Lennox KHA SERIES, Manual

Page: 37 / 49

Page 37
FIGURE 19
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 12. Setting A is recommended. See figure 19. 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 set-
ting 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 12
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 must be installed between TB1 R and
OC terminals to maintain occupied status (allowing mini-
mum fresh air). When using an electronic thermostat or
energy management system with an occupied/unoccu-
pied feature, remove jumper.
1− Set thermostat to occupied mode if the feature is avail-
able. Make sure jumper is in place between TB1 termi-
nals R and OC 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 require-
ments.
3− Measure outdoor air temperature. Mark the point on
the bottom line of chart 1 and label the point A" (40
_
F,
4
_
C shown).
4− Measure return air temperature. Mark that point on the
top line of chart 1 and label the point B" (74
_
F, 23
_
C
shown).
5− Measure mixed air (outdoor and return air) tempera-
ture. Mark that point on the top line of chart 1 and label
point C" (70
_
F, 21
_
C 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 potentiom-
eter 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 CO
2
sensor, dampers will start to open when
the IAQ sensor reads approximately 1000ppm. Adjust
the DCV SET potentiometer to the approximate setting
specified by the controls contractor. Refer to figure 19.
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 CO
2
rises
above setpoint. Adjust the DCV MAX potentiometer to
the approximate setting specified by the controls con-
tractor. Refer to figure 19.
Note − DCV Max must be set higher than economizer mini-
mum position setting for proper demand control ventilation.