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Line set

A line set is the pair of insulated copper refrigerant lines that connects a heat pump's outdoor unit to its indoor unit.

Editorial staffEdited by heatpumpwiki

History 1

The line set is the pair of copper tubes, usually one insulated, that carries refrigerant between the outdoor and indoor units.

Each model has maximum length and height limits. Mitsubishi's MUZ-FS06/09/12 allow 65 feet of piping and 40 feet of height difference; the FS15/18 allow 100 feet and 50 feet.Source 2 Units ship with refrigerant for a set length. Daikin's split-system charge covers 15 feet, with ".6 ounces per foot of liquid line" added beyond that.Source 3

NEEP's installation guide says the line set "shall be pressure tested using dry nitrogen and triple-evacuated."Source 1 See What a good heat pump installation looks like.

Sources

  1. 1.Guide To Installing Air-Source Heat Pumps in Cold Climates. Northeast Energy Efficiency Partnerships (NEEP). Accessed Oct 25, 2026
  2. 2.Service Manual MUZ-FS06NA, MUZ-FS09NA, MUZ-FS12NA, MUZ-FS15NA, MUZ-FS18NA (OBH873 Rev. B). Mitsubishi Electric. Accessed Oct 25, 2026
  3. 3.Condensing Unit / Heat Pump Installation Instructions (P/N IOD-4002G). Daikin Comfort Technologies. Accessed Oct 25, 2026

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