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HOUSED FAN DISCHARGE CONNECTIONS (NOT PLE-
NUM FANS)
Discharge air ducts must be attached directly to the discharge side
of the unit. This applies to both indoor and outdoor units.
For end or top discharge, apply 1/2 in. thick by 1-1/2 in. wide
closed cell neoprene gasketing or run a bead of silicone around the
fan discharge. Flange the ductwork out no more than 1-1/4 in. and
screw the flanged ductwork to the fan discharge.
For bottom discharge supply fan duct connections, connect a short
stub duct directly to the bottom of the unit. For smaller size open-
ings, gasket the discharge, flange the ductwork out no more than
1-1/4 in., and screw the flanged ductwork to the fan discharge. For
larger size units, build a short stub of ductwork with no flange, slip
it up between the framed opening, and screw the duct to the frame
members from the inside of the stub duct. See Fig. 40.
Use care when making turns and transitions in ductwork to avoid
excessive air friction. Duct elbows should contain turning vanes.
See Fig. 41.
Ductwork connected to the fan discharge should run in a straight
line for at least 2.5 times the outlet diameter dimensions and
should not be reduced in cross-section. See Fig. 42. Duct turns
should be in the same direction as fan rotation to minimize any
negative system effects.
Fig. 38 — Duct Connections — Mixing Box
Ductwork Attachment
A39-4314
a39-4229
Fig. 39 — Duct Connections — Full Open
a39-4316
NOT LESS
THAN
2-1/2
FAN DIA.
NOTE: Make turns in the same direction as fan rotation.
Fig. 41 — Recommended Discharge Duct
Arrangement When Turns are Required
101
Bottom (Except Housed Fans)
Fig. 40 — Bottom Duct Connection —
Housed Fans
TURNING
VANES
AIRFLOW
A39-3004
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