2.3.12. Oil return operation control 
Unitary:
A Entering condition 
When the compressor running frequency is lower than 58Hz continuously in all and outdoor 
unit Tcm is lower than 50 degree for 5 hours, the system will enter oil return operation. In the 
course  of  mode  changeover,  manual  unit  stop  or  protective  unit  stop,  the  time  will  be 
accumulative. After compressor restarts up, the time  will counted continuously. In counting 
time for 5 hour, if the compressor running frequency is over 80Hz for 10 minutes continuously, 
the time will be cleared. Also after the heating defrosting , the time will be cleared. 
B  Procedure 
Cooling mode: refer to “the oil return procedure in cooling mode” 
  Heating mode: refer to “the oil return procedure in heating  mode” 
C The protection treatment in oil return operation: 
In the course of cooling oil return, because of all kinds of protection or abnormal unit stop, 
after the unit restart, the time will not be cleared, the system need another oil return operation. 
In  the  refrigerant  flow  course  in  oil  return  of  cooling  mode  or  after  oil  re
turn,  and  within  5 
minutes  after  the  refrigerant  being  eliminated  is  over,  the  anti-freeze  protection  and  low 
pressure protection are invalid, other protection is valid. 
In the course of heating oil return ,because of all kinds of protection or abnormal unit stop, the 
system need  not another oil  return operation after the unit stop  for 3 minutes  and enter in 
heating  mode  directly.  In  the  course  of  changing  to  cooling  oil  return,  the  anti-freeze 
protection and low pressure protection are invalid, other protection is valid. 
Oil return procedure in cooling mode: 
Send oil return signal  oil return beginning  oil return over 
 ref.eliminated 30s
    80 Hz(E)  
    40HZ(E) 
Inverter compressor auto FQY  
  300pulse (E) 
outdoor unit PMV  auto open angle   auto open angle 
  120pulse(E) 
Outdoor fan motor  auto operation  auto(TC or ambient control)       auto operation 
running indoor motor auto operation  auto(set fan speed)  auto operation 
stop indoor motor  stop    stop   stop 
4-way valve    OFF    OFF     OFF 
60S
Unitary:
A: Entering condition 
When the compressor running frequency is lower than 58Hz continuously in all and outdoor unit Tcm is lower 
than 50 degree for 5 hours, the system will enter oil return operation. In the course of mode changeover, manual 
unit stop or protective unit stop, the time will be accumulative. After compressor restarts up, the time will counted 
continuously. In counting time for 5 hour, if the compressor running frequency is over 80Hz for 10 minutes 
continuously, the time will be cleared. Also after the heating defrosting , the time will be cleared. 
B: Procedure 
Cooling mode: refer to "the oil return procedure in cooling mode"
Heating mode: refer to "the oil return procedure in heatingmode" mode"
C: The protection treatment in oil return operation:
In the course of cooling oil return, because of all kinds of protection or abnormal unit stop, after the unit restart, the 
time will not be cleared, the system need another oil return operation. In the refrigerant ow course in oil return of 
cooling mode or after oil return, and within 5 minutes after the refrigerant being eliminated is over, the anti-freeze 
protection and low pressure protection are invalid, other protection is valid. 
In the course of heating oil return,
 
because of all kinds of protection or abnormal unit stop, the system need not 
another oil return operation after the unit stop for 3 minutes and enter in heating mode directly. In the course of 
changing to cooling oil return, the anti-freeze protection and low pressure protection are invalid, other protection is 
valid. 
Oil return procedure in cooling mode: