System information
26
Other types of override events do not override control guide
vane or VFD operation, but are reported:
• High compressor discharge temperature override — If
the COMP DISCHARGE TEMP is greater than the
COMP DISCHARGE ALERT threshold, then high dis-
charge temperature override will be displayed in the
main screen until the COMP DISCHARGE TEMP is less
than the COMP DISCHARGE ALERT threshold – 2° F
(1.1° C).
• High compressor bearing temperature override — If a
compressor bearing temperature is greater than the com-
pressor bearing temperature Alert (Configuration Menu
Protective Limit Config) threshold, then High Bearing
Temp Override shall be set to TRUE until all of the com-
pressor bearing temperatures are less than Comp Bearing
Temp Alert minus 2° F (1.1° C).
RECYCLE CONTROL — The chiller may cycle off and wait
until the load increases to restart when the compressor is run-
ning in a lightly loaded condition. This normal cycling is
known as “recycle.”
In cooling mode, a recycle shutdown is initiated when either
of the following conditions is true:
• Leaving chilled water temperature (or entering chilled
water temperature, if the EWT CONTROL OPTION is
enabled) is more than 5° F (2.8° C) below the CON-
TROL POINT.
• Leaving chilled water temperature (or entering chilled
water temperature, if the EWT CONTROL OPTION is
enabled) is below the CONTROL POINT, and the chilled
water temperature difference is less than the RECYCLE
SHUTDOWN DELTA T.
In heating mode, a recycle cycle shutdown occurs when ei-
ther of the following conditions is true:
• Leaving condenser water temperature (or entering con-
denser water temperature, if the EWT CONTROL
OPTION is enabled) is more than 5° F (2.8° C) below the
CONTROL POINT.
• Leaving condenser water temperature (or entering con-
denser water temperature, if the EWT CONTROL
OPTION is enabled) is above the CONTROL POINT,
and the condenser water temperature difference is less
than the RECYCLE SHUTDOWN DELTA T.
NOTE: Recycle shutdown will not occur if the CONTROL
POINT has been changed by more than 1° F (0.56° C) within
the previous 5 minutes of operation.
When the chiller is in RECYCLE mode, the chilled water
pump relay remains energized so the chilled water temperature
can be monitored for increasing load. The recycle control uses
RECYCLE RESTART DELTA T to check when the compres-
sor should be restarted. In cooling mode, the compressor will
restart when the leaving chilled water temperature (or entering
chilled water temperature, if the EWT CONTROL OPTION is
enabled) is greater than the CONTROL POINT plus the RE-
CYCLE RESTART DELTA T for 5 consecutive seconds. In
heating mode, the compressor will restart when the leaving
condenser water temperature (or entering condenser water tem-
perature, if the EWT CONTROL OPTION is enabled) is less
than the CONTROL POINT minus the RECYCLE RESTART
DELTA T for 5 consecutive seconds.
RUNNING TIMERS AND COUNTERS — The PIC 5 con-
trol maintains two run-time clocks: COMPRESSOR ONTIME
and SERVICE ONTIME. COMPRESSOR ONTIME indicates
the total lifetime compressor run hours. SERVICE ONTIME is
a resettable timer that can be used to indicate the hours since
the last service visit or any other event. A separate counter tal-
lies compressor starts as TOTAL COMPRESSOR STARTS.
All of these can be viewed on the RUN TIMES screen. Both
Ontime counters roll over to 0 at 500,000 hours. Manual
changes to SERVICE ONTIME from the screen are permitted
at any time. If the controller is replaced, one opportunity before
the first start-up with the new controller is provided to set
COMPRESSOR ONTIME and TOTAL COMPRESSOR
STARTS to the last readings retained with the prior controller.
The chiller also maintains a start-to-start timer and a stop-
to-start timer. These timers limit how soon the chiller can be
started and are displayed on the system overview (home) and
RUN TIMES screens. They can be configured in the Configu-
ration Menu GENERAL CONFIGURATION screen. They
must expire before the chiller starts. If the timers have not ex-
pired, the RUN STATUS parameter on the System Overview
(Home) and GENERAL PARAMETERS screen reads TIME-
OUT.
WATER PUMPS CONTROL (FREEZE PREVENTION)
NOTE: In order to energize the chilled and condenser pump to
prevent evaporator and condenser tube freeze-up, the hydraulic
system should be enabled first (this can be configured in the
Configuation Menu FACTORY PARAMETERS screen).
Evaporator Freeze Prevention
—When the evaporator satu-
rated refrigerant temperature or evaporator refrigerant tempera-
ture is less than the EVAP REFRIG TRIPPOINT + REFRIG
OVERRIDE DELTA T (configurable from 2° F to 5° F (1.1° C
to 2.8° C) in the Configuration Menu PROTECTIVE LIM-
IT CONFIG screen), an OVERRIDE—LOW EVAP REFRIG
TEMP event will occur.
For any running status, Protective Limit Alarm State 261
will be displayed and the unit will shut down if either of the fol-
lowing conditions is true:
• Evaporator saturated refrigerant temperature or evapora-
tor refrigerant temperature is equal to or less than the
EVAP REFRIG TRIPPOINT (33 F [0.6 C] for water,
(configurable for brine in Configuration Menu PRO-
TECTIVE LIMIT CONFIG screen) plus 1° F (0.56° C).
• Leaving chilled water temperature or entering chilled
water temperature is less than EVAP REFRIG TRIP-
POINT plus 1° F (0.56° C).
NOTE: If the chiller is in recycle mode, it will transition to
TRIPOUT, and the CHILLED WATER PUMP will remain on.
The alarm will be clearable when the evaporator saturated
refrigerant temperature, evaporator refrigerant temperature,
leaving chilled water temperature, and entering chilled water
temperature rise 5° F (2.8° C) above the EVAP REFRIG TRIP-
POINT.
Condenser Pump Control
—The chiller will monitor the con-
denser pressure and may turn on the condenser pump. If the
condenser pressure is greater than or equal to the COND
PRESS OVERRIDE, and the entering condenser water tem-
perature is less than 115 F (46.1 C), the condenser pump will
energize to try to decrease the pressure and alert 157 will be
generated. The pump will turn off when the condenser pressure
is 3.5 psi (24.1 kPa) less than the pressure override and the con-
denser refrigerant temperature) is less than or equal to the en-
tering condenser water temperature plus 3° F (1.7° C).
NOTE: COND PRESS OVERRIDE is found in the Configu-
ration Menu PROTECTIVE LIMIT CONFIG screen. The
default value is 140 psig (965 kPa) for low pressure condenser
and 250 psig (1724 kPa) for high pressure condenser.
Condenser Freeze Prevention
— This control helps prevent
condenser tube freezing by energizing the condenser pump re-
lay. The PIC 5 module controls the pump and, by starting it,
helps to prevent the water in the condenser from freezing.
When the chiller is off and condenser saturated refrigerant
temperature is less than or equal to the condenser freeze point,
the condenser water pump will be energized (Alarm State 262,
PROTECTIVE LIMIT - CONDENSER FREEZE). The fault
state will clear and the pump will turn off when the condenser
saturated refrigerant temperature is more than 5° F (2.7° C)
above the condenser freeze point and the entering condenser