3-11
T-294-01
Table 3-4. Controller Alarm Indications
Code
No.
TITLE
DESCRIPTION
AL20 Control Circuit Fuse
Open (24 vac)
Alarm 20 is triggered by fuse (F3) opening and will cause the software shutdown
of all control units. This alarm will remain active until the 10 amp fuse is replaced.
AL21 Micro Circuit Fuse
Open (18 vac)
Alarm 21 is triggered by one of the fuses (F1/F2) being opened on 18 volts AC
power supply to the Controller. The suction modulation valve (SMV) will be
opened and current limiting is halted. The compressor will cycle. Temperature
control will be maintained by cycling the compressor.
AL22 Evaporator Fan
Motor Safety
Alarm 22 is triggered by the opening of the evaporator motor internal protector.
This alarm will disable all control units until the motor protector resets.
AL23 KA2--KB10 Jumper
Disconnected
Alarm 23 is triggered by a missing jumper wire. The alarm will stay active until
the jumper wire is reconnected.
AL24 Compressor Motor
Safety
Alarm 24 is triggered by the opening of the compressor motor internal protector.
This alarm will disable all control units except for the evaporator fans and will
remain active until the motor protector resets. Also, refer to code Cd29.
AL25 Condenser Fan
Motor 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 is deactivated if the unit
is operating on water cooled condensing.
AL26
All Supply and
Return Air 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
--50
_
C to +70
_
C (--58
_
F to +158
_
F). This alarm triggers the failure action code
set by Function Code Cd29.
AL27 Probe Circuit
Calibration Failure
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
readings. 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.
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
involving alarm list activity that results in an error will cause Alarm 51 to be
activated.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.
AL53 NiCad Battery Pack
Failure
Alarm 53 is caused by the nicad battery pack being too low of a charge for
battery-backed recording.
NOTE
Check for recharging or replacing battery pack.
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