Toshiba MiNi-SMMS MCY-MAP0501HT Service Manual page 60

No. Item
5 Defrost control
(Reverse cycle
defrost method)
6 Solenoid valve
control
7 Frequency
release control
8 Compressor
stop due to high
pressure release
Operation explanation and applied data, etc.
(1) Defrost start condition
The defrost function is initiated when the measurement
temperature taken from the TE sensor is lower than –1°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.
(1) SV2 gas balance control
This control is executed to balance the gas when opening
SV2 while the compressor is off, in order to decrease the
activation load in the next compressor-ON time. This control
is individually executed by the header outdoor unit and each
follower outdoor unit.
(2) SV2 high-pressure release control
This control is to control pressure rising in low-frequency
operation of the inverter.
(3) SV2 low-pressure release control
This control is to prevent quick pressure dropping transient
operation. This control is individually executed by the header
outdoor unit.
This control is executed as necessary except during stop time
and thermostat-OFF time.
(4) SV4 low-pressure release control
This control is to prevent low-pressure dropping and is
individually executed by the header unit and each follower
unit.
This control executed during defrost operation, heating start
pattern control operation and cooling operation.
(5) SV5 high-pressure release control
This control is to prevent high-pressure rising and executed
for the header unit only.
(1) High pressure release control
This function is to correct the operation command of the
compressor and suppress the rise of high pressure.
1) Control contents
The operation frequency is decreased by 1 step when Pd
pressure ≥ 3.4MPa. It is decreased by 1 step every 10
seconds until Pd pressure drops below 3.4MPa.
2) Release condition
• When Pd pressure ≤ 3.2MPa
• When refrigerant recovery control starts in all heating
mode
• During defrost operation, stop, thermo OFF.
Each compressor is stopped should the Pd pressure sensor
reach a value of 3.5 MPa. This control is performed by the header
unit and any follower units.
60
Remarks
• During the defrost
operation, all solenoid
4-way valves are OFF
and all compressors
are operating.