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Ductless
Air
Conditioners
(Mini Split Systems)
Ductless AC - or mini split conditioning – can be a good
alternative to central air conditioning, especially for small
apartments, room additions and homes without ducted systems.
Elements of mini-splits
Like central air conditioners, mini splits use an outdoor
condenser unit to run power and the refrigerant elements; they
also involve small indoor wall mounted fans, with each indoor unit connected to the outdoor through conduits.
Instead of mounted in a window, the ductless unit are installed
anywhere on the walls.
The number of indoor units depends on cooling or heating needs,
but most models have three or four indoor air fans that can be
installed in different rooms (eventually, in the same
room), all linked with the outdoor unit.
Advantages of ductless air conditioning
The big advantage of ductless is their flexibility and small
size. The system can be dedicated to each space, allowing an
easy adaptation to the needs of individual rooms. Since each
indoor unit has its own thermostat, the system may operate only
where it is needed, saving energy.
Besides, by avoiding the use of ductwork, ductless AC also avoid
energy losses associated with central air-conditioning: duct
losses can be very significant, especially when ducts are
in unconditioned spaces as attics.
Ductless AC is also quieter than a central or window AC (the refrigeration takes place outside).
Disadvantages of ductless air conditioning
The main disadvantage of ductless AC is in the initial investment.
Ductless AC prices are decreasing, but they are higher
than similar room AC unit.
Prices between $700 and $1,500 per ton (12,000 Btu per hour of
cooling power) are now common.
Comparatively to central air conditioning, the higher initial
investment can be at least partially compensated by lower
operating costs and energy savings.
Installation of mini-splits
Mini-splits AC should be correctly sized and located. A too
large system has the same disadvantages as oversized room AC
systems (see Air conditioners Oversizing
and undersizing), and
wrongly located
air-handlers can cause short-cycling, with consequent wastes of
energy and losses of performance.
Ductless mini split systems are easy to install but there
are few qualified installers. Most installers are
accustomed to the most conventional heating and cooling systems, and often refuse to
recommend ductless systems.
In most cases installation involves a simple wall hole (3
inch/8 cm) to connect the outdoor and indoor units. The
connecting conduits are provided with a large variety of
lengths, which allows locating the outdoor unit at the most
convenient walls of the building.
Ductless systems manufacturers offer a large flexibility in
interior design options: the indoor air handlers can be mounted
on a ceiling, suspended on a wall, or placed on the floor (in
the case of floor-standing models).
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