Daikin VRV RXYQ72-384XAYCA, Service Manual

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SiUS342004EB Special Control
Part 4 Functions and Control 100
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
 RXYQ72XA, RXYQ72XB
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 name Electric symbol
Function of functional part
Normal cooling Normal heating
Compressor M1C 24 rps/37 rps

24 rps/37 rps

Fan motor M1F, M2F For heat exchanger mode For heat exchanger mode
Electronic expansion valve
(Heat exchanger upper)
Y1E
Same as normal control Same as normal control
Electronic expansion valve
(Heat exchanger lower)
Y3E
Electronic expansion valve
(Subcooling heat exchanger)
Y2E
0 pulse 0 pulse
Electric expansion valve
(Subcooling injection)
Y4E
760 pulse 760 pulse
Electronic expansion valve
(Refrigerant cooling)
Y5E
Same as normal control Same as normal control
Electronic expansion valve
(Receiver gas purge)
Y7E
Open slightly Open slightly
Solenoid valve
(Oil separator oil return)
Y1S
ON ON
Solenoid valve (Hot gas bypass) Y2S OFF OFF
Solenoid valve (Liquid shutoff) Y3S ON ON
Four way valve (HP/LP gas pipe) Y4S Hold Hold
Four way valve
(Heat exchanger lower)
Y5S
Hold Hold
Four way valve
(Heat exchanger upper)
Y6S
Hold Hold
Solenoid valve
(Accumulator oil return)
Y7S
ON ON
Ending condition
A lapse of 5 min u tes
Master u nit HTdi > 118
°
C (244.4°F)
Pc_max > 2.94 MPa (426 psi)
OR
A lapse of 3 min u tes
Pe_min < 0.19 MPa (27.6 psi)
Ta_min – Te_max > 8
°
C (14°F)
HTdi_max > 118
°
C (244.4°F)
OR
&