3-6T-309
1. Bulb mode code Cd35 is set to “Nor.”
2. Dehumidification code Cd33 is set to “Off.”
3. The user changes the set point to one
that is in the frozen range.
When bulb mode is disabled by any of the above, the
evaporatorfanoperationfordehumidificationrevertsto
“alt”andtheDTSterminationsettingresetstothevalue
determinedbycontrollerconfigurationvariableCnF41.
3.3.10 Temperature Control -- Frozen Mode
With configuration variable CnF26 (Heat Lockout
Temperature)setto --10_Cthefrozenmodeofoperation
is active with set points at or below --10_C(+14_F).
Withthevariablesetto --5_C,thefrozenmodeisactive
at or below --5_C(+23_F).
When in the frozen mode the controller maintains the
return air temperature at set point, the RETURN
indicatorlightwillbeilluminatedonthedisplaymodule
and the default reading on the display window will be
the return air probe reading.
When the return air temperature enters the in-range
temperature tolerance as selected at function code
Cd30, the in-range light will energize.
3.3.11 Frozen Mode -- Conventional
Frozen range cargos are not sensitive to minor
temperature changes. The method of temperature
control employed in this range takes advantage of this
facttogreatlyimprovetheenergyefficiencyoftheunit.
Temperaturecontrolinthefrozenrangeisaccomplished
bycyclingthecompressoronandoffastheloaddemand
requires.
When cooling from a temperature that i s more than
2.5_C (4.5_F)abovesetpoint, thesystemwillbe in the
frozenpulldownmode.Itwilltransitiontoeconomized
operation with a target SMV position of 100% open.
However, pressure and current limit functions may
restrict the valve, if either exceeds the preset value.
Once set point is reached, the unit will transition to the
frozen steady state mode. (Economized operation with
maximumallowedsuction m odulating valve opening.)
When temperature drops to set point minus 0.2_Cand
thecompressorhasrunforatleastfiveminutes,theunit
will transitionto thefrozenidle mode. The compressor
is turned off and the evaporator fans continue to run to
circulate air throughout the container. If temperature
rises above set point +0.2_C, the unit will transition
back to the frozen steady state mode.
If the temperaturedrops 10_C below setpoint, the unit
will transition to the frozen “heating” mode. In the
frozen heating mode the evaporator fansare brought to
high speed. The unit will transition back to the frozen
steadystatemodewhenthetemperaturerisesbacktothe
transition point.
3.3.12 Frozen Mode -- Economy
In order t o activate economy frozen mode operation, a
frozen set point temperature must be selected. The
economymodeisactivewhenfunctioncodeCd34isset
to “ON”. When economy mode 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 t he control
temperatureis less than orequal to the setpoint -- 2_C.
After an off-cycle period of 60 minutes, the unit will
turn on high 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.,theunitwillrestarttherefrigerationsystemand
continue to cool 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.
3.4 CONTROLLER ALARMS
Alarm display is an independent controller software
function. If an operating parameter is outside of
expected range or a components does not return the
correct signals back to the controller an alarm is
generated. A listing of the alarms is provided in
Table 3-6.
The alarm philosophy balances the protection of the
refrigeration unit and thatoftherefrigerated cargo.The
action taken when anerror isdetected alwaysconsiders
thesurvivalofthecargo.R echecksaremadetoconfirm
that an error actually exists.
Somealarmsrequiringcompressorshutdownhavetime
delaysbeforeandafterto tryto keepthe compressoron
line. An example is alarm code “LO”, (low main
voltage), when a voltage drop of over 25% occurs, an
indication is given on the display, but the unit will
continue to run.
When an Alarm Occurs:
a. The red alarm light will illuminate for alarm code
numbers 13, 17, 20, 21, 22, 23, 24, 25, 26, and 27.
b. If a detectable problem is found to exist, its alarm
code will be alternately displayed with the set point
on the left display.
c. Theusershouldscrollthroughthealarmlistto deter-
minewhatalarmsexistorhaveexisted. Alarmsmust
bediagnosedandcorrectedbeforetheAlarmListcan
be cleared.
To Display Alarm Codes :
a. While in the Default Display mode, press the
ALARMLISTkey.ThisaccessestheAlarmListDis-
playMode,whichdisplaysanyalarmsarchivedinthe
Alarm Queue.
b. The alarm queue stores up to 16 alarms in the se-
quence in which they occurred. The user may scroll
through the list by depressing an ARROW key.
c. The left display will show “AL##,” where ## is the
alarm number sequentially in the queue.
d. The right display will show the actual alarm code.
“AA##”will displayforanactivealarm,where“##”
isthealarmcode.Or“IA##”will displayfor aninac-
tive alarm. S ee Table 3-6.
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