Table 9 - Evaporator Pressure Thresholds - Johnson Controls YORK OPTIVIEW CONTROL CENTER Operation Manual

FORM 160.10-O1
ISSUE DATE: 4/27/2018
Condenser – High Pressure Contacts Open
This safety fault is set whenever the High Pressure
Cutout (HPCO) switch contacts are open. the fault is
released when the switch contacts close, and the com-
pressor switch is placed in the STOP/RESET (O) po-
sition.
Evaporator – Low Pressure
The evaporator pressure has decreased to the safety
shutdown threshold. For water cooling applications,
the safety shutdown threshold is a fixed value for the
respective refrigerant. For brine cooling applications,
the safety shutdown threshold varies according to the
concentration of the brine solution and is programmed
at the YORK Factory. This should not be changed by
anyone other than a qualified service technician fol-
lowing instructions in the OptiView Control Center
Retrofit Kit - Trane Service Manual (Form 160.10-M1).
The chiller can be started after the evaporator pressure
increases to the restart threshold and the compressor
switch is placed in the STOP/RESET (O) position.
Refer to Table 9 for shutdown and restart thresholds:

TABLE 9 - EVAPORATOR PRESSURE THRESHOLDS

SHUTDOWN THRESHOLD
(PSIA)
Refrig. Water Brine
0.0 to 12.5
R11 < 5.4
as
programmed
0.0 to 12.5
R123 < 4.4
as
programmed
Evaporator – Low Pressure – Smart Freeze
Smart Freeze protection is activated and has shutdown
the chiller because the evaporator temperature has been
below the Smart Freeze threshold for greater than the
allowable number of seconds. If the refrigerant tem-
perature sensor (RT7) is ENABLED, this parameter
is used as the evaporator refrigerant temperature and
the freeze threshold is 32.8°F. If RT7 is not enabled,
the refrigerant temperature displayed is the evapora-
tor saturation temperature, derived from the evaporator
pressure transducer. The freeze threshold is 34.0°F.
JOHNSON CONTROLS
RESTART THRESHOLD
(PSIA)
Water Brine
> Shutdown
> 5.4
threshold
> Shutdown
> 4.4
threshold
SECTION 3 - OPTIVIEW DISPLAY MESSAGES
The total count is incremented for every second the
evaporator refrigerant temperature is below the freeze
threshold (but is never decremented below zero). The
amount of seconds until the chilled liquid will freeze is
based on how far the evaporator refrigerant tempera-
ture is below the freeze threshold as follows:
# seconds to freezing = (4053.7) / (freeze
threshold – evap. refrigerant temp.)
Smart Freeze is activated only if the feature has been
enabled by a service technician and the leaving chilled
liquid temperature setpoint is less than 38.0°F.
Evaporator – Transducer or Leaving Liquid
Probe
The control center has detected a possible defective
evaporator pressure transducer or leaving chilled liq-
uid temperature thermistor. The OptiView Control
Center converts the evaporator pressure to a saturated
temperature value and compares this value to the leav-
ing chilled liquid temperature (difference = chilled liq-
uid temp – evaporator saturated temp). The difference
should not be outside the range of –2.5°F to +25.0°F. If
the transducer and thermistor are accurate, the evapo-
rator saturated temperature should not be more than
2.5°F warmer, or more than 25.0°F colder than the
leaving chilled liquid temperature. In order to initiate
a shutdown, the difference must be outside the accept-
able range continuously for ten minutes.
Evaporator – Transducer or
Temperature Sensor
The control center has detected a possible defective
evaporator pressure transducer or refrigerant tempera-
ture sensor. The control center converts the evaporator
pressure to a saturated temperature value and compares
this value to the evaporator refrigerant temperature
sensor (RT7, if enabled). If the difference between
these temperatures is greater than 3.0°F continuously
for one minute, this shutdown is performed. This check
is only performed under the following conditions:
• RT7 is enabled.
• Chiller has been running for ten minutes.
• Not in Brine chilled liquid mode.
• Smart Freeze is enabled.
• Evaporator temperature sensor (RT7) or evapora-
tor saturation temperature is indicating a tempera-
ture less than 32.0°F ).
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