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SECTION 3
3-17 T-268-07
3.1.7.2 Frozen R ange Below --10_C(+14_F), or
-- 5 _C(+23_F) Optionally
For set points below -- 1 0 _C(+14_F), or --5_C(+23_F)
optionally, theController maintains RETURN air at the
set point temperature using the following modes of
operation:
a. Operation in the conventional mode
(Code 33 OFF)
The return air probe is used for control and is so
indicated by the LED on the display board.
The Frozen temperature range is not sensitive to minor
temperature changes. The method of temperature
control employed in this range takes advantage of this
fact to greatly improve theenergy efficiency of theunit.
Temperature control in the Frozen range at or below
-- 1 0 _C(+14_F), or --5_C(+23_F) optionally, is
accomplished by cycling the compressor on and off as
the load demand requires.
Ifthereturnairtemperaturein the containerdrops0.2_C
(0.4_F)below theset pointtemperature, thecompressor
is cycled off. When the temperature is greater than
0.2_C (0.4_F) above the set point and the three minute
time delay has been met, the compressor will restart.
The unit will always operate at full capacity, with both
the suction m odulation (SMV) and suction solenoid
(SSV) valves fully open unless suction solenoid
override or current limiting is activated. See section
2.10 for explanation of suction solenoid override.
To prevent on/off cycling of the compressor from
occurring, a three minute compressor off time must be
satisfied before the compressor will restart. Under a
condition of rapidly changing return air temperature,
the time delay may allow the return air temperature to
rise slightly more than 0.2_C (0.4_F) above the set
point temperature before the compressor can restart.
b. Operation in the economy mode (Code 34 OFF)
The economy mode is deactivated by setting function
code Cd34 to the “OFF” status. Economy mode has no
active display indicator to show that it is enabled, so a
manual display of function code Cd34 must be
performed to enable the user to see its current status. A
second way to deactivate economy mode is to change
the set point. Once economy mode is deactivated, the
system will return to normal control mode operations.
In order to achieve economy mode frozen operation, a
frozen set point temperature must be selected PRIOR to
activatingeconomymode. When economym ode frozen
is active, the system will perform normal frozen mode
operations except that the entire refrigeration system,
excluding the Controller, will be turned off when the
controltemperatureisless than orequalto theset point--
2_C, (i.e., the set point is set at --11_C and the operator
subtracts --2_C, the result will equal --13_C). After an
off-cycle p eriod o f60minutes, theunit will t urn onhigh
speed evaporator fans for three minutes, and then check
the control temperature. If the control temperature is
greater than or equal to the set point + 0. 2_C., the unit
will restart therefrigeration system and continue tocool
until the previously mentioned off-cycle temperature
criteria are met. If the control temperature is less than
the set point + 0.2_C, the unit will turn off the
evaporator fans and restart another 60 minute off-cycle.
c. Operation in the bulb mode (Code 35 OFF)
The unit will not run in bulb mode if a frozen range set
point is selected. As described in section 3.1.7.1.d., if a
frozen set point is selected, dehumidification is
deactivatedand thetemperature above which DTSmust
go during defrost resets to 25.6_C(78_F).
3.2 PRE-TRIP DIAGNOSTICS
CAUTION
Pre-trip inspection should not be performed
with critical temperature cargoes i n the
container.
NOTE
When Pre-Trip is initiated, dehumidification
and bulb mode will be deactivated. At the
completion of Pre-Trip, dehumidification and
bulb mode must be turned back on again.
Pre-trip Diagnostics is an independentmode which will
suspend the normal Control Mode activities when
initiated by theuser.With pre-tripdiagnostics, eitherall
the pre-trip tests can be executed in a defined sequence
(Auto Mode), or one of the pre-trip tests can be selected
to be executed (Manual Mode), based on the sequence
of key selections made.
a. Starting and Terminating Pre-Trip
NOTE
Prior to starting tests, verify that C ontroller
functioncodesCd04, Cd05,Cd06 andCd07are
operational. Otherwise, tests may fail
incorrectly. All alarms must be rectified and
cleared.
A Pre-trip selection menu is displayed by pressing the
PRE-TRIP key. This accesses a test selection menu. If
no selection i smade, thepre-tripmenu selectionprocess
will terminate automatically. Pre-Trip will terminate if