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Window units, or the larger version known as through-the-wall units, are the smallest of the self contained machines. Inside of the cabinet is a compressor, condensing coil, evaporator coil, blower, controls, and maybe a little ductwork. The ductwork and possibly a damper will allow the unit to draw fresh air in or re-circulate 100% of room air. The high end units can have electronics with timers, accurate temperature sensors, and remote control. By using sound absorbing materials and quieter motors, manufacturers have improved these machines over the years.

The efficiency ratings are not as high as central systems (EER ratings) and versatility is limited because all of the cooling is blown into one room, but they get the job done when needed.

Not obvious is the fact that they need maintenance routinely, just like any other machine. The filter, usually located behind the front grill, needs to be washed. The condenser coil at the back of the unit can accumulate a lot of debris, and might require a special chemical bath. All air conditioning systems, large or small, need good air flow across the evaporator coil and the condenser coil. Efficiency and performance drop rapidly as air flow decreases. Lose enough air flow and the unit will burn out. Rodents can nest inside when not in use, and can foul up the unit in many ways. Wasps and hornets, as well as the honey bee find finned coils to be comfortable nesting places. Nests and dead insects can ruin the air conditioner.


All measurements on this form should be in feet. For inches 1 through 9 just add that number as a decimal value of the measurement. For inches 10 and 11 round up to the next foot. For example, 8 feet and 6 inches would be typed 8.6, or 13 feet and 11 inches would just be typed as 14 feet.

Enter room dimensions:
L: ft.
W: ft.
H: ft.
Enter area of shady glass doors and windows: ft2 Help
Enter area of sunny glass doors and windows: ft2 Help
Enter area of non-glass doors: ft2 Help
Is the room a kitchen or does it contain heat-producing appliances? Yes No Help
Enter the number of people that usually occupy the room: person(s) Help
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