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No.
5
6
7
Item
Oil short
protective
control
Refrigerant/Oil
recovery control
Defrost control
(Reverse cycle
defrost method)
Operation explanation and applied data, etc.
This control is provided to prevent oil shortage occurring in the
compressors of each outdoor unit.
The control is achieved by ON/OFF operation of the solenoid
valves SV3A, SV3B, SV3C and SV3D.
(1) Oil-short protective control
The oil shortage protection control function stops the outdoor
unit, if an oil shortage continues for 30 minutes, after 2
minutes, 30 seconds the outdoor unit restarts.
If this function is activated on 3 successive occasions, an error
check code (H07) is generated and the outdoor unit is
stopped.
(1) During cooling operation, this function is executed to regularly
to recover the refrigerant/oil from the indoor units and con-
necting pipe-work back to the outdoor unit.
This function is also performed to prevent stagnated refriger-
ant accumulating in the outdoor heat exchanger during low
ambient cooling.
The control is managed by the header outdoor unit.
1) Control conditions
• Cooling oil recovery operation is executed approximately
every 2 hours.
2) Contents of control
• The recovery period lasts for approximately 2 or 3
minutes though this is dependant on the system capacity.
(2) Refrigerant recovery control in heating room
This function is executed regularly to recover the liquid
refrigerant from the indoor unit.
It is also used to recover oil present in the outdoor heat
exchanger during the heating overload operation (except
during defrost operation).
The control is managed by the header outdoor unit.
1) Heating operation oil, recovery control is executed approxi-
mately every hour.
2) The period of recovery lasts for approximately 2 to 10
minutes though this is dependent upon the load condition.
(3) Control for refrigerating / whilst oil recovery in simultaneous
operation.
This function is executed to recover the refrigerating oil
accumulated in the low-pressure gas inter-unit piping.
(regardless of all cooling operation/all heating operation).
1) Control condition
• When the combined time of the compressor-ON has
reached 95 minutes in simultaneous operation.
2) Control contents
When the conditions have been satisfied, upon changing
the indoor unit mode from heating to cooling, (stop the
indoor fan) the oil is recovered for a period between 2
minutes 30 seconds to 10 minutes. The indoor unit in
cooling operation continues operation.
(1) Defrost start condition
The defrost function is initiated when the measurement
temperature taken from the TE sensor is lower than -2°C for a
period of 25 minutes after compressor initial start up and 55
minutes after subsequent start ups.
(2) Contents of control
• If the outdoor units are combined, the minimum duration for
the defrost operation is 2 minutes.
(3) Defrost stop condition
• The outdoor fan speed and compressor inverter frequency
are determined by the measurement of Pd pressure during
defrost operation.
Remarks
• Oil accumulated in the
oil separator is returned
to the compressor.
• Control for refrigerant/
oil recovery is per-
formed approximately
every 2 hours.
• Recovery lasts for
approximately 2 or 3
minutes though this is
dependent upon the
system capacity.
• Heating operation, oil
recovery is executed
approximately every
hour.
• Recovery lasts for
approximately 2 to 10
minutes though this is
dependent upon the
load condition.
• During the defrost
operation, all solenoid
4-way valves are OFF
and all compressors
are operating.