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Compressor Inhibits
Inhibits of compressors are typically recoverable without
requiring user interaction. The inhibit of a compressor will
be immediate once the request is issued. Inhibits originate
from undesirable refrigeration operating conditions and
may or may not be associated with a diagnostic event.
Once the condition has recovered, the compressor will be
un-inhibited and will be available for staging sequences.
Alternate Staging Sequence
When one or more compressors are unavailable due to
Lockouts and Inhibits, an alternate staging sequence will
be determined from a rule-based algorithm which selects
the best next stage from the available compressors.
Double Swaps will not be performed during Alternate
Staging Sequence.
Staging Up
On single circuit units, two circuit units with neither circuit
active, or two circuit units with both circuits active, the
smallest available compressor will be selected to start.
On two circuit units with one circuit active, the smallest
available compressor on the non-active circuit will be
chosen to start. If none are available on the non-active
circuit the next smallest available compressor on the active
circuit will be chosen to start.
Staging Down
On single circuit units, or two circuit units with one circuit
running, the largest running compressor will be chosen to
stop.
On two circuit units with both circuits active, the largest
running compressor that will not cause a circuit to stop will
be chosen. If there is only one compressor running per
circuit the larger of the two compressors will be chosen to
stop.
Transition Out of Alternate Staging
Transition to Normal Staging — When all compressors are
available on the next request to add or subtract the current
state will be evaluated against the Normal staging table. If
a match is found, the next staging decision will be made
following the Normal staging rules. If the normal table does
not contain a match for the current state, then the Alternate
Staging sequences will be used to process the command,
and the cycle will continue until a match has been found.
Transition to Balanced Compressor Staging — Balanced
Compressor Staging is a feature setting, when enabled
balanced staging rules will be used to process the next
staging request.
20 Ton Standard Exceptions
Due to Oil Management design constraints with the 20S
unit, there are specific rules implemented to deal alternate
staging to prevent the unit operating in compressor
sequences that have the potential to cause oil issues.
RT-SVX063G-EN
Compressor Staging with Variable Speed
Compressors
Units with Variable Speed Compressors will always attempt
to start the variable speed compressor first. Subsequent
stage increases start the preferred compressor next
according to the default factory staging sequence. Special
consideration during Alternate Staging Sequences are
defined as follows:
VSC Available During Alternate Staging Sequences
During inhibited fixed speed compressor operation, the
VSC will be utilized over its full range of designed speed
operation prior to a stage change. Stage change logic will
be determined based on the available compressors
following alternate staging rules.
VSC Inhibited During Alternate Staging Sequences
During inhibited VSC operation, stage change logic will be
determined based on the available fixed stage
compressors. If the circuit with the inhibited VSC also has
fixed stage compressors, (FSC) these compressors will be
available for the alternate staging sequence. All FSC must
be staged OFF before the non-inhibited VSC will become
available. When the VSC becomes available, it will be the
first compressor turned ON at the next ADD request.
Balanced Compressor Staging
The Balanced Staging function is a user-defined option for
fixed-speed compressor units. To perform Wear Balancing,
the Symbio 800 controller will keep track of each installed
compressor' number of starts, and run-time. The controller
will use this information to equalize wear across all
compressors installed in the unit. Double Swaps will not be
performed during Balanced Compressor Staging The
Balanced Compressor Staging function can be Enabled or
Disabled at the user interface. When disabled, compressor
staging follows the Normal Staging Sequence.
Wear Balancing Calculation
The wear balancing formula for compressor operation is
the number of compressor starts multiplied by a factory
determined wear factor, plus all of the normal run time.
Starting accounts for a significant amount of normal run
time wear and adds quickly to the wear calculation sum.
Single Circuit Units
The lowest wear compressor starts first. Subsequent stage
increases start the next lowest wear compressor. The final
stage increase starts the last compressor. Each stage
decrease de-energizes the highest wear compressor first.
Dual Circuit Units
The lowest wear compressor from either circuit starts first.
The second stage increase starts the next lowest wear
compressor from the "Off" circuit. Subsequent stage
increase requests will start the lowest wear compressor
available. Stage decreases with both circuits active, the
highest wear running compressor that will not cause a
circuit to stop will be chosen. If there is only one
Sequence of Operation
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