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2WAY SYSTEM
Control Functions - Outdoor unit
1
9. Defrost Control
2WAY VRF SYSTEM
Control Functions
(4)
When the heating operation time at system has exceeded “XX” minutes (40 minutes at initial setting), and at
least one unit satisfies the decision of defrosting, the defrosting operation is effective.
9. Defrost Control
Heating Operation Set Time (Defrosting Operation Prohibiting Time)
(5)
Defrost ends when either of the below defrost end judgment conditions is met.
Defrost End Judgment Conditions
(6)
If there is only 1 outdoor unit in the refrigerant system, a reverse cycle defrost will be carried out.
It is possible to change the stopped time according to the setting.
For the maximum defrost time, see the table shown above.
Reverse Cycle Defrost
* XX is able to set in EEPROM of main outdoor unit.
* Defrost control is also performed at outdoor units where the outdoor unit heat exchanger is not functioning as
an evaporator (such as stopped outdoor units).
EEPROM setting in main outdoor unit
CODE: A3
Setting No.
25
30
...
XX
25 (minutes)
40 (minutes)
(at factory shipment)
30 (minutes)
...
40
Condition 1: The temperatures are 15°C or higher at all heat exchanger sensors installed on the outdoor
unit.
Condition 2: 15 minutes have elapsed. (Reverse cycle defrost)
18 minutes have elapsed. (Outdoor unit cycle defrost)
Defrost flow E:
C:
Evaporator operation
Condenser operation
E → C:
C → E:
Switching evaporator operation to condenser operation
Switching condenser operation to evaporator operation
Indoor unit
Cooling mode
Heating mode
Defrost
preparation
Defrost in
progress
Defrost
end
judgment
Defrost end
Thermostat ON EC→E E → C
Thermostat OFF EC→E
E → C
Thermostat ON EC→E E → C
Fan (only) EC→E
E → C
Thermostat OFFEC→E
E → C
Compressor OperatingStopped Stopped
4-way valve OFFON→OFF OFF→ON
Stopped EC→E
E → C
Outdoor unit status CE → CC → E
TimeMaximum 15 minutes1 minute 1 minute
2WAY VRF SYSTEM
Control Functions
(7) Outdoor Unit Cycle Defrost
Outdoor unit cycle defrost is performed in systems where 2 or more outdoor units are connected to the
refrigerant system.
Outdoor unit cycle defrost is always completed in 2 defrost operations.
7-2. Defrost sequence
7-1. Description of outdoor unit cycle defrost
In the case of 2 outdoor units installed in the refrigerant system:
Switch to
First operation Second operation
In the case of 3 outdoor units installed in the refrigerant system:
Defrost
outdoor
unit
Evaporator
outdoor
unit
Defrost
outdoor
unit
Defrost
outdoor
unit
Defrost
outdoor
unit
Evaporator
outdoor
unit
Evaporator
outdoor
unit
Evaporator
outdoor
unit
Evaporator
outdoor
unit
Defrost
outdoor
unit
In the case of 4 outdoor units installed in the refrigerant system:
Switch to
Evaporator
outdoor
unit
Evaporator
outdoor
unit
Defrost
outdoor
unit
Defrost
outdoor
unit
Evaporator
outdoor
unit
Evaporator
outdoor
unit
Defrost
outdoor
unit
Defrost
outdoor
unit
Switch to
Heating mode indoor units
Defrost
Preparation
Defrost in
progress
Switch
Defrost in
progress
Defrost end
judgment
Defrost end
judgment
Defrost
end
Thermostat ON
Thermostat OFF
Indoor units where fan is operating
Outdoor compressor(s) where defrost occurs first
Stopped indoor unit(s)
Outdoor compressor(s) where defrost follows later
Outdoor unit(s) where defrost follows later
Outdoor unit(s) where defrost occurs first
C
S
C
ON
S
ON
E
C
C
S
C
OFF
S
ON
E
E → C
C
S
C
OFF
S
OFF
E→C
C → E
C
S
C
ON
S
ON
C
E
Time2 - 7.5 minutes1 minute 1 minute 2 - 7.5 minutes
C
S
C
OFF
4-way valve where defrost occurs first OFFON→OFF OFF→ONONON
S
OFF
4-way valve where defrost follows later ONON ON→OFF OFF OFF→ON
C → E or S
E or S
1 minute
Defrost flow E:
C:
Evaporator operation
Condenser operation
S: stop
E → C:
C → E:
Switching evaporator operation to condenser operation
Switching condenser operation to evaporator operation
1 2 1 2
1 2 31 2 3
1 2 34 1 2 34
In this defrosting, the outdoor units are divided into two groups.
When outdoor units in the first defrosting group operate in defrost mode (heat exchanger operating as a
condenser), outdoor units in the second defrosting group operates as an evaporator in heating mode.
In this way, outdoor units in the second defrosting group supply heat to the unit where defrost is occurring.
When outdoor units in the first defrosting group completes defrost, the other outdoor unit performs defrost
in the same way.
The defrosting group can be determined according to the outdoor unit capacity. The following chart shows
the number 1 , 2 , 3 , 4 for the outdoor unit capacity in order from small.
SM830253-00_欧州2way7_SM-TRSM.indb 31 16/08/26 19:23:19
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