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15RT-PRC010-EN
Duct Design
It is important to note that the rated
capacities of the rooftop can be met only
if the rooftop is properly installed in the
field. A well-designed duct system is
essential in meeting these capacities.
The satisfactory distribution of air
throughout the system requires that
there be an unrestricted and uniform
airflow from the rooftop discharge duct.
This discharge section should be straight
for at least several duct diameters to
allow the conversion of fan energy from
velocity pressure to static pressure.
However, when job conditions dictate
elbows be installed near the rooftop
outlet, the loss of capacity and static
pressure may be reduced through the
use of guide vanes and proper direction
of the bend in the elbow. The high
velocity side of the rooftop outlet should
be directed at the outside radius of the
elbow rather than the inside as
illustrated in Figure AC-5.
Figure AC-4 — Unit Placement
Figure AC-5 — Duct Design
1. 20-40 ton models have only one outdoor air intake.
50 - 75 ton models have two outdoor air intakes.
2. 90-130 ton models have two outdoor air intakes on
the backside of the unit and one small air intake at
the end of the unit.
Proper
Improper
1
2
Application
Considerations