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DCA & DAMPER SELECTION
Damper Sizing
Dampers can be sized using two different methods; actual sizing
and nominal sizing. When actual sizing is used the damper
dimensions will be the same as the sizes ordered. For example,
when a 24 inch x 24 inch D640 damper is ordered, it will be made
such that the height is 24 inches and the width is 24 inches. When
nominal sizing is used, the damper dimensions will be ¼ inch
smaller than the sizes ordered. For example, when a 24 inch x 24
inch D640 is ordered, it will be made such that the height is 23.75
inches and the width is 23.75 inches. No special allowances are
required for dampers that are constructed of multiple sections. For
example, a damper that is 24 inch x 60 inch will be constructed of
two sections. When ordered using nominal sizing, the damper size
will be 23.75 inches high by 59.75 inches wide.
Actual sizing is commonly used when the exact size of the
opening is known or if the damper is not meant to be installed
inside an opening or duct. Nominal sizing, with its ¼ inch
undersizing is commonly used when the damper will be installed
inside an opening or duct and space is needed for positioning or
seal material.
Honeywell’s sizing default is nominal sizing. If actual sizing is
required, please make sure this is specified on the order. For more
information on ordering Honeywell dampers, please contact your
local Honeywell distributor or sales representative.
Damper And Actuator Sizing
Table 2. Approximate industry standard damper lb-in.
per sq ft value.
Face Velocity (fpm)/
Static Pressure (in. wc
Leakage Damper
Blades
500/
1
1000/
2
1500/
3
2000/
4
2500/
5
Low Parallel 4 7 10.5 12 14
Low Opposed 3 5 7.5 8.5 10
Standard Parallel 3 4.5 6.5 7 8
Standard Opposed 2 3 4.5 5 6