Carrier Transicold X4 7300, Operation & Service Manual

Page: 76 / 282

4–3 62-11637
4.4 MODES OF OPERATION
Once the engine is started, the system will operate in
Start-Stop or Continuous Operation energizing and de-
energizing the following components:
• SV1 - Energized (closed) through main micro-
processor terminal 3MM-1.
• SV2 - Energized (opened) through main micro-
processor terminal 3MM-2.
• SV4 - Energized (opened) through main micro-
processor terminal 3MM-3.
• SPEED - Transition to high speed when main
microprocessor provides a signal through the
CAN system to the ENCU.
• CLUTCH - Energized (engaged) through main
microprocessor terminal 3MM-11.
• UL1 - Energized (unloaded) through main micro-
processor terminal 3MM-6.
• UL2 - Energized (unloaded) through main micro-
processor terminal 3MM-8.
• CSMV - Opened and closed by the Stepper
Valve Module (SVM) through module terminals
2SVM
− 2, 2SVM − 3, 2SVM − 4 & 2SM − 5.
• EVXV - Opened and closed by the Stepper
Valve Module (SVM) through module terminals
2SVM
− 6, 2SVM − 7, 2SVM − 8, 2SVM − 9 &
2SVM − 10.
4.4.1 Pull Down/Pull-Up
When in Pulldown or Pull-up, the refrigeration system
will operate with the compressor loaded (six cylinders)
and in high speed.
Pulldown/Pull-Up will be entered:
• following a Start-Up.
• following a setpoint change.
• following an operational change (Start-Stop
Operation vs Continuous Operation).
• following a defrost termination.
• following a pretrip termination.
• when in a Start-Stop ON Cycle and all other
Stop Parameters have been met except the
compartment temperature Stop Parameter.
Pulldown/Pull-Up will end when one of the following
occurs:
• when the control system is calling for low speed.
• when in Start-Stop Operation and the compart-
ment temperature Stop Parameter has been sat-
isfied while one or more of the other Stop
Parameters has not.
• when in continuous operation and the control sys-
tem has calculated pulldown or pull-up is to end.
4.4.2 Cooling
In the Cool Mode, the control system will operate the
unit controls as follows:
NOTE
1. The selected temperature control sensor deter-
mines if the unit is running high or low speed.
2. The control system monitors the suction pres-
sure & ambient temperature and calculates the
system load. If required, the system will unload
cylinders and modulate the CSMV to keep the
load within required limits. Refer to
Section
4.11.3 and Section 4.11.4 .
3. Modulated to control superheat.
4.4.3 Heating
When in Heat Mode, the control system will operate the
unit controls as follows:
• SV4 - SV4 is open.
• CSMV/EVXV - CSMV & EVXV are 100% open.
• Clutch - The clutch is engaged.
• SV1 - SV1 is closed. If discharge pressure rises
to 390psig (26.5 bar), the SV1 valve will open for
1 second and continue to cycle as often as every
30 seconds to reduce the pressure to less than
390psig (26.5 bar).
• Engine Speed - When in Start-Stop Operation
the engine will remain in high speed to raise the
control temperature as quickly as possible.
When in Continuous Operation the engine will
be in high speed when control temperature is
greater than 3.6°F (2°C) below set point and will
remain in high speed until the control tempera-
ture is raised to 3.2°F (1.8°C) below setpoint.
• Unloaders - When in Start-Stop Operation the
compressor will remain fully loaded to raise the
control temperature as quickly as possible.
When in Continuous Operation the compressor
will be fully loaded when control temperature is
greater than 2.7°F (1.5°C) below set point. UL1
& UL2 will unload when the control temperature
is raised to 2.3°F (1.3°C) below setpoint.
• SV2 - SV2 is closed. When conditions allow,
additional heating capacity is obtained by open-
ing SV2 to allow additional refrigerant to be
metered into the hot gas cycle (through the
evaporator expansion valve). This flow is estab-
lished (even though SV1 is closed) by the hot
gas bypass line which functions to raise the
receiver pressure.
SV1 SV2 SV4 Engine
Speed
Open Open Closed See Note 1
Clutch
Output
UL1 & UL2 CSMV EVXV
Engage See Note 2 See Note 2 Se Note 3