What line set means
A line set is the pair of copper refrigerant lines between the outdoor unit and the indoor coil: a larger insulated suction line and a smaller liquid line.
Also called refrigerant lines.
Where it matters on a HVAC job
Reusing an old line set saves money but can carry contamination into a new system and may be the wrong size. Price new lines as an option and say what you recommend. Line length past the maker's included charge adds refrigerant.
What the model code says
- Suction line insulation must be at least R-3, with an outer surface permeance no higher than 0.05 perm. (IRC 2021, Chapter 14)
Check which code edition your building department enforces for line set before you quote.
What it costs
Jobs that involve line set are priced in the central air conditioner installation cost guide: about $6,000 typical, usually $5,000 to $14,000. The guide shows its sources and what moves the price.
Work it out
- Cost guide: Central air conditioner installation cost
- Licensing: HVAC license rules by state
- Tools, templates and guides: Free HVAC resources
Sources: 2021 International Residential Code, Chapter 14, Heating and Cooling Equipment (ICC). Checked October 9, 2026.