Handbook of air conditioning and refrigeration / Shan K

5.32 CHAPTER FIVE
5.7 DAMPERS AND DAMPER ACTUATORS
A damper is a device that controls the airflow in an air system or ventilating system by changing the
angle of the blades and therefore the area of its flow passage. In HVAC&R systems, dampers can be
divided into volume control dampers and fire dampers. Fire dampers are covered in a later section.
In this section, only volume control dampers are discussed.
Types of Volume Control Dampers
Volume control dampers can be classified as single-blade dampers or multiblade dampers according
to their construction. Various types of volume control dampers are shown in Fig. 5.18.
Butterfly Dampers. A butterfly damper is a single-blade damper. A butterfly damper is made from
either a rectangular sheet mounted inside a rectangular duct or a round disk placed in a round duct,
as shown in Fig. 5.18a. It rotates about an axle and is able to modulate the air volume flow rate of
the duct system by varying the size of the opening of the passage for air flow.
Gate Dampers. A gate damper is a single-blade damper. It also may be rectangular or round. It
slides in and out of a slot in order to shut off or open up a flow passage, as shown in Fig. 5.18b.
Gate dampers are mainly used in industrial exhaust systems with high static pressure.
Split Dampers. A split damper is also a single-blade damper. It is a piece of movable sheet metal
that is usually installed at the Y connection of a rectangular duct system, as shown in Fig. 5.18c.
FIGURE 5.18 Various types of volume control dampers: (a) Butterfly damper; (b) gate damper; (c) split
damper; (d) opposed-blade damper; (e) parallel-blade damper.