Toshiba Super MMU-AP0091H Service Manual page 70

No. Item
5 Oil equation This control is provided to prevent the oil short in the compressor
control of each outdoor unit. This control is basically performed by ON/OFF
operation of the solenoid valves SV3A, SV3B, SV3C, SV3D.
(For the schematic diagram of oil equation control.)
(1) Oil equation control
(2) Oil-short protective control
6 Refrigerant/Oil (1) In cooling operation, this control is executed to regularly
recovery control
(2) Refrigerant recovery control in heating room
7 Defrost control (1) Defrost start condition
(Reverse
defrost method)
(2) Contents of control
(3) Stop conditions of defrost operation
Operation explanation and applied data, etc.
This control supplies oil accumulated in the oil tank of each
outdoor unit to the outdoor unit in which oil level moved down.
This control is performed during compressor-ON of the header
unit when oil level judgment result of the header unit shows
"Short" or the oil equation demand is issued from the system of
even a header unit. In a case of system with a header unit (No
follower unit is connected.), this control is not executed.
If an oil equation control is executed, the protection stops when
the status of oil short continues for 30 minutes, and it restarts
after 2 minutes and 30 seconds after. After then, if the protec-
tion stop is repeated 3 times, an error is determined.
(Restart is not performed.) The error code is "H07".
recover the refrigerating oil stagnated in gas inter-unit pipe or
indoor unit to the outdoor unit when the compressor driving
command is weak, and to prevent refrigerant accumulation in
the outdoor heat exchanger while low ambient cooling opera-
tion is performed.
This control is managed by the header outdoor unit.
1) Control conditions
• Cooling oil recovery control is executed every 2 hours
approximately.
2) Contents of control
• Recovery time continues for approx. 2 or 3 minutes though
it differs according to the system capacity.
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.
This control is managed by the header outdoor unit.
1) Heating refrigerant recovery control is executed every an
hour approximately.
2) Recovery time continues for approx. 2 to 10 minutes though
it differs according to the load condition.
In heating operation, the operating time is integrated when the
detected TE sensor temp was lower than -2°C, and when 25
minutes have passed in the initial time after the compressor
started and 55 minutes in the second time and after.
• If the outdoor units are combined, the defrost operation
forcedly continues for 2 minutes if the defrost operation has
been once started.
• If the outdoor units are combined, the fan drive and compres-
sor inverter frequency may be controlled by Pd pressure
during defrost operation.
70
Remarks
• During defrosting
operation, all the
solenoid valves of
4-way are OFF and all
compressors are
driven.