What Is a Line Set?

A line set is the pair of insulated copper refrigerant lines running between the outdoor unit and an indoor coil or head — a larger insulated suction line and a smaller liquid line. On ductless equipment it usually runs with the control wiring and condensate drain inside one covered chase.

Also called: refrigerant lines · lineset · refrigerant line set

Why it matters to you

The line set is the part of a coastal installation most often left exposed to weather and salt spray. Damaged or degraded insulation on the suction line causes condensation to form along its length, which shows up as dripping and staining well away from the equipment itself.

What to do about it

Check periodically that the exterior chase or insulation is intact and UV-degraded lagging is replaced. Line-set length and rise affect performance, so a long run should be part of the design conversation rather than improvised on the day.