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Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 1.8.5153
selected in the Control Mode dropdown selection
found in the Compressor Control screen. An alarm or
trip will be activated on a drop in process tempera-
ture below the setpoint value.
Low Suction Temperature (Alarm & Trip):
• This is the low suction temperature safety. The alarm
or trip will be activated if the suction temperature
drops below the setpoint value.
High Discharge Temperature (Alarm & Trip):
• This is the high discharge temperature safety. The
alarm or trip will be activated if the discharge tem-
perature rises above the setpoint value.
Low Oil Separator Start Temperature (Alarm & Trip):
• This is the starting low oil separator temperature
safety. The compressor is prevented from starting
or running if the oil in the separator is below the
alarm value. After a time delay (setting of the Oil
Separator Temperature Safety Changeover timer),
this safety is deactivated and the Low Oil Separator
Run Temperature alarm and safety setpoints become
active.
Low Oil Separator Run Temperature (Alarm & Trip):
• This is the running low oil separator temperature
safety. After a time delay, (setting of the Oil Separator
Temperature Safety Changeover timer), the Low Oil
Separator Start Temperature is bypassed and Low
Oil Separator Run Temperature alarm and safety set-
points become active. The alarm or trip will be acti-
vated if the oil temperature in the separator drops
below the setpoint value.
Low Oil Injection Temperature (Alarm & Trip):
• This is the low oil injection safety. The alarm and
trip setpoints are bypassed at start for a time pe-
riod (setting of the Oil Injection Temperature Safety
Changeover timer). The alarm and trip will be acti-
vated after the time delay has expired.
High Oil Injection Temperature (Alarm & Trip):
• This is the high oil injection temperature safety. The
alarm or trip will be activated if the oil injection tem-
perature rises above the setpoint value.
Pre-lube Oil Pressure (Alarm & Trip):
• This is the pre-lube oil pump failure safety. If the
pre-lube oil pressure does not rise above the alarm
setting with in 60 seconds for a minimum time set
at Minimum Comp. Pre-lube Time, then the start
sequence will be aborted. The Minimum Comp. Pre-
lube Time is set on the Timer screen. The pre-lube oil
pressure is defi ned as manifold pressure minus dis-
charge pressure. This safety insures adequate lubri-
cation of the the compressor at startup.
Low (Run) Oil Pressure (Alarm & Trip):
• This is the running oil pressure safety. The normal
alarm and trip setpoints of this safety are “messaged”
as soon as the compressor starts. The “Pre lube Oil
Pressure” Alarm and Trip setpoints are substituted
into this safety setpoints for a time of the “Oil Pressure
Bypass” timer (typically 60 seconds). After this timer
expires, then the setpoints return back to the normal
settings. The action of adjusting the setpoints for
about a minute allows the (Run) Oil Pressure to build
up to normal running pressures after the compressor
starts. After the Oil Pressure Bypass Timer has ex-
pired, the Oil Pressure must be above the normal set-
points, or else an Alarm or Trip will occur. An alarm or
trip will be active if the oil pressure drops below the
normal setpoint values after the Oil Pressure Bypass
timer has expired. This time limit is set on the Timer
menu screen. Run oil pressure is defi ned as manifold
pressure minus suction pressure.
High Filter Differential Pressure Start (Alarm & Trip):
• This safety allows a higher than normal fi lter differ-
ential pressure to exist during the fi rst minute after
a compressor starts. This allows time for cold oil that
is present in the oil piping and fi lters to be passed
and replaced with warmer oil. After a time delay (set-
ting of the Filter Diff Pressure Safety Changeover
timer), this safety is deactivated and the High Filter
Differential Pressure-Run alarm and safety setpoints
become active. An alarm or trip will be active if the
fi lter differential (= Filter Inlet Pressure minus Filter
Outlet Pressure) exceeds the setpoint value.
High Filter Differential Pressure Run (Alarm & Trip):
• This safety setpoint is active when the compres-
sor has started and the Filter Diff Pressure Safety
Changeover timer has timed out. An alarm or trip will
be active if the fi lter differential (= Filter Inlet Pressure
minus Filter Outlet Pressure) exceeds by the setpoint
value.
High Motor Amps:
• This safety setpoint is active after the Volume
Decrease At Start Timer expires (this timer is not set-
table by the operator). A trip will occur if the motor
amperage exceeds the safety setpoint value. For a
motor with a 1.15 Service Factor, the trip setpoint
should be set at 125% of the motor full load amper-
age value. The alarm setpoint should be set at 120%
of the motor full load amperage value.
Section 7 • Alarms and Trips