Figure 7-2. Alarms And Trips Screen - Page 3 - Emerson Vilter Vission 20/20 Operation And Service Manual

Section 7 • Alarms and Trips
After a time delay, (setting of the High Superheat
Temperature Safety Changeover timer), this safety is
deactivated and the High Superheat Run Temperature
alarm and safety setpoints become active. The trip
will be activated if the superheat temperature from
start rises above the superheat temperature plus the
setpoint value. There is no ALARM setpoint.
Use Figure 7-3. Alarms and Trips Screen - Page 3.
Prelube Oil Pressure (Alarm & Trip):
• This is the prelube oil pump failure safety. If prelube
oil pressure does not rise by prelube alarm setting
confi gured with in prelube oil pressure trials of pre-
lube oil pressure monitor time for a minimum time
set at Minimum Comp. Prelube Time, then the start
sequence will be aborted. The prelube oil pressure
trials, prelube oil pressure monitor time, Minimum
Comp. Prelube Time is set on the Timer screen. The
prelube oil pressure is defi ned as manifold pressure
minus discharge pressure during the start sequence,
7 – 4

Figure 7-2. Alarms and Trips Screen - Page 3

Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 1.9
zeroed prelube oil pressure difference value is shown
on main screen during start sequence. The prelube
oil pressure is redefi ned as manifold pressure minus
suction pressure after the start sequence. This safety
insures adequate lubrication of 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