Lennox KGA Series Service Literature page 34

A6 Enthalpy Control LEDs
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 28.
A6 ENTHALPY CONTROLLER
2V
EXH
Open
2V
DCV
2V
Free
Cool
B
A
FREE COOLING SETPOINT;
A=Completely counterclockwise
D=Completely clockwise
FIGURE 28
Free Cooling Setpoint
Outdoor air is considered suitable when temperature and
humidity are less than the free cooling setpoints shown in
table 15. Setting A is recommended. See figure 28. At set­
ting A, free cooling will be energized when outdoor air is ap­
proximately 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".
EXH
Set
10V
DAMPER
MINIMUM
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
ENTHALPY CONTROL SETPOINTS
Control Setting
A
B
C
D
Damper Minimum Position
NOTE - A jumper is factory-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 poten­
tiometer lower. Repeat steps 3 through 8 until calcula­
tion reads desired fresh air percentage.
Page 34
TABLE 15
Free Cooling Setpoint At 50% RH
° °
73 F (23 C)
° °
70 F (21 C)
° °
67 F (19 C)
° °
63 F (17 C)