4–15
62-11637
6. RAT & SAT Alarms.
When the A122 - “CHECK RETURN AIR SENSOR”
and A123 - “CHECK SUPPLY AIR SENSOR” alarms
are both active at the same time the control system will
enter Cargo Protect Mode. Refer to
7. Frozen Setpoint Override.
If the setpoint is in the frozen range and the tempera-
ture is below setpoint, the engine will operate in low
speed.
8. Air Flow.
When operating with a perishable setpoint and the AIR
FLOW Functional Parameter is set to HIGH, the engine
will operate in high speed.
9. Product Shield High Air.
The engine is forced to high speed if the PRODUCT
SHIELD HIGH AIR Configuration is active, refer to
10. High Speed Delay.
Whenever the engine starts, the unit will remain in low
speed according to the Continuous or Start-Stop High
Speed Delay Functional Parameter setting.
11. Start-Stop Frozen Range.
When in Start-Stop Operation with a setpoint in the fro-
zen range after the minimum run time has expired, the
engine will be forced to high speed if the refrigerated
compartment temperature is not yet down to setpoint.
12. High Speed Delay.
Whenever the engine is in low speed, transition to high
speed will be delayed for the HIGH SPEED DELAY
Configuration setting.
13. Range Protect.
When the unit is operating in Range Protect and the
compartment temperature is inside the protected
range, while all other conditions to allow an off cycle
are not met the engine will operate in low speed.
4.11.3
Unloader Control Overrides
This section lists the different factors that determine the
operation (de-energizing / loading and energizing /
unloading) of the unloaders in addition to the unloader
control used in temperature control.
There is a minimum delay of 10 seconds between
LOADING and UNLOADING cylinders under all operat-
ing conditions except when the engine is starting.
NOTE
In all of the following instances UL1 refers to
the Front Unloader and UL2 refers to the
Rear Unloader.
Unloader Overrides, in priority order, are as follows. If
an override only applies or takes effect for one
unloader, continue down the priority list for the other
unloader:
1. High Ambient.
If the ambient temperature is above 120°F (48.9°C)
when the engine starts UL1 and UL2 will both be
unloaded for the first 2 minutes of unit operation.
2. Discharge Pressure.
If discharge pressure is greater than 414.7 PSIG
(22.22 bar) UL1 and UL2 will unload.
3. Engine Power Unloading.
If the actual engine RPM is less than the desired RPM,
this is defined as engine RPM droop. When the system
is running in heating or cooling with the CSMV con-
trolling maximum operating pressure (refer to
) and the engine RPM droop is greater than 30
RPM, UL2 will unload for a minimum of two minutes. If,
the system is operating in cooling and, after 10 sec-
onds in 4 cylinder operation, the engine RPM drop is
still greater than 30 RPM, UL2 will unload for a mini-
mum of two minutes.
4. Throttle Position Delay.
If the unit is running in two or four cylinder operation
due to engine power unloading, and the rack position
sensor is greater than 90%, loading of cylinders will be
delayed until the rack position is less than 90% or for a
maximum of 80 seconds.
5. Low Suction Pressure/High Discharge Pressure.
Unloading is used along with low speed to increase the
suction pressure or decrease the discharge pressure.
These steps in capacity reduction are taken in the fol-
lowing order: 6-cylinder high speed to 4-cylinder high
speed to 4-cylinder low speed to 2-cylinder low speed.
Unloading will take place if the following conditions
occur: discharge pressure is greater than 435 PSIG
(29.6 bar) for 5 seconds or suction pressure is less
than 0 PSIG (0bar) for 30 seconds.
Therefore, if the engine is running in high speed 6 cyl-
inder operation and one of the conditions listed above
occurs, UL1 will be unloaded (6 to 4 cylinders) and the
engine will remain in high speed. If the discharge pres-
sure does not drop to less than 410 PSIG or suction
pressure does not increase to above 5 PSIG, the
engine will transition to low speed and the compressor
will remain running on 4 cylinders. If the condition still
does not change, UL2 will unload and the compressor
will operate on 2 cylinders, still in low speed.
Once the engine transitions to low speed, or one or
both of the unloaders unload due to these conditions
the unit will remain in low speed, and the unloader(s)
will remain unloaded for a minimum of 5 minutes.
6. Defrost.
Refer to
.
7. Cargo Protect Mode.
Refer to
.
Summary of Contents for Transicold X4 7300
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