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Form 201.23-NM2
Issue date: 12/19/2023
Table 38 - Low differential oil pressure cutout
AMBIENT TEMPERATURE
> 50ºF
> 45ºF
> 40ºF
> 35ºF
> 30ºF
>=30ºF
A 30 second safety bypass below 50 Hertz is employed
during rampdown. The bypass is primarily needed
under conditions where another compressor is be-
ing brought on and the running compressor is being
ramped down to 5 Hertz to add the additional compres-
sor due to load requirements.
Under these conditions, the slow speed of the running
compressor(s) causes the oil differential to become
very low, especially if the water temperature is high
and the suction pressure is high. The bypass assures
the compressor(s) will not trip on a nuisance low oil
differential fault.
High discharge temperature cutout fault
The High Discharge Temperature Cutout protects the
motor and compressor from overheating. A system will
fault and shut down with a controlled ramped shutdown
when its Discharge Temperature rises above 250°F. A
system will also be inhibited from starting if the dis-
charge temperature is above 200°F. The Status display
fault message for this safety is shown below:
SYS X YYYYYYYY HIGH DSCHARGE TEMP
X indicates the system and YYYYYYY indicates the
system is in a "FAULT" condition and will restart when
the 120 second anti-recycle timer times out or "LOCK-
OUT" and will not restart until the operator clears the
fault using the keypad.
High oil temperature cutout fault
The High Oil Temperature Cutout protects the com-
pressor from insufficient lubrication. A system will
fault and shut down with a controlled ramped shutdown
when its oil temperature rises above 225°F. The system
will be inhibited from starting if the oil temperature is
above 175°F. The Status display fault message for this
safety is shown below:
Johnson Controls
SYS X YYYYYYYY HIGH OIL TEMP
RAMP
TIME
X indicates the system and YYYYYYY indicates the
5 min
system is in a "FAULT" condition and will restart when
6 min
the fault clears or "LOCKOUT" and will not restart un-
7 min
til the operator clears the fault using the keypad.
8 min
9 min
Low suction superheat cutout fault
10 min
The Low Suction Superheat Cutout helps protect the
compressor from liquid floodback due to low suction
superheat. This safety is ignored for the first 30 sec-
onds of compressor operation. Low suction superheat
will fault a system when any one of the following con-
ditions occur:
• After the first 30 seconds of run time, if the suc-
tion superheat falls below 2.0°F, the discharge su-
perheat is less than 15°F, and the run time is less
than 5 minutes, the superheat safety will be ignored
for the next 30 seconds followed by setting the su-
perheat cutout to 0°F and linearly ramping it up to
2.0°F over the next 60 seconds.
If at any time during these 60 seconds the suc-
tion superheat falls below the ramped cutout, the
system will fault and shut down with a controlled
ramped shutdown.
• If the suction superheat less than 2°F, the dis-
charge superheat less than 15°F for 10 seconds,
and the run time is equal to or more than 5 min-
utes, the system will fault and shutdown with a
controlled ramped shutdown.
• If the suction superheat less than 0.5°F and dis-
charge superheat is more than 15°F for 60 seconds
and run time equal to or more than 5 minutes, the
system will fault and shutdown with a controlled
ramped shutdown.
• If suction superheat less than 5°F for 10 minutes,
the system will fault and shutdown with a con-
trolled ramped shutdown.
The Status display fault message for this safety is
shown below:
SYS X YYYYYYYY LOW SUCTION SUPERHEAT
X indicates the system and YYYYYYYY indicates the
system is "FAULT" and will restart after the 120 sec-
ond anti-recycle timer times out or "LOCKOUT" and
will not restart until the operator clears the fault.
Section 8 - Micropanel
8
241
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