7. Defrosting
control
(reverse
defrosting
method)
• Frost formation temperature
is -1.5 °C.
• During defrosting control,
compressors are controlled
so that their speeds do not
exceed 76.6 rps.
1.
Defrosting commencement conditions
• During heating operation, the cumulative duration of operation in which TE1 sensor
temperature falls below frost formation temperature is measured, and
When the
amount of frost formation exceeds a predetermined val
u
e or when
24
0 minutes
passed,
defrosting control is introduced. (Just after startup
or upon
changeover
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”.
• During standby operation,
compressor speed is in the
24-33.5 rps range.
(It varies from outdoor unit to
outdoor unit.)
Item
Description of operation, numerical data, and other information
Remarks
8.Hot gas
defrosting
control
•
During heating operation, the cumulative duration of operation in which
the
TE1 temperature sensor falls below the frost formation temperature is
recorded. Once the time duration exceeds 30 minutes, the hot gas
defrosting
control begins.
・
Frost formation temperature
is -1.5°C.
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.
・
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.
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.
• To protect the refrigerating
cycle circuit, the fan mode
may be controlled during
defrosting.
1.
Hot gas defrosting commencement conditions
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