Trane 4TVH0086FE000AA Service Manual page 53

7.2 Defrosting Operation
In order to recover heating capacity, the defrosting operation is conducted when the outdoor unit heat exchanger is
performing as an evaporator. The defrosting operation is controlled according to outdoor ambient temperature, outdoor
heat exchanger temperature, indoor heat exchanger temperature and outdoor unit running time. When the outdoor unit is
running in defrosting, the digital display on outdoor main PCB will display "df".
Table 3-7.5: Outdoor unit component control during defrosting operation
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 3-7.6: Indoor unit component control during defrosting operation
Component
Fan
Electronic expansion valve
14-18HP 20-24HP 26-28HP
● ● ●
● ●
● ● ●
● ●
● ● ●
● ●
● ● ●
●
● ● ●
● ● ●
● ● ●
●
● ●
●
● ●
Unit state Control functions and states
Thermo on Off
Standby Off
Thermo off Off
Thermo on 480 (steps)
Standby 480 (steps)
Thermo off 480 (steps)
52
30-32HP Control functions and states
●
Fixed frequency
●
●
Off
●
Position 480 (steps) or 3000
●
(steps)
Position 480 (steps)
●
Off
●
Normal control
Normal control
●
On
●
On
●
Normal control
●
Off
●
Off
●
Open before compressor
●
startup
B