OM 1263 • MICROTECH UNIT CONTROLLER 50 www .DaikinApplied .com
Operator’s Guide
Compressor Control PI_Loop
When normal inverter compressor operation is active, the
inverter compressor is controlled via a PI_Loop to maintain the
remote of the manual point .
The compressor control PI_Loop is active when inverter
operation is in either the Normal Cooling or, in the case of
a heat pump configuration, the Normal Heating state. The
PI_Loop is over-ridden when not in these states or when in
these states and any of the Compressor Protection Unloading
Control functions or Fixed Speed Compressor Step Transitions
are active .
Compressor Output Control
Inverter Compressor (INV)
ON/OFF and speed commands are communicated to the
inverter compressor control board via Modbus through the IFB
Communication board .
Fixed Speed Compressor (Comp3)
A digital output is energized on the main control board controls
the fixed speed compressor (Comp3).
Fixed Speed Compressor Step
Transitions
Under normal compressor control, when the unit is equipped
with a fixed speed compressor, special transition steps are
taken when starting and stopping the fixed speed compressor.
These steps are as follows:
Starting the Fixed Speed Compressor
Whenever the inverter compressor can not maintain sufficiently
cold discharge air temperature at maximum speed, and timers
are satisfied, the following fixed speed compressor stage up
sequence occurs:
• Inverter Compressor speed is set to the minimum
value . When the inverter compressor speed reaches
the minimum value then the fixed speed compressor is
turned ON .
• Inverter Compressor speed is held constant for 30
seconds
• Displayed compressor cooling/heating capacity is
released to normal operation .
Stopping the Fixed Speed Compressor
Whenever the two compressors provide excessively cold
discharge air temperature at minimum speed, and timers are
satisfied, the following fixed speed compressor stage down
sequence occurs:
• SVB bypass solenoid is opened
• Fixed speed compressor is turned OFF one second after
SVB is opened
• SVB remains open for one second and then is turned OFF
• Inverter Compressor speed is set to maximum .
• When the inverter compressor speed reaches the
maximum speed value, compressor cooling/heating
control is released to normal operation .
Summary of Contents for MicroTech III DPS
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