Toshiba MMY-SAP0806HT8P-E Service Manual page 43

Item Description of operation, numerical data, and other information
1. Defrosting commencement conditions
7. Defrosting
control • During heating operation, the cumulative duration of operation in which TE1 sensor
temperature falls below frost formation temperature is measured, and When the
(reverse
amount of frost formation exceeds a predetermined value or when 240 minutes
defrosting
passed, defrosting control is introduced. (Just after startup or upon changeover
method)
from cooling to heating, the target cumulative duration is 25 minutes.)
2. Details of defrosting control
1) All compressors currently in operation are operated at the minimum speed.
2) When a specified amount of time passes from the time the compressors reached
the minimum speed, the outdoor fan is turned off by closing the 4-way valve.
And the PMV4 opening operated at the target opening for defrosting control.
3) All compressors currently not in operation are turned on and operated at the target
rotational speed for defrosting control.
3. Defrosting termination conditions
• Defrosting termination conditions are met when the TE1 temperature sensor
measurement reaches a specified value (roughly 12 °C) a certain period of time
after the commencement of defrosting control. In that event, defrosting termination
control takes over.
4. Details of defrosting termination control
1) Compressors are operated at the standby operation speed.
2) When a specified amount of time passes, the 4-way valves are opened.
3) Indoor heating refrigerant recovery control is performed.
For control details, see " 6. Refrigerant/oil recovery control".
8.Hot gas
1. Hot gas defrosting commencement conditions
defrosting
• During heating operation, the cumulative duration of operation in which the
control
TE1 temperature sensor falls below the frost formation temperature is
recorded. Once the time duration exceeds 30 minutes, the hot gas defrosting
control begins.
2. Details of hot gas defrosting control
1) SV51 and SV52 are opened.
2) PMV1 is closed.
3) The outdoor fan is turned off.
4) Compressors are operated at the target rotational speed for hot gas
defrosting control.
3. Hot gas defrosting termination conditions
Hot gas defrosting termination conditions are met when the TS1
temperature sensor measurement reaches a value of 12°C for a specified
value of time (within 4.5 minutes) after the commencement of hot gas
defrosting control. In the event that these values are achieved the hot gas
defrosting termination control will take over.
4. Details of hot gas defrosting termination control
1) Open the PMV1 to a certain degree.
2) SV51 and SV52 are closed.
3) Normal heating operation resumes.
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Remarks
• Frost formation temperature
is -1.5 °C.
• To protect the refrigerating
cycle circuit, the fan mode
may be controlled during
defrosting.
• During defrosting control,
compressors are controlled
so that their speeds do not
exceed 76.6 rps.
• During standby operation,
compressor speed is in the
24-33.5 rps range.
(It varies from outdoor unit to
outdoor unit.)
・ Frost formation temperature
is -1.5°C.
・ When outside temperature
is –10°C or lower, hot gas
defrosting control is
disabled. (Only Reverse
defrosting). This is due to
insufficient capacity output,
from the outdoor unit,
resulting in potentially
unacceptable performance
・ During hot gas defrosting
control, compressors are
controlled so that their
speeds do not exceed
76.6 rps.