72 AGR 055A through 100A IOMM AGR
Circuit Alarm Conditions
The “Circuit Alarm Conditions” are those alarms which only affect one circuit and can stop the
compressors of that circuit. These alarms are:
• Compressor Motor Protection
• High Condenser Pressure
• Mechanical High Pressure Switch
• Low Evaporator Pressure
• Refrigerant Freeze Protection
• Bad Pressure Transducer
The chiller must have the manual reset system alarm conditions cleared before normal operation can
resume. If the alarm which occurred is an auto-clearing alarm, once the condition has corrected, the
chiller will resume normal operation provided the anti-cycle timers have cleared and sufficient load
exists.
System Alarm Conditions
The “System Alarm Conditions” are those alarms which are common to both refrigeration circuits
and require all compressors to be temporarily shut off or locked out, whichever applies. The
following alarm conditions are checked continuously during all modes of operation by the controller.
If one of the following alarm conditions is detected, the mode of the controller will switch to
“Off:Alarm “. The controller disables all compressor operation by turning off all Compressor
Enable Outputs. Alarm Output #0 will be turned on to notify the operator of the alarm condition.
The red “Alarm Status” light on the front of the control panel will be solid on the alarm condition
and the MicroTech display will show the current alarm condition.
• System alarm conditions are:
• Loss of Water Flow
• Bad Phase /Voltage
• Chilled Water Freeze Protection
• Volts Ratio Protection
• Bad Leaving Water Sensor
The chiller must have the manual reset system alarm conditions cleared before normal operation can
resume. If the alarm which occurred is an auto-clearing alarm, once the condition has corrected, the
chiller will resume normal operation provided the anti-cycle timers have cleared and sufficient load
exists.
Sequence of Operation
Off Conditions
With power supplied to the unit, 115Vac power is applied through the control fuse F1 to the
compressor crankcase heaters (HTR1-2), the compressors motor protectors (MP1-2), the evaporator
heater and the primary of the 24v control circuit transformer. The 24V transformer provides power
to the MicroTech controller and related components. With 24V power applied, the controller will
check the position of the front panel System Switch. If the switch is in the “stop” position the
chiller will remain off and the display will indicate the operating mode to be OFF:System Sw. The
controller will then check the PumpDown Switches. If either switch is n the “stop” position, that
circuit’s operating mode will be displayed as OFF:PumpDownSw. If the remote Start/Stop Switch is
open, the chiller will be OFF:Remote Sw. The chiller may also be commanded off via the
communications network if a separate System Master Panel is installed. The display will show
OFF:Remote Comm if this operating mode is in effect.
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