Controls - Carrier GEMINI SELECT 38APS025-065 Product Data

Controls (cont)
Sequence of operation
Cooling, constant volume (CV) units — On power up,
the control module will activate the initialization software.
The initialization software will determine the unit configu-
ration and also initialize any controls loops and input/out-
put devices. All alarms and configurations are saved in
memory and maintained during power outages. All alarms
will be maintained in memory and must be cleared through
the display.
Constant volume conventional thermostat con-
trol — If the unit is equipped with a conventional thermo-
stat with Y1, Y2, connections then the control will per-
form the following sequence.
If Y1 is closed and the fan status input is closed then the
control will stage the first compressor be sequenced on. If
Y2 closes the control will stage the second compressor on.
For units configured for TSTAT Multi, the control will add
and remove compressor stages to maintain the low and
high demand leaving air set points. If Y1 is closed at least
one compressor stage will be turned on.
Constant volume space temperature sensor con-
trol — If the space temperature operation has been select-
ed using a T55, T56, or T58 sensor then the following log-
ic will be used to control the operation of the unit. If the
94
internal timeclock is used, the control module determines
the occupancy state based on the system time schedules.
The set point for cooling is configurable through the dis-
play. If a T56 sensor is being used then the set point can
be shifted by has much as 5 degrees. If the space tempera-
ture goes above the cooling set point then the unit will go
into Cooling mode. The set point will depend on the space
temperature. Once the fan status input is closed then the
compressors will be sequenced on to maintain either the
low or high load temperature set points.
Variable air volume control — On power up, the con-
trol module will activate the initialization software. The ini-
tialization software will determine the unit configuration
and also initialize any controls loops and input/output de-
vices. All alarms and configurations are saved in memory
and maintained during power outages. All alarms will be
maintained in memory and must be cleared through the
display.
The unit will first determine the mode of operation. If
the Cooling mode is required and the fan status input
closed, then the controlling set point will be the leaving air
temperature set point then the leaving-air temperature will
sequence to compressors on and off using a PID control
loop.