Beat the Heat - choosing an Air Conditioner

July 31, 2010

What size air conditioner do I need?

A larger air conditioner will not always provide more
cooling. It should be sized for the room area. If properly
sized it should operate long enough to remove moisture from
the air. It is the moisture removed from the room which
actually produces the feeling of cooling. Unfortunately many
people in their rush to purchase a window air conditioner
buy too large a model.

Too large a unit can actually provide less cooling than a
smaller, properly sized unit. This is because with an
oversized air conditioner its run time is too short.
Consequently it does not remove enough moisture from the
room to produce a feeling of comfort. If youre A/C seems to
cycle off and then back on every few minutes and does a poor
job of cooling, it is probably oversized for the room.

Air conditioners are rated in BTUs. British Thermal Units
are a measurement of how much heat is being transferred form
the room being cooled to where the heat is dumped out of
doors. This is why the cooing coil inside the room is cool
to the touch, while the part that hangs outside is extremely
hot.

A window air conditioner used in the average household room
can be as low as 4000 BTU. While 5000, 6000, and 8000 are
the most common sizes purchased.

How do I determine what size A/C I need?

Following is a basic sizing chart for calculating the window
air conditioner needed for a room. Calculate the size of the
room by multiplying the width of the room by the length of
the room. Use your room size to determine what BTU's are
required to cool that particular room size.

ROOM IN SQ FT-------A/C SIZE IN BTU'S

100250 sq ft............50006000 BTU
250400 sq ft............60008500 BTU
400550 sq ft............800011000 BTU
550-875 sq st...........1100015000 BTU
Based on a room occupied by two adults, having an average
insulation, number of windows, and sun exposure.

Which is the best room for placement of an air conditioner?

Wherever it gives the most comfort is where it should be
installed. If you only have one air conditioner then we
usually suggest the bedroom. This is because most people
find that if they can sleep comfortably during a hot summer
night then their next days work will be a lot easier.
Getting through a hot day at work becomes a lot easier when
you know you will sleep comfortably that night.

Some people do not like a cool sleeping environment so they
will tend to place it in a living room or family room. Or
some people will place it in the family room because the
whole family can sleep there. Get out the sleeping bags and
turn it into an adventure for the young ones. Beats waking
up in the morning to find a dog, cat, and four kids in the
bed with you.

Also window air conditioner can be noisy, which may disturb
sleep. Others find the drone of the fan actually promotes
sleep because all the neighbourhood noises are drowned out.
Some people say the air conditioner works as well as a
sleeping pill

But whichever room you eventually pick dont expect the
impossible from youre A/C. It is not meant to cool more
than one room or one open area. Air conditioners will not
cool other rooms? This is because the blower in a window air
conditioner is not very powerful. It is sized to cool one
open area, not a number of interconnected rooms. Therefore
once again a couple of smaller units may be better for your
home than one large unit.

Lastly, remember to properly secure the air conditioner in
the window. Once installed a piece of wood to stop the
window from being lifted up is a good idea. If you have
wooden sills the simple addition of a wood screw at the top
of the raised window (the one you had to raise to install
the A/C) will only take a minute. Otherwise an intruder
could gain access to the house by lifting the window and
letting the A/C fall out. This could result in the loss of
both your valuables and the air conditioner.

About the Author

Copyright 2005 by Donald Grummett. All right reserved.
Service manager of MG Appliance Repair Services in Ottawa,
Canada. In the trade over 30 years as a technician, business
owner, and technical trainer. For more information about
appliances including FAQ, Stain guide, Recycling, and
Newsletter visit http://www.mgservices.ca

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Beat the Heat - choosing an Air Conditioner