Table 18 - Low Differential Oil Pressure Cutout - York YVAA Installation Operation & Maintenance

SECTION 7 - OPERATION
The 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
LOCKOUT and will not restart until the operator clears
the fault using the keypad.
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 4.48 barg (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 following is the Status display fault mes-
sage for this safety:
SYS X YYYYYYYY HIGH DIFF OIL PRESSURE
The 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
LOCKOUT 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
ensures that the compressor is pumping sufficiently to
push oil through the oil cooling circuit and through the
internal compressor lubrication system. The following
is the Status display fault message for this safety:
SYS X YYYYYYYY LOW DIFF OIL PRESSURE
The 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
LOCKOUT 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 barg to 2.09 barg (0 psid to
30 psid) in 5 to 10 minutes based on ambient tempera-
ture. See the following table for the ramp times for the
given ambient temperatures.
116

Table 18 - Low differential oil pressure cutout

Ambient temperature
more than 10°C (50ºF)
more than 7.2°C (45ºF)
more than 4.4°C (40ºF)
more than 1.6°C (35ºF)
more than 1.1°C (30ºF)
more than or equal to 1.1°C (30ºF)
A 30 second safety bypass below 50 Hz 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 Hz to add the additional compressor
due to load requirements. Under these conditions, the
slow speed of the running compressors cause the oil
differential to become very low, especially if the water
temperature is high and the suction pressure is high.
The bypass ensures the compressors 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
121°C (250°F). A system will also be inhibited from
starting if the discharge temperature is above 93°C
(200°F). The following is the Status display fault mes-
sage for this safety:
SYS X YYYYYYYY HIGH DISCHARGE TEMP
The 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
"LOCKOUT" and will not restart until the operator
clears the fault using the keypad.
Low economizer superheat fault
The Low Economizer Superheat Fault is to protect
against excessive liquid refrigerant carryover from the
economizer in cases, which may be a result of the EEV,
Sensor or other problems. It also protects the system
compressor from liquid refrigerant flood back from the
economizer feed line if the economizer valve fails to
close.
Form 201.47-ICOM1
Issue date: 17/11/2022
Ramp time
5 min
6 min
7 min
8 min
9 min
10 min
JOHNSON CONTROLS