Service manual

42
11
Outline of Control
Outdoor Unit
Item Operation explanation and applied data, etc. Remarks
5. Oil equalizing
control
This control is to prevent oil reduction in the
compressor between the outdoor units. This control is
classified into two functions, one is an individual
control in normal operation which is performed by the
master outdoor unit, and the other is a system control
which is executed when shortage has been detected in
the oil level detection control.
This control is executed by open/close operation of
solenoid valves SV3A, SV3B, and SV3C, and has the
following two patterns.
(1) Oil equalizing control 1
This is executed when the master outdoor unit has
continuously operated for 30 minutes or more, and
the result of the oil level detection judgment has
been adequate. If only one outdoor unit is present
this control is not implemented.
(2) Oil equalizing control 2
This is executed to supply oil collected in the oil
tank of each outdoor unit to the outdoor unit of
which the oil level has been reduced.
When the oil level judgment result of the master
outdoor unit has been insufficient while the
compressor of master outdoor unit was ON, or
when one of the slave outdoor units required oil
equalizing, this control is implemented. When only
one outdoor unit is present this control is not
implemented.
• Controls to divert oil
to the inverter unit in
operation.
• Normal oil equalizing
operation.
6. Refrigerant/Oil
recovery
control
(1) Oil recovery control in cooling mode, Refrigerant
recovery control in heating mode
During cooling/heating operation, this is executed to
recover the oil/refrigerant in gas crossover pipes or
indoor units to the outdoor unit when, the compressor
operation is reduced, this also prevents stagnation of
refrigerant in the outdoor heat exchanger while low
ambient cooling operation is performed. This control
is managed by the master outdoor unit.
1) Control conditions
• When compressor-ON status continued for
60 minutes.
• When the cooling thermostat-OFF timer
has finished.
2) Contents of control
60 minutes after cooling/heating operation has
been activated, the cooling/heating indoor
oil/refrigerant recovery signal is sent to the indoor
controller. The cooling thermostat-ON 60 minutes
timer starts counting again. At the same time, the
indoor PMV minimum opening signal is also sent to
the indoor controller.
• Recovery time:
Approx. 2 min to 6
min though it differs
according to the
system capacity.