Toshiba MCY-MHP0806HT8-C Series Service Manual page 32

Item Description of operation, numerical data, and other information
6.
2. Heating refrigerant (oil) recovery control
Refrigerant /
During heating operation, this control function is executed to recover liquid refrigerant
Oil recovery
from indoor units.It is also executed to recover indoor/outdoor refrigerant after defrosting
control and to recover oil in outdoor heat exchangers during heating overload operation.
(continued) 1) Control conditions
• When heating operation has started (compressors have just been turned on)
• When heating operation resumes after defrosting.
• When the oil level judgment result is continued to be "low" for 15 minutes.
2) Control details
• Compressor is operated at the refrigerant recovery control mode speed.
• Indoor units are set to the heating refrigerant (oil) recovery control mode, with
their indoor PMVs opened to a certain degree.
• After completion of refrigerant recovery for all the indoor units, heating operation
resumes.
• The recovery period lasts for approximately 2 to 10 minutes though this is
dependent upon the operated condition.
7. Defrosting 1. Defrosting commencement conditions
control 1) After the heating operation commences, the value detected for the TE sensor
(reverse temperature between 10 and 20 minutes, the value detected for the To sensor
temperature, the rotation speed of the compressor, and the super heat value are
defrosting
saved, and the estimated evaporation temperature for conditions without frost
method)
formation is calculated.
2) After the heating operation runs for 40 minutes, the defrosting control engages
when the value detected for the TE sensor temperature falls below the
cumulative TE temperature during the heating operation, and the frost formation
rate calculated from the estimated evaporation temperature for conditions
without frost formation, the value detected for the TE sensor temperature during
the heating operation, and the detection value of the To sensor temperature
exceeds a certain level.
3) In addition to (2) above, the total operation time is calculated when the value
detected for the TE sensor temperature falls below the cumulative TE
temperature during the heating operation, and the defrosting control engages
after 180 minutes.
(The cumulative operation time is 25 minutes right after startup or right after
changeover from the cooling to the heating operation.)
2. Details of defrosting control
1) The compressor currently in operation is operated at the standby operation speed.
2) When a specified amount of time passes from the time the compressor reached
the standby operation speed, the outdoor fans are turned off by closing the 4-way
valves.
3) The compressor operates at the target rotational speed for defrosting control.
3. Defrosting termination conditions
• Defrosting termination conditions are met when the TE temperature sensor
measurement reaches a specified value (roughly 12 °C) a certain period of time
after the commencement of defrosting control. In that event, defrosting termination
control takes over.
4. Details of defrosting termination control
1) Compressor is operated at the standby operation speed.
2) When a specified amount of time passes, the 4-way valve is opened.
3) Indoor heating refrigerant recovery control is performed.
For control details, see "6. Refrigerant / Oil recovery control".
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Remarks
• Frost formation temperature
is -1.5 °C.
• To protect the refrigerating
cycle circuit, the fan mode
may be controlled during
defrosting.
• During defrosting control,
compressor is controlled
so that its speed does not
exceed 77.0 rps.