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INSTRUCTIONS FOR USING COOLING LOAD ESTIMATE
FORM FOR ROOM AIR CONDITIONERS
(AHAM PUB. NO. RAC-1)
A.
This cooling load estimate form is suitable for estimating the cooling load for comfort air conditioning installations
which do not require specifi c conditions of inside temperature and humidity.
B.
The form is based on an outside design temperature of 95°F dry bulb and 75°F wet bulb. It can be used for areas
in the continental United States having other outside design temperatures by applying a correction factor for the
particular locality as determined from the map.
C.
The form includes “day” factors for calculating cooling loads in rooms where daytime comfort is desired (such as
living rooms, offi ces, etc.)
D.
The numbers of the following paragraphs refer to the corresponding numbered item on the form:
1.
Multiply the square feet of window area for each exposure by the applicable factor. The window area is the
area of the wall opening in which the window is installed. For windows shaded by inside shades or venetian
blinds, use the factor for “Inside Shades.” For windows shaded by outside awnings or by both outside aw-
nings and inside shades (or venetian blinds), use the factor for “Outside Awnings.” “Single Glass” includes
all types of single thickness windows, and “Double Glass” includes sealed airspace types, storm windows,
and glass block. Only one number should be entered in the right hand column for Item 1, and this number
should represent
only the exposure with the largest load.
2.
Multiply the total square feet of
all
windows in the room by the applicable factor.
3a.
Multiply the total length (linear feet) of all walls exposed to the outside by the applicable factor. Doors should
be considered as being part of the wall. Outside walls facing due north should be calculated separately from
outside walls facing other directions. Walls which are permanently shaded by adjacent structures should be
considered “North Exposure.” Do not consider trees and shrubbery as providing permanent shading. An
uninsulated frame wall or a masonry wall 8 inches or less in thickness is considered “Light Construction.” An
insulated wall or masonry wall over 8 inches in thickness is considered “Heavy Construction.”
3b.
Multiply the total length (linear feet) of all inside walls between the space to be conditioned and any uncondi-
tioned spaces by the given factor. Do not include inside walls which separate other air conditioned rooms.
4.
Multiply the total square feet of roof or ceiling area by the factor given for the type of construction most nearly
describing the particular application (use one line only.)
5.
Multiply the total square feet of fl oor area by the factor given. Disregard this item if the fl oor is directly on the
ground or over a basement.
6.
Multiply the number of people who normally occupy the space to be air conditioned by the factor given. Use
a minimum of 2 people.
7.
Determine the total number of watts for light and electrical equipment, except the air conditioner itself, that
will be
in use
when the room air conditioning is operating. Multiply the total wattage by the factor given.
8.
Multiply the total width (linear feet) of any doors or arches which are continually open to an unconditioned
space by the applicable factor.
NOTE:
Where the width of the doors or arches is more than 5 feet, the actual load may exceed the calculated
value. In such cases, both adjoining rooms should be considered as a single large room, and the room air
conditioner unit or units should be selected according to a calculation made on this new basis.
9.
Total the loads estimated for the foregoing 8 items.
10.
Multiply the subtotal obtained in item 9 by the proper correction factor, selected from the map, for the particular
locality. The result is the total estimated design cooling load in BTU per hour.
E.
For best results, a room air conditioner unit or units having a cooling capacity rating (determined in accordance
with the NEMA Standards Publication for Room Air Conditioners, CN 1-1960) as close as possible to the estimated
load should be selected. In general, a greatly oversized unit which would operate intermittently will be much less
satisfactory than one which is slightly undersized and which would operate more nearly continuously.
F.
Intermittent loads such as kitchen and laundry equipment are not included in this form.
