3--21
T-334
Table 3--6 Controller Alarm Indications (Sheet 2 of 4)
AL21 Micro Circuit Fuse
Open (18 VAC)
Alarm 21 is triggered by one of the fuses (F1/F2) being opened on 18 VAC power
supply to the controller. The suction modulation valve (SMV) will be opened and
current limiting is halted. Temperature control will be maintained by cycling the
compressor.
AL22 Evaporator Fan
Motor Safety
Alarm 22 responds to the evaporator motor internal protectors. On units with Nor-
mal Evaporator Fan Operation (CnF32 set to 2EFO), the alarm is triggered by
opening of either internal protector. It will disable all control units until the motor
protector resets. On units with Single Evaporator Fan Capability (CnF32 set to
1EFO), the alarm is triggered by opening of both internal protectors. It will disable
all control units until a motor protector resets.
AL23 Loss of Phase B
Alarm 23 is triggered if low current draw is detected on phase B and IPCP, HPS
or IPEM is not tripped. If the compressor should be running, the controller will
initiate a start up every five minutes and trigger off if current reappears. If the
evaporator fan motors only should be running, the alarm will trigger off if current
reappears. This alarm triggers failure action C (evaporator fan only) or D (all ma-
chinery off) of Function Code Cd29 if the unit has a perishable set point. Failure
action D (all machinery off) is triggered if the unit has a frozen set point.
AL24 Compressor Motor
Safety
Alarm 24 is triggered when compressor is not drawing any current. It also triggers
failure action “C” or “D” set by function Code 29 for perishable set point, or “D” for
frozen set point. If the compressor should be running, the controller will initiate a
start up every five minutes and trigger off, if current reappears. This alarm will
remain active until compressor draws current.
AL25 Condenser Fan Mo-
tor Safety
Alarm 25 is triggered by the opening of the condenser motor internal protector
and will disable all control units except for the evaporator fans. This alarm will
remain active until the motor protector resets. This alarm triggers failure action C
(evaporator fan only) or D (all machinery off) of Function Code Cd29 if the unit
has a perishable set point. Failure action D (all machinery off) is triggered if the
unit has a frozen set point.
AL26
All Supply and Re-
turn temperature
Control Sensors
Failure
Alarm 26 is triggered if the controller determines that all of the control sensors
are out-of-range. This can occur for box temperatures outside the range of -50C
to +70C (-58F to +158F). This alarm triggers the failure action code set by Func-
tion Code Cd29.
AL27 A/D Accuracy Fail-
ure
The controller has a built-in Analog to Digital (A-D) converter, used to convert
analog readings (i.e. temperature sensors, current sensors, etc.) to digital read-
ings. The controller continuously performs calibration tests on the A-D converter.
If the A-D converter fails to calibrate for 30 consecutive seconds, this alarm is
activated.This alarm will be inactivated as soon as the A-D converter calibrates.
AL28 Low Suction Pres-
sure
Alarm 28 is triggered if suction pressure is below 2 psia and alarm 66 (Suction
Pressure Transducer Failure) is not active. This alarm will be inactivated when
suction pressure rises above 2 psia for three continuous minutes. This alarm trig-
gers failure action C (evaporator fan only) or D (all machinery off) as determined
by User Selectable Failure Response if the unit has a perishable set point. Fail-
ure action D (all machinery off) if the unit has a frozen set point. Reset SMV.
AL50 Fresh Air Position
Sensor (VPS)
Alarm 50 is activated whenever the sensor is outside the valid range. There is a
4 minute adjustment period where the user can change the vent position without
generating an alarm event. The sensor requires 4 minutes of no movement to
confirm stability. If the vent position changes at any point beyond the 4 minute
adjustment period, the sensor will generate an alarm event. The alarm is trig-
gered off when the unit power cycles and the sensor is within valid range.
AL51 Alarm List Failure
During start-up diagnostics, the EEPROM is examined to determine validity of its
contents. This is done by testing the set point and the alarm list. If the contents
are invalid, Alarm 51 is activated. During control processing, any operation in-
volving alarm list activity that results in an error will cause Alarm 51 to be acti-
vated. Alarm 51 is a “display only” alarm and is not written into the alarm list.
Pressing the ENTER key when “CLEAr” is displayed will result in an attempt to
clear the alarm list. If that action is successful (all alarms are inactive), Alarm 51
will be reset.
AL52 Alarm List Full
Alarm 52 is activated whenever the alarm list is determined to be full at start-up
or after recording an alarm in the list. Alarm 52 is displayed, but is not recorded in
the alarm list. This alarm can be reset by clearing the alarm list. This can be done
only if all alarms written in the list are inactive.
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