AC replacement day: prepare, what happens, how long

At a glance

Replacement day goes smoothly when three things are settled in advance: the scope is in writing, the crew can reach every part of the system, and you know what to check before they leave. This guide covers the week before, the day itself hour by hour, and the paperwork afterward.

The week before: settle the paperwork

Most replacement-day problems start as gaps in the contract. Confirm these before anyone arrives, because they are much harder to fix with a crew in the driveway.

1. A signed written proposal listing the outdoor unit, indoor coil (or air handler or furnace) and their model numbers, plus the AHRI match for the combination.
2. The contractor's TDLR license number on the proposal. The licensee’s number must appear on all advertising, proposals and invoices, an invoice is required for all ACR work, and proposals, invoices and written contracts must carry the notice “Regulated by The Texas Department of Licensing and Regulation, P.O. Box 12157, Austin, Texas 78711, 1-800-803-9202, 512-463-6599; www.tdlr.texas.gov”.
3. The scope beyond the equipment: line set, pad, condensate drain, electrical disconnect, thermostat, duct connections, haul-away of the old unit.
4. The permit: who pulls it, and that the price includes it.
5. The schedule: arrival window, expected shut-off and restart times, and the inspection plan.
6. Payment terms: how much is due on completion, and what stays held until the inspection passes.

The contract checklist walks through each line, and you can confirm the license with the TDLR lookup guide.

How to prepare your home

Preparing takes an hour or two the evening before. The goal is a clear path from the front door or garage to the indoor unit, the attic hatch and the outdoor pad, so the crew spends its time installing rather than moving your belongings.

1. Clear the indoor unit. Move anything stored around the furnace or air handler in the closet, garage or utility room. Leave working room on every side the crew needs to reach.
2. Clear the attic access. Move boxes away from the attic hatch and pull-down stairs, and clear a path through the attic to the equipment if it sits up there.
3. Clear the outdoor pad. Move grills, hoses, planters and furniture away from the outdoor unit. Trim plants that crowd it.
4. Clear the path between them. Hallways, stairs and the garage route the old and new equipment will travel.
5. Make room to park and unload close to the house: the driveway or curb nearest the work.
6. Secure pets in a closed room or off site. Doors will be open and attic access in use.
7. Protect valuables and fragile items along the work path and under the attic hatch, where dust can fall.
8. Locate the electrical panel and check the outdoor disconnect box is reachable.
9. Note thermostat settings or take a photo of the schedule if the thermostat is being replaced.
10. Have the signed proposal to hand, so you can check the delivered model numbers.

What happens, step by step

Crews differ in order and detail, but a like-for-like split-system replacement usually follows this sequence.

1. Arrival and walk-through. The lead installer confirms the scope, looks at the equipment locations and asks where to stage tools and the old unit.
2. Protect and shut down. Floor coverings go down along the path, and power to the system is switched off at the disconnect and panel.
3. Recover the refrigerant. The old refrigerant is pumped into a recovery cylinder, not vented. Under EPA’s Section 608 rules, refrigerant for these systems may be sold only to certified technicians or to employers of certified technicians.
4. Remove the old equipment. The outdoor unit is disconnected and carried out; the old indoor coil is removed from the top of the furnace or air handler.
5. Set the new outdoor unit on a level pad with clearance for airflow.
6. Install the new indoor coil (or air handler or furnace) and connect it to the existing supply plenum and ductwork.
7. Connect the line set. The copper refrigerant lines are reused if compatible or replaced, and the joints are brazed or connected.
8. Pressure test and evacuate. The lines and coil are pressure-tested for leaks, then a vacuum pump pulls out air and moisture before refrigerant is released.
9. Electrical and controls. The disconnect, high-voltage wiring and thermostat wiring are connected, and any new thermostat is mounted.
10. Condensate. The drain line and the safety float switch are connected so a blocked drain shuts the system off rather than overflowing.
11. Commission and test. The system starts, the refrigerant charge is set to the manufacturer's method, and airflow and temperatures are checked in cooling (and heating for a heat pump).
12. Clean up and walk-through. The old unit is hauled away, and the installer shows you the thermostat, the filter and the drain, then reviews the paperwork.

How long it takes, and what slows it down

Trane puts the installation itself at about 4 to 8 hours, depending on complexity, and the whole process from research to finished install at a few days to two weeks. A straightforward swap on the same ducts sits at the short end. Each item below can add time, and some add a second day or a separate trade.

For budgeting, third-party pages publish a 100 A to 200 A panel upgrade at $1,800–$3,500 (national) and new ductwork for about a 2,000 sq ft home at $6,000–$7,000 (Dallas). These are published ranges from other companies, not this site's prices. See the cost guide for the full set.

During the day: your role

You do not need to watch the crew work, but a few moments matter. Be present at the start to confirm the scope and at the end for the walk-through and paperwork.

If the crew finds something unexpected, such as damaged ducts or a pad that has sunk, ask for the change and its price in writing before the work proceeds.

The permit and inspection

The City of Dallas issues mechanical permits through its DallasNow portal so that work complies with the Dallas Mechanical Code and is performed by a licensed air-conditioning contractor. Installing or replacing a central system is mechanical work; no City page we found states the replacement rule in one sentence, so confirm with Development Services for your job.

Most nearby cities also require a permit for replacing an AC; rules and fees vary, so check with your city or ask the contractor which permit they filed.

The inspection usually happens after the install, on a date the contractor arranges. Keep the permit number, and hold the last payment until it passes if your contract allows. The Dallas permits guide covers each city in more detail.

Before the installer leaves

1. The invoice, showing the TDLR license number and the TDLR consumer notice.
2. Model and serial numbers that match the proposal, and the AHRI certificate or reference number for the match.
3. Who is registering the equipment warranty, and when. Trane extends its warranty term only if the product is registered within 60 days of installation; registered late, it keeps the base warranty. Lennox requires registration within 60 days of installation (or closing, for new construction) for its extended limited warranty.
4. The workmanship (labor) warranty in writing, and how long it lasts.
5. The permit number and the inspection date.
6. Thermostat settings, the filter size and location, and where the drain and float switch are.
7. A sales tax treatment you understand. In Texas, labor to repair or remodel residential property is not taxable; the materials are. Your invoice can be lump-sum (tax built into the contractor's material cost) or separated (tax shown on the materials line). Both are normal.

Then use the after-installation checklist over the next few days.

Worked example: a hypothetical replacement day

Say a 1970s single-story house in Garland has its furnace and coil in a hall closet, the line set running through the attic, and the outdoor unit on a side-yard pad. The homeowner clears the closet, moves storage boxes from under the attic hatch, and pulls the grill away from the pad the night before.

The crew arrives in the morning, confirms the model numbers against the proposal, and shuts power off. They recover the refrigerant, remove the old outdoor unit and coil, and set the new equipment. The existing line set is the right size and compatible, so they reuse it after flushing, then pressure-test, evacuate and charge. By mid-afternoon the system is running, and the walk-through covers the thermostat, filter and float switch.

Now change one thing: the installer finds that the attic ducts are crushed and disconnected in two places. That is a change order. The homeowner asks for the scope and price in writing, decides, and the duct work either happens that day or is scheduled. The rest of the sequence does not change.

Common mistakes on replacement day

• Leaving the attic hatch blocked. Time spent moving storage is time not spent installing.
• Not checking model numbers. Substitutions happen; ask why in writing, and whether the replacement is an equivalent AHRI-matched combination with the same ratings.
• Paying in full before the inspection. Keep a holdback if the contract allows.
• Assuming the warranty is registered. Ask who does it and get confirmation within the 60 days.
• Skipping the walk-through. It is the best time to ask questions while the installer is still there.
• Approving extra work verbally. Any change should be written and priced first.

Sources

• Trane, how long does it take to install an AC unit (National, page dated 2025-07-16) (retrieved 2026-10-20)
• 16 Tex. Admin. Code §75.71 (Cornell LII mirror) (retrieved 2026-10-20)
• Texas Constitution Art. XVI §50; Property Code §53.254 (retrieved 2026-10-20) — verify before relying on it
• Texas Business and Commerce Code ch. 601 (retrieved 2026-10-20)
• NWS Fort Worth, "DFW 100° Info" (retrieved 2026-09-23)
• US EPA, Section 608 refrigerant sales restriction (retrieved 2026-10-20) — verify before relying on it
• ENERGY STAR HVAC fact sheet (retrieved 2026-10-20) — verify before relying on it
• City of Dallas Development Services, mechanical permits (Dallas Mechanical Code, Chapter 55 amendments); process and fee: verify with the City before relying on it (retrieved 2026-09-23) — verify before relying on it
• Trane, Warranty and Registration (retrieved 2026-10-20)
• Lennox, Extended Limited Warranty FAQ (retrieved 2026-10-20) — verify before relying on it
• Texas Comptroller, Publication 94-116, "Real Property Repair and Remodeling" (retrieved 2026-09-23)
• Voltflow, electrical panel upgrade cost 2026 (National, page dated 2026-04) (retrieved 2026-10-20)
• HVAC.com, HVAC replacement costs in Dallas, TX (Dallas, page dated 2024-05-22) (retrieved 2026-10-20)

Questions

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