Lennox Core Unit Controller Setup Manual page 33

10.5.1. Default Operation
The CORE Unit Controller has a 0-10VDC indoor air quality
input for a standard 0 - 2000ppm carbon dioxide sensor. The
economizer starts opening at a carbon dioxide level of 700
ppm (default) (start open set point) and reaches full open at
a carbon dioxide level of 1200ppm (default) (full open set
point).
The damper opens to a default position of 50% (see
Parameter 117). Determine damper travel position using the
following formula:
% Damper Travel = carbon dioxide ppm - Start Open ppm
Example: At a carbon dioxide level of 750ppm, the damper
will be approximately 50% open:
% Damper Travel = 750-500 = 50%
Use the menu interface to read carbon dioxide ppm.
Go to DATA > SYSTEM DATA / SENSORS / OUTPUTS > LOCAL
INPUTS > SENSORS > LOCAL
(scroll down to CO
10.5.2. Maximum and Minimum Demand
Control Ventilation Damper
Settings
Maximum position is set using the following menu path:
Go to SETTINGS > RTU OPTIONS > DAMPER > SET ECONOMIZER
OPTION > SET FREE COOLING SUPPLY AIR SETPOINT >
CLOSE DAMPER > OPEN DAMPER > TURN ON BLOWER >
MINIMUM DAMPER POSITION > and select DEMAND CONTROL
VENTILATION.
Options are:
• DEMAND CONTROL VENT > DAMPER START OPEN
= XXXX PPM
• DEMAND CONTROL VENT > DAMPER FULL OPEN =
XXXX PPM
• DEMAND CONTROL VENT > DAMPER MAX OA CFM
= X CFM (only visible if configuration id 1, position 2 is
set correctly).
• DEMAND CONTROL VENT > DAMPER MAX OPEN =
XXX.X %.
100
66
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Min. Position
0
Parameter 118
CO
Figure 33. Default Demand Control Ventilation (DCV)
5
5
)
2
Low Temp. Operation High Temp. Operation
40°F Parameter 75°F Parameter 121
123
30°F 85°F
20°F 95°F
10°F Parameter 122
105°F Parameter 120
700
1000
Parameter 119
(ppm)
2
Operation
10.5.3. 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 >
IAQ INPUT MODE
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
Example: An application requires the dampers open at 800
CO2 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 =
10.5.4. 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
airborne 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
6 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 manufactur-
er's warranty.
33
50%
1200 - 800 400