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Recycle Mode — The chiller may cycle off and wait until the
load is increased to meet restart requirements when the
compressor is running in a lightly loaded condition. This
cycling is normal and is known as “recycle.” A recycle
shutdown is initiated when any of the following conditions
are true:
Cooling Mode
- 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
CONTROL 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.
Heating Mode
- Leaving condenser water temperature (or entering
condenser water temperature, if the EWT CONTROL
OPTION is enabled) is more than 5° F (2.8° C) above
the CONTROL POINT.
- Leaving condenser water temperature (or entering
condenser 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 one degree F 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 compressor should be restarted. The
compressor will restart when the chiller is:
Cooling Mode
- Leaving chilled water temperature (or entering chilled
water temperature, if the EWT CONTROL OPTION
is enabled) is greater than the CONTROL POINT plus
the RECYCLE RESTART DELTA T for 5 consecutive
seconds.
Heating Mode
- Leaving condenser water temperature (or entering
condenser water temperature, if the EWT CONTROL
OPTION is enabled) is less than the CONTROL POINT
minus the RECYCLE RESTART DELTA T for 5
consecutive seconds.
19 Series PIC 5+ control 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 tallies
compressor starts as TOTAL COMPRESSOR STARTS. All
of these can be viewed on the RUN TIMES screen on the
HMI. Both Ontime counters roll over to 0 at 500,000 hours.
Manual changes to SERVICE ONTIME from the screen are
permitted at any time.
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. TIMERs are displayed on the RUNTIMES screen
and can be configured in CONFIGURATION MENU/
GENERAL CONFIGURATION screen.
These timers must expire before the chiller starts. If the timers
have not expired the RUN STATUS parameter on the
Default and GENERAL PARAMETERS screen reads
TIMEOUT.
The other two timers displayed on the RUNTIME screen
are ‘swift restarts in 1 hour’ and‘recy startup in 4 hours’. The
rst denes a maximum of 4 times of swift restarts can be
applied for the chiller in 1 hour. The other claries that recycle
restarts should be less than 5 times in 4 hours, otherwise
system will not pass prestart check.
NOTE: In order to energize the chilled and condenser pump
to prevent evaporator and condenser tube freeze-up, the
Hydraulic System should be enabled rst (this can be
congured in CONFIGUATION MENU/ FACTORY screen).
Evaporator Freeze Prevention
When the evaporator saturated refrigerant temperature or
evaporator refrigerant temperature is less than the EVAP
REFRIG TRIPPOINT plus the REFRIG OVERRIDE
DELTA T (congurable from 2^F to 5^ F (1.1^C to 2.8^C)
in CONFIGURATION MENU/ PROTECTIVE LIMIT
CONFIG screen), event “OVERRIDE – LOW EVAP
REFRIG TEMP” will occur.
In all running status, if either of the following conditions is
true:
- evaporator saturated refrigerant temperature or
evaporator refrigerant temperature is equal to or less
than the EVAP REFRIG TRIPPOINT (33° F or 0.6°
C for water, congurable for brine in CONFIGURATION
MENU/ PROTECTIVE LIMIT CONFIG screen) plus
one degree F.
- Leaving chilled water temperature or entering chilled
water temperature is less than EVAP REFRIG
TRIPPOINT plus 1 degree F.
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