens of years
Failed part	Contactor, capacitor, fan motor, belt, control board	Compressor, condenser or evaporator coil, heat exchanger
Refrigerant	Current and readily available	Being phased down, with recharge cost climbing
History	An isolated call	A recurring line on the emergency spend report
Fit to the space	Load unchanged since install	A remodel or change of use altered the load

When the answer is unclear, rooftop unit inspection and testing confirms what actually failed before anyone prices new equipment. The full decision framework lives in repair or replace a rooftop unit.

What has to be planned before crane day?

The curb, the permit, the lead time, the crane, and the store calendar. Any one of them can move the date, and each is cheaper to settle on paper than on the roof.

1. Survey the roof. The existing unit, curb, roof condition, gas and electrical service, and the path the crane will need.
2. Choose a curb strategy. Reuse, adapter, or new curb. Newer units seldom match an old footprint, and an adapter brings flashing, roofing, and sometimes structural review with it.
3. Pull the permit. California’s Title 24 energy code, seismic anchorage, and local mechanical requirements have moved since many units were set, so a like-for-like swap can still fail inspection. Kelly Purcell, our Installation Director, handles permitting, and in California that usually means the city rather than the county.
4. Confirm the lead time. Lock the delivery date first and the crane date second.
5. Book the pick. Crane size, staging in the lot or street, any closures, and a window outside trading hours.

What happens on the day of the change-out?

The old unit is disconnected and its refrigerant recovered, the crane swaps old for new, and the crew anchors and reconnects it. Good planning keeps the space without cooling for as little time as possible.

After the pick, the work is connections: electrical, gas, condensate, and ductwork, then controls integration with the thermostat or the building management system. Start-up and commissioning checks close the job, and the new unit should be entered in the site’s asset register the same week. Anthony Renteria, our Install Foreman, leads the team dedicated to this work. They are our own technicians, not a subcontracted crew.

What if a rooftop unit fails before its planned replacement?

The replacement moves up the list, and the store needs cooling while new equipment is ordered. At Southern California sites, temporary cooling through our Herc Rentals relationship can carry a site until the replacement unit is set and running.

A failure-driven change-out costs more in disruption than a planned one, which is the strongest argument for ranking units ahead of time. While the order is in, commercial AC repair and service may keep a struggling unit going, and temporary cooling rental and setup cover the gap when it cannot.

How do rooftop replacements fit a multi-year plan?

Rank every unit by age, condition, and what its failure would cost that store, then give each one a budget year. Group sites by area so crane days and permit work serve several stores at once.

Shoulder seasons are the natural window for roof work in Southern California and Arizona, before the summer load arrives. Read rooftop unit lifecycle planning for multi-site retail for a fuller approach. Units that are not due yet belong on a preventive maintenance program so they make it to their slot.

Where does REE Mechanical install rooftop units?

On commercial roofs throughout our six Southern California counties and across Arizona, with technicians based across Southern California and Arizona instead of driving out from a single yard.

Start with San Bernardino County or Orange County, or see every service area. REE Mechanical Inc. is licensed, bonded and insured for this work.

How do you start a rooftop unit project?

Call (800) 742-0910 or send the site list. Tell us the sites, the units you are worried about, and the budget year you are working toward, and we will plan the survey from there.