Unit installation

23
fan is not operating, the economizer position will be zero. If the
override is not active and the building is unoccupied, the
economizer position will be zero. The damper position may
exceed Econ Min at Max Fan Speed (MP.MX) or IAQ Override
Position (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 4mA signal corresponds to 0% and the 20
mA signal corresponds to 100%. In this mode, configurations such
as Econ Min at Max Fan Speed (Configuration→ECON
→MP.MX), Econo Min IAQ Position (Configuration→AIR.Q
→AQ.MN) and the economizer minimum position and DCV
minimum position curves in Fig. 6 and 7 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
IAQ Switch Input Config (Configuration→AIR.Q→II.CF).
Enthalpy and IAQ are controlled by the same switch input and
therefore 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 Econ Min at Max Fan Speed
(Configuration→ECON→MP.MX) and corresponding damper
position curve based on indoor fan speed when the space is
occupied and the indoor fan is on.
II.CF = 1 (DCV Normally Open) or II.CF = 2
(DCV Normally Closed)
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 Econo Min
IAQ Position (Configuration→AIR.Q→AQ.MN) when the indoor
fan is operating at Supply Fan Maximum Speed (Configuration
→UNIT→FS.MX). If IAQ is high, the economizer minimum
position is Econ Min at Max Fan Speed (Configuration→ECON
→MP.MX) when the indoor fan is operating at Supply Fan
Maximum Speed (FS.MX). If the fan speed is modulating, see Fig.
6 for higher or lower damper position setting at the specific fan
speed.
II.CF = 3 (Override Normally Open) or II.CF = 4 (Override
Normally Closed)
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 configured by the IAQ Override Position
(Configuration→AIR.Q→OVR.P).
Outdoor Air Quality (Analog Input)
The ComfortLink control can be configured for outdoor air quality
sensors which provide a 4 to 20 mA signal corresponding to 0 to
2000 ppm CO
2
. If a field supplied sensor has a different range, the
ppm display range must be reconfigured by entering new values
for the OAQ Sensor Value at 4mA (Configuration→AIR.Q
→O.4M) and OAQ Sensor Value at 20mA (Configuration
→AIR.Q→O.20M).
OA.CF = 0 (No OAQ)
This signifies that there is no outdoor air sensor installed. The
default value of OAQ is 400 ppm CO
2
when using demand control
ventilation (DCV).
OA.CF = 1 (DCV)
The outdoor air quality sensor analog input is the value of OAQ
for demand control ventilation (DCV).
OA.CF = 2 (OAQ Lockout)
The outdoor air quality analog input is only used to lock out the
outdoor ventilation. The economizer commanded position is set to
0% when the CO
2
ppm exceeds the OAQ lockout value configured
for the OAQ Lockout Limit (Configuration→AIR.Q →OAQ.L).
The default value for OAQ Lockout Limit (OAQ.L) is 600 ppm CO
2
.
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 IAQ Analog
Fan Config (Configuration→AIR.Q→IA.FN) 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 Econ Min at Max Fan Speed
(Configuration→ECON→MP.MX) and corresponding damper
position curve to provide economizer cooling.
IA.FN = 0 (Never)
When IA.FN = 0, the IAQ algorithm can never turn on the fan.
IA.FN = 1 (Occupied)
When IA.FN =1, the IAQ algorithm will turn on the indoor fan at
the ventilation speed whenever the building is occupied and
IAQ/OAQ differential is greater than the Fan On AQ Differential
(Configuration→AIR.Q →DF.ON). The indoor fan will turn off
when the IAQ/OAQ differential is less than the Fan Off AQ
Differential (Configuration →AIR.Q→DF.OF).
IA.FN = 2 (Always)
The indoor fan operation for IA.FN = 2, is the same as the
operation when IA.FN =1, except the algorithm is not limited to
the occupied periods only. The fan can be triggered on when the
space is occupied or unoccupied.
Fan Enable (Switch Input)
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 IAQ Switch
Fan Config (Configuration→AIR.Q→II.FN) 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 Econ Min at Max Fan Speed
(Configuration→ECON→MP.MX) and corresponding damper
position curve to provide economizer cooling.
II.FN = 0 (Never)
When the II.FN = 0, the IAQ algorithm can never turn on fan.
II.FN = 1 (Occupied)
When II.FN =1, the IAQ algorithm will turn on the indoor fan at
the ventilation speed whenever the building is occupied and IAQ is
high. The indoor fan will turn off when the IAQ returns to normal.
II.FN = 2 (Always)
The indoor fan operation for II.FN =2 is the same as the operation
when IA.FN =1, except the algorithm is not limited to the occupied
periods only. The fan can be triggered on when the space is
occupied or unoccupied.
Temperature Compensated Start
This logic is used when the unit is in the unoccupied state. The
control will calculate early Start Bias time based on Space
Temperature deviation from the occupied cooling and heating set
points. This will allow the control to start the unit so that the space
is at conditioned levels when the occupied period starts. This is
required for ASHRAE 90.1 compliance. A space sensor is required
for non-linkage applications.
48/50LC