50
→
EC.MN or Configuration
→
AIR.Q
→
OVR.P to provide
economizer cooling.
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.
Configuration
→
AIR.Q
→
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.
Configuration
→
AIR.Q
→
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).
Configuration
→
AIR.Q
→
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 sen-
sors which provide 4 to 20 mA for 0 to 2000 ppm. If a sensor
has a different range, the ppm display range must be reconfig-
ured by entering new values for Configuration
→
AIR.Q
→
O.4M and Configuration
→
AIR.Q
→
O.20M.
Configuration
→
AIR.Q
→
OA.CF = 0 (No OAQ) — This
signifies there is no outdoor air sensor installed. The default
value of OAQ is 400 ppm.
Configuration
→
AIR.Q
→
OA.CF = 1 (DCV) — The outdoor
air quality sensor analog input is for the value of OAQ.
Configuration
→
AIR.Q
→
OA.CF = 2 (OAQ Lockout) —
The outdoor air quality sensor analog input is only used to lock
out the outdoor ventilation. The economizer commanded posi-
tion 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.
FAN ENABLE (Analog IAQ Sensor) — The DCV algorithm
will operate whenever the building is occupied and the indoor fan
is operating or whenever the IAQ algorithm has caused the
indoor fan to operate. The configuration Configuration
→
AIR.Q
→
IA.FN (Fan Enable for IAQ), determines whether or
not the IAQ algorithm can turn on the indoor fan. If the indoor fan
is not operating, the economizer position will be zero. The damper
position may exceed Configuration
→
AIR.Q
→
EC.MN to pro-
vide economizer cooling.
Configuration
→
AIR.Q
→
IA.FN = 0 (Never) — When IA.FN
= 0, the IAQ algorithm can never turn on the fan.
Configuration
→
AIR.Q
→
IA.FN = 1 (Occupied) — When
IA.FN = 1, the IAQ algorithm will turn on the indoor fan
whenever the building is occupied and IAQ/OAQ differential
is greater than the configuration Configuration
→
AIR.Q
→
DF.ON (Fan On AQ Differential). The indoor fan will turn off
when the IAQ/OAQ differential is less than the configuration
Configuration
→
AIR.Q
→
DF.OF (Fan Off AQ Differential).
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
Fig. 11 — IAQ Control
a48-8154
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