Daikin DPS - Inverter Compressor Cooling Operation

Initialization to Standby for Restart
The Compressor Cooling State transitions from Initialization
to Standby for Restart if one of the Compressor Protection
functions force a transition to Standby for Restart, the inverter
compressor or outdoor fan board requests a transition to
Standby for Restart or if all compressor operation becomes
disabled for any reason.
Normal to Pumpdown
The Compressor Cooling State transitions from Normal
to Pumpdown if there is no longer a call for cooling or
dehumidication operation.
Normal to Standby for Restart
The Compressor Cooling State transitions from Normal to
Standby for Restart if one of the Compressor Protection
functions force a transition to Standby for Restart, the inverter
compressor or outdoor fan board requests a transition to
Standby for Restart or if all compressor operation becomes
disabled for any reason.
Pumpdown to Standby for Restart
The Compressor Cooling State transitions from Pumpdown
to Standby for Restart if one of the Compressor Protection
functions force a transition to Standby for Restart, the inverter
compressor or outdoor fan board requests a transition to
Standby for Restart or if all compressor operation becomes
disabled for any reason.
Pumpdown to Initialization
The Compressor Cooling State transitions from Pumpdown
to initialization if there is a call for cooling or dehumidication
operation.
Standby for Restart to Off
The Compressor Cooling State transitions from Standby for
Restart to Off after the cooling stage timer expires.
Inverter Compressor Cooling
Operation
Rebel units are always equipped with an inverter compressor.
A xed speed compressor is also provided on sizes 7.5–12.
The primary control devices related to inverter compressor
operation are the following:
• Inverter and Fixed Speed Compressors (INV, Comp3 )
• 1 or 2 Outdoor Fan(s)
• 4 Way Reversing Valve (4WV) – Heat Pump Units Only
• Refrigerant Receiver Solenoid Valve (SVR) – Heat Pump
Units Only
• Refrigerant Discharge to Suction Bypass Solenoid Valve
(SVB)
• Indoor Coil Expansion Valve (EVI)
• Outdoor Coil Expansion Valve (EVO) – Heat Pump Units
Only
Control of these devices is described in the following sections.
Input Devices
PTS (suction refrigerant pressure) – MicroTech III AI
PTD (discharge refrigerant pressure) – MicroTech III AI
DRT1 (INV compressor discharge refrigerant line temperature)
– MicroTech III AI
DRT3 (compressor discharge refrigerant line temperature) –
MicroTech III AI
SRT (suction refrigerant temperature) – MicroTech III AI
DFT (defrost temperature) – MicroTech III AI
IRT (indoor refrigerant temperature) – IFB (heat pump)
ORT (outdoor refrigerant temperature) – IFB (heat pump)
Compressor Control
DPS units will utilize one of the following Compressor Cooling
Congurations:
• Single inverter compressor (INV) on sizes 3-6 ton
• Single inverter compressor (INV) and a standard
compressor on all other sizes
When compressor operation is active the combination of
inverter and standard compressors is controlled to maintain the
applicable discharge air temperature set point. The applicable
set point varies depending on the unit operating state and
whether or not dehumidication is active.
The control of the inverter compressor is accomplished by
sending the analog output of a PI_Loop via Modbus to the
inverter compressor control board. As the PI_Loop output
varies from 0-100% the speed of the inverter compressor
increases from 0 to maximum. In the case where the unit is
also equipped with standard (xed) compressor, the xed
compressor is started and stopped via a digital output.
Upon an increasing call for cooling the inverter compressor
is modulated to its maximum capacity before the xed
compressor is turned on. When the load is such that the xed
compressor is required, the inverter compressor is slowed to
its minimum speed before turning on the xed compressor. The
inverter compressor is then modulated to maintain the load.
Upon a decreasing call for cooling the inverter compressor is
modulated to its minimum speed before the xed compressor
is turned off. Once the xed compressor is turned off the
inverter compressor is modulated maintain the load.
operator’s guIde
www.DaikinApplied.com 85 OM 1141-3 • MICROTECH UNIT CONTROLLER