Direct Gas Make-Up Air
43
OPTIONAL RECIRCULATION
Two Position Recirculation Control
• Power passes to inlet damper which opens.
• When damper is fully opened, normally open
damper limit switch (DL1) closes.
• Power passes to and energizes supply starter relay
(RF).
• Power passes to normally open fan contact (RF),
which is energized and closed. Power reaches and
energizes supply fan. The recirculation damper is
closed.
• When the recirculation contact (S3) is closed,
the recirculation damper is opened to allow
recirculated air to enter the unit and mix with the
heated outside air.
Potentiometer Recirculation Control
• Power passes to inlet damper which opens.
• When damper is fully opened, normally open
damper limit switch (DL1) closes.
• Power passes to and energizes supply starter relay
(RF).
• Power passes to normally open fan contact (RF),
which is energized and closed. Power reaches and
energizes supply fan.
• The potentiometer will output a 2-10 VDC signal
to the recirculation damper actuator to control
recirculation damper position.
External Signal Recirculation
• Power passes to inlet damper which opens.
• When damper is fully opened, normally open
damper limit switch (DL1) closes.
• Power passes to and energizes supply starter relay
(RF).
• Power passes to normally open fan contact (RF),
which is energized and closed. Power reaches and
energizes supply fan.
• An external source will provide a 2-10 VDC or
4-20 mA signal to the recirculation damper
actuator to control recirculation damper position.
Sequence of Operation
Building Pressure Recirculation Control
• Power passes to inlet damper which opens.
• When damper is fully opened, normally open
damper limit switch (DL1) closes.
• Power passes to and energizes supply starter relay
(RF).
• Power passes to normally open fan contact (RF),
which is energized and closed. Power reaches and
energizes supply fan.
• The photohelic building pressure controller will
monitor the pressure differential between the
pressure in the controlled space and the pressure
outside the controlled space.
• If the pressure differential is below the set point
range established on the photohelic controller,
the recirculation damper will be modulated further
closed.
• If the pressure differential is above the set point
range established on the photohelic controller,
the recirculation damper will be modulated further
open.
• If the pressure differential is within the set point
range established on the photohelic controller,
the recirculation damper will remain in its current
position.