McQuay AGS 225D, Operating Manual

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4 OM AGSD-1
Controller Features
•
Readout of the following temperature and pressure readings:
•
Entering and leaving chilled water temperature
•
Saturated evaporator refrigerant temperature and pressure
•
Saturated condenser temperature and pressure
•
Outside air temperature
•
Suction line, liquid line, and discharge line temperatures
−
calculated superheat for
discharge and suction lines
•
Oil pressure
•
Automatic control of primary and standby chilled water pumps. The control will start one
of the pumps (based on lowest run-hours) when the unit is enabled to run (not necessarily
running on a call for cooling) and when the water temperature reaches a point of freeze
possibility.
•
Two levels of security protection against unauthorized changing of setpoints and other
control parameters.
•
Warning and fault diagnostics to inform operators of warning and fault conditions in plain
language. All events and alarms are time and date-stamped for identification of when the
fault condition occurred. In addition, the operating conditions that existed just prior to an
alarm shutdown can be recalled to aid in isolating the cause of the problem.
•
Twenty-five previous alarms and related operating conditions are available.
•
Remote input signals for chilled water reset, demand limiting, and unit enable.
•
Test mode allows the service technician to manually control the controllers’ outputs and
can be useful for system checkout.
•
Building Automation System (BAS) communication capability via L
ON
W
ORKS
®
,
Modbus
®
, or BACnet
®
standard protocols for all BAS manufacturers-simplified with
McQuay’s Protocol Selectability
™
feature.
•
Pressure transducers for direct reading of system pressures. Preemptive control of low
evaporator pressure conditions and high discharge temperature and pressure to take
corrective action prior to a fault trip.