Carrier Transicold X4 7300, Operation & Service Manual

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62-11637 4–16
8. Start/Stop Override.
If the system is running in a Start/Stop run cycle, and
the minimum run time has expired and the compart-
ment temperature is not at setpoint, both unloaders will
be loaded to increase the unit capacity so that set point
may be reached more quickly, and allow an Off Cycle.
9. Continuous Run Low Speed Null Mode.
UL1 and UL2 will load and unload periodically as the
control system makes adjustments in the system’s
capacity to maintain compartment temperature when it
is close to setpoint.
10. Range Protect.
When the unit is operating in Range Protect IntelliSet
and the box temperature is inside the protected range,
and at least one other condition to allow an Off Cycle is
not met (i.e. Battery Volts, Battery Charging Amps,
Minimum Run Time, Engine Coolant Temperature)
UL1 & UL2 will unload.
4.11.4 CSMV Control Overrides
1. Engine Rack (Throttle) Position Limit.
The control system monitors the engine throttle posi-
tion reading provided by the ENCU rack position sen-
sor (RPS). If the position is greater than or equal to the
maximum position the CSMV will move toward the
closed position as required to lower the engine load,
and thereby, the rack position.
2. Engine RPM.
When the engine throttle position has been more than
90% for three seconds the control system will monitor
actual engine RPM verses desired engine RPM (if the
actual RPM is less than the desired RPM, this is
defined as engine RPM droop.) If the droop is above 30
RPM, the CSMV will move toward the closed position
as required to eliminate the droop by lowering the load
on the engine.
3. Discharge Pressure Control.
The control system monitors the discharge pressure.
When the pressure is above the calculated maximum
(absolute maximum is 435.3 PSIG = 29.62 bar), the
CSMV will move toward the closed position as required
to bring the pressure below 400.0 = 27.22 bar).
4. High Suction Pressure Control.
The control system monitors the suction pressure.
When the pressure is above the calculated maximum
the CSMV will move toward the closed position as
required to lower the pressure.
5. Low Suction Pressure Control.
The control system monitors the suction pressure.
When both UL1 & UL2 are unloaded and the pressure
is below the calculated minimum the CSMV will move
toward the open position as required to raise the pres-
sure.