50
33
66
100
700
Parameter 118
1000
Parameter 119
Low Temp. Operation
High Temp. Operation
CO
2
(ppm)
10°F
Parameter 122
20°F
30°F
40°F
Parameter
123
105°F
Parameter 120
95°F
85°F
75°F
Parameter 121
0
Min. Position
Damper T
ravel:
% of Maximum
Open
(Parameter
1
1
7
Figure 10. Default Demand Control Ventilation (DCV) Operation
9.4.
Parameter Adjustments
Default indoor air quality economizer operation is based on common or average applications. Adjustments may be made
to the indoor air quality parameters to alter operation or meet required specifications. Use the user interface to change
parameter 117 through 123.
Go to
SETTINGS > RTU OPTIONS > EDIT PARAMETER
Select a demand control ventilation mode with parameter 134. Modes 3 and 4 will bring on the unit blower when demand
control ventilation calls for maximum damper open, and returns to auto-blower when demand control ventilation damper
returns to 0. The other modes only operate when the unit blower is on, but will not bring it on themselves.
Some applications require a different carbon dioxide set point range than default settings. Damper
start open
(parameter 118) and
full open
(parameter 119) carbon dioxide set points may be adjusted from 0 to 2000 ppm. Use the
following formula to determine damper travel.
NOTE
: When changing carbon dioxide set point range, “start open" set point should be less than “full‐open" set point.
% Damper Travel
= carbon dioxide ppm - Start Open ppm X Max Open (parameter 117) Full Open - Start Open
Full Open - Start Open
Example:
An application requires the dampers open at 800 CO
2
ppm and reach full open at 1200. If the carbon
dioxide level in the space reads 1000 ppm, calculate the damper percent open as follows.
% Damper Travel
=
1000 - 800 or 200 or .5
=
0.5 x 100 = 50%
1200 - 800 400
9.4.1.
Set Point Control Option
Set point control mode is commonly used in areas with high occupancy and frequent change out such as classrooms or
conference rooms.
In applications requiring this on/off damper response to carbon dioxide
levels, set the start open (parameter 118 - DCV
DAMP START OPEN) set point higher than the full open (parameter 119 - DCV DAMP FULL OPEN) set point. The
dampers will drive to fully-open position immediately. Figure 11 shows the set point control option.
Change parameters 122 and 123 to set the minimum outdoor temperature limits. Change parameters 120 and 121 to set
the maximum temperature limits.
IMPORTANT
Mixed air temperatures less than 45°F (7°C) on units with an aluminized heat exchanger or less than 30°F (-1°C) on
stainless steel heat exchangers will void the manufacturer's warranty.
