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A6 ENTHALPY CONTROLLER
2V
EXH
Open
2V
DCV
2V
Free
Cool
B
A
FREE COOLING SETPOINT;
A=Completely counterclockwise
D=Completely clockwise
FIGURE 27
Free Cooling Setpoint
Outdoor air is considered suitable when temperature and
humidity are less than the free cooling setpoints shown
in table 13. Setting A is recommended. See figure 27. At
setting A, free cooling will be energized when outdoor air
is approximately 73°F (23°C) and 50% relative humidity.
If indoor 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 13
ENTHALPY CONTROL SETPOINTS
Control Setting
Free Cooling Setpoint At 50% RH
A
B
C
D
EXH
Set
10V
MUM POSITION
Min
IAQ MAXIMUM
Pos
POSITION
(set higher than
DCV
minimum position)
Max
10V
IAQ READING IS
ABOVE SETPOINT
DCV
Set
10V
IAQ SETPOINT
OUTDOOR AIR
C
SUITABLE LED
D
73° F (23° C)
70° F (21° C)
67° F (19° C)
63° F (17° C)
Damper Minimum Position
1 - Set thermostat to occupied mode if the feature is
available. Make sure unit 24V control leads R and
OC are connected if using a thermostat which does
not have the feature.
2 - Rotate MIN POS SET potentiometer to approximate
desired fresh air percentage.
Note - Damper minimum position can be set lower
than traditional minimum air requirements when
an IAQ sensor is specified. Dampers will open to
DCV MAX setting (if CO2 is above setpoint) to meet
traditional ventilation requirements.
3 - Measure outdoor air temperature. Mark the point
on the bottom line of chart 1 and label the point "A"
(40F, 4C shown).
4 - Measure return air temperature. Mark that point on
the top line of chart 1 and label the point "B" (74F,
23C shown).
5 - Measure mixed air (outdoor and return air)
temperature. Mark that point on the top line of chart
1 and label point "C" (70F, 21C shown).
6 - Draw a straight line between points A and B.
7 - Draw a vertical line through point C.
8 - Draw a horizontal line where the two lines meet.
Read the percent of fresh air intake on the side.
9 - If fresh air percentage is less than desired, adjust
MIN POS SET potentiometer higher. If fresh air
percentage is more than desired, adjust MIN POS
SET potentiometer lower. Repeat steps 3 through 8
until calculation reads desired fresh air percentage.
DCV Set and Max Settings
Adjust settings when an optional IAQ sensor is installed.
The DCV SET potentiometer is factory-set at approxi-
mately 50% of the potentiometer range. Using a standard
1-2000ppm CO2 sensor, dampers will start to open when
the IAQ sensor reads approximately 1000ppm. Adjust the
DCV SET potentiometer to the approximate setting speci-
fied by the controls contractor. Refer to figure 27.
The DCV MAX potentiometer is factory-set at approxi-
mately 50% of the potentiometer range or 6VDC. Damp-
ers will open approximately half way when CO2 rises
above setpoint. Adjust the DCV MAX potentiometer to the
approximate setting specified by the controls contractor.
Refer to figure 27.
Note - DCV Max must be set higher than economizer min-
imum position setting for proper demand control ventila-
tion.
Page 47
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