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Optional Sensors
An optional differential sensor (A62) may be used with the
A7 outdoor sensor to compare outdoor air enthalpy to re-
turn air enthalpy. When the outdoor air enthalpy is below
the return air enthalpy, outdoor air is used for free cooling.
A mixed air sensor (R1) is used in modulating the dampers
to 55
°
F (13
°
C) blower compartment air temperature.
FIGURE 23
INSTALL ENTHALPY CONTROLLER A6
B7
ECONOMIZER
MOTOR
J104
J105
A6
ENTHALPY
CONTROLLER
J3
ECONOMIZER
P4
OUTDOOR/
RETURN AIR
DIVISION PANEL
SIDE
PANEL
J10
P3
An optional IAQ sensor (A63) may be used to lower operat-
ing costs by controlling outdoor air based on CO
2
level or
room occupancy (also called demand control ventilation or
DCV). Damper minimum position can be set lower than
traditional minimum air requirements; dampers open to
traditional ventilation requirements when CO
2
level reach-
es DCV (IAQ) setpoint.
Refer to instructions provided with sensors for installation.
A6 Enthalpy Control LED’s
A steady green Free Cool LED indicates that outdoor air is
suitable for free cooling.
When an optional IAQ sensor is installed, a steady green
DCV LED indicates that the IAQ reading is higher than set-
point requiring more fresh air. See figure 24.
FIGURE 24
A6 ENTHALPY CONTROLLER
A
B
C
D
Open
Min
Pos
FREE COOLING SETPOINT;
A=Completely counterclockwise
D=Completely clockwise
OUTDOOR AIR
SUITABLE LED
Free
Cool
DCV
EXH
EXH
Set
2V
10V
DCV
Max
2V
10V
DCV
Set
2V
10V
IAQ SETPOINT
IAQ READING IS
ABOVE SETPOINT
DAMPER MINI-
MUM POSITION
IAQ MAXIMUM
POSITION
(set higher than
minimum position)
Free Cooling Setpoint
Outdoor air is considered suitable when temperature and
humidity are less than the free cooling setpoints shown in
table 17. Setting A is recommended. See figure 24. At set-
ting A, free cooling will be energized when outdoor air is
approximately 73°F (23°C) and 50% relative humidity. If in-
door air is too warm or humid, lower the setpoint to B. At
setting B, free cooling will be energized at 70°F (21°C) and
50% relative humidity.
When an optional A62 differential sensor is installed, turn
A6 enthalpy control free cooling setpoint potentiometer
completely clockwise to position D".
TABLE 17
ENTHALPY CONTROL SETPOINTS
Control Setting
Free Cooling Setpoint At 50% RH
A
73
°
F (23
°
C)
B
70
°
F (21
°
C)
C
67
°
F (19
°
C)
D
63
°
F (17
°
C)
Damper Minimum Position
NOTE − A jumper is factory−installed between TB1 A1
and A2 terminals to maintain occupied status (allowing
minimum fresh air). When using an electronic thermostat
or energy management system with an occupied/unoc-
cupied feature, remove jumper.
