24
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 (ConfigurationECON
MP.MX), Econo Min IAQ Position (ConfigurationAIR.Q
AQ.MN) and the economizer minimum position and DCV
minimum position curves in Fig. 7 and 8 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 (ConfigurationAIR.QII.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
(ConfigurationECONMP.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 (ConfigurationAIR.QAQ.MN) when the indoor
fan is operating at Supply Fan Maximum Speed (Configuration
UNITFS.MX). If IAQ is high, the economizer minimum
position is Econ Min at Max Fan Speed (ConfigurationECON
MP.MX) when the indoor fan is operating at Supply Fan
Maximum Speed (FS.MX). If the fan speed is modulating, see
Fig. 7 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
(ConfigurationAIR.QOVR.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 (ConfigurationAIR.Q
O.4M) and OAQ Sensor Value at 20mA (Configuration
AIR.QO.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 (ConfigurationAIR.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 (ConfigurationAIR.QIA.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
(ConfigurationECONMP.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
whenever the building is occupied and IAQ/OAQ differential is
greater than the Fan On AQ Differential (ConfigurationAIR.Q
DF.ON). The indoor fan will turn off when the IAQ/OAQ
differential is less than the Fan Off AQ Differential (Configuration
AIR.QDF.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 (ConfigurationAIR.QII.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
(ConfigurationECONMP.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
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.
Optional Humidi--MiZert Dehumidification
System
Units with the factory--equipped Humidi--MiZer option are capable of
providing multiple modes of improved dehumidification as a variation
of the normal cooling cycle. The Humidi--MiZer option includes
additional valves in the liquid line and discharge line of each
refrigerant circuit, a reheat coil downstream of the evaporator, and
Motormasterr variable--speed control of some or all outdoor fans. The
Humidi--MiZer Equipped (ConfigurationHMZRREHT)
configuration is factory set to Yes for Humidi--MiZer equipped units.
This enables Humidi--MiZer operating modes and service test.
Humidi--MiZer operation requires installation and configuration of
either a space relative humidity sensor or a relative humidity switch
input. Space Humidity Switch (ConfigurationUNITRH.SW)
set to 1 for use of a normally open switch or 2 for normally closed
switch. The switch is wired to field connection terminal board
terminal labeled HUM and the “R2” terminal. Set RH Sensor on
OAQ Input (ConfigurationUNITRH.S)toYesforuseofa4
to 20 mA output RH sensor wired to field connection terminal
board (TB) terminals SPRH and LPWR (for loop powered). RH
ComfortLINK v1.X
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