Central Air Conditioners : How They Work
The duct-system central air conditioner explained
using ductwork normally utilize the
ducts in existing air handling systems that have already been built into the
house, such as a forced air furnace. They tend to be
with the evaporator coil and air handler inside the building and the
compressor and condensing unit outside. These are connected by refrigerant
tubing and the ductwork circulates the cool air around the building or
house. The indoor unit is usually installed in the attic or another small
and out-of-the-way space. Many modern
central air conditioners are
small enough to fit into any number of small spaces, such as closets.
Central air conditioners using a duct system can easily be installed into
houses that already use a ducted furnace for heating. This is because the
ductwork is already in place and the air conditioner simply uses the
existing ducts to circulate the cool air.
Houses that are heated with baseboard heating, radiant heat or steam
radiators may not have any existing ductwork. In cases like this ducts would
have to be installed along with the central air conditioner making it a very
difficult, expensive and in some cases an impossible, job. A more practical
solution would be to opt for a
or mini-split air conditioner.
ductless air conditioner system uses tiny refrigerant lines that go through
a small three inch hole in the wall which connect the outside condenser unit
to the inside air handling unit. These refrigerant lines circulate
refrigerant into the house from the outside unit to the indoor air handling
units where it used to cool the air. The cooled air is then released into
the building while the refrigerant carries the excess heat back to the
outside unit for disposal. These systems do require good drainage otherwise
condensate may stain concrete and other building materials.
Another option would also be the flexible tubing ductwork known as
high-velocity or ‘mini-duct’ air conditioners. These tubes are the pliant
equivalent of the more conventional metal ductwork normally used but which
only take up about one tenth of the space.
perform the same functions as the metal ductwork the difference being that
they can weave behind walls, ceilings and floors without causing any damage
to building materials. It is a far cheaper and less intrusive installation
and means central air conditioners can be installed in just about any
building, old or new.
Split System Air
Online guide to split-system air conditioners
system air conditioner
is a term used to describe air conditioners that have been split into an
outdoor unit and an indoor unit, in effect separating the hot and cold
components of the system which
are then connected by refrigerant tubing. The indoor unit typically consists
and the air
This is where the air is cooled and distributed into the required space. The
outdoor unit consists of the compressor and condenser where the heat is
vented from the building and the refrigerant is cycled back through the
system air conditioners can range in size from large commercial
roof top air
to smaller residential systems used to cool the home.
use a split system whether it is a
or a system using ductwork to circulate the air throughout the building. The
main difference between a split system air conditioner using ductwork and
those that don’t, is that the ductless system combines the luxury of
whole-house cooling with the convenience of ‘spot cooling’.
split system air conditioners the indoor unit can be installed into a
variety of small crawl spaces, the most popular being the attic or a closet.
The outside unit is usually installed in the most convenient and
inconspicuous position possible but always ensuring that there is sufficient
drainage for the condensate. Where ductless systems are concerned this is
usually easier than with those using ductwork as they only require a small
hole in the wall and the condenser unit tends to be smaller. These do,
however, tend to be more expensive to purchase.
of the biggest advantages to a split system air conditioner is the
significant reduction in noise from the condenser unit simply due to the
fact that it is placed outside. They are also significantly more energy
efficient in their operation than standard room air conditioners, especially
in climates where homes or commercial buildings require a considerable
amount of cooling for long summer months.
drier climates where air cooling and humidification is required, an
alternative to the conventional refrigerant based air conditioner would be
an evaporative air conditioner. These can come in room-sized units or as a
split system air conditioner. They perform the same basic functions of air
cooling except water is used instead of a refrigerant. By filtering the air
through water-soaked filters, the air is cooled by as much as 20 degrees
while at the same time extra moisture is added.
Conditioner Parts : Your Online Guide
The principal parts and their functions
There are a number
conditioner parts whose functions are vital to the
performance of the cooling system. Most air conditioner systems include a
front cover, filter, thermostat, evaporator coils, selector switch, fan, fan
motor, capacitor, compressor, condenser coils and the cabinet or shroud.
people will be familiar with the front cover as this is the most visible of
all air conditioner parts.
These are usually fastened on with a couple of screws and tend to be easy to
remove when the air filter needs to be accessed for changing or cleaning.
thermostat’s main function is the regulation of air temperature. The
thermostat has a temperature sensor that reacts to the air temperature by
either opening or closing the electrical circuit that controls the air
conditioner. This causes the system to switch on or off according to the
settings. There are two main types of thermostats: the electromechanical
thermostat and the electronic thermostat. Electromechanical thermostats
utilize a small glass vial of mercury and a bi-metal strip or coil that
reacts to temperature changes by expanding or contracting.
evaporator coil is the part of the air conditioner that cools the air. These
coils do tend to get dirty on the inside after some years of use. You’ll
know this has happened if the evaporator coil starts to freeze up and that
usually means it needs to be serviced or replaced. The best thing to do in
this case is to get a new one directly from the manufacturer. Unfortunately
the evaporator and condenser coils are designed to work together and so if
one needs replacing, so does the other.
The condenser coil is very similar to the evaporator coil; they are both
made of copper or aluminum tubing with fins that lie vertically in relation
to the coils. They both contain refrigerant but in the condenser coil this
refrigerant is in the form of a hot gas rather than a cold vapor. If these
two air conditioner parts are not cleaned regularly then accumulated dirt
will affect their ability to dissipate or absorb heat.
selector switch allows the user to choose the fan speed. While the
compressor always runs at the same rate, thereby producing the same capacity
of cool air, the fan speed determines how much of that cool air is
circulated into the room. If this needs replacing, your best option (and in
many cases the only option) is to get a replacement part from the
There are two fan blades in an air conditioner. The one situated in the
condenser unit draws fresh air from outside and moves it over the condenser
coils to collect heat from the hot refrigerant which is then released
outside. The fan blade in the air handling unit draws air from inside the
building and blows it over the evaporator coils so that the cold refrigerant
can absorb heat from the air. This causes condensation to form on the coils
which is collected in a pan at the bottom of the unit. In packaged or
unit air conditioners
these fan blades would simply be placed on either side of a single fan
motor. Fan blades are normally fairly easy to replace but fan motors are so
varied that the best place to get a replacement, as with most other air
conditioner parts, is to contact the manufacturer of the cooling system in
question. To keep fan motors in top condition they should be oiled at least
twice every year.
Capacitors can be found in many different electronic devices and are used to
store energy in the form of an electrostatic field. If the capacitor should
need replacing, two important factors should be noted: the capacitance and
the voltage. The air conditioner manual should contain this information,
otherwise it can be found on the capacitor unit itself. The shape and size
of the capacitor should also be considered for fitting purposes. It is
always best to opt for the same or a very similar replacement model to
ensure that it works at optimum efficiency. Every precaution should be
followed when dealing with these as they can deliver a nasty shock if not
Compressor : Information and Buying
Your online guide to air conditioner compressors
air conditioner compressor
is the heart of the system because it pumps the refrigerant through the
system in a closed cycle in much the same way as the heart pumps blood
through the body’s system. The other main function of the
air conditioner compressor is
to compress low pressure refrigerant gas from the evaporator converting it
to a hot, high pressure gas. In doing this the compressor also removes vapor
to help maintain a constant temperature.
Scroll air conditioner compressors are favored for their efficiency as they
move refrigerant gas along in a continuous flow. This means the system runs
smoother, quieter and has less leakage than the other types. This is due
mainly to its efficient design which helps it to perform its functions more
effectively. It also has some built in mechanisms to help prevent damage to
the compressor. The refrigerant is pushed along by air that is compressed
between two spiral cogs that fit together in such a way that they form
curved gas pockets. One of these cogs is continuously moving around the
other in order to drive this air out through the exhaust. Gas is drawn into
one of several pockets which become gradually smaller as the cogs move
round. This motion compresses the gas which becomes very hot. Once it is
sufficiently compressed it is released and moved along to the condenser.
screw compressor is popular because of its simple design. It usually
consists of two intermeshed, screw shaped rotors or spindles that rotate in
opposite directions. The refrigerant gas enters the enclosed chamber where
it is trapped and compressed between the intermeshed spindles. The opposed
rotary directions of these spindles is what causes the gas to move from
entrance (suction) to the exit (discharge) where it is moved on to the
condenser. This design provides quiet and continuous flow but is not as
efficient as the scroll compressor.
Piston, or reciprocating air conditioner compressors, are less popular in
residential cooling systems because they are noisier than the other two
types. This is because they utilize pistons driven by a motor to compress
the gas in a cylindrical-shaped chamber. The gas is taken into the chamber
at one end and pistons are pushed in to reduce the amount of space inside.
This then compresses the gas which is released through the other end of the
chamber and on into the condenser. Aside from being noisy these are not able
to supply a smooth and steady flow of refrigerant as effectively as the
others are. They are used more frequently in high pressure systems rather
than conventional residential air conditioners.
Conditioners Work : Online Guide
How do air conditioners work?
basically the same way as a refrigerator except that the area it is designed
to cool is much larger than your average icebox. It utilizes the unique
cooling capabilities of a refrigerant
chemical to remove heat from the air.
There are three basic concepts on refrigeration that could help in
understanding how an air conditioner works. Firstly, heat always moves from
warm to cold. Secondly, the boiling point of a refrigerant will change
depending on its pressure. This means that the higher the pressure the
higher the boiling point and the lower the pressure the lower the boiling
point. And lastly, refrigerant will boil and absorb heat from its
surrounding environment when the environment is warmer than the refrigerant.
If the surrounding environment is cooler than the refrigerant while it is
boiling then it will condense, become a liquid, and lose heat.
conditioners work in a cycle which usually begins when the refrigerant is
compressed in the compressor causing it to heat up and become a hot, high
pressure gas. The heated gas is then moved through a series of coils in the
condenser in order to disperse the heat which converts the refrigerant into
liquid refrigerant then goes through to the evaporator coils where it
evaporates into a cold vapor. Warm air from inside the building is
circulated over these coils and the heat from the air is absorbed by the
refrigerant vapor. The newly cooled air is then circulated throughout the
building or room and the refrigerant returns to the compressor to begin the
cycle again. The evaporator and condenser are also sometimes referred to as
is well known that hot air rises, so vents are placed in the ceiling to suck
the warm room air into the air conditioner to be taken through to the
evaporator coils. This is where it will be cooled by the refrigerant gas
then sent back into the room by the fan through vents that are usually
placed at floor level.
thermostat constantly monitors the temperature of the room or building. Once
the required temperature has been reached it will turn the air conditioner
off. When the temperature begins to rise again, the thermostat will turn the
air conditioner back on. Most air conditioners, such as
and many room air conditioners, have this option.
air conditioners work in the same way as a central system but are far more
compact with the entire cycle taking place in a single unit placed in the
system air conditioners also work in the same way, but are divided into two
units. The air handling unit inside the building contains the evaporator
coil and the unit containing the condenser and compressor is placed outside.
They are connected via refrigeration pipes and utilize ductwork or tubing to
circulate air throughout the system and the chosen area.
Ductless Air Conditioner
Systems : Guide to Mini-Splits
The online guide to ductless air conditioners
Ductless air conditioners,
or mini-splits, are very similar in design to central air conditioners that
use ducts as they also consist of two units, one outside containing the
compressor and condenser, and one inside containing the evaporator and fan.
The inside unit is usually mounted on the wall or on the ceiling, the
difference between the two models is that ductless
systems are generally smaller and quieter and, of course, they don’t require
Ductless air conditioners
are ideal for buildings that have no built in ductwork such as homes that
have baseboard or radiant heating and old buildings where installing ducts
would be not be practical or feasible. They are also commonly used for home
extensions where the house already has a central system in place but
extending the ductwork is impractical.
There are a number of advantages to the ductless air conditioner, not the
least of which is that you can buy the system in small portions. You could
buy a unit for each ‘zone’ or area of your house separately and eventually
end up with a full central system. This is because the outside unit can
control between one and four indoor units at a time. They are easy to
install too; all that is needed is a three inch hole in the wall for the
refrigerant lines and wiring.
biggest advantage to ductless air conditioners is that they combine the
cooling capacity and efficiency of a central system with the ‘spot cooling’
capabilities of a
room air conditioner
This gives you more control over your cooling system enabling you to cool
specific rooms according to your requirements. This is a particularly
appealing notion for many as it is a feature that can be utilized to further
increase the efficiency on an already energy efficient product. This in turn
means lower electric bills, which is always a plus.
Conversely, the biggest disadvantage to ductless air conditioners is how
much they cost. They do tend to be fairly expensive to buy, approximately
30% more than conventional central air conditioners and about twice as much
as a room air conditioner. However, if you do require a central cooling
system in a building without ducts then this may still be a far cheaper
option than attempting to install ductwork.
Portable Air Conditioners
Convenient Cooling Systems USA
Online guide to the portable air conditioner
Portable air conditioners
have the obvious advantage
of being compact enough to be moved around from one location to another with
very little effort and without the hassle of complicated installation. These
small units usually come on wheels and can simply be plugged into the
nearest socket. Very easy and very convenient.
biggest disadvantage to this unit is that you will need to provide some sort
of water supply. They can be filled manually but most units come with a hose
that can be fitted onto an outside faucet. Evaporative coolers can use
anything from three to fifteen gallons of water a day and do need to have
access to outside air. At least one window needs to be open during use which
means these will not be effective in extremely hot weather.
second and more commonly used type of
portable air conditioner uses
the same methods of cooling as all standard room units, refrigerant. The
refrigerant is cooled in a condenser and is then pumped through an
evaporator coil. The air which is circulated around this coil is then cooled
by the refrigerant inside and is pumped out into the room. The heat is
discarded out the window through a vent.
There are two main characteristics that make portable air conditioners so
flexible. These are the vent and the draining system. The vent is installed
through a window and the condensate is either collected in an internal tray
(that needs to be emptied at least once a week) or is pumped out the window
from a hose along with the vented heat.
Portable air conditioners are one of the industries later additions to
residential cooling systems and are only suitable for ‘spot cooling’. They
can be effective in cooling one room but like
window air conditioners
they are usually best used as a support to existing
during periods of extreme heat. Some
can be easily adapted for use in cars, boats and recreational vehicles such
as camper vans.
Duct Systems : Guide
to Duct Air Conditioners
The online air conditioner guide
system air conditioners
usually use ducts that are already in place within a home or office
building. These systems tend to be split with a condensing unit and
compressor outside the building and
an interior evaporator coil and air handler.
people will have seen ductwork in films as the square-shaped, metallic
tunnels used as an escape route out of a building. The standard size is
usually approximately eight inches tall and eighteen inches wide, but it is
always determined by the amount of friction caused by the moving air in
opposition to the duct itself.
speed at which air flows through this ductwork is what determines the amount
of noise it makes and any bends or turns must be smooth and rounded to avoid
changes to this speed. Central air conditioners using ductwork are generally
known as low velocity systems. This refers to the speed at which the air
travels through the ductwork and is measured in cubic feet per minute (CFM).
Air Conditioner Filters
: User Guide
The functions of an air conditioner filter explained
trap small particles in the air and prevent them from entering a house or
commercial building. These are usually effective in trapping airborne
particles such as pollen, plant
spores, dust, bacteria and even some
airborne viruses. They are also effective against odors such as those from
cooking, pet smells and tobacco. Air
conditioner filters are very important in the overall
functioning of the system because keeping the air flowing through it clean
ensures that it runs more efficiently. If air conditioner filters are not
properly cleaned they can become clogged and the excess buildup of dirt will
cause extra resistance to the air flow. This could result in damage to other
air handling devices and functions, such as ventilation, and the air
conditioner could become damaged as a result.
There are four key types of air filters: electrostatic filters, electronic
filters, disposable fiberglass filters and permanent mesh filters.
cleaning, the filter needs to be removed from the air conditioner and
sprayed thoroughly with water. You need to spray in the opposite direction
to that at which the air would normally flow. There are usually arrows to
indicate this on the frame of the filter. Once you’ve dislodged the dirt
spray the filter down on the other side to free any remaining dirt. It is a
good idea to get some cleaner to spray on in order to remove any stubborn
stains and dirt and then give the filter another rinse. Once it has drip
dried it can be reinstalled. You can usually get cleaner from the
Electronic air conditioner filters work in the same way as the electrostatic
filters, but they use an electric charge to produce the magnetism that
attracts the particles. These types of filters can be just as effective as
the electrostatic filters but are not as energy efficient. This is because
they use power from the mains, meaning that the air conditioner would use up
more electricity resulting in higher electric bills.
disposable fiberglass filters are the least efficient as they consist of
meshed fiberglass and can only trap large particles. They are fairly cheap
but do need to be changed regularly as they can become clogged with large
dust particles and this would further reduce their efficiency.
Permanent mesh filters are more specific in what type of particles they
trap. This is because they come in a wide range of different materials which
determine what the filter is capable of trapping in its fibers. These are a
good option for anyone suffering any particular allergies, hay fever for
example; as a filter specifically designed to segregate pollen could be
used. This type of air conditioner filter can be cleaned using water and,
once dry, can be reused. Although it is a good idea to have it replaced with
a new filter on a regular basis because wear and tear will eventually affect
Air Conditioner Unit
The online guide to unit air conditioners
are cooling units that are designed to cool only one room or a single space.
These units come in various sizes developed for cooling a wide variety of
different sized rooms, so choosing the right one is essential for it to
function efficiently and effectively. The cooling capacity in unit air
conditioners can range from 5,000 to 30,000 BTUs/hr.
window and casement air conditioners are fundamentally the same thing, the
only difference being the sort of window they can be installed into. A
will fit into most standard windows that slide up and down. The
designed to fit into narrower windows that open outwards or windows that
slide open, to the left or right. They do tend to be fairly cheap which
makes these an ideal choice if you don’t want to spend too much on
installing a permanent unit air conditioner when you’ll only be needing it
for a short period during the hottest summer months. This is mainly because
they are easy to install and shouldn’t require the help of a contractor. The
only exception with this air
conditioner unit is that in some situations you may need to
remove a window panel to install it. This may mean spending a little more,
but certainly not as much as the installation of a wall unit.
are the cheapest of the unit air conditioners as they don’t require any
installation, all you need is a window for the vent. These are freestanding
air conditioners, usually on wheels or coasters, making them easy to move
from room to room. They would certainly be the best option for those on a
tight budget. They serve well as an extra support for an existing central
system during the most extreme summer months. They can be moved around
according to where you may require the extra cooling. These could also save
you from high utility bills as you can use it only where it is needed
instead of cooling the whole house, for example, at night when you may only
need the cooling in the bedroom. They are also ideal for those living in
less extreme climates where cooling is only required for a short duration in
the warmer summer months.
wall unit is built into the wall and requires a sleeve with which to secure
it (usually sold separately by the manufacturer). Wall units perform the
same functions as the window units but come in bigger sizes and tend to be a
more permanent fixture. They will need their own power line whilst in use
and can be fairly expensive, mainly due to the high installation costs. This
is because a contractor will need to be brought in to correctly install the
unit through the wall, ensuring all safety precautions are taken. For this
reason wall air conditioners are best suited to those who require a fair
amount of cooling but may not be able to afford a central air conditioner.
homes and larger commercial buildings situated in an area with a dry and
arid climate, a good alternative is the evaporative cooling system. These
can come in many sizes from portable units to bigger systems that utilize
large cooling towers positioned outside the building. These cooling systems
use water pumped through a system of pipes leading to any number of room
cooling units to cool the air. The air is passed through water soaked
filters which serves to cool it whilst at the same time adding moisture.
Window Air Conditioners :
Cooling Unit Guide
Online guide to the window air conditioner
are self contained units that are designed to fit into a standard window
that slides up or down. These are fairly low-cost room air conditioners that
are easy to install as all you need is a window and an electric plug; no
additional wiring is required and most units will simply slide into the
window. The only real disadvantage is that they can
be a little drafty and so may need to be removed during winter. Some window
air conditioners double as heaters but these tend to be slightly more
the area to be cooled is of small or medium size then a window unit should
be enough to keep the temperature and humidity levels down. It would also be
far more cost effective than a central air conditioner as it would be
cheaper to purchase and cheaper to operate in the long run.
is, however, important that the unit is the correct size for the space that
it will be required to cool. If it is too big it will continuously be
shutting on and off as it will cool the room too quickly. This will use up a
lot of energy meaning higher than necessary electric bills. It also means
that the air conditioner will not be able to dehumidify the air in the room
effectively leaving it cold and clammy. If the window unit is too small it
will run continuously without properly cooling the room. For these reasons,
having the correct measurements at hand when buying your unit is crucial.
Measuring the window is also important because you need to ensure the air
conditioner you purchase will fit into the window space. If it is too small
it will let in too much warm air from outside and if it’s too big it simply
won’t fit. So make sure you measure the window correctly, possibly more than
once, so you are absolutely sure of the measurements before you purchase
your window air conditioner.
Roof Top Air Conditioners
External Cooling Units
Online guide to the roof-top air conditioner
top air conditioners
cool more than half of America’s
small commercial buildings, from schools and retail stores to hospitals,
restaurants and office buildings. They range from 65,000 to 135,000 BTUs/hr
capacity and are usually
central air conditioners providing cooling through ductwork. The outdoor
unit consists of the
and the condenser and is installed onto the rooftop. This is due to a number
of reasons, most notably because of the large amount of space on the roof,
but also because it is well out of the way and doesn’t cause unattractive
obstructions to the building.
Roof-top air conditioners
can also come as a packaged unit where all the mechanics are enclosed in one
unit. These tend to be used for larger commercial buildings where the
distance between the indoor air handling units and outdoor cooling units is
too great causing problems with lubrication in the ductwork and making it
unmanageable. These are usually known as chilled water systems.
type of roof top air conditioner uses refrigerant to cool the water which is
then pumped throughout the building via ducts and on to the air handling
units. This cooled water is then used to chill the air as needed. There is
no limit on the length of ductwork on these systems as there is no issue
with lubrication all that is required is that they are sufficiently
insulated. These types of roof top air conditioners would also be ideal for
use in arid climates as the water would add moisture to the air as it cools.
top air conditioners are central systems that are used to cool entire
buildings but the main problem with their position on the roof is that they
are exposed to direct sunlight. This means they can get very hot during the
day which reduces efficiency. Wherever possible these units should be
installed in an area that gets the least sunlight, especially during
roof top air conditioners in use today are not as energy efficient as they
could be simply because many buyers opt for the cheaper units without
realizing that the cost of operating a lower efficiency model will be more
expensive in the long run. More expensive variations that meet Energy Star
standards may be more expensive to purchase but will almost certainly be
more cost effective in the long term.
commercial buildings, such as those mentioned above, will have built-in
ductwork as part of a ventilation or heating system, whilst others will have
been built with an air conditioner system in mind. Some older buildings may
not have been built with any ductwork included. In some cases it would still
be possible to install a central air conditioner with a mini-duct or
mini-split system. These systems have been designed specially for buildings
where installing ducts would be impossible.
Room Air Conditioners :
Types of Air Con
Online guide to the choosing the right room air conditioner
you are looking for an air
conditioner to cool a particular
room, there are a number
of options open to you. There are a number of different types of unit air
conditioners such as the window, casement, portable and wall air
conditioners all of which perform the same functions. Choosing the most
suitable of these depends on your cooling requirements, budget and personal
Below we have included an introduction to each of the five most popular
varieties of room air conditioners;
a fuller explanation of each can also be found within this section (simply
click on the appropriate link).
Casement air conditioners tend to be a little more expensive than the
standard window unit as they may require the removal of a window panel for
installation. Most of these units can simply be plugged in and don’t require
any extra electrical wiring.
There are two kinds of portable air
conditioners. The first is what is known as an evaporative
cooler which uses water to cool the air. The air is brought in from outside
and passes through wet pads which also act as air filters. The air is cooled
by as much as twenty degrees and the water-based filter means that the air
entering the room will have an increased amount of moisture. This system is
good for dry climates as more humidity is added to the dry air.
Window units are useful for cooling office spaces and can provide more
cooling support for a central system during extreme weather. This may be of
particular importance for use in computer rooms or any room that may be
especially susceptible to heat.
Casement Air Conditioners
Information on Window Units
Online guide to the casement air conditioner
Casement air conditioners
are essentially window units but are designed for narrower windows that
swing outwards or slide across rather than those that slide up and down.
These units are sometimes also known as a slider air conditioner. They are
self contained units, or packed terminal units, as all the mechanisms are
contained within one large compartment.
obvious advantages to casement air
conditioners are that they are low cost, do not require
additional electrical wiring and are easy to install. The downside is that
they may need to be removed during winter as they can occasionally get a
little drafty. There are some casement cooling units that can provide
additional heating but you may need to spend a bit more for these. If you
only have one space to cool it would be far more beneficial to get a
casement or unit air conditioner as they are cheaper than a central air
conditioner both to buy and to run.
Casement units are only suitable for cooling one room and you do need to
ensure that the size of the unit is sufficient for the size of the room. If
the unit is too big it will cool the room too quickly and it will switch on
and off constantly, using up more energy than is necessary. Not only will
this be more expensive to operate but it will also cause the air in the room
to feel clammy and damp as the air conditioner will not be able to
effectively remove excess humidity. If the unit is too small it will simply
run all the time without sufficiently cooling the room. You need to measure
both the window and the room in order to determine what size you need and to
ensure the casement air conditioner you select will fit into the chosen
These units are also good if you need additional cooling support for a
central system in one room of the house, such as computer room, but they
would not be the most cost effective or practical way of cooling an entire
house or building.