Figure 48: Improper return-air ducting
Figure 49: Proper return-air ducting
WSHP-PRC001-EN
Application
Considerations
Sound control applies to the return
side of the duct design as well as the
supply side. Figure 48, demonstrates
a poor installation. Note that the
return air opening is close to the
cabinet of the unit.
Figure 49 graphic represents proper
installation of return-air duct. This
includes
•
Two 90-degree bends prior to the
intake
•
Lining the first 10 feet of the
return air duct
•
Locating the return-air intake
away from the unit blower
A duct system with noise control
in-mind can be designed by:
•
Keeping air flow velocities low
•
Using aerodynamic fittings
•
Using a duct liner if metal duct is
applied
•
Avoiding line-of-sight connec-
tions between a noise source and
an outlet
•
Avoiding line-of-sight connection
between a noise source and an
inlet
•
By properly locating balancing
dampers
•
Sealing cracks, seams and joints
in the duct run and equipment
panels
•
Blocking transmission through
walls, ceiling and floors
•
Mounting and supporting the
ductwork with isolation devices
that absorb vibration
•
Using flexible duct connections
•
Using flexible braided hoses on
the water connections
37