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SECTION 7 - OPERATION
JOHNSON CONTROLS
125
FORM 201.28-NM1.1
ISSUE DATE: 1/31/2018
7
The start inhibit thresholds for each sensor are shown
in the following table.
TABLE 21 - START INHIBIT SENSOR THRESHOLDS
SENSOR
LOW
THRESHOLD
HIGH
THRESHOLD
Suction
Transducer
0.3VDC 4.7VDC
Oil
Transducer
0.3VDC 4.7VDC
Discharge
Transducer
0.3VDC 4.7VDC
Motor Temp.
Sensor
0°C (0ºF) 116°C (240ºF)
High Motor Temperature Cutout Fault
The High Motor Temperature Cutout prevents a
compressor from running when its motor temperature
is too high. A system will fault and shut down when
any compressor motor temperature sensor rises above
121°C (250°F). The system will be inhibited from start-
ing if its motor temperatures sensors indicate tempera-
tures above 116°C (240°F). If any single temperature
sensor is being ignored under the Unit Set-up Mode,
that sensor will not be utilized when evaluating motor
temperature.
Below is a sample Status display fault message:
SYS X YYYYYYYY HIGH MOTOR TEMP
The X indicates the system and YYYYYYY indicates
the system is in a “FAULT” condition and will restart
when the fault clears or “LOCKOUT” and will not
restart until the operator clears the fault using the
keypad.
System Control Voltage Cutout Fault
The System Control Voltage Cutout alerts the operator
the 115VAC Control voltage to one of the systems is
missing. This could be due to a system fuse that has
been removed or is blown. The affected system will
fault and shut down immediately when the 115VAC
supply is lost.
The safety will “not” shut down a system if the UNIT
switch is OFF, which electrically removes the 115VAC
to “all” systems. The safety is only used to indicate a
situation where a single system is missing the 115VAC.
The safety will not cause a lockout and the system fault
will reset when power is returned. A sample message
is shown below:
SYS X YYYYYYYY CONTROL VOLTAGE
The X indicates the system and YYYYYYY indicates
the system is in a “FAULT” condition and will restart
when the fault clears or “LOCKOUT” and will not re-
start until the operator clears the fault using the keypad.
Eductor Clog Fault
To sense a loss of oil return to the compressor, an educ-
tor clog detection safety is utilized. The safety moni-
tors the temperature of the line between the eductor
and the suction line.
The control algorithm looks at the eductor line temper-
ature once a second. At start, a clog timer is set at 600
seconds. If the eductor line temperature is less than the
saturated suction temperature plus 5.5°C (10°F) each
time the control circuit looks at the temperature, the
clog timer is reset to 600 seconds.
If the eductor line temperatures is greater than the satu-
rated suction temperature plus 5.5°C (10°F), the clog
timer is decremented one second. If the temperature
remains above the saturated suction temperature plus
5.5°C (10°F) for 600 seconds, the clog timer will count
to “0” and the system will shut down and lock out. The
status fault will indicate an eductor clog fault.
EDUCTOR CLOG FAULT
Whenever this fault occurs, the eductor filter should
be changed. The clog timer resets to 600 seconds
whenever the control algorithm sees the eductor line
temperature is less than the saturated suction pressure
plus 5.5°C (10°F). This prevents nuisance eductor clog
faults.