JOHNSON CONTROLS
90
FORM 160.81-O1 (1020)
ISSUE DATE 10/05/2020
SECTION 3 - DISPLAY MESSAGES
SAFETY SHUTDOWN MESSAGES
EVAPORATOR – LOW PRESSURE
(This message is applicable only if the Smart Freeze
feature is not activated. If Smart Freeze is activated and
has initiated the shutdown, “Evaporator - Low Pressure
- Smart Freeze” is displayed. Its description follows).
The evaporator pressure, as sensed by the Evapora-
tor Transducer, 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 concentra-
tion of the Brine solution. The Brine shutdown thresh-
old is programmed at the Johnson Controls. It should
not be changed by anyone other than a qualified Service
Technician following instructions in OptiView Control
Center Service Instructions (Form 160.81-M1). The
chiller can be started after the evaporator pressure in-
creases to the restart threshold and the COMPRESSOR
switch is placed in the Stop-Reset (O) position.
SHUTDOWN
(PSIG)
RESTART (PSIG)
Water cooling
-R134a
25.0 25.1
Brine cooling -
R134a
6.0 to 25.0 as
programmed
+0.1 more
than shutdown
threshold
EVAPORATOR – LOW PRESSURE - SMART
FREEZE
(Not applicable to Software version C.MLM.05.04.
xxx (and later).
Smart Freeze Protection is activated and has shut down
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 (us-
ing procedure in OptiView Control Center Service In-
structions (Form 160.81-M1), this parameter is used as
the evaporator refrigerant temperature and the freeze
threshold is 32.8ºF. If RT7 is not enabled, the evapo-
rator refrigerant temperature used is the Evaporator
Saturation Temperature, derived from the Evaporator
Pressure Transducer and the freeze threshold is 34.0°F.
The 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:
Number of seconds to freezing = (4053.7) / (freeze
threshold-evaporator refrigerant temperature)
Smart Freeze is activated only if the feature has been
enabled by a Service Technician (following instruc-
tions in OptiView Control Center Service Instructions
(Form 160.81-M1) and the Leaving Chilled Liquid
Temperature setpoint is less than 38.0ºF.
The Smart Freeze feature has been removed from pres-
ent production software. It is no longer available in
software versions C.MLM.05.04.xxx (and later).
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 indicating are not in the correct relation-
ship 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 – evap-
orator saturated temp). The difference should not be
outside the range of –2.5ºF to +25.0ºF. If the transducer
and thermistor are accurate, the Evaporator Saturated
Temperature should not be more than 2.5º warmer or
more than 25.0ºF colder than the Leaving Chilled Liq-
uid Temperature. In order to initiate a shutdown, the
difference must be outside the acceptable range contin-
uously for 10 minutes. The chiller can be started after
the COMPRESSOR switch is placed in the Stop-Reset
(O) position. This check is not performed when the op-
tional Hot Gas feature is enabled in Brine mode.
EVAPORATOR – TRANSDUCER OR TEMPERA-
TURE SENSOR
(Not applicable to software version C.MLM.05.04.xxx
(and later).
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 3.0ºF, continuously for 1 minute, this shut-
down is performed.
This check is only performed under the following con-
ditions:
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