Q: Several rooms in my house are uncomfortably hot, but I don't want noisy
window air conditioners and I cannot afford a central system. Will a quiet ductless
system, often used with hot water heat, work for me too?-Mike R.
A: A ductless mini-split air conditioner is an excellent choice for almost
any home and climate. As you indicated, these systems are also often used for
whole-house cooling in homes with hot water radiant heat that do not have central-air
ductwork. Ductless heat pump models are also available for efficient heating in
the winter too.
For homes with central air conditioning in which some rooms do not stay
comfortably cool, adding a ductless unit is a good idea. This allows for a specific
area of the house to be zone cooled for an overall electricity savings. If certain
rooms are used at only certain times of the day, it makes economic sense not
to keep them extremely cool when they are not being used. With computerized
thermostats, ductless systems also offer this advantage.
Ductless air conditioners are called "mini-split" systems because they
are similar to a regular ducted split central air conditioner, only on a smaller
scale. A split system means that the compressor/condenser unit is located outdoors
and "split" from the indoor cooling coils/blower. Just a small 3-inch-diameter
hole is cut in the wall to run the tiny refrigerant lines and electric wires
to the indoor cooling units.
With the compressor outdoors and an indoor cooling unit mounted high
on a wall or ceiling, they are super-quiet. These units are typically even quieter
than many ducted central air conditioners. In a central unit, huge amounts of
air must wind through complex ducts with many bends and shape changes, all of
which contribute to noise.
Mini-split ductless air conditioners are a preferred option to trying
to use several room air conditioners to cool an entire house. Window units block
the window and can be a security risk: it is not terribly difficult for a thief
to remove a window unit and get indoors. Also, a window unit is not located
near the ceiling, the preferred location to introduce cool air into your room.
Each outdoor compressor unit is small and quiet. The typical indoor cooling
units are also small: only 32"x11"x 7" deep, weighing 18 pounds.
For convenience and comfort, the better ductless models have hand-held
remote controls that control everything: temperature, louver directions, programmed
on/off times, etc. If you live in an area with high humidity, select a model
with a dry-mode switch setting. This adjusts the airflow and compressor for
comfortable, low-humidity indoor air.
Although the Seasonal Energy Efficiency Rating of ductless systems (SEER
from 10 to 12) is not as high as the top-of-the-line central air conditioner
(SEER up to 16), they can still be more efficient. Many old and new house duct
systems have so many leaks and uneven airflow patterns that a substantial amount
of the cool air never gets to the rooms where you want it. With the ductless
cooling unit in the room, these transport losses are negligible.
For winter heating too, you can choose a heat pump model. If you hate that first
shot of chilly air in the winter each time the furnace or heat pump blower starts,
select a ductless model with a soft, slow start and a preheater for the air.