Damper Selection; Damper Types; Parallel And Opposed Blade Dampers; Round Dampers - Honeywell AUTOMATIC CONTROL SI Edition Engineering Manual

DAMPER SELECTION AND SIZING

DAMPER SELECTION

DAMPER TYPES

PARALLEL AND OPPOSED BLADE DAMPERS

Parallel blade dampers are constructed so each blade rotates
in parallel with or in the same direction as the blade next to it
(Fig. 1). The rotation changes the direction of airflow and can
provide mixing with only a small increase in airflow resistance.
PARALLEL
BLADE
ACTION
Fig. 1. Parallel Blade Damper.
Opposed blade dampers are constructed so adjacent blades
rotate opposite to each other (Fig. 2). The rotation does not change
the direction of airflow, but it does increase resistance to and
stratification of airflow since the air is funneled through a smaller
opening. An opposed blade damper must be open further to obtain
the same resistance to airflow as a parallel blade damper.
OPPOSED
BLADE
ACTION
Fig. 2. Opposed Blade Damper.
AIRFLOW THROUGH
PARALLEL BLADE DAMPER
AT ONE-THIRD CLOSED.
M10414
AIRFLOW THROUGH
OPPOSED BLADE DAMPER
AT ONE-THIRD CLOSED.
M10415
448

ROUND DAMPERS

Round dampers (Fig. 3) are typically used to control flow in
ducts that usually have high static pressure and high velocity
characteristics. Round dampers can be installed in air handling
systems with spiral-wound ducts in sizes similar to rectangular
ducts. The smallest sizes of round dampers have a butterfly
type blade while larger ones might be multiblade.
Fig. 3. Round Damper.

LOW LEAKAGE DAMPERS

Low leakage dampers minimize the amount of leakage through
a fully closed damper. This can increase the energy efficiency of
the control system, the comfort level in occupied spaces, and the
safe operation of control elements such as coils. Low leakage is
achieved through a variety of damper features and parameters,
including blade edge seals, blade side seals, blade linkage, blade
and frame reinforcements, and seal material.
Damper blade edge seals that work in compression between
the blades e.g., cellular foam strip, (Fig. 4) are effective when
blades are rigid enough to prevent misalignment and bending.
Other types of blade edge seals include:
Fig. 4. Cellular Foam Blade Edge Seal.
— Snap-on seals, extruded plastic or dual durometer elastomer
types (Fig. 5)
— Over-center compression seals, extruded plastic or roll-form
construction (Fig. 6)
— Inflatable seals (rubber or silicone) that use the pressure
differential across the damper for tight sealing when closed
(Fig. 7)
ENGINEERING MANUAL OF AUTOMATIC CONTROL
M10412
BLADE
EDGE
CELLULAR FOAM SEAL
WORKS WITH
COMPRESSION
C2385