Troubleshooting guide

31
Setpoints on this screen:
· Suction Pressure On/Off – The compressor
will automatically cycle ON and OFF at the
setpoints entered. Suction Pressure On/Off
control is only active if the Compressor Con-
trol Via Suction Pressure option is selected
on the Setup screen. If a compressor shut-
down is desired on a suction pressure drop
and a manual reset is required, set the OFF
value below the Low Suction Pressure Safety
Trip value. This will shut down the unit and
a reset will be required to restart it.
· Suction Pressure Capacity Increase – The
capacity of the compressor will increase when
suction pressure is at or above the Increase
ON setpoint, and the increase “off” timer has
cycled. Capacity will continue to increase
until the Suction Pressure Capacity Increase
OFF setpoint is reached. If closer system
control is desired, set the ON and OFF
setpoints at the same values. This will es-
sentially eliminate any differential between
the ON and OFF setpoints.
· Suction Pressure Capacity Decrease – The
capacity of the compressor will decrease
when suction pressure is at or below the ON
setpoint, and the decrease “off” timer has
cycled. Capacity will continue to decrease
until the Suction Pressure Capacity Decrease
OFF setpoint is reached. If closer system
control is desired, set the ON and OFF
setpoints at the same values. This will es-
sentially eliminate any differential between
the ON and OFF setpoints. While this set-
ting is only available for adjustment on the
Control Setpoints screen when the Compres-
sor Control Via Suction Pressure option is
selected on the Setup screen, it has an over-
ride effect when control is via process tem-
perature as described below.
· Capacity Control °F On/Off – The compres-
sor will automatically cycle ON and OFF at
the setpoints entered. Capacity Control °F
On/Off is only active if the Compressor Con-
trol via Process Temperature option is se-
lected on the Setup screen. If compressor
shutdown is desired on a process tempera-
ture drop and a manual reset is required, set
the OFF value below the Low Control Tem-
perature safety trip value. This will shut down
the unit and a reset will be required to restart
it.
· Capacity Control °F Increase – The capac-
ity of the compressor will increase when pro-
cess temperature is at or above the ON
setpoint, and the increase “off” timer has
cycled. Capacity will continue to increase until
the Capacity Control °F Increase OFF setpoint
is reached. If closer system control is desired,
set the ON and OFF setpoints at the same val-
ues. This will essentially eliminate any differ-
ential between the ON and OFF setpoints.
Process temperature control of the capacity is
active only if the Compressor Control Via Pro-
cess Temperature option is selected on the
Setup screen.
· Process Temperature Control – Provides for
a Suction Pressure Override feature. If the
suction pressure should drop below the Suc-
tion Pressure Capacity Decrease OFF setpoint,
the Suction Pressure Capacity Decrease OFF
setpoint will override the Capacity Control °F
Increase and prevent the compressor capac-
ity from increasing (loading). If the suction
pressure should continue to decrease below
the Suction Pressure 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 Pressure Capacity Decrease ON and
OFF setpoints can be viewed or adjusted by
temporarily selecting “Processor Control Via
Suction Pressure” on the Setup screen.
· Capacity Control °F Decrease – The capac-
ity of the compressor will decrease when the
process temperature is at or below the ON
setpoint and the decrease “off” timer has
cycled. Capacity will continue to decrease
until the Capacity Control °F Decrease OFF
setpoint is reached. If closer system control
is desired, set the ON and OFF setpoints at
the same values. This will essentially elimi-
nate any differential between the ON and OFF
Compressor Control