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COMPONENT DESCRIPTIONS
(27) Fresh Air Damper – (OPT)
When a fresh air damper is supplied with the unit, the damper is
factory installed in the blower section. The fresh air damper is
used as an outside air shut-off damper, so ultra low leak, Class I
leakage resistance (less than 4 CFM/ft² at 1" W.C.) dampers
with self-compensating stainless steel side seals and
santoprene and galvanized steel blade seals are used.
(28) Enthalpy Sensor – (OPT) (All Except Digit 12=9)
Refer to Option #31.
(30) Direct Drive Damper Actuator – (OPT)
The direct drive damper actuator is factory installed in the
blower section on the side of the fresh air damper. The actuator
controls the position of the fresh air damper. The return air
damper, if provided, is controlled by the damper linkage
between the two dampers. All damper actuators are low voltage
(24V). For Right Hand units (Digit 9 = R), during operation the
actuator should rotate in the counterclockwise direction when
viewed from the service side of the unit. For Left Hand units
(Digit 9 = L), during operation the actuator should rotate in the
clockwise direction when viewed from the service side of the
unit. Three different types of dampers actuators can be
provided: Two-position, Modulating, and Floating.
•
Two-Position Damper Actuator: A two-position actuator is
provided with Air Control options (Model Digits 20-21=DA
and EA). The actuator provides open/closed operation of
the fresh air damper. When the actuator is energized, the
fresh air damper is opened to 100% outside air in 75
seconds (for outside air percentages lower than 100%, refer
to the following section, "Setting the Damper Limiter").
Actuators are spring return, so when the damper is
de-energized, the fresh air damper will spring closed.
Actuator include auxiliary switches (one normally open and
one normally closed) that reverse when the damper actuator
is at 85° rotation (adjustable).
Setting the Damper Limiter: The two-position damper limiter
can be factory set to prevent the outside air damper from
opening 100%. Field adjustment of the two-position damper
limiter is accom plished by the following:
1.
Determine the maximum outside air % required.
2.
Locate the angle of rotation limiter on the actuator so
that its edge lines up with the degree graduation on the
actuator face corresponding to the required rotation.
(See Figure 30.1 which is shown at 50% rotation limit.)
3.
Position the limiter to the desired position, making sure
the locating "teeth" on the limiter are engaged into the
locating holes on the actuator.
4.
Fasten the limiter to the actuator using the screw
provided.
5.
Test the damper rotation either manually with the
manual crank or apply power. Re-adjust if necessary.
6.
If the damper end switch is being used in the control
circuit and needs to be adjusted for the new limit
position, refer to the next section, "Adjusting the
Damper End Switch".
30
Figure 30.1 - Two-Position Damper Actuator Limiter
PHILIPS SCREWDRIVER
Adjusting the Damper End Switch
If the damper limiter was adjusted in the previous section, it may
be required to adjust the Damper End Switch as follows:
1.
The actuator must be in its fail-safe position.
2.
Insert the crank handle into the torx shaped hole located in
the center of the adjustable switch pointer as shown in
Figure 30.2.
3.
Gently rotate the crank until the switch pointer is at the
desired switch point in degrees as shown.
Figure 30.2 - Adjusting the Damper End Switch
•
Modulating Damper Actuator: A modulating actuator is
provided with Air Control options (Model Digits 20-21=GA,
GB, GC, GD, GE, GG, GH, and GJ). The actuator provides
incremental operation of the fresh air damper (the return air
damper is controlled by the fresh air damper position). Full
90° rotation of the actuator requires 150 seconds. Actuators
operate using a 0-10 Vdc input signal (Air Control GB
utilizes a resistor to convert from a 4-20 mA to 0-10 Vdc)
from a damper controller. Actuators are spring return, so
when the damper is de-energized, the fresh air damper will
spring closed.
For units with the Modine Control System option (Model
Digit 12=9), when the damper control is modulating, Model
Digits 20-21 will always be GA and the control will be
integral to the Modine Control System control logic. Refer
to the latest revision of the Modine Control System Manual,
literature 74-510 for additional information.
•
Floating Damper Actuator (All Except Model Digit
12=9): A floating actuator is provided with Air Control
option (Model Digits 20-21=HP). The actuator provides
forward and reversing damper operation in response to
contact closures from the space pressure controller. When
above the desired high pressure setpoint, a contact on
5-594.10
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