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RW SERIES REVERSIBLE CHILLER INSTALLATION MANUAL
Control Features cont.
• When the controlling temperature sensor is set to select the
Load LW Temp, the setpoint control will operate strictly in
a proportional mode with offsets and differentials used to
determine the appropriate capacity to use. In this mode, the
following parameters are used:
• Stage Delay (30)
• Gain (2)
• PIDY1 Ref (7.2)
• PID Y1 Diff (7)
• PID Y2RefShift (5)
• PID Y2 Diff (6)
• The default values were used in the test lab and seem to be
a reasonably good beginning point for parameter settings.
Compressor Lead-Lag Operation
In the Maint menu of the MUI, Lead –Lag operation may be enabled
or disabled. When disabled, a Y1 call will always be a request for
compressor 1 and a Y2 call will be a request for compressor 2.
When Lead-Lag is enabled, the operation is as follows:
• If only a single Y call is introduced (either Y1 or Y2), then
one compressor will start and it will be the compressor that
has been Off the longest. When that call is removed, the
compressor will stop—if the compressor minimum run time
has been satisfied.
• If the single Y call is re-introduced, then the ‘other’
compressor will start. In this manner, if single compressor
operation is used, then each time a call is given, the
compressors will alternate.
• If a Y call is existing and a compressor is running, then adding
a second Y call will bring on the second compressor. When
one of the Y calls is dropped and the other remains, then
the compressor that was first started will be dropped. In
this manner, if the chiller is alternating between one and two
compressor operation, both compressors will be cycled.
• If no Y calls exist and a sudden and simultaneous application
of both Y1 and Y2 occur, then fist the ‘longest off’ compressor
will start. After 150 seconds, the second compressor will start.
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