Toshiba MMY-MUP0721FT6P-UL Service Manual page 74

Item Description of operation, numerical data, and other information
7. Defrosting
• The reverse defrosting method is used for the outdoor unit in a single system, and the
control individual reverse defrosting method is used for the outdoor units in a connected system.
(Reverse
• In the individual reverse defrosting, in order to prevent the cold air from dropping during
defrosting
defrosting, the Gr in which the unit that satisfies the defrosting start condition exists is
method) switched to the cooling position of the four-way valve to perform the defrosting operation
while Since PMV-D and PMV-S of the FS unit is fully closed, there is no refrigerant flow
to the indoor unit. It will be the operation method to continue the heating operation.
• Only when the outside air temperature is low and the defrosting capacity of the previous
defrosting is lack, both reverse defrosting and individual reverse defrosting preform
"2Step defrosting". In the 2Step defrosting, the heat exchanger of the outdoor unit is
divided into two, and only the upper heat exchanger is defrosted for, after that, only the
lower heat exchanger is defrosted for
[1] [Defrosting start condition (single and common system common)]
• During the heating operation, if the TE sensor detected temperature falls below the
predicted TE sensor temperature by a specified amount, or if the TE sensor detected
temperature falls below the frosting temperature for 300 minutes, the defrosting
operation starts. (After start-up or when switching from cooling to heating, frost
judgment is performed and the defrosting operation is started according to the
judgment result.)
* In the case of the coupled system, when any of the outdoor units satisfies the
defrosting start condition, all the units in the group to which the unit belongs start
defrosting operation, and the other Gr units continue heating operation.
Reverse defrosting method (the outdoor unit is a single system)
[2] Defrost control content
1) Stop the compressor that is running.
2) After a certain period of time, the four-way valve is turned off and the outdoor fan is
stopped.
3) Turn on the compressor that is off and operate it at the target speed for defrost
control.
[3]
Defrost termination condition
When the TE sensor temperature detection value exceeds a certain value (standard
53.0°F(12°C)) after a certain time has passed since the defrost control was started,
the defrost end condition will be set and the defrost end control will be performed.
[4]
Defrost end control content
(1) Stop the compressor again.
(2) Turns on the four-way valve after a certain period of time.
(3) Control the refrigerant recovery in the heating room. For control details, see
"6. Heating refrigerant (oil) recovery control".
Individual defrost method (outdoor unit is combined system)
[1] Outdoor unit grouping method
The outdoor unit is divided into Gr1 and Gr2 when the power is turned on.
[2] Defrost control content
1) If any of the units satisfy the defrosting start conditions, all the stopped outdoor units are
started, the operating unit operates the compressor at the minimum speed, and after a
certain period of time, only the defrosting unit has a four-way valve. To turn off the
outdoor fan.
2) Heating Gr continues heating operation as it is
3) PMV-D and PMV-S of the FS unit is fully closed
[4] Defrost termination condition
When the TE sensor temperature detection value exceeds a certain value
(standard 53.0°F(12°C)) after a certain time has passed since the defrost control was
started, the defrost end condition will be set and the defrost end control will be performed.
* When the defrosting end conditions are met for all outdoor units, the defrosting end
control is performed. If any unit does not meet the defrost termination conditions, the
outdoor unit that satisfies the defrost termination conditions continues defrosting operation.
[5] Defrost end control content
• Defrosting Gr unit
(1) Operates the compressor at standby speed.
(2) After a certain period of time, the four-way valve turns on.
(3) Shift to heating start pattern control.
• Unit of heating Gr
(1) When all the outdoor units included in the defrosting Gr turn on the four-way valve,
the normal heating operation is restored.
(2) The outdoor unit to be stopped stops its operation.
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Remarks
• TE sensor detection
temperature is the lowest
temperature of TE1, TE2,
TE3
• Frosting temperature is
-29.3°F(-1.5°C)
• After the power is turned
on, for the first time, the
defrosting operation is
continued for 25 minutes
below the frosting
temperature only when the
heat exchanger is frosted.
• Fan mode may be
controlled during defrosting
for cycle protection.
• The compressor speed
during defrost control is
controlled below 85.0rps.
• TE sensor detection
temperature is the lowest
temperature of TE1, TE2,
TE3
• Frosting temperature is
-29.3°F(-1.5°C)
• Fan mode may be
controlled during defrosting
for cycle protection.
• The compressor speed of
the defrost unit during
individual reverse defrost
control is controlled at
90rps or less.
• The compressor speed
during standby operation is
15.0 ~ 30.0rps.