Air conditioning installation: what to know

What the job involves, what changes the price, and what to ask a pro.

What air conditioning installation is

Air conditioning installation sets in a new central air conditioner or a ductless mini-split in place of an old one, or adds cooling where none exists. It covers sizing, refrigerant lines, electrical hookup and a start-up test, so the system cools well and runs safely.

Signs you need it

  • The current system is old, has been repaired many times, or no longer cools the house evenly.
  • Some rooms are much hotter than others, which can mean the system was never sized for the house.
  • The outdoor unit is rusted badly, its coil is damaged or the compressor has failed.
  • Electric bills climb while cooling output falls.
  • You want central air in a home that has ducts but no cooling, or a cooling unit in a home with no ducts.
  • The old system uses a refrigerant that is hard to service, which makes repairs expensive and slow.

What the pro does

  • Run a load calculation to size the new outdoor unit and indoor coil, and inspect the ducts and airflow.
  • Remove the old outdoor unit and indoor coil, and recover the old refrigerant as a certified technician.
  • Set the new condenser on a level pad, connect the refrigerant lines and pull a vacuum to remove air and moisture before charging.
  • Make the electrical hookup, including the disconnect, circuit size, wire gauge and control wiring to the thermostat.
  • Charge the system to the manufacturer's specification and check the line set for leaks.
  • Run the start-up test, recording pressures, temperatures, amp draw, airflow and condensate flow, and walk the homeowner through the results.

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • The size of the system in tons, set by the load calculation rather than by the old unit.
  • Ductwork condition, including whether it can be reused, needs resizing or needs sealing.
  • Refrigerant line length, and whether the lines are replaced or reused.
  • Electrical service, such as a new circuit, a larger breaker or a panel upgrade.
  • Install location, such as a tight side yard, a rooftop mount or an air handler on a second floor.
  • Efficiency level, and whether a variable-speed or smart system is chosen.
  • Whether the indoor coil or air handler has to be matched to the new outdoor unit.

What a written quote should spell out

  • The model and size of the new condenser and indoor coil, with the load calculation attached.
  • Removal and recovery of the old refrigerant, and disposal of the old equipment.
  • Line set size, length and insulation, and whether the lines are new or reused.
  • Electrical work, such as disconnect, circuit, breaker, wire size and any panel work, shown as separate lines.
  • The start-up test readings, written down after the charge is set.
  • Warranty terms for the equipment and for the installation work.

Questions to ask before you hire

  • How did you calculate the size of the new system, and can you show me the load calculation?
  • Will you check my ducts and airflow before you connect the new unit?
  • Will the lines be replaced or reused, and what vacuum level will you pull on the system?
  • What electrical work is included, and will my panel need an upgrade?
  • Who pulls the permit, and will the installation be inspected?
  • What start-up readings will you give me in writing?
  • Who handles a warranty claim on the equipment and on the installation?

Red flags

  • The pro sizes the system to match the old unit without a load calculation.
  • The pro skips the vacuum step on the lines to save time.
  • The pro wants to reuse old lines without checking their condition or insulation.
  • The quote leaves out refrigerant recovery, electrical work or the start-up test.

What you can do yourself

Clear the outdoor pad area and the indoor space where the air handler or coil sits, and make sure the installer can reach the attic, crawl space or closet. Write down the model and serial numbers of your old equipment and keep the warranty paperwork. Refrigerant, electrical hookup, line vacuuming and charging belong to a licensed technician with refrigerant handling certification.

Licenses and permits

Air conditioning installation is commonly done under a contractor license, and it often requires a permit and an inspection, especially for electrical work and refrigerant lines. Check with your state or local licensing agency for the exact requirements of your installation.

Air conditioning installation questions

Why not just install the same size as my old unit?

The old unit was sized for the house as it was. Insulation, windows, additions and duct changes can make the old size wrong in either direction. A load calculation shows the right size for your home.

Should I replace the ductwork with a new AC?

Often you should at least have it inspected. Undersized, leaking or dirty ducts reduce what the new system delivers, so ask for a duct check with the quote.

How do I know the new system is working right?

Ask for a start-up report with pressures, temperatures, amp draw and airflow. A good installer walks you through the readings and the thermostat settings.

Can I install an AC unit myself?

Not safely. Refrigerant lines and the refrigerant charge need a certified technician, and the electrical hookup often must be done by a licensed professional.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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