216
JOHNSON CONTROLS
FORM 201.21-NM4 (616)
216
JOHNSON CONTROLS
MICRO PANEL
High Differential Oil Pressure Cutout Fault
The High Differential Oil Pressure Cutout protects the
compressor from low oil flow and insufficient lubrica
-
tion, possibly from a dirty oil filter. A system will fault
and shut down with a controlled ramped shutdown when
its Discharge to Oil Differential Pressure rises above the
cutout of 65 PSID. This safety is ignored for the first 90
seconds of run time. This safety measures the pressure
differential between discharge and oil pressure, which is
the pressure drop across the oil filter. The Status display
fault message for this safety is shown below:
SYSTEM SAFETIES (FAULTS)
SYS X YYYYYYYY HIGH 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.
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
display 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 lin
-
early ramped from 0 PSID to 30 PSID in 5 to 10 minutes
based on ambient temperature. See TABLE 13 for the
ramp times for the given ambient temperatures.
TABLE 13 - LOW DIFFERENTIAL OIL PRESSURE
CUTOUT
AMBIENT TEMPERATURE
RAMP
TIME
> 50ºF
5 Minutes
> 45ºF
6 Minutes
> 40ºF
7 Minutes
> 35ºF
8 Minutes
> 30ºF
9 Minutes
>=30ºF
10 Minutes
A 30 second safety bypass below 50 Hertz is employed
during rampdown. The bypass is primarily needed under
conditions where another compressor is being brought
on and the running compressor is being ramped down
to 5 Hertz to add the additional compressor 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 as-
sures 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 DISCHARGE 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.
