Specifications

When heating, the heat stages respond to the demand from
W1 and W2 of the thermostat input. Heating and cool-
ing will be mutually locked out on demand on a first call
basis. The heating and the cooling functions cannot operate
simultaneously.
Cooling, Variable Air Volume (VAV) Units — On
power up, the control module will activate the initialization
software. The initialization software reads each DIP switch
to determine the unit configuration. The initialization
sequence: clears all alarms and alerts; re-maps the input/
output database for VAV operation; sets maximum heat stages
to 1; and sets maximum cool stages to 6. The control module
reads DIP switch no. 3 and determines if the unit will use
expansion mode operation. Power up takes a random time of
1 to 63 seconds plus 5 minutes the first time power is sent
to the control board after a power outage.
The control module will determine if an interface (link-
age) is active and if the unit will operate in a Digital Air
Volume (DAV) mode. In a DAV system, the room terminals
are equipped with microprocessor controls that give com-
mands to the base unit module. If a linkage is active, the
control module will replace local comfort set points, space
and return air temperatures, and occupancy status with
the linkage data supplied.
The control module will determine occupancy status from
Time Schedules (if programmed), Remote Occupied/
Unoccupied input, global occupancy schedules, or DAV. If
temperature compensated start is active, the unit will be con-
trolled as in the Occupied mode.
Temperature compensated start is a period of time calcu-
lated to bring the unit on while in Unoccupied mode to reach
the occupied set point when occupancy occurs.
The control module will set the appropriate operating mode
and fan control. The control module will turn on the variable
frequency drive (VFD) if Occupied mode is evident. If in
Unoccupied mode and a valid return-air temperature read-
ing is available (either from a sensor or DAV), the control
module will monitor return-air temperature against unoccu-
pied heat and cool set points. The control module will start
the VFD whenever return-air temperature is outside of the
set points (Unoccupied Heat or Unoccupied Cool). The VFD
may also be started by nighttime thermostat via remote
Occupied/Unoccupied input or by a temperature compen-
sated start algorithm. When the VFD is running in a normal
mode, the control module will start heating or cooling as
required to maintain supply-air temperature at the supply air
set point plus the reset (when enabled). The reset value is
determined by SAT (supply-air temperature) reset and/or space
temperature reset algorithms. The space temperature reset
(requiring a space temperature sensor) is only available when
enabled through software.
When cooling, the control module will energize the power
exhaust enable output to the external power exhaust control-
ler (when power exhaust is used).
The control module will run continuous diagnostics for
alarms/alerts; respond to CCN (Carrier Comfort Network)
communications; perform any configured network POC (Prod-
uct Outboard Control) functions such as time/outdoor air tem-
perature broadcast and global broadcast; and perform Fire/
Smoke control.
Heating, Constant Volume (CV) Units
48 SERIES UNITS — The gas heat units incorporate 2 sepa-
rate systems to provide gas heat. Each system incorporates
its own induced-draft motor, Integrated Gas Control (IGC)
board, 2 stage gas valve, manifold, etc. The systems are op-
erated in parallel; for example, when there is a call for first
stage heat, both induced-draft motors operate, both gas valves
are energized, and both IGC boards initiate spark.
All of the gas heating control is performed through the
IGC boards (located in the heating section). The base mod-
ule board serves only to initiate and terminate heating
operation.
The base module board is powered by 24 vac. When the
thermostat or room sensor calls for heating, power is sent
from the base module board to W on each of the IGC boards.
An LED on the IGC board will be on during normal opera-
tion. A check is made to ensure that the rollout switches
and limit switches are closed and the induced-draft motors
are not running. The induced-draft motors are then ener-
gized, and when speed is proven with the hall effect sensor
on the motor, the ignition activation period begins. The burn-
ers will ignite within 5 seconds.
When ignition occurs the IGC board will continue to mon-
itor the condition of the rollout and limit switches, the hall
effect sensor, as well as the flame sensor. If the unit is
controlled through a room thermostat set for fan auto.,
45 seconds after ignition occurs, the indoor-fan motor will
be energized and the outdoor-air dampers will open to their
minimum position. If for some reason the overtemperature
limit opens prior to the start of the indoor fan blower, on the
next attempt, the 45-second delay will be shortened to 5 sec-
onds less than the time from initiation of heat to when the
limit tripped. Gas will not be interrupted to the burners and
heating will continue. Once modified, the fan on delay will
not change back to 45 seconds unless power is reset to the
control. If the unit is controlled through a room sensor, the
indoor fan will be operating in the Occupied mode and the
outdoor-air dampers will be in the minimum position.
If the unit is controlled with a room sensor in the Unoc-
cupied mode, the indoor fan will be energized through the
IGC board with a 45-second delay and the outside-air damp-
ers will move to the IAQ (indoor air quality) position (gen-
erally closed in the Unoccupied mode). If IAQ is not enabled,
dampers will move to the minimum position.
When additional heat is required, W2 closes and initiates
power to the second stage of the main gas valves. When the
thermostat is satisfied, W1 and W2 open and the gas valves
close interrupting the flow of gas to the main burners. If the
call for W1 lasted less than 1 minute, the heating cycle will
not terminate until 1 minute after W1 became active. If the
unit is controlled through a room thermostat set for fan auto.,
the indoor-fan motor will continue to operate for an addi-
tional 45 seconds then stop and the outdoor-air dampers will
close. If the overtemperature limit opens after the indoor mo-
tor is stopped within 10 minutes of W1 becoming inactive,
on the next cycle the time will be extended by 15 seconds.
The maximum delay is 3 minutes. Once modified, the fan
off delay will not change back to 45 seconds unless power
is reset to the control. If the unit is controlled through a room
sensor, the indoor fan will be operating in the Occupied mode
and turned off after 45 seconds in the Unoccupied mode.
50 SERIES UNITS — The control module is powered by
24 vac. If the unit is controlled with a room sensor, the fan
will run continuously in the Occupied mode, with the outside-
air damper in the minimum position. If the unit is controlled
through a room thermostat (with FAN set to AUTO), upon
a call for heat the first stage of heat is energized, the indoor-
fan motor will turn on, and the outdoor-air damper will move
to the minimum position. Upon a call for additional heat (if
the unit is equipped with a two-stage heater), the second stage
of heat is energized. When the call for heat is satisfied, the
heaters will deenergize. The indoor-fan motor will also de-
energize (unless controlled by a room sensor) and the outdoor-
air damper will move to the closed position.
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