Installation and Maintenance Manual

Controls Interface
RLC-SVX09H-EN 137
Active Chilled Water Setpoint
The active chilled water setpoint is the setpoint that is
currently in use. It results from the logical hierarchy of
setpoint arbitration by the main processor. It will be
displayed to 0.1 degrees Fahrenheit or Celsius.
Touching the double arrow to the left of the Active Chilled
Water Setpoint will take the user to the active chilled water
setpoint arbitration sub-screen.
Active Chilled Water Subscreen
The active chilled water setpoint is that setpoint to which
the unit is currently controlling. It is the result of arbitration
between the front panel, BAS, schedule, external, and
auxiliary setpoints (schedule and auxiliary not shown in
the following diagram), which in turn may be subjected to
a form of chilled water reset.
The chilled water reset status area in the right most column
will display one of the following messages
• Return
Current Limit
The compressor is running and its capacity is being limited by high currents. The
current limit setting is 120% RLA (to avoid overcurrent trips) or lower as set by the
compressor's "share" of the active current limit (demand limit) setting for the entire
chiller.*
High Condenser Pressure Limit
The circuit is experiencing condenser pressures at or near the condenser limit
setting. Compressors on the circuit will be unloaded to prevent exceeding the
limits.*
Low Evaporator Rfgt Temperature Limit
The circuit is experiencing saturated evaporator temperatures at or near the Low
Refrigerant Temperature Cutout setting. Compressors on the circuit will be
unloaded to prevent tripping. *
Hot Start Limit
This mode will occur if the leaving evaporator water temperature exceeds 75ºF (for
SW version 6.30 and earlier) or 90ºF (for software 7.01 and later) at the point at
which the step load for the respective circuit would be desired. This is often the case
in a high water temperature pull-down. While in this mode, no compressor on the
circuit will be allowed to load past its minimum load capacity step, but it will not
inhibit other compressors from staging on. This mode is necessary to prevent
nuisance trips due to Compressor Overcurrent or High Pressure Cutout. Reasonable
pull-down rates can still be expected despite this limit, since the compressor's
capacity even at partial load is much greater at high suction temperatures.
Shutting Down The circuit is preparing to de-energize the compressor.
Preparing Shutdown Sub-mode
Operational Pumpdown
The circuit is in the process of shutting down by performing an operational
pumpdown just prior to stopping the last running compressor. The EXV is
commanded closed. Pumpdown will terminate when both the liquid level and the
evap pressure are low (below specific criteria) or after a specific time has expired.
Compressor Unloading: min:sec
The compressor is in its run unload time. The number of seconds remaining in run
unload is shown in the submode. The run unload time must expire before the
compressor will shut down.
Misc These sub modes may be displayed in most of the top level circuit modes
Misc. Sub-modes
Service Pumpdown The circuit is currently performing a service pumpdown.
Restart Time Inhibit: min:sec
If there is accumulated Restart Inhibit Time, it must expire before a compressor is
allowed to start.
Table 108. Circuit modes (continued)
Circuit Modes Description
Top Level Mode Further information is provided by the submode
Sub-modes