Introduction; Definitions - Honeywell AUTOMATIC CONTROL Engineering Manual

INTRODUCTION

This section familiarizes the reader with dampers, including
types, construction, performance, environment capability,
actuators, and linkages, and describes criteria used for proper
selection and sizing of dampers. Dampers are typically chosen
based on duct size and convenience of location. Rather than using
duct size, criteria and methods are provided to select and properly
size dampers which will produce desired control results. This can
eliminate the undesirable effects of oversized dampers.

DEFINITIONS

Actuator: A device used to operate a damper or control valve
in a control system.
Baffle: An orifice placed in the duct to reduce the duct size to
the damper size.
Damper seals: Construction features used to minimize the
leakage through a damper.
Damper system: The damper plus the series resistance that
relates to it (e.g., duct work, mixing boxes, diffusers,
and coils).
Damper: A device used to regulate the flow of air in an HVAC
system by modulating or two-position control.
Drive blade: A damper blade that is driven directly by an
actuator or by a linkage, axle, or jackshaft connected
to the drive blade in an adjacent damper section.
DAMPER SELECTION AND SIZING
The information provided is general for all dampers. Selection
and sizing of specific dampers can only be accomplished through
the use of specific manufacturer's documentation.
Dampers in HVAC systems regulate the flow of air either by
modulating or two-position control. They are normally connected
to actuators by linkages and operate in response to a pneumatic,
electric, or electronic control signal. In theory, the application of
dampers in HVAC systems closely parallels that of control valves.
Fire damper: A thermally actuated damper arranged to
automatically restrict the passage of fire and/or heat
at a point where an opening violates the integrity of a
fire partition or floor.
Ideal damper system: A system with a linear relationship
between the percent open damper position and the
percent of full airflow.
Leakage: The amount of air passing through a damper with a
given pressure drop and a given torque holding the
damper closed.
Opposed blade damper: A damper constructed so adjacent
blades rotate opposite to each other.
Parallel blade damper: A damper constructed so each blade
rotates in the same direction as the blade next to it.
Smoke damper: A damper arranged to control passage of
smoke through an opening or a duct.
453 ENGINEERING MANUAL OF AUTOMATIC CONTROL