IM-738 Page 21
Ventilation Clearance
Following are minimum ventilation clearance recommenda-
tions. The system designer must consider each application
and provide adequate ventilation. If this is not done, the unit
will not perform properly.
Unit(s) surrounded by a screen or a fence:
1. The bottom of the screen or fence should be at least 1 ft.
(305 mm) above the roof surface.
2. The distance between the unit and a screen or fence
should be as described in “Service Clearance” on page
20. See also Figure 19 on page 20.
3. The distance between any two units within a screen or
fence should be at least 120" (3048 mm).
Unit(s) surrounded by solid walls:
1. If there are walls on one or two adjacent sides of the unit,
the walls may be any height. If there are walls on more
than two adjacent sides of the unit, the walls should not be
higher than the unit.
2. The distance between the unit and the wall should be at
least 96" (2438 mm) on all sides of the unit.
3. The distance between any two units within the walls
should be at least 120" (3048 mm).
Do not locate outside air intakes near exhaust vents or other
sources of contaminated air.
If the unit is installed where windy conditions are common,
wind screens should be installed around the unit, maintaining
the clearances specified (see Figure 20). This is particularly
important to prevent blowing snow from entering outside air
intakes, and to maintain adequate head pressure control when
mechanical cooling is required at low outdoor air temperatures.
Overhead clearance
1. Unit(s) surrounded by screens or solid walls must have no
overhead obstructions over any part of the unit.
2. The area above the condenser must be unobstructed in all
installations to allow vertical air discharge.
3. The following restrictions must be observed for overhead
obstructions above the air handler section (see Figure 20):
a. There shall be no overhead obstructions above the fur-
nace flue, or within 9" (229 mm) of the flue box.
b. Overhead obstructions shall be no less than 2" (51 mm)
above the top of the unit.
c. There shall be no overhead obstructions in the areas
above the outside air and exhaust dampers that are far-
ther than 24" (610 mm) from the side of the unit.
Figure 20. Overhead Clearance
2 4 " ( 6 1 0 m m )
M a x i m u m
2 " ( 5 1 m m )
M i n u m u m
T o p o f U n i t
t o O v e r h e a d
O b s t r u c t i o n
2 4 " ( 6 1 0 m m )
M a x i m u m
O v e r h e a d
C a n o p y
9 " ( 2 2 9 m m )
M i n u m u m t o F l u e B o
T y p i c a l A l l S i d e s
F l u e B o x
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