The HVAC Replacement Process, Step by Step

The short answer

Replacing a residential HVAC system is a sequence of eight steps, and the order matters. The first three happen before anyone touches the equipment: a consultation, an on-site evaluation with a load calculation, and written options. Then, when the job needs one, the permit is pulled; the installation is done; the system is started up and commissioned; where they apply, an independent verifier tests the ducts and the refrigerant charge and the city or county inspects; and finally the old equipment is recycled and the new equipment is registered with the manufacturer.

Before installation: consultation, evaluation and written options

Consultation

It starts with a conversation, by phone or at the house. We want to know how old the system is, what refrigerant it uses, whether the furnace is as old as the condenser, what has failed, and what has never worked well. A back bedroom that has been hot for twenty years is useful information, because it is a design problem that a like-for-like swap will not fix. We also ask whether you are interested in a heat pump, since that changes what we look at on the electrical panel. We do not price anything at this stage. A number given without seeing the house is a guess.

Evaluation and load calculation

A technician comes to the house and measures it: the rooms, the window area and orientation, the insulation in the attic and walls, and the construction. They inspect the ducts and measure static pressure, check the coil and the drain, look at the electrical panel and the gas line, and note where the equipment sits and how it can be accessed. From those measurements we run a Manual J load calculation, which sets the capacity the new system needs, and a Manual S equipment selection, which matches real equipment to that load at San Diego design temperatures. If the ducts need replacing, Manual D sizes the new ones. Our sizing guide explains why we do this instead of copying the tonnage on the old unit.

Written options

You receive two or three configurations in writing. Each lists the model numbers of the outdoor unit and the indoor equipment, the AHRI-certified SEER2, EER2 and HSPF2 or AFUE ratings for that matched combination, the scope of any duct or electrical work, the permit, the energy-code testing and the manufacturer warranty terms. Where it makes sense, one option is a heat pump and another is an AC and furnace, so you can compare them on the same footing; the heat pump comparison explains the trade-offs. You take the time you need. If you are comparing our proposal with someone else's, the contractor guide shows how to line them up.

The permit

Every jurisdiction in San Diego County requires a mechanical permit for a system changeout, from the City of San Diego to the unincorporated county. When a job needs one, Superior Air can pull it. For a heat pump conversion the permit may also cover the new electrical circuit and the gas cap. Once a permit is issued, we schedule the installation, order the equipment, and confirm the date with you. The permit guide has the detail by jurisdiction and what the inspector looks at.

Installation day

A typical changeout follows the same order every time.

1. Protect the house. Drop cloths on the floors along the path to the indoor unit, shoe covers, and protection at the attic access if the equipment is up there.
2. Power down and recover the refrigerant. The old system's refrigerant is pumped into a recovery cylinder with a recovery machine, as the EPA requires. It is never vented. Our technicians hold the EPA Section 608 certification that the law requires for handling refrigerant.
3. Remove the old equipment. The condenser, the furnace or air handler and the coil come out. Gas and electrical are disconnected safely and the old line set is removed or flushed, depending on what the new equipment allows.
4. Set the new outdoor unit. A level pad with the manufacturer's clearances, a new disconnect where the old one does not meet code, and the line set routed and insulated.
5. Set the indoor equipment. The furnace or air handler is set and secured, the matched coil is installed, the plenum transitions are sealed, and the condensate drain gets a float switch so a clogged drain shuts the system off instead of flooding the closet.
6. Connect everything. Refrigerant lines are brazed with nitrogen flowing through them to prevent oxidation inside the pipe. Electrical and control wiring is connected. For a furnace, the gas line is connected and leak-tested and the flue is connected; for a heat pump, the gas line is capped.
7. Pressure-test. The refrigerant circuit is pressurized with nitrogen and held to confirm there are no leaks before any refrigerant goes in.
8. Evacuate. A vacuum pump pulls the lines down to a deep vacuum to remove air and moisture, and the vacuum is held to confirm the system is tight and dry. Moisture in a refrigerant circuit is what kills compressors years later.
9. Charge by weight. The refrigerant is weighed in according to the manufacturer's charge for the equipment and the length of the line set. It is then fine-tuned during startup, not guessed by feel.

Most changeouts are finished in one working day. Duct replacement, moving equipment to a new location, a panel upgrade or an attic conversion can make it two. Someone 18 or older needs to be home, because the crew works inside and the walkthrough at the end is with you.

Startup and commissioning

Commissioning is the difference between a system that is installed and a system that works as rated. With the system running, the lead technician measures the static pressure and the airflow across the coil, records the temperature split between return and supply air, and checks the refrigerant charge by superheat and subcooling against the manufacturer's targets. The thermostat is configured for the specific equipment: staging on a two-stage or variable-speed system, the reversing valve and any heat-strip lockout on a heat pump, and the schedule you asked for. Safety controls, including the float switch, are tested.

Then the walkthrough. You see the thermostat, the filter location and size, the drain, the disconnect, and hear what normal sounds like. The readings from commissioning are recorded and stay with the job file, so a technician on a future maintenance visit can compare against day one.

Verification and inspection

California's Title 24 energy code requires third-party field verification of duct leakage and refrigerant charge on many changeouts. Since January 1, 2026 that verification has run under the California Energy Commission's Energy Code Compliance program, the successor to what the industry called HERS testing. An independent verifier, not Superior Air, comes to the house, tests the duct system with a calibrated fan and confirms the refrigerant charge, and files the results with the state registry. Which tests apply depends on the climate zone and on what was replaced.

After that, on jobs with a permit, the city or county inspector visits. They confirm the equipment matches the permit, check clearances and the disconnect, the electrical connections, the condensate drain, the flue and gas connections on a furnace, and the smoke and carbon monoxide alarms that a California permit typically triggers. The permit is finaled when the inspection passes. If either the verification or the inspection flags something, we fix it and reschedule. On those jobs, the job is not closed until both are done.

After the job: haul-away, recycling and registration

The old condenser, furnace or air handler and coil leave with the crew on installation day. The refrigerant was recovered before removal, and the metal is recycled. You do not arrange disposal.

Within days of installation, we register the new equipment with the manufacturer so that the warranty is on record from the installation date. The warranty terms are the manufacturer's and are listed on your proposal. You also receive the commissioning readings and the model and serial numbers, plus the finaled permit and verification certificate on jobs that had one, which you will want at resale.

From there the system needs a filter change on the schedule that fits your filter type and household, and an annual maintenance visit that re-measures what commissioning measured and catches drift before it costs you a compressor.

How Superior Air approaches this

Every replacement follows the sequence above, whether it is a single-story tract home in Mira Mesa or a two-system house in Carmel Valley. What we think sets the process apart:

• One team from evaluation to inspection. The technician who measured the house is involved in the installation, so nothing is lost between the proposal and the crew.
• No phone pricing. We would rather lose a job than size a system without seeing the house.
• Commissioning readings in writing. Static pressure, airflow, temperature split and charge are recorded and given to you, not just checked.
• Permit and testing in the scope. They are line items on the proposal, not extras discovered later.
• Honesty about ducts. If the duct test shows the old ducts will drag the new system down, we say so and price the fix separately, and you decide.

If you are at the beginning, the AC replacement page covers the service and the cost guide explains what drives the number. When you are ready for step one, schedule a consultation.