Specifications

3
Configurable Features — The unit and the controls
are capable of a large range of configurable features as standard
and also support additional features using factory-supplied op-
tions and field-installed accessories. The A series units can be
used with CV, VVT, and VAV applications. The following fea-
tures are common to all units:
• Optional two-stage demand economizers with fully propor-
tional dampers and integrated compressor capacity to pro-
vide the greatest amount of free cooling savings.
• Digitally controlled communicating economizer motors
providing diagnostic feedback.
• Support of minimum economizer position for ventilation.
• Support of remote economizer position input.
• Support of economizer changeover using outdoor air dry
bulb, differential dry bulb, outdoor air enthalpy, differential
enthalpy, custom enthalpy/dewpoint and dry bulb change-
over control or remote enable/disable control.
• High outdoor air dewpoint economizer lockout.
• Use of humidity sensors and drybulb sensors to measure
outdoor and return air enthalpy.
• Support of indoor or return air CO
2
IAQ (indoor air quality)
sensor or a remote IAQ input signal for use in demand con-
trol ventilation.
• Support on an optional outdoor air CO
2
sensor.
• Demand control routines allowing for adjustable response
curves to the differential IAQ levels.
• All units are equipped with supply air, return air, and out-
side air temperature sensors and the control automatically
calibrates the economizers to allow for mixed-air tempera-
tures after the economizer dampers.
• Outdoor-air temperature/supply-air temperature monitoring
with logic to lock the compressors out at low ambient
conditions.
• All units are equipped with suction pressure transducers for
low pressure protection and coil freeze protection.
• All condensers are equipped with saturation temperature
sensors and, combined with the suction pressure transduc-
ers, allow for direct readout of suction and discharge
pressures and saturation temperatures.
• Integral reverse rotation protection for compressors.
• Compressor safety overrides (power up and minimum on
and off timers) ensure oil return in low load conditions.
• Automatic lead-lag control of compressors reduces the
number of compressor cycles.
• Direct control of optional hot gas bypass.
• Control of the indoor fan on/off operation including
occupied and unoccupied control as well as delayed on/off
control.
• Control of the power exhaust fans based on configurable
damper positions or input from an optional building pres-
sure sensor.
• Control of a condenser fan based on outdoor-air and con-
densing pressures.
• Support of an accessory Motormaster® V control for low
ambient applications when an economizer cannot be used.
• Scrolling Marquee display is standard on all units and
includes 4-character alpha-numeric display that can be
expanded to 24-character text message for easy operation,
configuration, and troubleshooting of the ComfortLink™
control.
• All units equipped standard with an alarm relay output.
• Control and system diagnostics with alarm history and full
text descriptions.
• Support a field test for field check out and diagnostics.
• Support of remote occupied/unoccupied input to start and
stop the unit.
• Support of remote start/stop input.
• Support of a field-installed accessory or factory-installed
option filter pressure switch.
• Support of an accessory, field-installed fan status pressure
switch.
• Enable heating (if installed) or cooling during unoccupied
periods as required to maintain space temperature within the
unoccupied set points.
• Support of demand limiting using external switch inputs or
an external 4 to 20 mA signal.
• For units connected to the CCN (Carrier Comfort Network),
the user can also display all the unit information including
I/O values for Maintenance, Configuration, Service, and Set
Point data tables.
Constant Volume Features — For constant volume
applications, the ComfortLink control can support electro-
mechanical or electronic thermostats that use a Y1, Y2, W1,
W2, and G inputs. The control can also support the use of
a 10K space temperature thermistor. The following are addi-
tional features with constant volume applications.
CONVENTIONAL THERMOSTAT CONTROL
• Control of unit using Y1, Y2, W1, W2, and G thermostat.
• Interface with remote time of day scheduling.
• Use of the internal ComfortLink timeclock routines for
control of the occupied and unoccupied modes and the min-
imum ventilation position of the economizer.
• Two-stage heating (if installed).
• Multiple stage gas heating controlled to a supply air temper-
ature set point if equipped with the staged gas heat option.
• Two-stage cooling or adaptive multiple stage cooling which
can provide up to 6 stages of capacity with a 2-stage
thermostat.
• Support of thermostat alarm light output.
SENSOR CONTROL OF UNIT — Unit that are equipped
10K space temperature thermistor sensors can be used on CV
applications. The set point is configured in the unit Scrolling
Marquee display and can be set from 55 F to 80 F. There are
3 sensor options available:
The T-55 sensor monitors room temperature and provides
unoccupied override capability (1 hour).
The T-56 sensor monitors room temperature, provides un-
occupied override capability (1 hour), and provides a tempera-
ture offset at the thermostat of 10° F maximum.
The T-58 is a CCN communicating sensor that provides set
point configuration and space temperature.
Standard features are:
• Occupied or unoccupied set points.
• Fully closed ventilation economizer positions during unoc-
cupied conditions.
• Adjustment of space temperature set points of ± 10° F when
using a T-56 sensor.
• Two-stage cooling or adaptive multiple stage cooling which
can provide up to 6 stages of capacity.
• Two-stage heating (if installed).
• Multiple stage gas heating controlled to a supply air temper-
ature set point if equipped with the staged gas heat option.
• 365-day timeclock with backup (supports minute, hour, and
day of week, date, month, and year access). The unit time-
clock includes or enables the following features:
— Daylight savings time function.
— Occupancy control with 8 periods for unit operation.
— Holiday table containing up to 9 holiday schedules when
programmed from the Scrolling Marquee and up to 30
when programmed from CCN.
— Ability to initiate timed override from T-55 or T-56
sensors (for a timed period of 1 to 4 hours).
— Temperature compensated start to calculate early start
times before occupancy.
— Pre-occupancy purge cycle.
— For units connected into a CCN network, the timeclock
can be integrated into the overall building Energy
Management System and be updated remotely.