Unit installation

32 OMRCPMICRO
Safety Systems
MicroTech continuously performs self-diagnostic checks, monitoring all system temperatures, pressures and
safeties, and will automatically shut down a refrigerant circuit or the entire unit should a fault occur. The cause
of the shutdown, time and date of occurrence and limited conditions at the time of alarm will be retained in
memory and can be displayed for operator review. Current alarm conditions are displayed on Menus 24 and 25
by pressing the "Alarms" category on the keypad. MicroTech also records the type, time and date of previous
faults (see Menus 26 and 27).
MicroTech has several safety systems to safeguard against potential damage of the chiller equipment. There
are alarm and pre-alarm conditions. Alarm conditions cause the compressors to shut off and/or lock out. Pre-
alarm conditions cause the unit to stage down in capacity in an attempt to avoid an alarm condition. For alarm
conditions, the red "Alarm Status" light on the control panel will be solid. When an alarm or a pre-alarm
condition exists, the MicroTech display automatically switches to the alarm menu to alert the user of the
condition.
MicroTech 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. Autoclearing 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 autoclearing. After the controller stages down the unit
on a pre-alarm condition and the potential alarm condition has been avoided, the alarm will clear by 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 Reciprocating Chiller with MicroTech 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.