RXB PLUS ROTARY SCREW COMPRESSOR UNITSS70-101 IOM
Page 24
OPERATION
LEAD-LAG OPTION
The lead-lag compressor sequencing option provides the
controls for operating two RXB compressors in one system.
AUTO CYCLE DISPLAY *
AUTO CYCLE Start[40.0 g ] Timer[01 min]
F1 To Exit Stop [25.0 g ] Timer[01 min]
Suct Press Min SV-[50%] Lead [Yes]
=[35.5 g ] Active-[No ]
The software includes user adjustable setpoints on the Auto
Cycle setpoints screen (F4 on Main Menu) for the following:
START - The suction pressure must be greater than or equal
to the “START” setpoint in order to start the compressor.
This setpoint works in conjunction with the “Timer” setpoint
located to the right of it on the Auto Cycle setpoints screen.
(Start) TIMER - This is a time delay used to start the com-
pressor. The timer only accumulates time whenever the pres-
sure rises to or above the “START” setpoint and will reset if
the pressure drops below the “START” setpoint.
STOP - The suction pressure must be less than or equal to
the “STOP” setpoint in order to stop the compressor. This
setpoint works in conjunction with the “Timer” setpoint lo-
cated to the right of it on the Auto Cycle setpoints screen.
(Stop) TIMER - This is a time delay used to stop the com-
pressor. The timer only accumulates time whenever the pres-
sure drops to or below the “STOP” setpoint and will reset if
the pressure rises above the “STOP” setpoint.
MIN SV -This setpoint is the minimum slide valve position
and is shown as a percentage. It will limit the slide valve
position to the displayed setpoint.
LEAD - This setpoint assigns the compressor as the lead or
the lag unit. Press the [CHANGE] key while at this setpoint
to change the status.
ACTIVE - This setpoint indicates whether the Auto Cycle
Mode is active or not. Press the [CHANGE] key while at this
setpoint to change the status.
OPERATION
For operation of the LEAD-LAG sequence, both units must
be in Auto Cycle compressor mode - one compressor micro
selected as the LEAD compressor, the other compressor
selected as the LAG compressor - and the slide valves must
be in Auto mode.
With NO Compressor Running
The lead will start when its “START” setpoint is reached for
the amount of time selected for the “TIME” setpoint.
With ONE Compressor Running
If the load rises:
The lag compressor will start when its “START” setpoint is
reached for the amount of time selected for the “TIME” set-
point and the lead compressor is running at 100% slide valve
or running with the motor load inhibit.
If the load falls:
The lead compressor will stop when its “STOP” setpoint is
reached for the amount of time selected for the “TIME” set-
point.
With TWO Compressors Running
If the load rises:
The lead and lag compressor will load independently.
If the load falls:
The lag compressor will unload to its “MIN SV” setpoint.
Then the lead compressor will unload to its “MIN SV” set-
point. The lag compressor will stop when the suction pres-
sure drops below the “STOP” setpoint for the amount of time
selected for the “TIME” setpoint.
NOTE: Be careful not to select both compressors as lead
compressors or as lag compressors as improper op-
eration will result.
NOTE: One compressor will operate as a normal auto
cycle compressor when any one of the following oc-
curs:
a. Power is removed from one of the two compressors,
b. Either of the compressors is NOT selected to “AUTO”, or
c. If communication is lost between the compressors for any
reason.
COMMUNICATIONS TROUBLESHOOTING
Troubleshooting the communications:
Go to the SETPOINTS DISPLAY FIXED Page 2 by using
the [CHANGE] key and the [ * ] key. The display will appear
as:
SETPOINTS DISPLAY *
FIXED PAGE 2 Comm. Activity-[ ]
Hi Oil Temp Cutout --[167F] Alarm --[158F]
Lo Oil Temp Cutout --- [49F] Alarm --- [58F]
Lo Oil Press. Cutout --- [005] Alarm --- [010]
If the microprocessor is receiving information in the com-
munications port from the other compressor, a “1” will flash
between the brackets. During normal operation a “1” will
flash every 5 seconds.
At the same time information is displayed on the lower right
hand corner of the Auto Cycle display concerning the lead-
lag information:
AUTO CYCLE DISPLAY *
AUTO CYCLE Start[20.0 g] Timer[01 min]
F1 to Exit Stop-[25.0 g] Timer[01 min]
Suct Press Min SV-[50%] Lead-[Yes]
=[35.5 g ] Active-[Yes] 0101
This information is either “0” or “1” and represents what is
being sent from the other compressor. Consult Frick Com-
pany if additional information is required.
*Display for illustrative purposes only.
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