Emerson VSG & VSSG Troubleshooting Guide download pdf (Page 31)

VSG/VSSG • Compact Logix PLC Manual •Vilter/Emerson • 35391CL

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.

Process Temperature Control

Compressor Control Setpoints

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Emerson VSG & VSSG Troubleshooting Guide Page 31