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E. STEAM DAMPER ACTUATOR SYSTEM
The system consists of a hinged damper plate, a pneumatic piston (with an airflow needle valve) to control the speed of
the piston actuation, and a 24 volt solenoid valve.
On a call for heat, a 24 volt signal is applied to the 3-way/2-position solenoid valve. This signal switches the valve so
that compressed air is sent to the piston. The piston rod extends, pushing the hinged steam damper plate to the opened
position. This allows room air to be drawn through the hot steam coil and then through the tumbler.
When the temperature set point has been reached, the 24 volt signal is removed from the solenoid valve, so that the
solenoid valve blocks the air supply to the pistons, and the air in the pistons is bled to the atmosphere. The springs in the
pistons now retract the piston rods, closing the steam damper. The steam damper plate now covers the steam coil and
allows room air to bypass the coil before entering the tumbler for a rapid cool down.
The steam damper plate should open and close slowly and smoothly. The speed can be modulated by adjusting both
needle valve knobs. Turning the knob clockwise restricts the compressed airflow and slows down the steam damper
movement. Counterclockwise adjustment speeds up the steam damper motion. Upon completion of adjustment,
tighten the needle valve’s locking nut.
NOTE: Turning knob on flow control clockwise will restrict airflow. Turning knob counterclockwise will
allow higher airflow.
