2WAY VRF SYSTEM
Control Functions
1
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1
2
3
4
5
6
7
8
9
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.
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)
(factory preset code)
30 (minutes)
...
...
40
85
...
85 (minutes)
90
90 (minutes)
Condition 1: The temperatures are 59°F (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
E
C→E
E → C
Thermostat OFF
E
C→E
E → C
Thermostat ON
E
C→E
E → C
Fan (only)
E
C→E
E → C
Thermostat OFF
E
C→E
E → C
Compressor
Operating
Stopped
Stopped
Stopped
E
C→E
E → C
Outdoor unit status
C
E → C
C → E
Time
Maximum 15 minutes
1 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.
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.
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
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
Time
1 - 7.5 minutes
1 minute
1 minute 1 - 7.5 minutes
C
S
C
OFF
S
OFF
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
9. Defrost Control
3WAY SYSTEM
Control Functions
9. Defrost Control
EEPROM setting in main outdoor unit
CODE: A3
Setting No.
20
21
XX
20
21
40
Interval of “1”
40 (factory preset mode)
90
Never use
41
System employs
1 outdoor unit in the refrigerant system
2 or more outdoor units in the refrigerant system
Defrost control method
Reverse cycle defrost
Ambient temperature
Minute
XX + 6
XX + 3
XX
Outdoor unit cycle defrost
This system uses the following 2 defrosting systems.
Time until next defrost permission when defrost was completed is changed according to the ambient temperature.
Frost detection does not occur for 10 minutes after operation starts.
Defrost does not begin again for 40 minutes of operation after defrost was once completed.
If all indoor units are stopped while defrosting, or if the outdoor unit is stopped due to protection control or
another reason, then defrost control will not start for a minimum of 5 minutes after restart occurs.
9-1. Defrost Methods
(4) Constraint Conditions
To ≤
14°F (-10°C)
14°F (-10°C) <
To ≤ 23
°F (-5°C)
23°F (-5°C) < To
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