Johnson Controls YORK YK MaxE, Operation Manual

Page: 158 / 184

JOHNSON CONTROLS
158
FORM 160.54-O1
optiView Control Center
safetY shUtdoWN Messages
“
EVAPORATOR – LOW PRESSURE
”
The evaporator pressure, as sensed by the Evaporator
Transducer, has decreased to the Safety shutdown thresh-
old. 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. The Brine shutdown threshold is pro-
grammed at the YORK Factory. It should not be changed
by anyone other than a qualified Service Technician fol -
lowing instructions in YORK Service Manual 160.54-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.
shutdown (psig) restart (psig)
water Cooling - R22 54.3 54.4
- R134a 25.0 25.1
brine Cooling - R22
25.0 to 54.3
as programmed
+0.1 >
Shutdown threshold
- R134a 6.0 to 25.0
as programmed
+0.1 >
Shutdown threshold
“EVAPORATOR – LOW PRESSURE - SMART
FREEZE”
(Flash memory card version C.MLM.01.02 or late
r)
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 al-
lowable number of seconds. If the Evaporator Refrigerant
Temperature sensor RT7 is Enabled, (using procedure
in Service Manual 160.54-M1), this parameter is used
as the evaporator refrigerant temperature and the freeze
threshold is 32.8°F. If RT7 is not enabled, the evaporator
refrigerant temperature used is the Evaporator Saturation
Temperature, derived from the Evaporator Pressure Trans-
ducer and the freeze threshold is 34.0°F.
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 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
(
following instructions
in Service Manual 160.54-M1) and the Leaving Chilled
Liquid temperature Setpoint is less than 38.0°F.
“ 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 de-
vices are indicating 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 to +25.0°F. 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
colder than the leaving chilled liquid temperature. In or-
der to initiate a shutdown, the difference must be outside
the acceptable range continuously for 10 minutes. For
Steam Turbine drive applications, this check is bypassed
for the first 20 minutes of chiller operation. The chiller
can be started after the COMPRESSOR switch is placed
in the Stop-Reset (O) position.
“ 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 Sat-
urated 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 Service Manual 160.54.M1
•
Not in Brine cooling mode (If compressor appli-
cation other than “P”, applies only to Flash memory
card version C.MLM.01.02 and later)
•
Smart Freeze is enabled (If compressor application
other than “P”, applies only to Flash Memory Card
version C.MLM.01.05.xxx and later)
•
Evaporator Temperature Sensor (RT7) or Evaporator
Saturation Temperature is indicating a temperature
of less than 32.0°F (If compressor application other
than “P”, applies only to Flash Memory Card version
C.MLM.01.05.xxx and later)
The chiller can be started after the temperatures are
within 3.0°F of one another and the COMPRESSOR
switch is placed in the Stop-reset (O) position.