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evaporator, the chiller is enabled to run
only if the required flow proving device
indicates there is flow present. If the chiller
is active and flow is lost; the chiller will
lock out and an alarm is generated.
• Low Suction Pressure – To protect the
compressors and evaporator, if the
refrigerant suction pressure drops below
the set point value for a specified period of
time, a safety trip occurs. This safety is
bypassed when the compressor is in a
Pump Down state.
• Unsafe Suction Pressure – To protect the
compressors and evaporator, if the
refrigerant suction pressure drops below
the set point value for a specified period of
time, the chiller will immediately lock out,
and an alarm is generated.
• Heat Exchanger Freeze Protection – To
protect the evaporator from low water
temperatures, the chilled water
temperature is monitored inside the core of
the evaporator and leaving the evaporator.
If these temperatures fall below their set
point temperatures for the set period of
time, the entire system will lock out and an
alarm is generated.
• Active Freeze Protection System –
Working in conjunction with the low
suction pressure and freeze protection
safeties to avoid nuisance safety trips, the
active freeze protection valve is opened
when the suction pressure goes below the
lower set point value and warms the
evaporator until the freeze conditions are
abated. The valve will stay open until the
suction pressure rises safely above the
upper set point level.
• High and Low Discharge Pressure, High
and Low Superheat, High and Low
Compressor Amps – The compressors
will be locked out if any one of these
control variables rises above the upper set
point value or falls below the lower set
point value for the set amount of time for
each, and an alarm is generated.
• Optional Phase/Power Monitor – The
factory-installed phase/power monitor
continuously monitors the incoming power
supply to the chiller for low voltage, phase
rotation reversal, loss of phase and phase
imbalance. Should one of these parameters
be incorrect, the phase/power monitor
relay will lock out (de-energize) and the
fault LED on the monitor will blink. The
unit controller will indicate the lockout,
and an alarm is generated.
As an additional layer of system protection,
mechanical high- and low-pressure switches
are used in conjunction with the refrigerant
circuit high- and low-pressure transducers and
unit controller.
Standard Peripheral Control Features
The following peripheral control features and
program logic come standard on all FWCD
Series chillers. Designated terminals on the
field connection terminal strip in the control
panel are provided for field connection of:
• Remote Off/Auto (dry contact closure
from a remote device - input)
• Required Chilled Water Flow Proving
Device (dry contact closure from a remote
device - input)
• Remote Alarm (dry contact closure to a
remote device - output)
• Required Chilled Water Pump Enable
(dry contact closure for 1 chilled water
pump - output)
• Condenser Water Pump Enable (dry
contact closure for 1 condenser water
pump - output)
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General