Lennox ALLIED Commercial TCA180S2B Standard Manual page 40

Optional manual and motorized outdoor air dampers pro-
vide fresh outdoor air.
Follow the steps to determine fresh air percentage
1− Measure outdoor air temperature. Mark the point on
the bottom line of chart 1 and label the point A" (40_F,
4_C shown).
2− Measure return air temperature. Mark that point on the
top line of chart 1 and label the point B" (74_F, 23_C
shown).
3− 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).
4− Draw a straight line between points A and B.
5− Draw a vertical line through point C.
6− Draw a horizontal line where the two lines meet. Read
the percent of fresh air intake on the side.
7− If fresh air percentage is less than desired, adjust
thumbwheel higher. If fresh air percentage is more
than desired, adjust thumbwheel lower. Repeat steps
until calculation reads desired fresh air percentage.
See figure 26.
Set damper minimum position in the same manner as
economizer minimum position. Adjust motorized damper
position using the thumbwheel on the damper motor. See
figure 26. Manual damper fresh air intake percentage can
be determined in the same manner.
DAMPER
ASSEMBLY
DAMPER
MOTOR
P4
ECONOMIZER
PLUG
END PLATE
ADJUST LEVER TO DESIRED SETTING.
OUTDOOR AIR DAMPER
J3
UNIT JACK
FIGURE 27
Page 40
MANUAL OUTDOOR AIR DAMPER
LOOSEN WING NUT AND
FIGURE 25
DAMPER MOTOR
THUMBWHEEL
FIGURE 26
BOTTOM OF
DAMPER ASSEMBLY
DAMPER
SUPPORT BRACKET