Compressor Inhibits; Safety Failure Messages - Emerson Vilter Vission 20/20 Operation And Service Manual

Section 7 • Alarms and Trips
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.
Low Run Pressure Ratio (Alarm & Trip):
• This is the low run pressure ratio safety. This safety is
active when Cool Compression is enabled in the con-
fi guration screen. An alarm or trip will be active if the
pressure ratio drops below the setpoint values after
the Low Pressure Ratio Bypass timer has expired.

Compressor Inhibits

The Vission 20/20 uses several start inhibits to prevent
the compressor from starting to protect the compres-
sor and the refrigeration system. While starting the
compressor, the inhibits are checked fi rst before the oil
pump is started or the motor is started. The failed starts
due to an inhibit does not count toward any of the anti-
recycle timers including hot starts. The Inhibits uses the
alarm setpoint to trigger an aborted start and message.
All inhibits will be logged in the event list.
Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 1.9

Safety Failure Messages

Low Suction Pressure Trip
• This message will appear when the suction pressure
falls below the safety setting of the Low Suction Pres-
sure Trip Setpoint No.1 or No. 2.
High Discharge Pressure Trip
• This message will appear when the discharge pres-
sure exceeds the safety setting of the Hi Dsch Press
Trip Setpoint No. 1 or No. 2.
Low Suction Temp Trip
• This message will appear when the suction tempera-
ture falls below the safety setting of the Low Suction
Temperature Trip setpoint.
High Discharge Temp Trip
• This message will appear when the discharge tem-
perature rises above the safety setting of the High
Discharge Temperature Trip setpoint.
Low Oil Separator Temp Trip
• This message will appear when the Oil Separator
Temp is below the Low Oil Separator Start Temp Trip
setpoint. In addition this message will appear after
the Oil Separator Temp Safety Changeover timer
times out and the Oil Separator temperature fails to
rise above the Low Oil Separator Start Temp Reset af-
ter the compressor is started.
Low Oil Separator Temp Trip
• This message will appear when the Oil Separator
Temp is below the Low Oil Separator Run Temp
Reset setpoint after the Oil Separator Temp Safety
Changeover timer times out.
Low Process Temp Trip
• This message will appear when the Process Control
Temperature falls below the safety setting of the Lo
Control Temperature Trip Setpoint.
Prelube Oil Pump Inhibit
• This message will appear when the Prelube Oil
Pressure (Manifold minus Discharge) has remained
below the Prelube Oil Pressure Reset setpoint. The
oil pump will try to generate "prelube pressure" for
the time period of the Low Oil Pressure Safety Bypass
timer setting.
Low Oil Pressure Trip
• This message will appear when the Running Oil
Pressure (Manifold minus Suction) has remained be-
low the low Oil Pressure Reset setpoint when the Oil
Pressure Bypass Start timer times out. This message
will also appear when the Running Oil Pressure falls
below the Low Oil Pressure trip setpoint after the Low
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