Daikin MicroTech III Operation Manuals page 130

Sump Drain Valve Control
When the sump temperature gets too cold, the sump needs to
be emptied to prevent freezing . The Sump Drain Valve Output
is used to control a sump drain valve . This output is turned ON
if the sump temperature drops below the Sump Dump Setpoint,
default = 35°F for more than 30 seconds .
This output is turned back OFF if the sump temperature rises
above this setpoint by more than the Sump Dump Differential,
2°C (hardcoded), and the unit is in the Cooling state .
If Dolphin System= Yes and the pump does not run for five
days, the sump needs to be emptied . This would occur when
cooling is not required and the OAT remains below 35°F . Sump
heaters are used to keep the sump temperature above 35°F
when the OAT drops below that value so an additional means
of turning on the Sump Drain Valve is required . In addition to
the requirement that the Sump Drain Valve Output be turned
ON to open the valve when the sump temperature drops below
35°F, the Sump Drain Valve Output is also turned ON if both of
the following are true:
• Dolphin System= Yes
• The Sump Pump Output has been off for 120 hours or
more .
Once on the Sump Drain Valve is turned back OFF as
described above .
Separator Flush Valve Control
On units equipped with a Dolphin System the system
Separator needs to be flushed of its collected solids every
so often. An ON/OFF flush valve actuator is used to flush the
separator . Every 8 hours the Purge Valve Binary Output is
turned ON for the Separator Flush Time (default 1 minute) .
Sump Temperature Control
Two configurations of evaporative condensing units are
provided . One will have two condenser fan outputs per circuit
(Unit Size<110), and one will have three condenser fan outputs
per circuit (Unit Size≥110). The two lead condenser fans are
controlled through a single VFD .
Whenever any compressor is turned ON, the lead condenser
fan on both circuits is turned ON by the Microtech III controller
sending a signal to the VFD via Modbus . The lead condenser
fans on both circuits are turned OFF when all compressors are
OFF or they are turned OFF as described in paragraphs that
follow when the sump temperature gets low .
Whenever any condenser fan is ON, a signal is sent to the
VFD to control connected fans to a setpoint . The speed
setpoint is calculated based on the sump temperature .
OM 920-6 • MICROTECH UNIT CONTROLLER
A single Condenser Fan Output A is controlled to turn ON the
second condenser fan on both circuits . A single Condenser Fan
Output B is controlled to turn ON the second condenser fan
on both circuits . The second and third fans on the circuits are
mechanically prevented from operating when no compressor
on that circuit is operating . When compressors are operating
on both circuits, the number of fans operating on the two
circuits is the same .
The number of fans operating per circuit will increase if the
time since the last change in the number of operating fans
exceeds the Evap Condensing Stage Time and the sump
temperature exceeds the Max Sump Temperature setpoint .
This condenser fan stage increase may occur as soon as the
temperature rises above the Maximum Sump Temperature .
The temperature does not have to remain above the Maximum
Sump Temperature for longer than the stage timer .
The number of fans operating per circuit will decrease if the time
since the last change in the number of operating fans exceeds
the Evap Condensing Stage Time, and the sump temperature
drops below the Min Sump Temperature setting . This condenser
fan stage decrease may occur as soon as the temperature drops
below the Minimum Sump Temperature setting . The temperature
does not have to remain below the Minimum Sump Temperature
setting for longer than the stage timer .
After the two lead condenser fans are turned OFF via the VFD,
they are turned back ON as soon as the sump temperature
rises above the Maximum Sump Temperature setting . This
transition from stage zero to stage one is the only transition
that does not require the Stage Timer to expire .
All of the condenser fans need to be run periodically when
evaporative condensing is used to prevent damage to the
motors due to their high humidity environment . As indicated
above, the condensing fans controlled by the VFD always run
when evaporative operation is in effect so no special control
of these fans is required . The fan motors controlled directly
through the Condenser Fan A and Condenser Fan B outputs
are turned ON and OFF based on time ON and time OFF .
When a condenser fan output must be turned ON for normal
operation, the output that has been OFF for the longest period
of time is started . When a condenser fan must be turned
OFF for normal operation, the output that has been on for the
longest period of time is turned OFF .
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