CLCH-SVX07C-EN 71
Component Installation Requirements
Opposed-Blade and Parallel-Blade Dampers
Opposed-blade and parallel-blade airfoil dampers in unit sizes 3-120 have centered dampers with
an internal jack-shaft (see Figure 56). A 95-degree actuator rotation gives a 90-degree blade travel.
Note: Damper blades should be checked for proper operation from full open to full closed position
before unit start up. Damper blade positioning may have changed due to shipping and
handling vibrations.
Duct Connections
All duct connections to the air handlers should be installed in accordance with the standards of the
National Fire Protection Association (NFPA):
• NFPA 90A for installing air conditioning and ventilating systems other than residence type.
• NFPA 90B for residence-type warm air heating and air-conditioning systems.
Fan Discharge Connections
To ensure the highest fan efficiency, duct turns and transitions must be made carefully, minimizing
air friction losses and turbulence. Proper ductwork installation, as outlined by such organizations
as SMACNA (Sheet Metal and Air Conditioning Contractors National Association, Inc.), should be
followed closely.
Fan sections with rectangular and round openings have a one-inch flange on the discharge that can
be used to attach the duct. When using lined ducts, the insulation should not obstruct the discharge
opening. For plenum fan sections with bellmouth fittings, see “Bellmouth Discharge Connections”
on page 75.
Figure 56. Typical mixing box configurations for unit sizes 3 to 120
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