Product manual

IOMM ACR/AGR-1 69
The MicroTech controller alarms can either be of the manual reset type or the auto reset type. Critical
alarm conditions such as High Condenser Pressure, Refrigerant Freeze Protection, and Low
Evaporator Pressure which protect against equipment damage are manual reset, which means they
lockout compressor operation and must be cleared at the MicroTech keypad before operation can
resume. Auto-clearing alarm conditions cause the compressors to shut off on the affected circuit until
the condition is corrected. When the condition is corrected, the chiller will resume normal operation
on that circuit, provided the anti-cycle timers have cleared and sufficient load exists. All pre-alarm
conditions are auto clearing. After the controller stages down the unit on an alarm condition and the
potential alarm condition has been avoided, the alarm will clear itself and the unit will resume normal
operation. If the alarm condition is not avoided, the alarm will be logged on the MicroTech display,
causing lockout of compressors. Thus, the alarm must be manually cleared.
When a McQuay Chiller with a MicroTech controller is used with the McQuay RMS (Remote
Monitoring and Sequencing) Panel, the user must note that alarm nomenclature varies. The RMS has
three possible categories of alarms: faults, problems, and warnings. The chiller alarm condition
corresponds with the RMS “fault” condition. Thus, there are system and circuit faults. Chiller pre-
alarm conditions correspond to the RMS “problem” designation. Reciprocating chillers do not have
warning alarms.
Circuit Alarm Conditions
The “Circuit Alarm Conditions” are those alarms that 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 that 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 that 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 that 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.