Central (ducted) air conditioning
Central ducted air conditioning offers whole-house or large-commercial-space cooling, and often offers moderate multi-zone temperature control capability by the addition of air-louver-control boxes.
In central air conditioning, the inside heat-exchanger is typically placed inside the central furnace/AC unit of the forced air heating system which is then used in the summer to distribute chilled air throughout a residence or commercial building.
Split-system air conditioners come in two forms: mini-split and central systems. In both types, the inside-environment (evaporative) heat exchanger is separated by some distance from the outside-environment (condensing unit) heat exchanger.
Mini-split (ductless) system
A mini-split system typically supplies air conditioned and heated air to a single or a few rooms of a building. Mutli-zone systems are a common application of ductless systems and allow up to 8 rooms (zones) to be conditioned from a single outdoor unit. Multi-zone systems typically offer a variety of indoor unit styles including wall-mounted, ceiling-mounted, ceiling recessed, and horizontal ducted. Mini-split systems typically produce 9,000 to 36,000 Btu per hour of cooling. Multi-zone systems provide extended cooling and heating capacity up to 60,000 Btu’s.
Advantages of the ductless system include smaller size and flexibility for zoning or heating and cooling individual rooms. The inside wall space required is significantly reduced. Also, the compressor and heat exchanger can be located farther away from the inside space, rather than merely on the other side of the same unit as in a PTAC or window air conditioner. Flexible exterior hoses lead from the outside unit to the interior one(s); these are often enclosed with metal to look like common drainpipes from the roof. In addition, ductless systems offer higher efficiency.