Special Control - Trane 4TVH0086FE000AA Service Manual

7 Special Control

7.1 Oil Return Operation
In order to prevent compressors from running out of oil, the oil return operation is conducted to recover oil that has
flowed out of the compressor(s) and into the piping system. This operation is performed for all units including units that
are in standby. When the outdoor unit is running in oil return, the digital display on outdoor main PCB will display "d0".
Timing of oil return operation:
 When the initial cumulative operating time reaches 140 minutes and then every 8 hours.
Tables 3-7.1 and 3-7.2 show component control during oil return operation in cooling mode.
Table 3-7.1: Outdoor unit component control during oil return operation in cooling mode
Component
Inverter compressor A
Inverter compressor B
DC fan motor A
DC fan motor B
Electronic expansion valve A
Electronic expansion valve C
Four-way valve
Solenoid valve (liquid refrigerant
injection)
Solenoid valve (oil balance)
Solenoid valve (fast defrosting)
Solenoid valve (EXV bypass)
Solenoid valve (indoor units
bypass)
Solenoid valve (inverter
compressor A vapor injection)
Solenoid valve (inverter
compressor B vapor injection)
Solenoid valve (inverter
compressor B pressure balance)
Wiring
8-12HP
diagram label
COMP(A)
COMP(B)
FANA
FANB
EXVA
EXVC
ST1
SV2
SV4
SV5
SV6
SV7
SV8A
SV8B
SV9
Table 3-7.2: Indoor unit component control during oil return operation in cooling mode
Component
Fan
Electronic expansion valve
14-18HP 20-24HP
● ● ●
●
● ● ●
●
● ● ●
● ●
● ● ●
●
● ● ●
● ● ●
● ● ●
●
● ●
●
Unit state Control functions and states
Thermo on Remote controller setting
Standby Off
Thermo off Off
Thermo on Normal control
Standby 300 (steps)
Thermo off 300 (steps)
50
26-28HP 30-32HP Control functions and states
● ●
Fixed frequency
● ●
Fan speed controlled according
● ●
to discharge pressure
● ●
Position 480 (steps) or 3000
● ●
(steps)
Position 96 (steps)
● ●
Off
● ●
Normal control
Normal control
● ●
On
● ●
On
● ●
Normal control
●
Controlled according to inverter
● ●
compressor A
Controlled according to inverter
● ●
compressor B
Open
● ●
startup
before compressor B