York YMC2 - Page 101

JOHNSON CONTROLS
101
SECTION 3 - OPTIVIEW™ CONTROL CENTER FUNCTIONS AND NAVIGATION
FORM 160.84-OM1
ISSUE DATE: 9/21/2017
3
MESSAGE DESCRIPTION
EVAPORATOR – LOW
PRESSURE
The evaporator pressure, as sensed by the Evaporator Transducer, has decreased to the
shutdown threshold and caused cycling shutdown three times in a 90 minute period. For water
cooling applications, the shutdown threshold is a xed value. For Brine cooling applications, the
shutdown threshold varies according to the concentration of the Brine solution. The Brine shut-
down threshold is programmed at the YORK Factory. It should not be changed by anyone other
than a qualied Service Technician following instructions in YORK YMC
2
Service Manual (Form
160.84-M2). The chiller can be started after the evaporator pressure increases to the restart
threshold and the CLEAR FAULT key is pressed.
SHUTDOWN
(PSIG)
RESTART
(PSIG)
Water Cooling 25.0 25.1
Brine Cooling
6.0 to 25.0
as programmed
+0.1>
Shutdown threshold
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 Evaporator Refrigerant Temperature sensor RT7 is Enabled, (using procedure
in YORK YMC
2
Service Manual (Form 160.84-M2)), this parameter is used as the evaporator
refrigerant temperature and the freeze threshold is 32.8°F (.4°C). If RT7 is not enabled, the
evaporator refrigerant temperature used is the Evaporator Saturation Temperature, derived from
the Evaporator Pressure Transducer and the freeze threshold is 34.0°F (1.1°C).
The total count is incremented once for every second the evaporator refrigerant temperature is
below the freeze threshold (but is never decremented below zero). The number of seconds it
will take the chilled liquid to freeze is based on how far the evaporator refrigerant temperature 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 (following
instructions in YORK YMC
2
Service Manual (Form 160.84-M2)) and the Leaving Chilled Liquid
temperature Setpoint is less than 38.0°F (3.3°C).
EVAPORATOR –
TRANSDUCER OR
LEAVING LIQUID
PROBE
A possible defective Evaporator pressure Transducer or Leaving Chilled Liquid temperature
Thermistor has been detected. The pressure and temperature that these devices are indicat-
ing are not in the correct relationship to each other. The control center converts the evaporator
pressure to a Saturated Temperature value and compares this value to the Leaving Chilled
Liquid temperature (difference = chilled liquid temp – evaporator saturated temp). The difference
should not be outside the range of –2.5°F (1.4°C) to +25.0°F (14.75°C). If the Transducer and
Thermistor are accurate, the Evaporator Saturated temperature should not be greater than 2.5°F
warmer nor greater than 25.0°F (14.75°C) colder than the leaving chilled liquid temperature. In
order to initiate a shutdown, the difference must be outside the acceptable range continuously
for 10 minutes. The chiller can be started after the CLEAR FAULT key is pressed.
EVAPORATOR –
TRANSDUCER OR
TEMPERATURE
SENSOR
A possible defective Evaporator pressure Transducer or Refrigerant Temperature Sensor has
been detected. The control center converts the evaporator pressure to a Saturated Temperature
value and compares this value to the optional Evaporator Refrigerant Temperature Sensor. If
the difference between these temperatures is greater than 3.0°F, continuously for 1 minute, this
shutdown is performed. This check is only performed under the following conditions:
• Chiller has been running for at least 10 minutes
• Evaporator Refrigerant temperature (RT7) has been enabled by a Service technician using
instructions in YORK YMC
2
Service Manual (Form 160.84-M2).
• NOT in Brine cooling mode
• Smart Freeze is enabled
• Evaporator Temperature Sensor (RT7) or Evaporator Saturation Temperature is indicating a
temperature of less than 32.0°F (0°C).
The chiller can be started after the temperatures are within 3.0°F (1.77°C) of one another and
the CLEAR FAULT key is pressed.
TABLE 12 - SAFETY SHUTDOWN MESSAGES (CONT'D)