Special Control; Pump Down Residual Operation; Oil Return Operation - Daikin VRV RXYQ72-384XAYCA Service Manual

SiUS342004EB

7. Special Control

7.1

Pump Down Residual Operation

If the liquid refrigerant stays in the evaporator at the startup of a compressor, this liquid refrigerant
enters the compressor, thus resulting in diluted oil in the compressor and then degraded lubrication
performance.
Consequently, in order to recover the refrigerant in the evaporator while the compressor stops, the
pump down residual operation is conducted.
Pc: High pressure sensor detection value
Pe: Low pressure sensor detection value
Ta: Outdoor air temperature
Te: Low pressure equivalent saturation temperature
DSH: Discharge pipe superheating degree
Part name
Compressor
Fan motor
Electronic expansion valve
(Heat exchanger upper)
Electronic expansion valve
(Heat exchanger lower)
Electronic expansion valve
(Subcooling heat exchanger)
Electric expansion valve
(Subcooling injection)
Electronic expansion valve
(Refrigerant cooling)
Electronic expansion valve
(Receiver gas purge)
Solenoid valve
(Oil separator oil return)
Solenoid valve (Hot gas bypass)
Solenoid valve (Liquid shutoff)
Four way valve (HP/LP gas pipe)
Four way valve
(Heat exchanger lower)
Four way valve
(Heat exchanger upper)
Solenoid valve
(Accumulator oil return)
Ending condition
7.2

Oil Return Operation

In order to prevent the compressor from running out of oil, the oil return operation is conducted to
recover oil that has flowed out from the compressor to the system side.
Tc : High pressure equivalent saturation temperature
Te : Low pressure equivalent saturation temperature
TsA: Suction pipe temperature detected by thermistor R3T
Part 4 Functions and Control
Electric symbol
M1C 24 rps/37 rps
M1F, M2F For heat exchanger mode
Same as normal control
Y1E
Y3E
0 pulse
Y2E
760 pulse
Y4E
Same as normal control
Y5E
Open slightly
Y7E
ON
Y1S
Y2S OFF
Y3S ON
Y4S Hold
Hold
Y5S
Hold
Y6S
ON
Y7S
A lapse of 5 minutes
OR Master unit HTdi > 118°C (244.4°F)
Pc_max > 2.94 MPa (426 psi)
Function of functional part
Normal cooling
Special Control
Normal heating
24 rps/37 rps
For heat exchanger mode
Same as normal control
0 pulse
760 pulse
Same as normal control
Open slightly
ON
OFF
ON
Hold
Hold
Hold
ON
A lapse of 3 minutes
Pe_min < 0.19 MPa (27.6 psi)
&
Ta_min – Te_max > 8°C (14°F)
OR
HTdi_max > 118°C (244.4°F)
RXYQ72XA, RXYQ72XB
100