Wall-mounted heads, ceiling cassettes or small ducted units are tied to the outdoor unit by a line set and a communication cable. Inverter-driven compressors modulate capacity, so mini-splits hold temperature closely and many heat well below freezing. They suit additions, retrofits without ductwork and rooms with their own needs, and multi-zone units serve several heads from one outdoor unit.
Mini-split head is blinking a code and blowing warm, check the comm wire at the outdoor unit before you put gauges on it.
Flare connections on mini-splits must be torqued to spec with a torque wrench; a hand-tight flare is a slow leak.
Also heard as
- ductless
- ductless mini-split
- minisplit
Related terms
Heat pump
A refrigeration system that can reverse its flow to move heat indoors in winter as well as outdoors in summer.
Line set
The pair of copper refrigerant lines, one insulated suction line and one smaller liquid line, linking indoor and outdoor units.
HSPF
Heating seasonal performance factor: a heat pump's seasonal heating output in Btu divided by its electricity use in watt-hours.
SEER
Seasonal energy efficiency ratio: an air conditioner's cooling output over a typical season divided by its electricity use.