Trane IntelliPak Installation, Operation And Maintenance Manual page 24

General Information
Figure 11. Control module locations for 40 - 89 ton units
eFlex Variable Speed Compressor Staging
Note: The eFlex variable speed compressor can be
manually controlled only in service test mode
through the Intellipak controller human interface.
TheTRV200 inverter keypad has been
programmed purposely to provide stop, reset, and
diagnostics functions only.This is to prevent
bypass of compressor protection functions
provided by the Intellipak control logic.
Figure 12 generally describes how the Intellipak controller
sequences the eFlex variable speed compressor as
building load increases. It is assumed that the unit is
equipped with an economizer.
At low building loads, the economizer will often meet the
building load and compressor cooling will not be required.
Then as the building load increases and the economizer no
longer can maintain setpoint, the Intellipak controller
sends a signal to theTRV200 inverter to start the variable
speed compressor (1A).TheTRV200 inverter ramps the
compressor up to 50Hz for 10 seconds to insure
compressor startup lubrication. Control is released back to
the Intellipak controller and the compressor runs at
minimum speed command (0 VDC from VSM board).
Until the building load exceeds the variable speed
compressor capacity at minimum speed, the Intellipak
compressor will cycle the variable speed compressor to
meet setpoint (4 minute minimum on/off time). However,
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since variable speed unit minimum capacity is about 15%,
this transition cycling will be less than a typical fixed speed
compressor unit which may have 25% minimum capacity.
As the building load increases and eventually equals the
variable speed compressor capacity at minimum speed,
the compressor will run continuously and no longer cycle.
Then as the building load increases, the Intellipak
controller will increase compressor speed to meet the
setpoint. When the variable speed compressor eventually
reaches maximum speed and more capacity is required, a
fixed speed compressor is started while the variable speed
compressor speed is simultaneously ramped back down
to minimum. Note that capacity overlap is provided
between each stage of operation to provide continuous
capacity modulation and minimize compressor cycling
between stages.
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