Toshiba MMY-MAP0806HT7(J)P, Service Manual

Page: 73 / 350

7. Defrosting
control
(reverse
defrosting
method) • Frost formation temperature
is -1.5 °C.
• If the outdoor units are a
combination of different
models, defrosting
operation, once started,
cannot be manually
terminated for about 2
minutes.
•
In case of All Fresh Air
Intake Unit connection
system, replace 55 minutes
with 30 minutes.
• 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.
1.
Defrosting commencement conditions
• During heating operation, the cumulative duration of operation in which TE1
and
TE2
sensor temperature falls below frost formation temperature is measured, and
when this reaches 55 minutes, defrosting control is introduced. (Just after startup
or upon changeover from cooling to heating, the target cumulative duration is 25
minutes.)
* If the outdoor units are a combination of different models, all the units begin engaging
in defrosting control as soon as one of them satisfies defrosting commencement
conditions.
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 fans are turned off by closing the 4-way valves.
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
and TE2
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.
* If the outdoor units are a combination of different models, defrosting termination
control commences when all the units satisfy the defrosting termination conditions.
As long as one or more outdoor units are yet to satisfy the defrosting termination
conditions, those that have engage in standby operation.
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
− 7 2 −
8.Hot gas
defrosting
control
1. Hot gas defrosting commencement conditions
• During heating operation, the cumulative duration of operation in which
the TE1 (or TE2) temperature sensor falls below the frost formation
temperature is recorded. Once the time duration exceeds 30 minutes, the
hot gas defrosting control begins.
*If the outdoor units are in a combination (module), only the outdoor units
that are operating their compressors, will perform the hot gas defrosting
control.
・
Frost formation temperature
is -1.5°C.
・
In case of All Fresh Air
Intake Unit connection
system, hot gas defrosting
is not operated.
2. Details of hot gas defrosting control
1) SV51 and SV52 are opened.
2) PMV1 (and PMV3) are closed.
3)The outdoor fans are turned off.
4) Compressors are operated at the target rotational speed for hot gas
defrosting control.
・
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
3. Hot gas defrosting termination conditions
• Hot gas defrosting termination conditions are met when the TS1 (or TG1
and TG2) 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.
*For module installations (multiple outdoor units). During Hot gas
operation, ALL outdoor units must meet the termination conditionings for the
hot gas control. If not the following defrost operation (25 minutes later if TE1
(or TE2) temperatures measurements continues below the frost formation
temperature) will results in a standard reverse defrosting operation.
・
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 (and PMV3) to a certain degree.
2) SV51 and SV52 are closed.
3) Normal heating operation resumes.