JOHNSON CONTROLS
237
SECTION 8 - MICROPANEL
FORM 201.23-NM2
ISSUE DATE: 09/25/2020
8
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.
Low Differential Oil Pressure Cutout Fault
The Low Differential Oil Pressure Cutout protects the
compressor from low oil flow and insufficient lubrica-
tion. A system will fault and shut down with a controlled
ramped shutdown when it’s differential between oil
and suction pressure falls below the cutout. This safety
assures that the compressor is pumping sufficiently to
push oil through the oil cooling circuit and through the
internal compressor lubrication system. The Status dis-
play fault message for this safety is shown below:
SYS X YYYYYYYY LOW DIFF OIL PRESSURE
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.
The safety is ignored for the first 60 seconds of run
time. After the first 60 seconds of operation, the cutout
is linearly ramped from 0 psid to 30 psig in 5 minutes
to 10 minutes based on ambient temperature. See Table
17 on page 237 for the ramp times for the given ambi-
ent temperatures.
TABLE 17 - LOW DIFFERENTIAL OIL PRESSURE
CUTOUT
AMBIENT TEMPERATURE
RAMP
TIME
> 50ºF 5 min
> 45ºF 6 min
> 40ºF 7 min
> 35ºF 8 min
> 30ºF 9 min
>=30ºF 10 min
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:
SYS X YYYYYYYY HIGH OIL TEMP
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 un-
til the operator clears the fault using the keypad.
Low Suction Superheat Cutout Fault
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:
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