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100
700
INSIDE/OUTSIDE CO
2
DIFFERENTIAL
AQ
DIFFERENTIAL
LOW (AQD.L)
AQ
DIFFERENTIAL
HIGH (AQD.H)
MINIMUM
IAQ
DAMPER
POSITION
(AQ. MN)
ECONOMIZER
MINIMUM
DAMPER
POSITION
(EC. MN)
INCREASING VENTILATION
VENTILATION FOR PEOPLE
VENTILATION FOR SOURCES
C07010
Fig. 20 − IAQ Control
IA.CF = 3 (Control Minimum Position)
When IA.CF = 3, an external 4 to 20 mA source is used to set the
minimum position. The 4 mA signal corresponds to 0% and the 20
mA signal corresponds to 100%. In this mode, configurations such
as Configuration→AIR.Q→EC.MN and Configuration→
AIR.Q→AQ.MN are not used.
If the indoor fan is not operating, the economizer position will be
zero. The damper position may exceed the economizer minimum
position to provide economizer cooling.
IAQ (Switch Input)
Indoor air quality can also be measured using a switch input. For
the purpose of specifying the type of switch input, low CO
2
levels
are considered normal. The IAQ switch input is defined by the
configuration by Configuration→AIR.Q→II.CF IAQ Level
(Switch Input). Enthalpy and IAQ are controlled by the same
switch input and therefore they cannot be used simultaneously.
II.CF = 0 (No IAQ)
The II.CF = 0 configuration signifies that there is no IAQ switch
input. The damper will operate at the EC.MN position when the
space is occupied and the indoor fan is on.
II.CF = 1 (DCV NO) or II.CF = 2 (DCV NC)
The Demand Control Ventilation (DCV) allows the economizer
minimum position to be decreased when there is no IAQ problem.
If IAQ is low, the economizer minimum position is Minimum IAQ
Damper Position (Configuration→AIR.Q→AQ.MN). If IAQ is
high, the economizer minimum position is the Economizer
Minimum Position (Configuration→AIR.Q→EC.MN).
II.CF = 3 (Override NO) or II.CF = 4 (Override NC)
The damper override function permits absolute positioning of the
economizer damper for ventilation purposes. The override is active
when IAQ is high and inactive when IAQ is low. The override
position is configurable by the configuration by Configuration
→AIR.Q→OVR.P (Economizer Override Position).
Outdoor Air Quality (Analog Input)
The ComfortLink control is configured for outdoor air quality
sensors which provide 4 to 20 mA for 0 to 2000 ppm. If a sensor
has a different range, the ppm display range must be reconfigured
by entering new values for Configuration→AIR.Q →O.4M and
Configuration→AIR.Q→O.20M.
OA.CF = 0 (No OAQ)
This signifies there is no outdoor air sensor installed. The default
value of OAQ is 400 ppm.
OA.CF = 1 (DCV)
The outdoor air quality sensor analog input is for the value of OAQ
during demand control ventilation operation.
OA.CF = 2 (OAQ Lockout)
The outdoor air quality sensor analog input is only used to lock out
the outdoor ventilation. The economizer commanded position is set
to 0% when the ppm exceeds the OAQ lockout value configured
for Configuration→AIR.Q→OAQ.L. The default value of OAQ.L
is 600 ppm.
48/50PG and PM