Daikin MicroTech III Operation Manuals page 114

Compressor Stage Down Transition
When the VFD compressor has been operating at minimum
capacity for the cooling stage time period and less capacity is
needed, the fixed compressor with the highest run hour total is
turned off (fixed speed compressors on the circuit opposite the
VFD compressor are stopped first). The VFD compressor is
held at its maximum value for 30 seconds
Dehumidification Transition During Cooling State
When dehumidification becomes active while the unit is in
the Cooling operating state the VFD compressor is set to
its maximum value and held there for 1 minute . In addition
if the VFD compressor was operating above 75% when
dehumidification became active, a fixed compressor with the
fewest run hours is turned ON .
VFD Compressor Enable/Disable
If the VFD compressor becomes unavailable normal staging
operation (based on run hours) occurs with the available fixed
compressors .
VFD Emergency Stop Output
In normal operation the VFD Emergency Stop Output (EMC
DO4) will be energized (ON) . When any cooling related
alarm that shuts off the VFD compressor is active the VFD
Emergency Stop Output will be de-energized (OFF)
OM 920-6 • MICROTECH UNIT CONTROLLER
Oil Boost Sequence
The VFD compressor is equipped with an oil level sensor .
If low oil level is detected the compressor speed must be
increased for a time period to force oil in the system to
be returned to the compressor . The low oil condition is
communicated to the MicroTech III controller via a digital input
(EMC-X3) signal from the VFD compressor .
When the VFD compressor is ON and low oil level is detected
(digital input EMC-X3 is open) for 10 consecutive minutes
(default) or if oil boost is manually initiated (VFD compressor
must be running for manual initiation of oil boost) the oil boost
sequence is activated . The oil boost sequence is as follows:
• Upon entering into the oil boost operation the MTIII
controller logic captures the current VFD compressor
capacity and fixed speed compressor status.
• If one or more fixed speed compressors are operating
the fixed compressor with the highest run hour total is
staged OFF .
• If the oil boost sequence is activated while the
compressor capacity is less than 60 rps (46 .7%) the
VFD compressor capacity is increased to 60 rps (46 .7%)
and runs at that capacity for an Oil Boost Timing period
(default 15 minutes) .
• If the low oil input (EMC-X3) still open after the Oil
Boost Timing period expires, the compressor capacity is
increased to the High Oil Boost value .
• If the oil boost sequence is activated when the
compressor capacity is equal to or greater than 60 rps
(46 .7%) the compressor capacity is increased to the High
Oil Boost value .
• If the VFD compressor has been operating at the High
Oil Boost value for the Oil Boost Timing period and the
low oil input (EMC-X3) is still open the VFD compressor
is stopped and a Low Oil problem alarm is generated .
The alarm is also generated if the oil boost sequence
becomes active 5 times in a 24 hour operating period .
• Once active the oil boost sequence remains active until the
low oil input (EMC-X3) closes continuously for 3 minutes,
until boost mode is manually stopped via the HMI, the Low
Oil: Problem alarm is generated or the compressors are all
stopped due to normal temperature control .
• When the oil boost sequence becomes active an event
is entered in the Event Log, an event is also entered
when the oil boost sequence becomes inactive and VFD
compressor operation returns to normal .
• Once the low oil input (EMC-X3) closes continuously for
3 minutes, compressor capacity reverts to the condition
captured when the oil boost mode became active .
NOTE: This only applies when the current oil boost cycle
returns to inactive in the "normal" manner . It does
not apply for example if the oil boost cycle returns
to inactive due to the Low Oil: Problem alarm being
generated .
The High Oil Boost Value varies with unit size .
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