Unit installation

96 ACZ / AGZ-BM IOMM ACZ/AGZ-3
Events (Limit Alarms)
The following alarms do not cause a rapid shutdown, but limit operation of the chiller in some way
as described in the Action Taken column. All limit alarms do the following while active:
• Appear in the active alarm menu
• Light the alarm signal on the controller
• Log the alarm in the Alarm Log.
Table 56, Limit Alarms
Description Occurs When: Action Taken Reset
High Condenser
Pressure Stage Down
Any Comp on Circuit Running AND
Pressure > High Condenser Stage
Down setpoint
Stage off one compressor
on the circuit
Condenser Press
drops below
(SP – 100psi) AND
OAT drops 5
o
F
CT
Low Evaporator
Pressure – Hold
One Comp Running on Circuit AND
Pressure < Low Evap Pressure–
Hold setpoint
Inhibit staging on of
additional compressors on
the circuit
Evap Press rises
above (SP + 8psi)
CT
Low Evaporator
Pressure – Unload
Both Comp Running on Circuit AND
Pressure < Low Evap Pressure–
Unload setpoint
Stage off one compressor
on the circuit
Evap Press rises
above (SP + 10 psi
+
Stage Up Delta T)
CT
Can’t Pumpdown
Circuit State = Pumpdown for more
than 60 sec
Shut off circuit Circuit shutdown CT
NOTE: UT = entire Unit (Both Circuits), CT = that Circuit Only
Logging
When a shutdown or limit alarm occurs, the description, date, and time are stored in the active alarm
buffer corresponding to that alarm (viewed on the Alarm Active screens), and also in the alarm
history buffer (viewed on the Alarm Log screens). The active alarm buffers hold a record of all
current alarms. The active alarms can be cleared by pressing the Edit (Enter) key when the end of
the list has been reached by scrolling. Active alarms may only be cleared after the appropriate
password level is active.
A separate alarm log stores the last 25 alarms and events to occur. When an alarm or event occurs, it
is put into the first slot in the alarm log and all others are moved down one, dropping the last entry.
The alarm log stores the date and time of the occurrence, as well as a list of other parameters. These
include unit state and OAT for all alarms. If the alarm is a circuit alarm, then the circuit state,
refrigerant pressures and temperatures, and number of fans on are also stored. The parameters may
be accessed by scrolling to the last line on the alarm log screen (similar to a setpoint).
Control Logic
Unit Enable
Enabling and disabling the chiller is controlled by the Unit Enable Setpoint with options of OFF and
ON. This setpoint can be altered by the Unit OFF input, Remote input, Keypad entry, and BAS
request. The Control Source SetPoint determines which sources can change the Unit Enable
Setpoint with options of SWITCHES, KEYPAD or NETWORK (BAS).
Changing the Unit Enable Setpoint can be accomplished according to the following table.