Mini Split glossary

Mini split glossary

The ductless mini-split terms, defined in plain English. For cross-system terms like SEER2, condenser, and refrigerant, see the master glossary.

Cassette

A recessed indoor head that mounts flush in a ceiling and blows in several directions, a lower-profile alternative to the common wall-mounted head.

Ductless

A system that delivers conditioned air straight into the room through indoor heads, with no ducts — eliminating the 20–30% of air a ducted system loses to leaks. See mini-split vs central.

Indoor head

The wall-, ceiling-, or floor-mounted unit that conditions a single zone in a ductless system. Each head has its own controls, which is how mini-splits do room-by-room temperature.

Line set

The pair of insulated copper refrigerant lines that connect a mini-split's outdoor unit to each indoor head, running through a small wall penetration instead of ductwork.

Multi-zone

A mini-split setup where one outdoor unit runs several indoor heads, each its own zone. It's the whole-home ductless configuration, and per-zone pricing is what drives its cost.