Toshiba MMU-P0121H Service Manual page 32

Item
5. Oil equalizing This control is to prevent oil reduction in the compressor between
control the outdoor units. This control is classified into two, one is an
individual control in a 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. Basically, this control is executed by open/close operation
of solenoid valves SV3A, SV3B, and SV3C, and has the following
three 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 master
outdoor unit is provided (when no server outdoor unit is not
connected), 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 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 even one of the server outdoor units required
oil equalizing, this control is implemented. When only one
master outdoor unit is provided, this control is not implemented.
(3) Oil equalizing control 3 ................................................................
This is executed when the oil level has not been appropriate
even if the oil equalizing control 2 was executed. However, it is
not executed in 1 unit system of the master outdoor unit.
6. Refrigerant/ (1) Oil recovery control in cooling room
Oil recovery
During cooling operation, this is executed to recover the
control
refrigerating oil stagnated in gas crossover pipe or indoor unit to
the outdoor unit when the compressor driving command is small,
and to prevent 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 time of the cooling thermostat-OFF calculation timer
2) Contents of control
After cooling operation has been activated, the cooling indoor
oil recovery signal is sent to the indoor controller when the
cooling thermostat-ON status continued for 60 minutes.
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.
(2) Refrigerant recovery control in heating room
During heating operation, this is executed to recover liquid
refrigerant stagnated in the stopped indoor unit. It is also used to
recover oil in the outdoor heat exchanger in heating overload
operation except with defrost condition.
1) After heating operation has been activated, it is executed
when thermostat is ON or the operation is shifted to the
normal heating operation after defrost operation and
compressor ON status continues for 60 minutes.
2) While controlling refrigerant recovery in the heating room, the
heating room refrigerant recovery signal is sent to the indoor
controller for 10 minutes. According to the target operation
command, it controls compressor capacity based upon each
operation pattern at time of heating activation, time of heating
operation, and finish time of defrost operation.
Operation explanation and applied data, etc.
has finished.
3-29
Remarks
• Controls so that oil is
gathered in the inverter
with high operation ratio.
• Normal oil equalizing
operation.
• The last oil equalizing
means to be used when
the oil level down has been
detected for a long time.
• Recovery time : Approx. 2
min to 6 min though it
differs according to the
system capacity.
• The recovery time differs
according to the load
condition. However, it is
usually executed for 2 to
10 minutes.