ACONT900AC43UA
Pub. No. 11-HD04D1-2
19
69-2080—05
The Frost Setting can be accessed by pressing the More
key until the Frost Setting is displayed on the screen. It
has a value range of 0 to 10, with 0 representing glass
with poor insulation and 10 representing glass with
perfect insulation. If the factory setting (5), results in too
much condensation or frost on the windows, lower the
setting. When the air seems too dry, raise the setting.
Dehumidification
Integrated Temperature and Humidity Control
(ITHC)
The dehumidification control attempts to control the
indoor humidity to the user’s dehumidification setpoint by
running the compressor. The dehumidification setpoint
can be accessed by pressing the More key until the
dehumidification setpoint is displayed on the screen. The
setpoint can range between 40% and 80% in 5%
increments. When enabled, the default dehumidification
setpoint is 50%. In extremely high humidity conditions, the
Comfort Control keeps the compressor running for up to
3°F (-1.7°C) below the temperature setpoint. It does this
while trying to achieve the desired dehumidification
setpoint and balancing that with the temperature setpoint.
The maximum allowable dehumidification droop can be
selected in ISU 0383.
American Standard Heating & Air Conditioning
Droop
American Standard Heating & Air Conditioning Droop is a
feature that cycles the compressor on to improve indoor
comfort by removing moisture from the air. The Droop
cycle is activated when the indoor humidity is above the
user’s dehumidification setpoint. When this function is
active, the Comfort Control will control temperature at 1 or
2 degrees F below the cooling setpoint. The Droop cycle
is deactivated when the indoor humidity drops below the
user’s dehumidification setpoint. If the indoor humidity
sensor fails, the droop logic will always be enabled while
in cooling mode.
Comfort-R
TM
Delay
When the indoor humidity is above the users
dehumidification setpoint, Comfort-R
TM
Delay will remove
humidity from the air by implementing a blower turn-on
delay of 15 or 30 seconds to “pre-chill” the coil. Comfort-
R
TM
Delay applies to non-variable speed indoor unit types
only.
Dehumidification Airflow
During any dehumidification control option, a lower speed
fan can be activated. The settings range from 80% to
100% in 5% increments (see Table 4, Installer Setup
number 0387). The default dehumidification airflow is
100%.
American Standard Heating & Air Conditioning
Proprietary Humidity Control
When enabled, this feature will disable any blower off
delays and disable continuous fan mode when the indoor
humidity is above the dehumidification setpoint. This will
help prevent coil condensation from being evaporated
back into the air stream.
NOTE: This feature, ISU 0388, is not shown unless
some form of dehumidification control is
selected.
NOTE: American Standard Heating & Air Conditioning
Proprietary Humidity Control does not affect the
fan operation when the fan setting at the comfort
control is in Auto or Circ Modes.
Special Heat Pump Features
Auxiliary Heat Lockout Temperature
When an outdoor temperature sensor has been
discovered/ enabled, none of the installed auxiliary heat
stages will turn on during heating operation above the
selected outdoor temperature. When the outdoor
temperature is less than the auxiliary heat lockout
temperature (ISU Number 0360), the Comfort Control
may cycle the indoor heat on and off to satisfy the load.
During defrost, this outdoor temperature setting is ignored
and the defrost heater balance point outdoor temperature
thresholds are used.
NOTE: For Dual Fuel applications, if the heat pump fails
to maintain heat while the outdoor temperature is
above the auxiliary lockout temperature, the fur-
nace will be used until the setpoint is reached, at
which time heat pump operation will resume.
Compressor Heat Lockout Temperature
When an outdoor temperature sensor has been
discovered/ enabled, only the installed auxiliary heat
stages will turn on during heating operation below the
selected outdoor temperature. When the outdoor
temperature is greater than the compressor heat lockout
temperature (ISU Number 0350), the heat pump attempts
to satisfy the load.
If the heat pump can not satisfy the load and the outdoor
temperature is less than the compressor lockout
temperature (ISU Number 0350), the Comfort Control will
transition to auxiliary heat operation and will turn off the
heat pump. During defrost, this outdoor temperature
setting is ignored and the defrost heater balance point
outdoor temperature thresholds are used.
NOTE: There is a 5°F deadband between the Compres-
sor and auxiliary heat lockout temperatures.
Operation in Heat Mode
When the outdoor temperature is below the compressor
lockout temperature, only the auxiliary heat operates.
When the outdoor temperature is above the auxiliary
lockout temperature, only the Compressor operates. See
Figure 9. When the outdoor temperature is between the
two temperatures, both the Compressor and auxiliary
heat operate.
Fig. 9. Heat Pump Operation with Lockout
Temperatures Set.
35
COMPRESSOR
LOCKOUT
TEMPERATURE
AUXILIARY
LOCKOUT
TEMPERATURE
COMPRESSOR ONLY
BOTH COMPRESSOR AND
AUXILIARY HEAT
AUXILIARY ONLY
50
OUTDOOR TEMPERATURE
