Emerson VSG Operation Manual page 31

Setpoints on this screen:
· Process Temperature Control – Provides for a Suction Pressure Override feature. If the suction pressure
should drop below the Suction Pressure Capacity Decrease OFF setpoint, the Suction Pressure Capacity
Decrease OFF setpoint will override the Capacity Control F Increase and prevent the compressor capacity
from increasing (loading). If the suction pressure should continue to decrease below the Suction Pres-
sure Capacity Decrease ON setpoint, the compressor capacity will be forced to decrease until the suction
pressure is just above the Suction Pressure Capacity Decrease ON setpoint. This will help stabilize the
suction pressure, allowing for the process temperature to be gradually pulled down. The Suction Pres-
sure Capacity Decrease ON and OFF setpoints can viewed or adjusted by temporarily selecting "Processor
Control Via Suction Pressure" on the Setup screen.
Note: Capacity Control for Refrigeration Only.
· Capacity Control °F On/Off – The compressor will automatically cycle ON and OFF at the setpoints entered.
Capacity Control °F On/Off is only active if the Compressor Control Via Process Temperature option is
selected on the Setup screen. If compressor shutdown is desired on a process temperature drop and a
manual reset is required, set the OFF value below the Low Control Temperature Safety trip valve. This
will shut down the unit and a reset will be required to restart.
VSG/VSSG • Compact Logix PLC Manual •Vilter/Emerson • 35391CL
Compressor Control Setpoints
Process Temperature Control
31